Beyond familiar particles such as electrons and protons, scientists have discovered a zoo of "quasiparticles" with exotic names, such as magnons, angulons, dropletons and polaritons. But what are quasiparticles, exactly? And given the "quasi" in their name, are they considered real particles?

One way to understand quasiparticles is to explore what a particle is. The standard mental picture of a particle "is of a discrete object, like a ball," Douglas Natelson, a condensed matter physicist at Rice University in Houston, told Live Science. However, this classic image of particles changed with the advent of quantum physics, which revealed that the universe becomes fuzzy at its smallest levels. For example, in 1924, French physicist Louis de Broglie showed that particles such as electrons could also behave as waves ‪—‬ a discovery that earned him a Nobel Prize.

Modern physics suggests that particles are excitations in fields that permeate the entire universe, a bit like a ripple in a pond, Ross McKenzie, a theoretical condensed matter physicist and professor emeritus at the University of Queensland in Australia, told Live Science. Each type of particle has its own corresponding field. For instance, photons of light are ripples of the electromagnetic field, McKenzie noted.

The quantum nature of particles means they can not only fly through an empty vacuum but also ripple through matter. For instance, photons can zip through transparent and translucent materials, and electrons can flow inside wires.

If you can picture a standard particle, such as an electron, as a ripple traveling within a material, you can also envision other kinds of excitations within matter. These other types of ripples are quasiparticles.

For example, think of "the wave" done at a sporting event. "You can watch it propagate around a football stadium; it has a location and a speed," Natelson said. "It only exists within the stadium, though, and it's made up of the collective response of all the interacting fans."

In much the same way, "quasiparticles can only exist within some medium or material, because they are built up from the response of that material's constituents or building blocks," Natelson said; in contrast, particles such as electrons and protons "can exist in free space."

In other words, quasiparticles can't exist in a vacuum and they can't exist on their own. They're reliant on particles acting together and being in a material where they can emerge, just as a wave carried out in a stadium can only exist when there is a group of people there who can perform it.

A philosophical question concerning quasiparticles is whether they are real, McKenzie noted. After all, "quasi" in Latin means "almost."

"Fundamental particles can exist in isolation in a vacuum, and quasiparticles need many interacting particles to exist," McKenzie said. "Still, I would say quasiparticles are, for all intents and purposes, just as real as particles, in how you can detect them and manipulate them."

A zoo of quasiparticles

The concept of quasiparticles originated with theoretical physicist Lev Landau in the 1950s, McKenzie said, and the idea ultimately helped Landau win the Nobel Prize in physics in 1962. Scientists have now proposed the existence of dozens of quasiparticle types, including the following:

• The phonon, which is a quasiparticle of sound — it is the smallest packet of vibrational energy that makes up sound in matter, McKenzie said.
• The electron hole, often simply called a hole, is the positively charged vacancy left behind once an electron has left its original place, McKenzie noted.
• The electron quasiparticle, which essentially consists of an electron and its interactions with its surrounding environment. This combined package means the electron quasiparticle requires more force to move, so it effectively has more mass than a regular electron, McKenzie explained.
• The exciton, a quasiparticle made of an electron and a hole orbiting each other.
• The anyon, a kind of quasiparticle so far only seen in two-dimensional systems, which may carry only a fraction of an electric charge.

"How many kinds of quasiparticles are there?" McKenzie said. "Just like there are an infinite number of possible states of matter, I would say that, in principle, there are an infinite number of types of quasiparticles."

Scientists describe activity in material as quasiparticles "because it simplifies everything dramatically," McKenzie said. In the same vein, Natelson said that "very often the math behind physical phenomena in solids is described well by quasiparticles."

Quasiparticles are not simply useful for bookkeeping. For instance, researchers typically describe the behavior of electricity in electronic devices in forms of quasiparticles such as holes and excitons, Natelson said.

All in all, the answer to the question of whether quasiparticles are real is a matter of interpretation. If the question is whether or not a quasiparticle is an elementary particle such as an electron, the answer is no — they cannot exist on their own, and they depend on the materials in which they manifest.

However, if the question is whether or not quasiparticles are real phenomena, the answer is yes — they are things that scientists can measure that can behave like particles and effectively have many of the same properties that other particles do.

The Large Hadron Collider (LHC), the world's largest and most powerful atom smasher, has entered a planned four-year shutdown that will upgrade it to its most capable form yet.

The particle accelerator was switched off Monday (June 29) and is scheduled to come back online in 2030 as the High-Luminosity Large Hadron Collider (HiLumi LHC), with improvements that will allow it to smash together roughly 10 times more particles than its original design. That data could help spark new discoveries in fundamental physics and shed light on the nature of dark matter, antimatter and the early universe.

"This is a very important moment," HiLumi LHC project chief Markus Zerlauth told Agence France-Presse. "From Monday, we will be entering a new phase."

Since its first successful proton collision in 2009, the LHC has allowed physicists to test theories about particle physics and the Standard Model of the subatomic world. It was essential to the discovery of the Higgs boson in 2012, which helped explain how tiny fundamental particles acquire mass. The collider covers a 17-mile (27 kilometers) loop at the border between France and Switzerland near Geneva.

The current shutdown is the third long-term, planned pause in the collider's operations. The first, a two-year shutdown beginning in 2013, consolidated connections between superconducting magnets and boosted the energy of the colliding proton beams. A second pause, from 2018 to 2022, involved a series of upgrades, replacements and preventive maintenance.

In the current period of dormancy, dubbed Long Shutdown 3 (LS3), specialists will install upgrades to boost the collider's luminosity by a factor of 10. That will increase the number of particle collisions, roughly tripling the number of times particles will smack into each other compared with the existing setup. Once the final version of the particle accelerator is online, it will run until the end of its operational lifespan in the 2040s and will be earmarked for replacement by a new, higher-energy particle accelerator in the years that follow.

"It really is an opportunity to explore the universe in a way we haven't done before," Mark Thomson, director general of CERN (the European Organization for Nuclear Research), where the LHC is housed, told New Scientist.

That jump means that experiments will produce much more data, which will allow scientists to study known phenomena, such as the Higgs boson, in more detail and increase the odds of observing rare events. For example, the HiLumi LHC is expected to produce about 380 million Higgs bosons over its lifetime of a decade or so, compared with the 55 million it's made to date. The data could help scientists solve problems with the Standard Model, which currently doesn't incorporate dark matter or dark energy, the primary forms of mass and energy in the universe.

"The LS3 represents a huge and complex logistical and engineering undertaking," Jean-Philippe Tock, head of the LS3 coordination team, said in a statement. "In the LHC alone, 1.2 km [0.75 miles] of magnets and components will be removed and replaced with new equipment, and across the whole complex, dozens of projects are planned, involving thousands of engineers, physicists, technicians and support personnel."

While the LHC won't be smashing any particles together during the shutdown period, researchers will continue to analyze data already collected during experiments during the prior operational window.

Though the LHC's primary purpose is fundamental physics research, technologies used to upgrade the collider could find their way into everyday life. For example, some instruments and techniques originally developed at CERN are now being used in medical imaging, sensors and art restoration.

Physicists recently wondered what would happen if you tried to split a photon ‪—‬ and they found some unexpected behavior that may transform the way we think about particles.

The experiment, in which researchers simulated a photon being sliced by a shutter under various conditions, showed that a severed photon can lead to a complex mixture of zero to infinitely-many photons — raising some big questions about the nature of particle interactions.

Photons are elementary packets of light, which means they are not made up of anything else. So what does it even mean to try splitting a photon? It may be possible thanks to wave-particle duality — a core principle of quantum mechanics, the bizarre physics of the very small.

According to wave-particle duality, a photon is not only a particle but also a wave. Using theoretical calculations, the researchers investigated what would happen if you sent this photon through a shutter and closed it while the photon was passing through, effectively cutting off the tail end of the photon wave.

"I think that most physicists would expect there to be a certain probability that you have zero photons and a certain probability that you have a single photon left after you have done this," Johannes Skaar, co-author of the new study and a professor of theoretical physics at the University of Oslo, told Live Science. "And that is approximately true, but it is not exactly true."

What are the chances?

This brings up another strange aspect of quantum mechanics: its probabilistic nature. Particles exist as a cloud of probabilities stretching to infinity. Until a particle is observed, its properties, such as its position or energy, are in a superposition of possible values; all we can know are the chances of finding it in a certain state.

Through their calculations, Skaar and his colleagues determined how cutting a photon affects these probabilities. In their study, recently accepted in the journal Physical Review Letters, they found that it would create a complex mixture of photon states, including one with an infinite number of photons.

Each of these states has a probability that depends on how quickly the shutter cuts the photon. The expected number of photons becomes infinite only if the shutter is closed infinitely quickly. For realistic shutter speeds, even a thousand photons would be extremely unlikely.

This may sound very strange, but the quantum physicists were unfazed. In fact, what surprised Skaar and his colleagues was what happens if you make measurements of the cut photon from different perspectives.

"When you measure from one side of the shutter, then it will look like a single photon state," Skaar said. "Then, on the other side, it will look like a vacuum state — that means no photons. And that is very strange because the actual state globally is this mixture from zero to infinity."

Changing how we think about particles

The fact that these complex mixtures can be treated locally as very simple states raises fundamental questions about the nature of particles. Skaar said they are still reckoning with the full extent of these implications and they are now considering how this process could play out for other quantum particles, such as electrons.

They hope that by following this theoretical thread through, they may be able to develop a neater way of describing particle interactions. Currently, particles' infinite stretching means they have been interacting for an infinite amount of time. This then poses a problem for causality ‪—‬ the order of cause and effect ‪—‬ in particle interactions, the team said.

These new theoretical photons with a cutoff tail would not have this problem, meaning the causal link in an interaction would be clear, Skaar said. He admitted that there is much more work to be done to develop the theoretical description of this interaction. However, the new result is an important step toward describing particle interactions with a clear causal relationship, which Skaar described as the team's "ultimate goal."

For decades, physicists have pursued a goal that sounds nearly impossible: to build a clock that keeps time using an atom's nucleus rather than the electrons orbiting it.

Now, researchers have demonstrated the first functioning nuclear clock ‪—‬ an advancement that could eventually lead to more robust timekeeping devices and new ways to search for dark matter and physics beyond the Standard Model.

"Having worked in this field for more than 15 years, it is just beautiful, how a very 'wild' idea such as manipulating an atomic nucleus with a laser has turned into reality," Thorsten Schumm, a professor of quantum metrology at the Vienna University of Technology and a member of the research team, told Live Science via email.

How is a nuclear clock different from an atomic clock?

Today's most accurate clocks are optical atomic clocks, which measure the frequency of electrons jumping between different energy levels inside atoms. These clocks are so precise that they would lose less than a second over a 100 million years.

A nuclear clock works similarly, but it uses a transition within the nucleus itself, where the nucleus jumps between energy levels. Because the nucleus sits deep inside the atom, it's far less affected by external disturbances from things like electric or magnetic fields. According to Schumm, the nuclear transition can be 1,000 to 10,000 times less sensitive to environmental noise than atomic transitions are.

"This means that it would be easier to stabilize a nuclear clock over long periods of time," Jacob Higgins, a postdoctoral researcher at Northwestern University who previously worked on thorium clock experiments at JILA in Colorado but was not affiliated with the study, told Live Science in an email. "The transition used for the nuclear clock experiment has a higher quality factor than optical atomic clock transitions, which means that in principle, it can be measured more precisely given the same amount of measurement time."

Together, those advantages could allow nuclear clocks to outperform even today's best atomic clocks according to Higgins.

Why thorium-229 is special

The nuclear clock relies on a rare isotope called thorium-229, whose nucleus contains an unusually low-energy excited state that can be manipulated with ultraviolet laser light.

For decades, scientists had suspected thorium had a low transition, but identifying and controlling it proved extremely challenging. Researchers spent years testing different thorium-containing materials, laser systems and detection methods before finally pinning down the transition.

"It was a long road," Higgins said.

One key advancement was the development of continuous-wave lasers that operate at the precise wavelength needed to excite the thorium nucleus. Before those lasers existed, researchers had to excite the nucleus and then wait several minutes for it to decay and emit a detectable signal. That process was too slow to build a practical clock.

"With the continuous lasers, we can measure the nucleus in absorption and get an immediate response, whether the laser is still at the right frequency (and if not, correct it back)," Schumm said. "Once we had that, it was 'just' implementing some electronics and atomization to have the clock stabilize itself to the nucleus."

Thanks to this set-up, the researchers kept the nuclear clock running continuously for 24 hours.

Unlike many optical atomic clocks, which require ultracold atoms to be suspended in a vacuum chamber, the thorium nuclei are embedded inside a crystal at room temperature.

Because the thorium transition remains stable inside a solid material, researchers may eventually be able to build compact clocks that are useful for navigation systems, telecommunication networks and data synchronization.

A tool for studying the universe

Some physicists are more excited about what nuclear clocks could reveal about fundamental physics, rather than the clocks' timekeeping abilities.

Atomic clocks primarily probe electromagnetic interactions involving electrons. Nuclear clocks, by contrast, are sensitive to the strong nuclear force, weak nuclear force and electromagnetism — three of the four fundamental forces of the universe, along with gravity. This can make them useful detectors of new physics, in a way.

"The nuclear clock is foremost a different clock, ticking on different fundamental physics mechanisms," Schumm said. "Essentially all modern theories beyond the standard model predict additional particles or 5th forces … which can be probed with the nuclear clock in some parameter regime."

Thorium-229 is particularly intriguing because the energy difference between its two nuclear states results from a delicate balance between electromagnetic and nuclear forces. Because those large contributions nearly cancel each other out, even tiny changes in the underlying forces could shift the clock's frequency.

"So small shifts in these forces — like if the nucleus were to couple to certain forms of dark matter or if there were an oscillation of a fundamental constant — will be amplified in our measurement," Higgins said.

Researchers, including Higgins, have already used early versions of the clock to place constraints on some dark matter models, and they expect its sensitivity to improve as the technology itself gets better.

Although the first functioning nuclear clock is a major achievement, these timekeepers remain in their infancy. Scientists still need to gain a better understanding of how the thorium transition responds to factors like temperature and magnetic fields while developing more powerful and stable laser systems.

"I think it will be many years before the thorium clock can compete with today's best optical atomic clocks," Higgins said, "but we will learn a lot of new science on the pathway to getting there."

A new theoretical study suggests that black holes may never fully evaporate, which contradicts an infamous Stephen Hawking theory that seems to violate fundamental laws of quantum mechanics. Instead, black holes could leave behind tiny, stable remnants that store all the information they once consumed, the study suggests.

But there's a twist — literally. For the theory to work, the universe must have three extra hidden dimensions that humans cannot perceive, making space-time seven-dimensional. As these hidden dimensions fold and twist, they create a repulsive force that prevents black holes from evaporating entirely.

The work, while hard to test directly, links black holes to the geometry of extra dimensions, offering a fresh approach to one of the deepest puzzles in physics.

A paradox that challenges the foundations of physics

Black holes are often thought of as cosmic traps from which nothing escapes. Yet, since the 1970s, physicists have known that these cosmic behemoths are not entirely black. Famed theoretical physicist Stephen Hawking proposed that black holes emit radiation and slowly evaporate over time, which leads to a troubling contradiction known as the information loss paradox.

"Imagine you throw a book into a fire," study co-author Richard Pinčák, a senior researcher at the Slovak Academy of Sciences' Institute of Experimental Physics, told Live Science via email. "The book is destroyed, but in principle you could reconstruct every word from the smoke, ash, and heat — the information is scrambled, not lost."

But when a black hole evaporates completely, the information about everything that fell into it appears to vanish, violating a core principle of quantum mechanics.

For decades, physicists have struggled to resolve this paradox. Now, the new study, published March 19 in the journal General Relativity and Gravitation, suggests the answer may lie in the hidden structure of space-time itself.

Extra dimensions and the hidden structure of space-time

The new research explores a universe with more dimensions than the familiar four. In this framework, the cosmos contains seven dimensions, three of which are compact and invisible at everyday scales.

"We experience three dimensions of space and one of time — four dimensions in total," Pinčák said. "Our model proposes that the universe actually has seven dimensions: the four we know, plus three tiny extra dimensions curled up so tightly that we cannot directly perceive them."

These extra dimensions are arranged in a highly symmetrical structure known as a G₂ geometry. This mathematical framework, often explored in advanced theories such as a version of string theory known as M-theory, determines how the hidden dimensions are "folded."

"Think of it like origami," Pinčák said. "The way you fold the paper determines what the final shape can do."

In the new model, this geometric structure produces a physical effect called torsion, which can be thought of as a twisting of space-time. This torsion field turns out to play a crucial role in black hole physics.

Torsion and the birth of stable black hole remnants

The study shows that torsion generates a repulsive force that becomes important at extremely small scales, near the end of a black hole's life. As the black hole shrinks through Hawking radiation, this force eventually counteracts further collapse.

"This repulsive force acts as a brake, halting the evaporation before the black hole vanishes completely," Pinčák said.

Instead of disappearing, the black hole stabilizes into a tiny remnant. According to the model, this leftover object has a mass of about 9 × 10⁻⁴¹ kilograms ‪—‬ some 10 billion times smaller than an electron.

Crucially, this remnant can store the information that fell into the black hole, avoiding any violation of quantum mechanics. The information is encoded in subtle oscillations known as quasinormal modes, which act as carriers of the lost data.

The model also reveals an unexpected connection to particle physics: The existence of three hidden dimensions, together with the presence of torsion, produces the pattern of particle interactions responsible for the Higgs mechanism, the phenomenon that gives mass to elementary particles like electrons and quarks.

"The same torsion field… generates a potential energy landscape that is identical in form to the one responsible for giving mass to the W and Z bosons — the carriers of the weak nuclear force," Pinčák said.

This link ties the behavior of black holes to the electroweak scale, a well-known energy scale in particle physics.

Where the new theory reaches its limits

Despite its appeal, the model faces important challenges. The standard description of black hole evaporation relies on a semiclassical approximation, which is expected to break down at extremely small scales near the Planck mass — approximately 10^-5 grams. This is the mass scale at which quantum gravitational effects become strong and impossible to ignore.

"As the black hole shrinks toward the Planck scale, all existing models — ours included — must eventually confront the transition into the deep quantum-gravity regime," Pinčák noted.

In this regime, a full theory of quantum gravity is required, but such a theory remains incomplete. The new work does not claim to solve this problem entirely. Instead, it provides a concrete mechanism for how new physics could emerge at the final stage of evaporation.

"What distinguishes our approach is that we do not claim semiclassical evaporation operates all the way down to the remnant mass," Pinčák said. "At that point, a new physical effect … takes over and stabilises the configuration."

Testing the theory directly will be extremely difficult; the relevant energy scales are far beyond the reach of current particle accelerators. However, the model makes clear predictions that could, in principle, be tested.

For example, it predicts that hypothetical Kaluza-Klein particles associated with extra dimensions should have masses of around 10¹⁶ gigaelectronvolts ‪—‬ about 14 orders of magnitude heavier than the top quark, the most massive known elementary particle. Detecting lighter versions of these particles with current or future accelerators would rule out the model.

Another possibility involves observing the final stages of black hole evaporation, particularly for primordial black holes. Future gamma-ray telescopes or gravitational wave detectors could provide indirect evidence for stable remnants.

"The important point is that the predictions are concrete — the model can be wrong, which is what makes it scientific," Pinčák said.

Looking ahead, the researchers aim to connect their framework more directly to fundamental theories such as M-theory and to better understand how information is stored in the remnants. If confirmed, the idea that black holes leave behind tiny, information-rich remnants could reshape our understanding of gravity, quantum mechanics and the fundamental structure of the universe.

How much do you know about black holes? Test your cosmic knowledge with our black hole quiz!

For the first time, researchers have detected empty voids moving faster than the speed of light — and they blazed past that cosmic speed limit without breaking the laws of relativity.

A recent study shows the voids' acceleration. Researchers used recent advances in ultrafast electron microscopy to measure voids in phonon-polariton waves zooming around inside a thin flake of boron nitride. Phonon-polaritons are quasiparticles formed from photons (quantized light) coupled with tiny vibrations, and they act like light and sound waves combined.

Waves are often visualized as a single squiggle, but in many applications, imagining them as a lake could give a better idea of what's going on. Lakes are full of waves and ripples that interfere with each other. If the waves interact when they're at their maximum height, they combine to create an even higher wave. But if they make contact when they're at their lowest points, they create deeper troughs than they would on their own.

Sometimes, waves cancel each other out, creating points where the waves' magnitude drops to zero. In a lake, this would make a temporary whirlpool (a vortex) that moves around that empty point, also called a singularity. These singularities are found throughout nature and mathematics and, since the 1970s, have been theorized to move faster than light speed in some instances, according to a recent statement from the Technion-Israel Institute of Technology.

Blazing past the limit

Einstein's theory of special relativity states that the speed of light in a vacuum ‪—‬ 299,792,458 meters per second, or about 186,000 miles per second ‪—‬ is the fastest speed information, matter and energy can travel through space. So how do singularities move faster than light speed? Because singularities are empty points of nothingness, they contain no information, no matter and no energy. They are tiny voids, so they don't have to obey the cosmic speed limit.

These voids don't just exceed the speed of light ‪—‬ they blaze past it. When two singularities encounter each other, they can sometimes exponentially speed up toward each other until their velocities approach infinity just before they cancel each other out. However, the faster they go, the harder it is to observe them. The recent study, published March 25 in the journal Nature, shows researchers doing just that.

"Our discovery reveals universal laws of nature shared by all types of waves, from sound waves and fluid flows to complex systems such as superconductors," Ido Kaminer, an electrical and computer engineering professor at the Technion-Israel Institute of Technology and a member of the research team, said in the statement.

The study's results apply to more than just tiny whirlpools; the null points act enough like particles that scientists can study them to better understand particle interactions. To do this, researchers need to know where the comparison breaks down. The new study shows the voids' need for speed is a point where the singularities stop acting like particles, since particles obey the cosmic speed limit that voids ignore.

In addition, the team's new techniques for observing very small, very fast things could light up some previously unexplored pockets across multiple scientific disciplines.

"We believe these innovative microscopy techniques will enable the study of hidden processes in physics, chemistry, and biology, revealing for the first time how nature behaves in its fastest and most elusive moments," Kaminer added.

For the first time, scientists have observed quantum entanglement in the way atoms physically move — bringing a phenomenon once described by Albert Einstein as "spooky action at a distance" into even sharper reality.

In the new study, published in the journal Nature Communications, researchers demonstrated that pairs of ultracold helium atoms can be quantum mechanically linked through their momentum — a measure of how fast and in which direction a particle moves, factoring in its mass.

Quantum entanglement is one of the strangest features of quantum mechanics. When two particles are entangled, a measurement of one instantly affects the other. Scientists had demonstrated this before in photons (packets of light) and in the internal spin states of atoms but never in the motion of particles with mass. This is important because atoms have mass, and mass responds to gravity; photons don't. Momentum-entangled atoms could one day power quantum sensors precise enough to detect space-time ripples called gravitational waves or to map Earth's interior.

Catching entanglement in the act

First, the team chose helium as their atom, because it can be held in a long-lived excited state with a lifetime of around two hours — which is “essentially infinite” in experiments that only last 20 to 30 seconds, Sean Hodgman, an experimental physicist at the Australian National University and senior author of the study, told Live Science. That internal energy means each atom hits a detector with enough force to register individually. It allows the team to reconstruct the full three-dimensional momentum of the cloud with single-atom resolution.

To create momentum-entangled atom pairs, the team started with a cloud of helium cooled to near absolute zero. Normally, atoms zip around independently. But if you cool them enough, they slow to a near standstill. Their quantum identities blur together into a single collective object called a Bose-Einstein condensate.

Then, they used tuned laser pulses to split that condensate into three groups: one kicked upward, one kicked downward, and one left stationary. As the moving clouds passed through the stationary one, pairs of atoms collided and scattered in opposite directions, forming spherical shells of correlated pairs. Physicists call it "scattering halos." At low enough density, only a single pair scatters per experimental shot. "You either have a pair at one position, or a pair at another," Hodgman said. "Your entangled state is a superposition of both."

To prove the entanglement was real, the team used a device called a Rarity-Tapster interferometer. This method, first demonstrated with photons in 1990, now extended to matter waves for the first time.

"The atoms scatter apart; then you reflect them back onto themselves and interfere with them together," Hodgman explained. "Interference only occurs if the atom is truly in a superposition of both states." The correlations the team measured cannot be explained by any classical theory.

To get their final result, the team collected data continuously for nearly a month and spent a month to a year just setting up the experiment.

"This has kind of been a long-term goal for our lab for probably 20 years or so," Hodgman said. "To be able to finally demonstrate it is really exciting."

A surreal win for quantum mechanics

The result, while exciting, mainly served to validate “textbook” physics theories, Hodgman added. Quantum mechanics predicts this exact kind of behavior, but that doesn't make it any less disorienting.

"Our brains aren't really equipped to process it," Hodgman added. "Atoms appear as smeared out at small scales, not concrete blobs or little balls. And that just seems really, really weird."

The team is already working on a stronger version of the test. But the experiment Hodgman describes as the most consequential next step involves colliding two isotopes of helium ‪—‬ helium-3 and helium-4, which are fundamentally different kinds of particles — to create pairs entangled in both momentum and mass simultaneously.

"From a quantum gravity point of view, how do you even write down the gravitational description of that kind of state?" Hodgman said. "You can't really describe it in a general relativity framework at all. These sorts of states would provide a real challenge for quantum gravity theories to explain."

Athreya, Y. S., Kannan, S., Yan, X. T., Lewis-Swan, R. J., Kheruntsyan, K. V., Truscott, A. G., & Hodgman, S. S. (2026). Bell correlations between momentum-entangled pairs of 4He* atoms. Nature Communications, 17(1). https://doi.org/10.1038/s41467-026-69070-3

How much do you know about Albert Einstein and quantum physics? Try your luck with our Einstein quiz!

Physicists have successfully transported antimatter by truck for the first time — a milestone that allows them to study the elusive material with unprecedented precision and could eventually help to explain how matter came to dominate the universe.

The short, tightly controlled journey around the campus of the European Organization for Nuclear Research (CERN) in Geneva demonstrated that antimatter, one of the most fragile substances known to science, can be moved without being destroyed. That capability allows scientists to transport antimatter to quieter labs across Europe, where ultrasensitive experiments are less affected by interference than they are at CERN.

"This opens, in principle, an entire new universe for precision measurements outside of CERN," Stefan Ulmer, a spokesperson for the BASE (Baryon Antibaryon Symmetry Experiment) collaboration that carried out the experiment, said in a recent video.

What’s the matter with antimatter?

According to current theories, the Big Bang should have produced equal amounts of matter and antimatter. If that were the case, the two would have annihilated each other completely, leaving behind a dark, empty universe. Instead, the observable universe is puzzlingly, overwhelmingly made of matter, and physicists believe that any measurable difference between matter and antimatter could offer a crucial clue to resolving that mystery.

CERN has been producing antimatter for decades through high-energy particle collisions at its "antimatter factory." But the same powerful equipment used to create the particles also generates tiny magnetic fluctuations that can disrupt the extremely precise measurements scientists are trying to make. Relocating antimatter to more stable environments could help, but transporting it is notoriously difficult.

When antimatter comes into contact with ordinary matter, both are instantly destroyed in a burst of energy. To prevent that, scientists confine antimatter particles using carefully tuned electric and magnetic fields in a near-perfect vacuum — conditions that are challenging to maintain even in a stationary laboratory, let alone in a moving vehicle.

To test whether transport was feasible, Ulmer and his team loaded 92 antiprotons, the antimatter counterparts of protons, into a portable trap and drove them about 5 miles (8 kilometers) around CERN's campus.

Inside the device, the particles were suspended in a near-perfect vacuum and held in place by electric and magnetic fields, preventing them from touching the container walls. The team monitored the particles throughout the trip and reported that they remained stable despite road vibrations and motion, according to a CERN statement.

Even in a worst-case scenario, the experiment posed little risk. The amount of antimatter involved was extremely small, and its annihilation would have released only a negligible amount of energy. According to CERN, even all the antimatter ever produced at the facility would generate only enough energy to power a single light bulb for just a few minutes.

Beyond the Standard Model

The successful test does not immediately change how antimatter is studied, but it demonstrates that transporting it is technically feasible. That, in turn, opens the possibility of moving antiprotons to quieter laboratories across Europe, such as the Heinrich Heine University Düsseldorf in Germany, located about eight hours by road from CERN, where quieter conditions could enable more precise measurements.

Such measurements could help scientists detect even the faintest differences between matter and antimatter. If those differences exist, they could point to why matter came to dominate the universe, offer clues to physics beyond the Standard Model, and ultimately explain why anything — from stars, to planets, to people — exists at all.

"We are at the beginning of an exciting scientific journey that will allow us to further deepen our understanding of antimatter," Gautier Hamel de Monchenault, CERN's director for research and computing, said in the statement.

Molecular vibrations can "catapult" electrons across solar materials in quadrillionths of a second‬ ‪— much faster than previously thought, a new study shows.

The findings could help scientists find more efficient ways to convert solar energy into electricity, according to the study, which was published March 5 in the journal Nature Communications.

"We're effectively watching electrons migrate on the same clock as the atoms themselves," study co-author Pratyush Ghosh, a researcher who studies ultrafast spectroscopy at the University of Cambridge, said in a statement.

Organic molecules go solar

Organic solar cells use carbon-based molecules, rather than silicon, to convert sunlight into electricity. In theory, organic solar cells could provide that electricity at lower cost than conventional solar cells, but they are much less efficient.

In a typical organic solar cell, an electron donor and an electron acceptor are sandwiched between two conductive electrodes. When light hits the cell, it generates an "exciton," an electron-hole pair. Excitons split at the interface between the donor and the acceptor, generating electricity.

To achieve fast charge transfer at the interface and limit energy loss, the donor and acceptor molecules usually have strong electronic coupling, or overlap between their electronic states, which allows charges to move easily between molecules. They also often have a large energy difference between them, but that limits the voltage available from the device.

In the new study, researchers observed ultrafast charge transfer at a junction between the electron donor and electron acceptor in an organic solar cell, without needing to conform to either of these constraints. The team used a short laser pulse to excite the electron donor, a polymer called TS-P3, and then used a different laser to measure how the system changed during charge transfer.

That charge transfer happened in 18 femtoseconds ‪—‬ about as fast as an individual molecule vibrates. A few other systems without strong driving forces exhibit charge transfer over 100 to 200 femtoseconds, but most take ten to a thousand times that long.

"Seeing it happen on this timescale within a single molecular vibration is extraordinary," Ghosh said in the statement.

A 'molecular catapult'

That similar timescale wasn't a coincidence. In a second set of laser experiments, the team found that vibrations in the polymer donor molecule launched an electron across the junction to an acceptor molecule. When the electron arrived, it triggered overlapping vibrations in the acceptor molecule. This overlap allowed charge transfer to happen much more quickly than expected, and without the need for strong coupling or a large energy difference.

"Instead of drifting randomly, the electron is launched in one coherent burst," Ghosh said in the statement. "The vibration acts like a molecular catapult. The vibrations don't just accompany the process, they actively drive it."

The findings help to explain the processes that control the speed of charge transfer and establish new strategies for designing more efficient organic solar cells and materials, the researchers wrote in the study.

"Instead of trying to suppress molecular motion, we can now design materials that use it ‪—‬ turning vibrations from a limitation into a tool," study co-author Akshay Rao, a physicist at Cambridge, said in the statement.

Researchers have developed a method for steering microscopic swimming robots using light patterns and the principles of Einstein's theory of relativity. The technology is a potential first step toward deploying tiny robots in applications ranging from medicine to manufacturing.

One of the major challenges of developing microrobots for practical applications is creating ones capable of navigation without the inclusion of bulky sensors and other electronics, which would make the machines too large to operate at the desired scale (like inside a human body). In an attempt to overcome this issue, physicists at the University of Pennsylvania created "artificial space-time" to direct machines to travel in the same way that spacecraft or light does while crossing the universe.

In the study, researchers submerged 100-micron (roughly the width of a human hair) electrokinetic (EK) swimming robots in an ionized solution and tasked them with navigating a simple maze. The bots were covered with tiny solar cells with electrodes on both ends; when the solar cells were exposed to light, they powered the electrodes, which created an electric field that propelled the robots through the solution.

The challenge was to guide the microscopic machines with enough precision for them to reach a specific point in space, without being stymied by the maze's walls. That's where relativity came in. According to Einstein's theory of general relativity, gravity bends space-time around objects with mass. Light and objects follow "straight" geodesics ‪—‬ the shortest paths ‪—‬ that look bent around masses. A great example of this is gravitational lensing: Although light travels in a straight line across the cosmos, it can appear bent and magnified when passing through the gravitational well of a massive object, such as a large galaxy cluster.

"We showed that the way EK robots behave in patterned light fields is identical to the paths light follows in general relativity," lead study author Marc Miskin, an assistant professor of electrical and systems engineering at the University of Pennsylvania, told Live Science in an email. "Amazingly, you can use the robots as a gravity analog since the correspondence is exact. Alternatively, you can turn general relativity ideas around to use them to guide robots: in the same way gravity pulls objects together, you can guide robots to a specific spot."

Artificial space-time

To mimic the effect, the team modeled the maze as curved virtual space using relativity equations. Paths to the target inside the maze became simple straight lines in the model. Then, they converted the model back to a 2D light map. Dark spots naturally attracted the bots, while brighter spots repelled them. The end point of the maze was the darkest spot (a kind of faux black hole), with obstacles being more brightly lit.

Regardless of where they were initially placed, the EK bots naturally followed these geodesics, dodging walls automatically, as if sliding downhill in warped space. The team published their findings in November 2025 in the journal npj Robotics.

For Miskin, the study is a bridge between the worlds of physics and technology, "rather than a competition between them," he said. "On the one hand, relativity and light are very well understood; connecting reactive control to them invites new ways of thinking and established tools for robotics. On the other hand, general relativity and optics are also very abstract (think bending spacetime), while robotics is mechanistic and concrete (it's very easy to understand why the robot does what it does). In addition to showing how new types of robots behave according to known theories of optics, the experiments give researchers "a bit more" insight into general relativity, particularly in exploring the impact of "flat space-times" in 2D spaces, Miskin added.

While the maze study is a very early step, Miskin said practical applications may emerge over the next 10 years.

"Some use cases we're interested in exploring include checking up on teeth following a root canal, a kind of dental biopsy to make sure everything was cleared, eliminating tumors after making local measurements to confirm cells are cancerous, or even, outside of bio, assembly of microchips with tiny robotic helpers," Miskin said. "The microworld is a fascinating place; I wouldn't be surprised if these ideas are just the tip of the iceberg."

Heavy collisions at the Large Hadron Collider (LHC) have revealed the faintest trace of a wake left by a quark slicing through trillion-degree nuclear matter — hinting that the primordial soup of the universe may have literally been more soup-like than we thought.

The new findings from the LHC's Compact Muon Solenoid (CMS) collaboration show the first clear evidence of a subtle "dip" in particle production behind a high-energy quark as it traverses quark-gluon plasma — a droplet of primordial matter thought to have filled the universe microseconds after the Big Bang.

A study describing the results, published Dec. 25, 2025, in the journal Physics Letters B, provides a tantalizing look at the universe in its first moments.

Re-creating early-universe conditions in the lab

When heavy atomic nuclei collide at near-light speed inside the LHC, they briefly melt into an exotic state known as quark-gluon plasma.

In this extreme environment, "the density and temperature is so high that the regular atom structure is no longer maintained," Yi Chen, an assistant professor of physics at Vanderbilt University and a member of the CMS team, told Live Science via email. Instead, "all the nuclei are overlapping together and forming the so-called quark-gluon plasma, where quarks and gluons can move beyond the confines of the nuclei. They behave more like a liquid."

This plasma droplet is extraordinarily small — about 10^-14 meters across, or 10,000 times smaller than an atom — and vanishes almost instantly. Yet within that fleeting droplet, quarks and gluons — the fundamental carriers of the strong nuclear force that holds atomic nuclei together — flow collectively in ways that resemble an ultrahot liquid more than a simple gas of particles.

Physicists want to understand how energetic particles interact with this strange medium. "In our studies, we want to study how different things interact with the small droplet of liquid that is created in the collisions," Chen said. "For example, how would a high energy quark traverse through this hot liquid?"

Theory predicts that the quark would leave a detectable wake in the plasma behind it, much as a boat slicing though water would. "We will have water pushed forward with the boat in the same direction, but we also expect a small dip in water level behind the boat, because water is pushed away," Chen said.

In practice, however, disentangling the "boat" from the "water" is far from straightforward. The plasma droplet is tiny, and the experimental resolution is limited. At the front of the quark's path, the quark and plasma interact intensely, making it difficult to tell which signals come from which. But behind the quark, the wake — if present — must be a property of the plasma itself.

"So we want to find this small dip in the back side," Chen said.

A clean probe with Z bosons

To isolate that wake, the team turned to a special partner particle: the Z boson, one of the carriers of the weak nuclear force — one of the four fundamental interactions, along with the electromagnetic, strong, and gravitational forces — responsible for certain atomic and subatomic decay processes. In certain collisions, a Z boson and a high-energy quark are produced together, recoiling in opposite directions.

Here's where the Z boson becomes crucial. "The Z bosons are responsible for the weak force, and as far as the plasma is concerned, Z just escapes and is gone from the picture," Chen said. Unlike quarks and gluons, Z bosons barely interact with the plasma. They leave the collision zone unscathed, providing a clean indicator of the quark's original direction and energy.

This setup allows physicists to focus on the quark as it plows through the plasma, without worrying that its partner particle has been distorted by the medium. In essence, the Z boson serves as a calibrated marker, making it easier to search for subtle changes in particle production behind the quark.

The CMS team measured correlations between Z bosons and hadrons — composite particles made of quarks — emerging from the collision. By analyzing how many hadrons appear in the "backward" direction relative to the quark's motion, they could search for the predicted wake.

A tiny-but-important signal

The result is subtle. "On average, in the back direction, we see there is a change of less than 1% in the amount of plasma," Chen said. "It is a very small effect (and partly why it took so long for people to demonstrate it experimentally)."

Still, that less-than-1% suppression is precisely the kind of signature expected from a quark transferring energy and momentum to the plasma, leaving a depleted region in its wake. The team reports that this is the first time such a dip has been clearly detected in Z-tagged events.

The shape and depth of the dip encode information about the plasma's properties. Returning to her analogy, Chen noted that if water flows easily, a dip behind a boat fills in quickly. If it behaves more like honey, the depression lingers. "So studying how this dip looks … gives us information on the plasma itself, without the complication of the boat," she said.

Looking back to the early universe

The findings also have cosmological implications. The early universe, shortly after the Big Bang, is believed to have been filled with quark-gluon plasma before cooling into protons, neutrons and, eventually, atoms.

"This era is not directly observable through telescopes,” Chen says. "The universe was opaque back then.” Heavy-ion collisions provide "a tiny glimpse on how the universe behaved during this era," she added.

For now, the observed dip is "just the start," Chen concluded. "The exciting implication of this work is that it opens up a new venue to gain more insight on the property of the plasma. With more data accumulated, we will be able to study this effect more precisely and learn more about the plasma in the near future."

An ice-bound "ghost particle" detector at the South Pole just got a major upgrade.

The IceCube Neutrino Observatory has expanded for the first time in its 15 years of service. Technicians have added more than 600 new instruments to the bottom of the detector, which now consists of 92 strings of neutrino detectors buried in a cubic kilometer of ice near Amundsen-Scott South Pole research station.

The observatory is designed to search for high-energy neutrinos — nicknamed "ghost particles" because they are nearly massless and chargeless subatomic particles that zip through space and matter at nearly the speed of light. Neutrinos are everywhere; about 100 trillion pass through every person on Earth every second. But because they rarely interact with the matter they pass through, they're hard to detect.

Scientists would like a better understanding of neutrinos because they're produced in important processes, like the Big Bang that kick-started the universe, the nuclear fusion that powers stars, and the supernova explosions that signal violent stellar deaths.

At IceCube, scientists detect tiny flashes of light that occur when neutrinos do interact with matter and produce secondary particles. This requires a remote and quiet environment, which is readily available at the South Pole, as well as a lot of transparent matter in which to detect the light — in this case, ice. IceCube scientists have already successfully traced the arrival of a single neutrino from a blazar, a distant galaxy surrounding a supermassive black hole. They've also used the particles to map all of the matter in the Milky Way.

In 2019, the U.S. National Science Foundation (NSF) approved funding to upgrade the detector from 86 to 92 strings of detectors. The six new strings hold new detector modules with multiple types of photosensors in each module. It took three 10-week field sessions from 2023 to 2026 to drill more than a mile into the Antarctic ice and place the sensors.

The new sensors will allow scientists to more precisely measure properties such as neutrino oscillations, which happen when neutrinos formed by cosmic rays in Earth's atmosphere change into different types. This will improve their ability to measure cosmic rays and to detect neutrinos from extraplanetary sources, such as supernovas, according to the IceCube Collaboration. Researchers will also be able to better calibrate the detector retrospectively, which will allow them to refine previously collected data from the past 15 years.

"This upgrade will secure the nation's continued leadership in neutrino physics for years to come, paving the way for new cosmic discoveries," Marion Dierickx, director of the NSF's Antarctic Astrophysics and Geospace Sciences Polar Cyberinfrastructure program, said in a statement.

An impossibly powerful "ghost particle" that recently slammed into Earth may have come from a rare type of exploding black hole, researchers claim.

If true, the extraordinary event may prove a theory that could upend our understanding of both particle physics and dark matter, the team argues. However, this is just one theory, and there is no direct evidence to confirm that this is indeed what happened.

In early 2023, researchers at the Cubic Kilometre Neutrino Telescope (KM3NeT) — a massive, newly constructed array of sensors at the bottom of the Mediterranean Sea — detected a neutrino, a ghostly particle that has almost no mass and does not readily interact with most matter.

In addition to neutrinos' typical weirdness, this specific particle was noteworthy for its unusual intensity. It hit our planet with an estimated energy of up to 220 quadrillion electron volts, which is at least 100 times more powerful than any other neutrino detected to date and around 100,000 times greater than anything observed within human-made particle accelerators, like CERN's Large Hadron Collider.

Explaining the impossible

Researchers were initially unsure what caused this "impossible" neutrino to appear. It may have been birthed when a cosmic ray entered Earth's atmosphere, unleashing a cascade of high-energy particles that rained down on the planet's surface. However, its unprecedented power led experts to assume that it must have originated from some high-energy cosmic event that we don't fully understand.

In the new paper, which has been accepted for publication in the journal Physical Review Letters, one research group believes they have finally identified what really birthed the neutrino: an exploding, primordial black hole (PBH).

PBHs are a hypothetical class of black holes that are extremely small — potentially ranging from the size of an atom to a pinhead — and likely date back to the first moments after the Big Bang. The concept was first popularized by British physicist Stephen Hawking in the early 1970s, who also hinted that these miniature singularities would emit large quantities of high-energy particles, dubbed Hawking radiation, as they slowly evaporated. In theory, this would also mean they have the capacity to explode.

"The lighter a black hole is, the hotter it should be and the more particles it will emit," study co-author Andrea Thamm, a theoretical physicist at the University of Massachusetts Amherst, said in a statement. "As PBHs evaporate, they become ever lighter, and so hotter, emitting even more radiation in a runaway process until explosion."

One of the biggest mysteries surrounding the impossible neutrino, aside from its immense power, is that it was not observed by other neutrino detectors around the world, such as the IceCube Neutrino Observatory buried beneath Antarctica's icy surface. Given that PBHs are supposed to be fairly common throughout the universe, one would reasonably expect that similarly powerful particles also would have been detected before or since this possible discovery, especially as the number of neutrino detectors is quickly increasing.

The researchers said this is because the neutrino was emitted by a special type of PBH, dubbed a quasi-extremal PBH, which has a "dark charge" — a version of regular electric force that includes a very heavy, hypothesized version of the electron dubbed a "dark electron."

The dark properties of this theoretical type of PBH make it less likely that these black holes' explosions would be detected, the researchers suggested. It may also be that some of the less-powerful neutrinos detected to date may be partially incomplete detections of these events, they added.

"A PBH with a dark charge has unique properties and behaves in ways that are different from other, simpler PBH models," Thamm said. "We have shown that this can provide an explanation of all of the seemingly inconsistent experimental data."

Upending cosmic understanding

While the new research hints at the existence of quasi-extremal PBHs, it does not confirm them or prove that they explode as the researchers think. (Regular PBHs have never been directly observed, either, although there is a strong consensus that they exist.)

However, the team is confident that it will not take long to prove these dark explosions are real. The same research group recently predicted that there is a 90% chance we will see the first quasi-extremal PBH blow up by 2035, which would be extremely exciting for two main reasons.

First, these explosions would be so powerful that they would probably emit "a definitive catalog of all the subatomic particles in existence," including known entities, like the Higgs boson; theorized particles, like gravitons or time-traveling tachyons; and "everything else that is, so far, entirely unknown to science," the researchers wrote in the statement.

Second, these black holes could help reveal the mysterious identity of dark matter — the invisible stuff that we cannot see, yet whose gravitational force we can detect within almost every observed galaxy, including the Milky Way. The researchers wrote that quasi-extremal PBHs "could constitute all of the observed dark matter in the universe," so finding one could help put this mystery to bed. (Despite the similar names, dark matter is not directly related to dark charge or dark electrons.)

The researchers, along with several other teams in the fields of physics and cosmology, are now holding their collective breath to see when the first explosion might be detected.

This "incredible event" would provide a "new window on the universe" and help us "explain this otherwise unexplainable phenomenon," study lead author Michael Baker, a theoretical physicist at UMass Amherst, said in the statement.

Two of the universe's most mysterious particles may be colliding invisibly throughout the cosmos — a discovery that could solve one of the biggest lingering problems in our standard model of cosmology.

Those two elusive components — dark matter and neutrinos (or "ghost particles") — are ubiquitous throughout the cosmos, yet they remain poorly understood. In a study published Jan. 2 in the journal Nature Astronomy, an international team of researchers found evidence that dark matter and neutrinos may collide, transferring momentum between them in the process.

This surprising interaction may help to explain why the universe is less populated by dense regions, like galaxies, than predicted — in other words, the universe is less "clumpy" than cosmologists think it should be, the researchers said in a statement.

Dark matter and neutrinos remain a riddle

Dark matter is the mysterious, invisible substance that constitutes 85% of the matter in the universe. As its name suggests, dark matter does not emit light, so its existence has been only indirectly inferred from its gravitational influence, as observed in cosmological surveys.

Neutrinos are subatomic particles with infinitesimally low masses and no electric charge, so they very rarely interact with other particles. They're produced by various nuclear processes, including stellar fusion and supernovas, in prodigious quantities: Every second, approximately 100 billion neutrinos pass through each square centimeter of your body, Live Science previously reported.

Yet dark matter and neutrinos should not interact, according to the leading model of cosmology, known as the lambda cold dark matter model (lambda-CDM). This standard model aims to theoretically explain the large-scale structure of the cosmos.

Cosmological conundrum

However, this recent study provides new evidence that dark matter and neutrinos may interact after all, as other researchers have posited over the past two decades.

If dark matter and neutrinos do collide, and transfer momentum to one another in the process, this discovery would inspire a rethink of the lambda-CDM model. Such collisions could also help to explain the "S8 tension," a mismatch between the expected and actual "clumpiness" of the universe.

"This tension does not mean the standard cosmological model is wrong, but it may suggest that it is incomplete," Eleonora Di Valentino, study co-author and a senior research fellow at the University of Sheffield in the U.K., explained in the statement. "Our study shows that interactions between dark matter and neutrinos could help explain this difference, offering new insight into how structure formed in the Universe."

The mismatch stems from researchers' findings that the current cosmos isn't as packed together as predicted, based on observations of the cosmic microwave background (CMB) — the first light in the universe, emitted when the cosmos was only 380,000 years old.

"The statement that cosmic structures are 'less clumped' is best understood in a statistical sense, rather than as a change in the appearance of individual galaxies or clusters. It refers to a reduced efficiency in the growth of cosmic structures over time," study co-author William Giarè, a cosmologist at the University of Hawaii, told Live Science via email.

Unraveling multiple threads of evidence

The researchers tried to unite evidence from energy and density fluctuations in the CMB and from baryon acoustic oscillations (BAO) — pressure waves "frozen" in time from the beginning of the cosmos — with more recent observations of the universe's large-scale structure.

The early-universe data come from the Atacama Cosmology Telescope in Chile and the European Space Agency's space-based Planck telescope, which was designed to study the CMB. The later-universe data come from the Victor M. Blanco Telescope in Chile and the Sloan Digital Sky Survey, a two-decade effort to create a 3D map of millions of galaxies across more than 11 billion light-years.

The researchers also incorporated cosmic shear data from the Dark Energy Survey. Cosmic shear is the distortion of distant celestial objects due to weak gravitational lensing, which occurs when massive foreground structures bend the fabric of space-time and alter the paths of light traveling from those distant celestial objects to our detectors.

Finally, the researchers combined these data and modeled the evolution of the universe. When accounting for collisions between dark matter and neutrinos and the resulting momentum exchange, the simulations generated a model universe that better agrees with real observations.

There's reason to remain cautious, however, as the interaction between dark matter and neutrinos has only a 3-sigma level of certainty — meaning there is a 0.3% chance that this result is a fluke. Though short of the scientific gold standard of 5 sigma, it is significant enough to warrant additional research because, if confirmed, the interaction would prove a "fundamental breakthrough in cosmology and particle physics" — and a potential solution to the cosmic clumpiness quandary.

"The final verdict will come from upcoming large sky surveys, such as those from the Vera C. Rubin Observatory, and more precise theoretical work," research team leader Sebastian Trojanowski, a theoretical physicist at the National Centre for Nuclear Research in Poland, explained in a separate statement. "These will allow us to determine whether we are witnessing a new discovery in the dark sector or whether our cosmological models require further adjustment. However, each of these scenarios brings us closer to solving the mystery of dark matter."

On a December day, Richard Feynman gave a fun little lecture at Caltech — and dreamed up an entirely new field of physics.

During the talk, entitled "Plenty of room at the bottom," he described the enormous potential that could be realized if scientists could manipulate and control things at a "small scale."

How small? Feynman went on to discount advances of the time, such as writing the Lord's Prayer on the head of a pin, as trivial.

"But that's nothing; that's the most primitive, halting step in the direction I intend to discuss. It is a staggeringly small world that is below," Feynman said in his lecture. Rather, he suggested, people could write the entire 24-volume encyclopedia on the head of a pin, and elegantly showed that there's enough space there to write it legibly and read it out.

He then explored the possibility of a number of then-futuristic ideas: electron microscopes capable of manipulating individual atoms, ultracompact data storage, miniaturized computers, and powerful, ingestible biological machines that travel into organs like the heart, find defects, and repair them with tiny knives. He proposed a number of ways to create these small-scale innovations, including manipulating light and ions.

He ended the lecture by offering a reward of $1,000 to anyone who could miniaturize the text in a book 25,000-fold, such that it could be read using an electron microscope. He offered another $1,000 to anyone who could make a motor no bigger than 1/64th of an inch cubed.

The latter of these prizes was scooped up the following year by engineer William McLellan, who created a 250-microgram motor composed of 13 parts. In his award letter, Feynman congratulated McLellan on the feat but joked that he shouldn't "start writing small," lest he solve the first challenge, too and expect to receive the other $1,000 prize.

"I don't intend to make good on the other one. Since writing the article I've gotten married and bought a house!" Feynman wrote.The former challenge was eventually solved in 1985, when Stanford graduate Thomas Newman miniaturized the first page of the Dickens classic "A Tale of Two Cities." Feynman did, ultimately, pay up for the second prize.

Feynman's Caltech talk is now mythologized as having ushered in the field of nanotechnology. And yet, the term "nanotechnology" itself was not coined until 15 years after his talk, when scientist Norio Taniguchi penned a paper about manipulating material at the atomic scale.

In that 1974 paper, Taniguchi described nanotechnology as "the processing of separation, consolidation, and deformation of materials by one atom or one molecule." Many science historians now argue that the field was following its own trajectory, and that Feynman's talk, while prescient, wasn't the actual driver of future innovations. Prior to 1980, his talk was cited less than 10 times.

Whether it drove innovation or not, since Feynman's famous lecture, many of his predictions have proven true. The scanning tunneling microscope manipulated individual xenon atoms in 1990. Computers more powerful than he described now sit in our pockets, rather than taking up whole rooms. And indeed, tiny nanobots have been designed that can repair damaged blood vessels.

A record-breaking investigation, using a particle detector a mile underground in South Dakota, may have revealed new insights about dark matter, the mysterious substance believed to make up most of the matter in the universe.

Using the largest dataset of its kind, the experiment — called LUX-ZEPLIN (LZ) — constrained the potential properties of one of the leading candidates for dark matter with unprecedented sensitivity. The research did not uncover any evidence of the mysterious substance, but will help future studies avoid false detections and better hone in on this poorly understood piece of the universe.

"This quest is to try to solve this huge problem, this huge missing piece that we have in terms of understanding our universe," Rick Gaitskell, head of the particle astrophysics group at Brown University and part of the LZ research team, told Live Science.

The results, released Monday (Dec. 8), have been submitted to the journal Physical Review Letters and are available as a preprint via arXiv. The results were also presented at a scientific talk at the Sanford Underground Research Facility, where LZ's detector is hosted.

WIMPs vs. neutrinos

The team had two goals for the new study: to elucidate the properties of a low-mass "flavor" of proposed dark-matter particles called weakly interacting massive particles (WIMPs), and to see if the detector could view solar neutrinos — nearly mass-less subatomic particles produced by nuclear reactions inside the sun. The team suspected that the detection signature of these particles could be similar to that predicted by certain models of dark matter, but needed to spot the solar neutrinos to know for sure.

Before the experiment, which took 417 days to perform between March 2023 and April 2025, the detector's sensitivity was upgraded to search for rare interactions with fundamental particles. A cylindrical chamber filled with liquid xenon was the theater for action. Researchers could watch for either WIMPs or neutrinos colliding with the xenon, either of which produces flashes of photons, along with positively charged electrons.

The experiment pushed forward the science for both the WIMP and neutrino questions. For the neutrinos, researchers improved their confidence that a type of solar neutrino, known as boron-8, is actually interacting with the xenon. This knowledge will help future studies avoid false detections of dark matter.

Physics discoveries typically must reach a confidence level called "5 sigma" to be considered valid. The new work achieved 4.5 sigma — a considerable improvement over sub-3-sigma results reported in two detectors last year. And that was especially notable given that boron-8 detections happen only about once a month in the detector, even when monitoring 10 tons of xenon, Gaitskell said.

As for the dark matter question, however, the researchers didn't find anything definitive for the low-mass types of WIMPs they were seeking. Scientists would have known it if they saw it, the team said; if a WIMP hits the heart of a xenon molecule, the energy of the collision creates a distinctive signature, as best as models predict.

"If you take a nucleus, it is possible for dark matter to come in and actually simultaneously scatter from the entire nucleus and cause it to recoil," Gaitskell explained. "It's known as a coherent scatter. It has a particular signature in the xenon. So it's those coherent, nuclear recoils that we're looking for."

The team did not detect this signature in their experiment.

Doubling the run

The experiment continues now, with a longer run ongoing until 2028. By then, the detector will have collected a record-breaking 1,000 days of data. Longer runs give researchers a better chance of catching rare events.

The detector will hunt not only for more solar neutrino or WIMP interactions but also other physics that may fall outside the Standard Model of particle physics said to describe most of the environment around us.

Gaitskell emphasized that the role of science is to keep pushing forward even when "negative" results arise.

"One thing I've learned is, don't ever assume that nature does things in the way that you think it should, exactly," said Gaitskell, who has been studying dark matter for more than four decades.

"There are plenty of elegant [solutions] that you would say, 'That's so beautiful. It has to be true.' And we tested them … and it turned out, nature ignored it and nature did not want to go down that particular route."

Editor's note: This article was updated on Dec. 10 at 5 p.m. ET with a correction. The detector's next run won't begin in 2028, but rather end then, after a cumulative 1,000 days of data have been collected.

The first results from the world's largest neutrino detector have just been published, and they reveal the most precise measurements of neutrino parameters yet.

After running the detector — the Jiangmen Underground Neutrino Observatory (JUNO), in southern China — for just shy of two months, the researchers were able to measure the parameters of the different types, or "flavors," of neutrinos with unprecedented precision.

The results narrow down the value of two key neutrino parameters: the mixing angle describing how different neutrino mass states combine to form the neutrino flavors, and the difference between these mass states squared.

"Before switching on JUNO, these parameters came from a long series of experiments … Half a century of effort is distilled in the numerical value of these two parameters," Gioacchino Ranucci, deputy spokesperson for JUNO, told Live Science. "In 59 days we have overcome 50 years of measurement. So this gives an idea of how powerful [JUNO] is."

The facility's first results were published to the preprint server arXiv and have been submitted to the journal Chinese Physics C for peer review.

The ghostly mystery of neutrinos

Neutrinos are perhaps the most mysterious of the known particles. Every second, trillions of them pass through your body. However, they very rarely interact with you or any other matter and weigh next to nothing, giving them the nickname "ghost particles." This makes the neutrino one of the hardest particles to study, as most will simply go through a detector without leaving a trace.

But physicists are eager to know more about neutrinos because they may be able to break the Standard Model of particle physics, which is our best explanation of the subatomic world. While it is an incredibly successful theory, it is not quite complete — and something that it did not predict was that neutrinos would have mass.

The discovery that ghost particles do, in fact, have mass (for which the 2015 Nobel Prize in physics was awarded) is due to something called neutrino oscillation. Neutrinos come in three flavors (electron, muon and tau), and they switch between these identities as they move through time and space. The reason for this strange phenomenon is not yet fully understood, but it may hold the key to exciting new physics.

"The oscillation phenomenon means that neutrinos are so far the only particle for which there is a property that the Standard Model does not predict," Ranucci said. "So, neutrinos are the only portal to physics beyond the Standard Model."

To explore neutrino properties and probe beyond the Standard Model, scientists have built large detectors deep underground. Here, Earth's crust forms a natural shield from most other particles, while the ghost particles pass through and have the chance to make their presence known in the detector.

JUNO is the latest and largest of these neutrino detectors. It is a 115-foot-wide (35 meters) sphere that holds 19,700 tons (20,000 metric tons) of a liquid scintillator. This liquid is specially formulated to interact with a neutrino and produce a flash of light. Around the edge of the tank, there are sensors that can pinpoint the flash and provide useful information about the neutrino that caused it.

Previous neutrino detectors have worked on the same principle; JUNO is simply much bigger. It contains 20 times more liquid scintillator than any previous experiment, making JUNO significantly more sensitive to neutrinos. This has allowed physicists to measure the parameters that describe the oscillation between different neutrino flavors with unprecedented precision, according to the researchers.

A hunt for new physics

The JUNO team has high ambitions for the future, and these first results show they are on track to meet those goals. With more time and more data, the researchers hope to achieve even better precision on these oscillation parameters.

Over its lifetime, JUNO may be able to solve longer-standing mysteries in physics. Physicists expect to be able to order the neutrino mass states from the heaviest to the lightest and perhaps even find clues as to why we don't see as much antimatter as matter in the universe.

For now, these ghostly particles have given tantalizing whispers of physics beyond our current theories. With bigger and better neutrino detectors, our understanding of the universe is coming into sharper focus.

Editor's note: The headline and lead image of this story was updated on Nov. 27, 2025

Physicists have studied a rare molecule to look at how magnetism is distributed within a radioactive nucleus for the first time.

The rules of nature don’t, generally speaking, change. If you toss a ball in Seattle or in Tokyo, it falls the same way. Physicists call this “symmetry”, and they use symmetry as a guide to how the universe ought to behave. It’s what keeps the world consistent — if the laws of physics worked differently on Tuesdays, the universe would be chaos.

But some parts of nature don’t seem to follow this perfect balance. For example, it may seem fair to assume that the universe should treat matter and antimatter as equals. Yet our universe is made almost entirely of matter, and physicists still don’t know why.

One promising place to search for answers is inside radioactive nuclei. That is because the uneven arrangement of protons and neutrons can magnify the tiniest breaks in symmetry. If scientists are able to detect those small asymmetries, it could reveal new physics beyond the Standard Model, according to Silviu-Marian Udrescu, a physicist at MIT and co-author of a new study into the phenomenon.

In a study published Oct. 23 in the journal Science, scientists at CERN and MIT examined a short-lived radioactive molecule called radium monofluoride (RaF) to measure its energy spectrum. But, surprisingly, they ended up making the first observation of how magnetism is distributed within one of its nuclei. That phenomenon, known as the Bohr–Weisskopf effect, had never been seen in a molecule before.

The avocado of the atom

The RaF molecule is made of two atoms: radium and fluoride. Each with its own nucleus. The radium nucleus has a property called “octupole deformation”.

“You can think of it as the nucleus itself having the shape of a pear or an avocado,” ‪Shane Wilkins‬, a physicist at MIT and the study’s first author, told Live Science. Because of its asymmetric shape, RaF makes a perfect candidate to find the asymmetries the team was looking for.

“It’s a very rare property,” Udrescu added. “It only occurs in a few handfuls of atomic nuclei across the entire nuclear chart. And all of those nuclei that have this pear shape are radioactive.”

That radioactivity makes such nuclei difficult to study because these isotopes are unstable and short-lived. That means they decay within around 15 days, and can disappear before researchers can make many measurements. “We can only produce them in very small quantities,” Wilkins said.

The Bohr-Weisskopf effect has been observed in individual atoms, where electrons interact with a single nucleus. However, detecting it inside a molecule is more challenging. That is because electrons constantly move between the two nuclei. The movement can blur magnetic signals and make them harder to detect. In a RaF molecule, the fluoride atom is a simpler bond partner. It allows scientists to focus on the magnetic structure of the heavier radium nucleus.

The team first created radium monofluoride at CERN’s ISOLDE facility. They blasted a uranium target with high-energy protons to produce the rare isotope radium-225 and combined it with fluorine gas. Each molecule existed for only fractions of a second. The researchers could detect only about fifty per second in the right state for measurement.

Then, they directed multiple laser beams of slightly different frequencies at the molecules. When the molecule absorbed or emitted light, scientists recorded the tiny changes in that light. This produced a spectrum. Normally, those patterns tell scientists about how the electrons move around the nucleus. But in this case, some of the shifts revealed that the electrons were being influenced by the inside of the nucleus.

“The electron actually probes inside the nucleus, so you can no longer treat it as a long-range interaction. Instead, it starts to sense the internal properties of the radium nucleus itself,” said Wilkins.

“This effect is called the Bohr–Weisskopf effect,” Wilkins added. “To the best of our knowledge, it’s never been seen in a molecule before. The fact that we could both observe this effect experimentally and describe it with theory tells us a lot about how suitable these molecules are for future precision measurements.”

Now that the researchers have mapped RaF’s internal structure, they can use it to probe even smaller effects that might break nature’s symmetries. The next step, Wilkins said, is to slow and trap these molecules with lasers to perform even more precise measurements.

“Now we know they can be powerful tools to look for new physics,” said Udrescu.

Physicists have measured both the momentum and position of a particle without breaking Heisenberg’s iconic uncertainty principle.

In quantum mechanics, particles don’t have fixed properties the way everyday objects do. Instead, they exist in a haze of possibilities until they’re measured. And when certain properties are measured, others become uncertain. According to Heisenberg's uncertainty, it’s not possible to know both a particle’s exact position and its exact momentum at the same time.

But a new study has shown a clever loophole around this restriction. Physicists in Australia have demonstrated that by focusing on different quantities, known as modular observables, they can simultaneously measure position and momentum.

"You can’t violate Heisenberg’s uncertainty principle," Christophe Valahu, a physicist at the University of Sydney and lead author of the study, told Live Science. "What we do is shift the uncertainty. We throw away some information we don’t need, so we can measure what we do care about with much greater precision."

The trick for Valahu and his team was, instead of measuring momentum and position directly, to measure the modular momentum and modular position — which capture the relative shifts of these quantities within a fixed scale, rather than their absolute values.

"Imagine you have a ruler. If you’re just measuring the position of something, you’d read how many centimeters in, and then how many millimeters past that." Valahu said. "But in a modular measurement, you don’t care which centimeter you’re in. You only care how many millimeters you are from the last mark. You throw away the overall location and just keep track of the small shifts."

Valahu said this kind of measurement is important in quantum sensing scenarios because the goal is often to detect minuscule shifts caused by faint forces or fields. Quantum sensing is used to pick up signals that ordinary instruments often miss. That level of precision could someday make our navigation tools more reliable and our clocks even more accurate.

In the lab, the team turned to a single trapped ion — a lone charged atom held in place by electromagnetic fields. They used tuned lasers to coax the ion into a quantum pattern called a grid state.

In a grid state, the ion’s wave function is spread out into a series of evenly spaced peaks, like the marks on a ruler. The uncertainty is concentrated in the spaces between the marks. The researchers used the peaks as reference points: when a small force nudges the ion, the entire grid pattern shifts slightly. A small sideways shift of the peaks shows up as a change in position, while a tilt in the grid pattern reflects a change in momentum. Because the measurement only cares about the shifts relative to the peaks, both position and momentum changes can be read out at the same time.

That’s where force comes in. In physics, a force is what causes momentum to change over time and position to shift. By watching how the grid pattern moved, the researchers measured the tiny push acting on the ion.

The force of roughly 10 yoctonewtons (10-23 newtons) isn't a world record. "People have beaten this by about two orders of magnitude, but they use huge crystals in very large and costly experiments." Valahu told Live Science. "The reason we’re excited is because we can get really good sensitivities using a single atom in a trap that’s not that complex, and is somewhat scalable."

Even though the force achieved is not the lowest, it proves that scientists can get very extreme sensitivities from very basic setups. The ability to sense tiny changes has wide implications across science and technology. Ultra-precise quantum sensors could improve navigation in places where GPS doesn’t reach, such as underwater, underground, or in space. It could also enhance biological and medical imaging.

"Just as atomic clocks revolutionized navigation and telecommunications, quantum-enhanced sensors with extreme sensitivity could open the door to entirely new industries,” Valahu said in a statement.

Some atoms are stable, while others seem to fall apart. Lead-208 will probably last forever, while the synthetic isotope technetium-99 exists for just hours. The difference lies in the structure of the atom's nucleus, with certain "magic numbers" of nuclear particles making some isotopes especially resistant to radioactive decay.

So what are these magic numbers, and why are they so special?

The stability of atomic nuclei varies wildly with the number of nuclear particles they contain. Some, like lead-208 and calcium-40, have been around since Earth first formed. Known as primordial isotopes, they will likely survive until the end of time. Others, like oganesson-294 and tennessine-294, are lost to radioactive decay in an instant, with fleeting half-lives of just 0.89 and 0.80 milliseconds, respectively.

This stability seems partly connected to the mass of the atom, with heavier elements proving less stable. But in the 1940s and '50s, scientists observed that many of the lighter elements also had radioactive isotopes; both carbon-14 and potassium-40 undergo radioactive decay slowly and are responsible for much of the planet's background radiation.

Intriguingly, these scientists noticed that very particular numbers of protons and neutrons appeared to result in unusually stable nuclei, and these values became known as magic numbers.

"The magic numbers are 2, 8, 20, 28, 50, 82 and 126," said David Jenkins, a nuclear physicist at the University of York in the U.K. "If you take the lightest one — two protons and two neutrons — that's the nucleus of the helium atom, and we know that's a very stable combination of protons and neutrons."

Related: Why isn't an atom's nucleus round?

Shell game

Helium nuclei, also known as alpha particles, are spontaneously emitted from heavier, unstable atoms as they undergo nuclear decay.

"If you think about it, that's very weird," Jenkins said. "If an atom is going to decay, why doesn't it lose protons or neutrons one at a time? The reason is that the alpha particle is very very stable, and that's related to this idea of magic numbers."

Other magic nuclei include oxygen-16 (eight protons and eight neutrons), calcium-40 (20 protons and 20 neutrons) and lead-208 (82 protons and 126 neutrons), the heaviest stable element known.

To understand these bizarre observations, physicists proposed the "nuclear shell model," which draws parallels with the electronic shells used to explain the chemical behavior of atoms.

"The idea was that protons and neutrons sit in shells, a bit like the electrons in an atom, and nuclear excitations would involve protons and neutrons jumping up and down between those shells," Jenkins explained.

Like their electron analogues, these nuclear shells have fixed energy values known as quantized states, and the system is most stable when these shells are completely filled. The exact reasoning behind this is a complex combination of quantum mechanical factors, but it's thought that the strong force — the fundamental interaction that holds the protons and neutrons together in the nucleus — is higher than expected per particle in completed shells.

Magic numbers are therefore simply the numbers of particles required to fill each of these nuclear shells, with separate levels for protons and neutrons. Individual isotopes can correspondingly be singly magic, with a magic number of either protons or neutrons (for example, the primordial isotope iron-56), or doubly magic, with magic numbers of both protons and neutrons (like oxygen-16 and lead-208).

These doubly magic systems are few and far between, but they possess some intriguing quantum properties, Jenkins said.

"The doubly magic systems have a spherical distribution of matter and charge" — a completely round nucleus, he said. "Most nuclei are deformed and rotate. They have a very different structure."

No one knows how far this model will stretch. Tin-100 — the heaviest doubly magic nucleus, with 50 protons and 50 neutrons — has a half-life of just 1.2 seconds, while unbihexium, the next magic element after lead, has never been synthesized. Therefore, whether this magic stability boost will be enough to allow scientists to add an eighth row to the periodic table remains an open question.

Periodic table of elements quiz: How many elements can you name in 10 minutes?

Is there a scientific reason why the universe exists? In other words, what is the science of why there is anything at all, instead of only nothing?

The answer has to do with opposites. Scientists have found that the universe exists because it began with a slight imbalance between matter and antimatter. Particles of matter — that is, all of the electrons, protons and neutrons in the atoms and molecules of regular stuff — differ from particles of antimatter, which carry the opposite electric charge but are similar in many ways.

Matter and antimatter do not get along. When their particles collide, they annihilate each other in an intense burst of gamma-rays. Fortunately, antimatter is now extremely rare. Although antimatter had a foundational role in the formation of the universe, the fact that there is now so little of it is one of cosmology's great mysteries.

Antimatter was predicted by English physicist Paul Dirac almost 100 years ago as part of his pioneering work on quantum mechanics, and it has been confirmed experimentally since the 1930s. Nowadays, scientists can create antimatter in particle colliders like the Large Hadron Collider.

But Dirac predicted there should be equal amounts of matter and antimatter, according to Pasquale Di Bari, a professor of physics and astronomy at the University of Southampton in the U.K. So the fact there is now so little antimatter and so much matter — including all the stars in all the galaxies in the universe, although some scientists once suggested there might be "anti-galaxies" of "anti-stars" — is a big scientific problem.

Related: Do quantum universes really exist?

"We think the universe started as 50-50 matter-antimatter in the Big Bang but very quickly afterwards became dominated by matter," Tara Shears, a particle physicist at the University of Liverpool, told Live Science in an email. "For this to occur there needs to be a very slight difference, or asymmetry, in the behaviour of matter and antimatter to allow one to ultimately dominate over the other."

But "this difference is not predicted, it is not understood and it is certainly not explained," Shears continued. "Understanding this difference is the problem we want to solve; this is the matter-antimatter asymmetry problem."

According to Dirac, the terms "matter" and "antimatter" are almost arbitrary. "Matter" refers to regular particles, and "antimatter" refers to antiparticles — but it could have been the other way around. If they weren't mostly annihilated, antimatter particles might have formed a universe of anti-atoms and anti-molecules. In the end, whatever predominated was named matter, and its opposite was named antimatter.

Cosmic leftovers

Using observations from particle colliders, traces of the decay of antimatter in astronomical spectra, and gravitational waves, physicists are trying to better understand why there is this large unexplained discrepancy in the universe that has given rise to everything it contains.

Di Bari estimates there might originally have been many billions of times more matter and antimatter particles than there are now, before they mostly annihilated each other in the first fractions of a second after the Big Bang. "What we are made of is the leftovers," he told Live Science.

Raymond Volkas, a theoretical particle physicist at the University of Melbourne, added that a reason for the asymmetry was outlined in 1967 by Soviet physicist Andrei Sakharov. (Sakharov, a critic of the Soviet system, was sentenced to "internal exile" for political dissent in 1980; he was freed in 1986, and died in 1989.)

Sakharov proposed that the asymmetry existed because matter and antimatter particles were not exact opposites but instead reacted differently to some fundamental forces in certain circumstances — a phenomenon known as "C and CP violation."

The general principles of "C and CP violation" are known, but the specifics are not, Volkas told Live Science in an email. "There are many possibilities on the table!" he said. "The challenge is to experimentally distinguish between them."

Solar system quiz: How well do you know our cosmic neighborhood?

For the first time, scientists have used ultrafast X-ray flashes to take a direct image of a single electron as it moved during a chemical reaction.

In the new study, published Aug. 20 in the journal Physical Review Letters, the researchers accomplished this incredible feat by imaging how a valence electron — an electron in the outer shell of an atom — moved when an ammonia molecule broke apart.

For decades, scientists have used ultrafast X-ray scattering to image atoms and their chemical reactions. The scattering uses supershort bursts of X-rays to freeze tiny, fast-moving molecules in action. X-rays have the perfect wavelength range for capturing details at the atomic scale, which is why they're ideal for imaging molecules.

However, X-rays interact strongly only with core electrons near the atom’s nucleus. Valence electrons — the outermost electrons in an atom and the ones actually responsible for the chemical reactions — were hidden.

"We wanted to take pictures of the actual electrons that are driving that motion," Ian Gabalski, a physics doctoral student and lead author of the study, told Live Science.

If scientists can understand how valence electrons move during chemical reactions, it could help them design better drugs, cleaner chemical processes, and more efficient materials, Gabalski said.

To get started, the team needed to find the right molecule. It turned out to be ammonia.

"Ammonia is kind of special," Gabalski said. "Because it has mostly light atoms, there aren't a lot of core electrons to drown out the signal from the outer ones. So we had a shot at actually seeing that valence electron."

The experiment was conducted at the SLAC National Accelerator Laboratory's Linac Coherent Light Source, a facility that produces intense, short X-ray pulses. First, the team gave the ammonia molecule a tiny jolt of ultraviolet light, which made one of the electrons "jump" to a higher energy level. Electrons in molecules usually stay in low-energy states, and if they are pushed to a higher one, it triggers a chemical reaction. Then, with the X-ray beam, the researchers recorded how the electron's "cloud" shifted as the molecule began to break apart.

Related: The shape of light: Scientists reveal image of an individual photon for 1st time ever

In quantum physics, electrons aren't seen as tiny balls orbiting the nucleus. Instead, they exist as probability clouds, "where higher density means you're more likely to see the electron," Gabalski explained. These clouds are also known as orbitals, and each one has a distinct shape depending on the energy and position of the electron.

To map this electron cloud, the team ran quantum mechanical simulations to calculate the molecule's electronic structure. "So now this program that we use for these kinds of calculations goes and it figures out where the electrons are filling up those orbitals around the molecule," Gabalski said.

The X-rays themselves act like waves, and when they pass through the electron's probability cloud, they scatter in different directions. "But then those X-rays can go and interfere with each other," Gabalski said. By measuring this interference pattern, the team reconstructed an image of the electron's orbital and saw how the electron moved during the reaction.

They compared the results to two theoretical models: one that included valence electron motion, and one that didn't. The data matched the first model, confirming that they had captured the electron's rearrangement in action.

The researchers hope to adapt the system for use in more complex, 3D environments that better mimic real tissues. That would move it closer to applications in regenerative medicine, such as growing or repairing tissue on demand.

The universe's invisible dark matter might swirl into spinning clumps laced with countless tiny vortices, new theoretical work suggests.

The findings, published May 30 in the journal Physical Review D, offer a fresh perspective on the strange behavior of "ultralight" dark matter — a hypothetical substance made of extremely light elementary particles.

In the new study, physicists explored what happens when a dark matter halo rotates — a natural expectation for real galaxies, which typically spin as they evolve. Based on their theoretical modeling and detailed simulations, the authors found that this exotic material could behave like a superfluid, forming stable, rotating cores threaded with vortex lattices much like those seen in laboratory experiments.

A special kind of dark matter

Unlike the standard view of dark matter as a cloud of heavy, sluggish particles with no internal structure, the new research focuses on dark matter made of particles lighter than a millionth of an electron's mass. These particles may not float passively in space; if they interact slightly with one another through a repulsive force, they can behave more like a quantum fluid.

That fluid-like behavior allows the formation of "solitons" — compact, coherent structures where gravity's pull inward is balanced by an outward pressure from self-interactions.

"Solitons are classical solutions of the equations of motion," Philippe Brax, a theoretical physicist at Université Paris-Saclay and co-author of the study, told Live Science. "They correspond to hydrostatic equilibria where the attractive gravitational force is balanced by the repulsive particle self-interaction, somewhat like the Sun, which is also in hydrostatic equilibrium."

These solitons could range from the size of stars to entire galaxies, depending on the unknown mass of the dark matter particle. In larger cases, they could help explain why the centers of galaxies appear less densely packed with dark matter than predicted — a long-standing issue in cosmology.

From spinning clouds to vortex lattices

The researchers simulated what happens when clouds of this unusual dark matter rotate. The result was surprising: Instead of spinning smoothly like a hurricane or a solid sphere, the solitons developed an internal lattice of microscopic vortices.

"When the initial conditions are such that the dark matter cloud rotates, the end result is a rotating soliton at the center of the collapsed halo," said study co-author Patrick Valageas, also of the Université Paris-Saclay. "This soliton shows an oblate shape aligned with the initial rotation axis, and displays a solid-body rotation supported by quantized vortices."

These vortices aren't like swirling winds or whirlpools in water. Rather, they resemble the quantized vortex lines that appear in superfluids like liquid helium, where the fluid rotates not as a whole but through an array of discrete spinning threads. At the center of each vortex, the dark matter density drops to zero, and together, the vortices align into a regular, lattice-like pattern.

"Our simulations show that these vortex lines are aligned with the total angular momentum and follow circular orbits inside the soliton," Valageas said. "The rotation is not like a smooth wind but more like a bundle of microscopic tornadoes arranged in a crystal pattern."

One intriguing idea the researchers raised is whether these tiny vortex structures have implications on much larger scales. In particular, they speculated that some vortex lines might extend beyond a single halo, connecting galaxies through the vast filaments of the cosmic web — the gigantic tendrils of dark matter that shape the universe's large-scale structure.

"At this stage, the idea that some of these vortex lines could join different halos through the filaments of the cosmic web is a hypothesis," Brax noted. If true, it could mean that quantum effects in dark matter subtly influence how galaxies align and move within these colossal threads.

Detecting such vortex structures would be challenging. Because dark matter doesn't emit or absorb light, scientists can only infer its presence from its gravitational influence on visible matter like stars and gas.

Still, there may be ways to glimpse their effects. "These vortices are associated with troughs in the dark matter density," Brax said. "As such, they imprint characteristic features in the gravitational potential, which may influence the orbits of stars or gas clouds in galaxies like the Milky Way."

In more speculative scenarios, if dark matter interacts even weakly with ordinary matter or light, the vortices might leave more direct fingerprints — but for now, that remains an open question.

The team plans to investigate whether the predicted vortex lattices can be detected through astronomical observations and whether they truly connect to the cosmic filaments that stretch across space.

For now, these ghostly whirlpools remain invisible — but as theory and technology advance, scientists may find that the cosmos is not just filled with unseen matter but woven with patterns of spinning quantum threads.

Instruments flying more than 18 miles (29 kilometers) above Antarctica detected two unexplainable radio pulses coming from below the ice — and these signals seem to defy particle physics.

Researchers determined the radio pulses came from angles around 30 degrees below Antarctica's surface, which the laws of physics theoretically prohibit. Calculations suggest the signals had to pass through thousands of miles of rock to get to the surface; however, scientists expect the pulses to be absorbed by the rock on this journey, rendering them undetectable.

The research team is now looking deeper into what could have caused the unexpected pulses. They ruled out some possible explanations using the Pierre Auger Observatory in Argentina and shared those findings in a study published March 27 in the journal Physical Review Letters.

"It's an interesting problem because we still don't actually have an explanation for what those anomalies are," Stephanie Wissel, a particle physicist and co-author of the study, said in a statement.

Excluding neutrinos

The mysterious pulses were first detected by the Antarctic Impulsive Transient Antenna (ANITA) experiment. ANITA comprises 24 radio antennas attached to a NASA balloon, located near the south pole to avoid signal interference.

Related: Antimatter detected on International Space Station could reveal new physics

The project was designed to capture data about neutrinos — subatomic particles that are especially difficult to study because they lack electric charge and have minimal mass. These elusive characteristics have earned them the nickname "ghost particles".

But the confusing radio signals are "most likely not representing neutrinos," Wissel said. Existing models, she explained, predict that pulses caused by neutrinos would originate from angles very far from 30 degrees under the surface. The new study provides further evidence that neutrinos are probably not involved.

Using complex mathematical models and simulations, the research team also ruled out noise and known particle interactions as sources of the signals. They even examined data from other experiments to see if they observed any interaction that could cause the pulses, to no avail.

Since these observations can't be explained by the Standard Model, the theory that describes subatomic particles, the phenomenon responsible for these pulses could be key to unlocking new scientific understanding.

"More research needs to be done on this," Benjamin Flaggs, a physics graduate student at the University of Delaware and co-author of the study, told Live Science. "There are theorists proposing some beyond-standard-model interactions from different types of particles," he said.

Searching for the cause

If neutrinos aren't responsible for the radio signals, then what is?

Some theories suggest the signals are coming from dark matter — the invisible entity that makes up about 27% of the universe, but which remains poorly understood — Wissel said. But more data is needed before coming to any meaningful conclusion. Wissel favors the theory that the origin of these pulses may be explained by some as-of-yet unknown behavior of radio waves, but there's no evidence to support this guess, either. "So, right now, it's one of these long-standing mysteries," she said.

The Payload for Ultrahigh Energy Observations, a new balloon-based instrument, with advanced levels of sensitivity, is expected to help solve this puzzle by detecting more anomalies, thus providing more data to be scrutinized. "The more data we can get, the better we can get our statistical error," Flaggs said. The instrument will launch from Antarctica in December.

"We haven't discovered everything yet," Flaggs added. "It's exciting for researchers because these are problems that no one else has figured out before."

A mysterious second flavor of hydrogen atoms — one that doesn't interact with light — may exist, a new theoretical study proposes, and it could account for much of the universe's missing matter while also explaining a long-standing mystery in particle physics.

The mystery, known as the neutron lifetime puzzle, revolves around two experimental methods whose results disagree on the average lifetime of free neutrons — those not bound within atomic nuclei — before they decay to produce three other particles: protons, electrons and neutrinos.

"There were two kinds of experiments for measuring the neutron lifetime," Eugene Oks, a physicist at Auburn University and sole author of the new study published in the journal Nuclear Physics B, told Live Science in an email.

The two methods are called beam and bottle. In beam experiments, scientists count protons left behind immediately after neutrons decay. Using the other approach, in bottle experiments, ultra-cold neutrons are trapped and left to decay, and the remaining neutrons are counted after the experimental run is over — typically lasting between 100 and 1000 seconds, with many such runs performed under varying conditions like trap material, storage time, and temperature to improve accuracy and control for systematic errors.

These two methods yield results that differ by about 10 seconds: beam experiments measure a neutron lifetime of 888 seconds, whereas bottle experiments report 878 seconds — a discrepancy well beyond experimental uncertainty. "This was the puzzle," said Oks.

Solving the puzzle… with invisible atoms

In his study, Oks proposes that the discrepancy in lifetimes arises because a neutron sometimes decays not into three particles, but just two: a hydrogen atom and a neutrino. Since the hydrogen atom is electrically neutral, it can pass through detectors unnoticed, giving the false impression that fewer decays have occurred than expected.

Although this two-body decay mode had been proposed theoretically in the past, it was believed to be extremely rare — occurring in only about 4 out of every million decays. Oks argues that this estimate is dramatically off because previous calculations didn't consider a more exotic possibility: that most of these two-body decays produce a second, unrecognized flavor of hydrogen atom. And unlike ordinary hydrogen, these atoms don’t interact with light.

"They do not emit or absorb electromagnetic radiation, they remain dark," Oks explained. That would make them undetectable using traditional instruments, which rely on light to find and study atoms.

Related: How many atoms are in the observable universe?

What distinguishes this second flavor? Most importantly, the electron in this type of hydrogen would be far more likely to be found close to the central proton than in ordinary atoms, and would be completely immune to the electromagnetic forces that make regular atoms visible.

The invisible hydrogen would be hard to detect. "The probability of finding the atomic electron in the close proximity to the proton is several orders of magnitude greater than for ordinary hydrogen atoms," Oks added.

This strange atomic behavior comes from a peculiar solution to the Dirac equation — the core equation in quantum physics that describes how electrons behave. Normally, these solutions are considered unphysical, but Oks argues that once the fact that protons have a finite size is taken into account, these unusual solutions start to make sense and describe well-defined particles.

By considering a second flavor of hydrogen, Oks calculates that the rate of two-body decays could be enhanced by a factor of about 3,000. This would raise their frequency to around 1% of all neutron decays — enough to explain the gap between beam and bottle experiments. "The enhancement of the two-body decay by a factor of about 3000 provided the complete quantitative resolution of the neutron lifetime puzzle," he said.

That's not all. Invisible hydrogen atoms might also solve another cosmic mystery: the identity of dark matter, the unseen material that’s thought to make up most of the matter in the universe today.

In a 2020 study, Oks showed that if these invisible atoms were abundant in the early universe, they could explain an unexpected dip in ancient hydrogen radio signals observed by astronomers. Since then, he has argued that these atoms may be the dominant form of baryonic dark matter — matter made from known particles like protons and neutrons, but in a form that’s hard to detect.

"The status of the second flavor of hydrogen atoms as baryonic dark matter is favored by the Occam’s razor principle," said Oks, referring to the idea that the simplest explanation is often best. "The second flavor of hydrogen atoms, being based on the standard quantum mechanics, does not go beyond the Standard Model of particle physics."

In other words, no exotic new particles or material are needed to explain dark matter — just a new interpretation of atoms that we already thought we understood.

Testing the new theory

Oks is now collaborating with experimentalists to test his theory. At the Los Alamos National Laboratory in New Mexico, a team is preparing an experiment based on two key ideas. First, both flavors of hydrogen can be excited using an electron beam. Second, once excited, ordinary hydrogen atoms can be stripped away using a laser or electric field — leaving behind only the invisible ones. A similar experiment is also being prepared in Germany at the Forschungszentrum Jülich, a national research institute near Garching.

The stakes for these tests are high. "If successful, the experiment could yield results this year," said Oks. "The success would be a very significant breakthrough both in particle physics and in dark matter research."

In the future, Oks plans to explore whether other atomic systems might also have two flavors, potentially opening the door to even more surprising discoveries. And if confirmed, such findings could also reshape our understanding of cosmic history.

"The precise value of the neutron lifetime is pivotal for calculating the amount of hydrogen, helium and other light elements that were formed in the first few minutes of the universe's life," Oks said. So his proposal doesn't just solve a long-standing puzzle — it could rewrite the earliest chapters of cosmic evolution.

Using optical tweezers composed of laser light, researchers have developed a novel way to manipulate individual atoms and create a state of hyper-entanglement.

This breakthrough could lead to new forms of quantum computing and advances in quantum simulations designed to answer fundamental questions about physics.

Caltech scientists have been using optical tweezers to control individual atoms for several decades, leading to a number of advances, including quantum error correction and a method for creating the world's most accurate clocks.

One persistent issue in the process, however, has been the natural motion of atoms, which can introduce noise (and errors) into a quantum system. But in the breakthrough study, published in the journal Science, that weakness has been transformed.

"We show that atomic motion, which is typically treated as a source of unwanted noise in quantum systems, can be turned into a strength," said Adam Shaw in a statement on Caltech's website, a postdoctoral researcher and first author on the study.

Instead of a disruptive influence, Shaw and colleagues have harnessed that movement to create hyper-entangled sets of atoms. Hyper-entanglement is distinct from traditional quantum entanglement, which describes two or more particles that are in-sync and share a property across vast distances. Hyper-entangled atoms, by contrast, can share multiple properties at the same time.

In the experiment, the Caltech team was able to link both the states of motion and electronic states (a measure of an atom's internal energy level) in a pair of atoms at the same time.

Related: Physicists create hottest Schrödinger's cat ever in quantum technology breakthrough

This achievement is an important step in terms of both volume and efficiency, according to Manuel Endres, a professor of physics at Caltech and co-lead author of the study. "This allows us to encode more quantum information per atom," he said in the statement. "You get more entanglement with fewer resources."

To achieve that state of hyper-entanglement, the team first had to cool an alkaline earth atom with no charge using a novel method that Endres said involved "detection and subsequent active correction of thermal motional excitations." By deploying this method, the team was able to almost completely freeze the atom's motion.

The next step was to cause atoms to oscillate like a pendulum on a tiny scale in two different directions simultaneously, creating a state of superposition — when a particle exhibits opposite properties at the same time. These oscillating atoms were then entangled with partners that matched their motion, and finally hyper-entangled to also mirror their electronic states.

According to Endres, the point of the experiment was to find the limit of control they could exercise over the atoms. "We are essentially building a toolbox," he said. "We knew how to control the electrons within an atom, and we now learned how to control the external motion of the atom as a whole — it's like an atom toy that you have fully mastered."

One of the most exciting facets of this discovery is the implication that even more states or properties could be entangled, which Endres said could lead to a number of potential applications.

"Motional states could become a powerful resource for quantum technology, from computing to simulation to precision measurements."

Medieval alchemists were obsessed with the idea of turning lead into gold, a concept known as chrysopoeia. But they may have had more luck swapping out the philosopher's stone for a particle accelerator, new results suggest.

Scientists at the Large Hadron Collider (LHC) at CERN, near Geneva, have revealed that some 86 billion gold nuclei were created during the accelerator's second run, between 2015 and 2018 — all from smashing together lead atoms at 99.999993% the speed of light.

The result is a tiny quantity of gold — amounting to just 29 trillionths of a gram — that then collides with the beam pipe and fragments in a fraction of a second. Yet even this near-instantaneous life and death showed up in the ALICE (A Large Ion Collider Experiment) collaboration's detectors.

"It is impressive to see that our detectors can handle head-on collisions producing thousands of particles, while also being sensitive to collisions where only a few particles are produced at a time, enabling the study of rare electromagnetic 'nuclear transmutation' processes," Marco van Leeuwen, a spokesperson for ALICE, said in a statement.

Drawing upon the philosophical conjectures of Aristotle, alchemists believed that the similar densities of lead and gold were signs that lead was "sick" and could be cured by transmutation into valuable gold. Despite being wrong, the ancient alchemists' beliefs did contain a nugget of truth: The two metals are very close to each other on the periodic table, with gold having 79 protons — just three fewer than lead.

Related: 'Beauty' particle discovered at world's largest atom smasher could unlock new physics

That means that collisions at powerful particle accelerators need to rip only three protons from lead (alongside some neutrons) to make gold. Shaving off one or two protons, on the other hand, creates thallium and mercury, respectively.

To quantify these metals produced inside the LHC, the physicists used ALICE's highly sensitive Zero Degree Calorimeters (ZDCs), which measure the protons and neutrons streaming from the billions of particle interactions happening inside the collider every second.

The results showed that, although it's produced less frequently than thallium or mercury, gold is currently generated by the experiment’s third run at a maximum rate of around 89,000 nuclei per second — nearly double the amount produced by the previous run, due to the third run's increased energy.

"Thanks to the unique capabilities of the ALICE ZDCs, the present analysis is the first to systematically detect and analyze the signature of gold production at the LHC experimentally," Uliana Dmitrieva, a physicist at the ALICE collaboration, said in the statement.

"The results also test and improve theoretical models of electromagnetic dissociation which, beyond their intrinsic physics interest, are used to understand and predict beam losses that are a major limit on the performance of the LHC and future colliders," added John Jowett, another physicist at the experiment.

Physicists at the world's largest particle accelerator have made a first-of-its-kind discovery about antimatter that could help solve one of the universe's biggest mysteries.

The discovery — made at the Large Hadron Collider (LHC) at CERN, near Geneva — has revealed that a short-lived cousin of protons and neutrons, the beauty-lambda baryon, decays at a different rate than its antimatter counterpart.

Called charge-parity (CP) violation, this effect refers to particles of opposite charge, like matter and animatter, behaving differently. It's a crucial explanation for why matter was able to dominate over antimatter in the early universe — without it, the universe would be an empty void.

Despite being a key reason why we're here in the first place, the amount of CP violation predicted by the Standard Model of particle physics is far too small to explain the abundance of matter in our universe.

What's more, this violation has previously been only detected in particles made up of quark-antiquark pairs, called mesons. It has not been observed in baryons — three-quark particles, such as protons and neutrons, that make up most of the universe's visible matter.

Related: 'The Majoron' — a bizarre particle that's its own opposite — could explain the biggest mysteries of the universe, scientists claim

This first-of-its-kind detection has changed that, potentially opening up an avenue to search for physics beyond the Standard Model. The researchers presented their findings March 24 at the Rencontres de Moriond conference in La Thuile, Italy, and posted a non-peer-reviewed study on the preprint server arXiv.

"The reason why it took longer to observe CP violation in baryons than in mesons is down to the size of the effect and the available data," Vincenzo Vagnoni, a spokesperson for the Large Hadron Collider beauty (LHCb) experiment that made the detection, said in a statement. "It took over 80,000 baryon decays for us to see matter–antimatter asymmetry with this class of particles for the first time."

The broth of creation

According to the standard model of cosmology, in the aftermath of the Big Bang, the young cosmos was a roiling plasma broth of matter and antimatter particles that popped into existence and annihilated each other upon contact.

Theory predicts that the matter and antimatter inside this plasma soup should have annihilated each other entirely. But scientists believe that some unknown imbalance — likely CP violation in decays involving the weak nuclear force — enabled more matter than antimatter to be produced, sparing it from self-destruction.

To search for CP violation in baryons, the researchers at the LHCb combed through data of the countless particle interactions (where protons collide roughly 25 million times a second) that occurred between 2009 and 2018.

They tallied up the decays of the beauty-lambda baryon by searching for the telltale paths made by its decay products — a proton, a kaon and a pair of oppositely charged pions — alongside the decays of its corresponding antimatter counterpart.

Their analysis revealed that the difference between the decay numbers of beauty-lambda baryons and anti-beauty-lambda baryons was 2.45% from zero with an uncertainty of about 0.47%. This was measured to a statistical significance of 5.2 sigma, passing the the five-Sigma result physicists use as the "gold standard" for heralding a new discovery.

With the finding sealed, the physicists say they will look for even more CP violations when the LHC fires up again in 2030, and collect further data on the key mechanism that likely enabled our universe to exist.

"The more systems in which we observe CP violations and the more precise the measurements are, the more opportunities we have to test the Standard Model and to look for physics beyond it," Vagnoni said. "The first ever observation of CP violation in a baryon decay paves the way for further theoretical and experimental investigations of the nature of CP violation, potentially offering new constraints for physics beyond the Standard Model."

This article was originally published Mar 31, 2025.

Physicists have scaled down the maximum possible mass of an elusive "ghost particle" called a neutrino to at least one-millionth the weight of an electron. The revision takes scientists one more step toward a discovery that could alter or even upend the Standard Model of particle physics.

Our universe is awash with phantom specks of matter. Every second, around 100 billion neutrinos pass through each square centimeter of your body. They're produced in multiple places: the nuclear fire of stars, in enormous stellar explosions, by radioactive decay and in particle accelerators and nuclear reactors on Earth.

Even though they're the most common form of matter in the cosmos, neutrinos' minimal interactions with other matter types makes them notoriously difficult to detect, and they're the only particles in the Standard Model whose precise mass remains unaccounted for.

Searching for this mass could have a significant impact on our understanding of the cosmos. Despite ample experimental hints to the contrary, the Standard Model predicts that neutrinos shouldn't have any mass at all. Finding it, therefore, could poke a hole in the model wide enough for new physics. It may even explain why we exist in the first place.

Related: Most energetic neutrino ever found on Earth detected at the bottom of the Mediterranean Sea

Now, new findings from the Karlsruhe Tritium Neutrino (or KATRIN) experiment in Germany have advanced closer to this goal — setting a ceiling for the ghost particle's mass at 0.45 electron volts, which reduces the experiment's previous upper limit by nearly half. The researchers published their results Thursday (April 10) in the journal Science.

Neutrinos come in three different flavor states called electron, muon and tau neutrinos, based on the different particles they interact with. These flavor states are believed to be mixtures of mass states, and the strongest evidence that neutrinos have mass is because, weirdly, they can spontaneously switch between flavors on the fly — a finding that won its discoverers the Nobel Prize in Physics in 2015.

Yet this mass is vanishingly tiny, and physicists don't really have a solid explanation for why.

To search for an answer, the physicists behind the new research turned to radioactive decays of the unstable hydrogen isotope tritium, which splits into an electron and an electron antineutrino — the electron neutrino's antimatter counterpart.

Neutrinos, or antineutrinos for that matter, cannot be directly detected, but the energy their mass subtracts from the speed of the accompanying electron can. The KATRIN researchers detected a mind-boggling 36 million of these electrons as the particles arrived at the detector at the other end of the experiment. This enabled the researchers to deduce the maximum electron antineutrino mass.

With this upper limit set, the physicists will continue to collect more data until the end of 2025 to constrain the neutrino mass even further.

Meanwhile, other scientists are searching for the mass using similar tritium decays, by studying other decays of particles called pions and kaons, and even by staring out into space at ancient shockwaves etched out across the early universe. What they find could bring our picture of the universe into sharper focus, or alter it forever.

The world's biggest atom smasher could be getting an upgrade.

The Large Hadron Collider (LHC), situated at the CERN laboratory on the Swiss-French border, was built over a decade ago with two goals in mind. First, to establish the existence of the Higgs boson, the cornerstone particle of the Standard Model of particle physics, predicted all the way back in the 1960s; And second, to find any new particles, especially ones that could validate one of the many competitors to physical theories beyond the Standard Model.

But while the LHC has proven a success when it comes to the Higgs, whose existence was confirmed by CERN scientists in 2012, the atom smasher has also been a failure when it comes to new particles. Despite more than a decade of searching, the collider has found no traces of any physics beyond the Standard Model.

Failing to find new particles is not exactly a bad thing. The continuous negative results have disproven many alternative models, which means that at least scientists know which ideas are bad and no longer worth working on. But a lack of positive results has also left modern particle physics in the dark, with little to no clues about which hypothetical ideas might still be worth pursuing.

The LHC, as powerful as it is at seeing subatomic particles, does have a blind spot. It was designed with certain hypothetical particles in mind, especially ones that have electric charge and don't have long lifespans. And there is a class of hypothetical particles, known as long-lived neutral particles, that can slip by LHC's two main detectors without notice. So the giant machine may have been revealing new physics every single day, but those particles were undetectable.

Related: Scientists claim to find 'first observational evidence supporting string theory,' which could finally reveal the nature of dark energy

This fact was not lost on the LHC's original designers. Soon after the collider began operations, a team gathered to design an add-on detector to look for long-lived particles. That detector, known as MATHUSLA — named for Methuselah, the Biblical character who supposedly lived for over 900 years, and stands for MAssive Timing Hodoscope for Ultra-Stable neutraL pArticles — is in its final design stages, according to a report by more than 30 scientists involved in the project, published March 26 to the preprint server arXiv.

If funding stays on track, the team hopes to begin construction this year.

Waking MATHUSLA

MATHUSLA will consist of a giant chamber 130 feet (40 meters) across, filled with nothing but air and surrounded by banks of detectors. It would be placed about 330 feet (100 m) away from the main collider beam, with dirt and rock filling the space between.

In particle physics, "long-lived" is a relative term. In this case, many hypothetical particles have lifespans of around a few hundred nanoseconds — an eternity compared to the vast majority of particles that are currently being studied at the LHC.

If MATHULSA works, the add-on detector will wait for one of these long-lived particles to make its way into the main chamber. There it will decay into a shower of other particles, and banks of sensors will look for their telltale glow.

Long-lived particles could give physicists insights into the detailed nature of the Higgs boson, possible companions to the Higgs and explanations as to why the force of gravity is so weak. They may even help reveal the identity of dark matter — the mysterious substance that is predicted to make up about 85% of all matter in the universe and yet remains largely unknown to science.

With such exciting results potentially within reach, let's just hope that we won't have to wait 900 years for MATHUSLA to be built.

Scientists have peered inside protons and discovered that quarks and gluons, their fundamental building blocks, experience quantum entanglement.

Entangled particles are connected to each other, so that a change to one instantaneously causes a change to the other, even if they are separated by vast distances. Albert Einstein famously dismissed the idea as "spooky action at a distance," but later experiments proved that the bizarre, locality-breaking effect is real.

Physicists have observed entanglement between quarks before but had never found evidence that they exist in a quantumly connected state inside protons.

Now, a team of researchers has discovered entanglement between quarks and gluons inside protons over a distance of one quadrillionth of a meter — allowing the particles to share information across the proton. The researchers published their findings Dec. 2, 2024 in the journal Reports on Progress in Physics.

"For decades, we've had a traditional view of the proton as a collection of quarks and gluons, and we've been focused on understanding so-called single-particle properties, including how quarks and gluons are distributed inside the proton," study co-author Zhoudunming Tu, a physicist at Brookhaven National Laboratory in Upton, New York, said in a statement. "Now, with evidence that quarks and gluons are entangled, this picture has changed. We have a much more complicated, dynamic system."

'Spooky action' at the smallest scale

Experimental proof of quantum entanglement first emerged in the 1970s, but many aspects of the phenomenon remain relatively unexplored — including the entangled interactions between quarks. This is mainly because the subatomic particles don't exist on their own and instead fuse into various particle combinations known as hadrons. For example, baryons, such as protons and neutrons, are combinations of three quarks bound tightly together by strong force-carrying gluons.

Related: Heaviest antimatter particle ever discovered could hold secrets to our universe's origins

When individual quarks are ripped from hadrons, the energy used to extract them makes them unstable, transforming them into branching jets of particles in a process called hadronization. This makes the task of sifting through the trillions of particle decay products to reconstruct their original state incredibly difficult.

But that's exactly what the researchers did. To probe the inner workings of protons, the scientists mined data collected by the Large Hadron Collider (LHC) and Hadron-Electron Ring Accelerator (HERA) particle collider experiments.

Then they applied a principle from quantum information science that says a system's entropy (a measure of how many energy states a system can be arranged in, often incorrectly referred to as "disorder") increases with its entanglement — causing the distribution of the particle sprays to appear messier.

By comparing the particle sprays to calculations of their entropy, the physicists discovered that the quarks and gluons inside the colliding protons existed in a maximally entangled state, each sharing the most information possible.

"Entropy is usually associated with uncertainty on some information, while entanglement leads to information 'sharing' between the two entangled parties. So these two can be related to each other in quantum mechanics," Tu told Live Science in an email. "We use the predicted entropy (with entanglement assumed) to check with what the data says, and we found great agreement."

The scientists say their discovery could help to glean more insights into fundamental particles — such as how quarks and gluons remain confined within protons. The research has also prompted further questions about how entanglement changes when protons are locked inside atomic nuclei.

"Because nuclei are made of protons and neutrons, it is natural to ask what would the entanglement do to nuclei structure," Tu said. "We plan to use the electron-ion collider (EIC) to study this. This will come in 10 years. Before that, some collision types, so-called ultra-peripheral collisions in heavy-ion collisions, may work too."

A hidden family of "ghost particles" may be responsible for all the dark matter in the universe — and the reason that there is any matter at all, a recent preprint study suggests.

One of the most puzzling questions in modern cosmology is why the universe is filled with matter in the first place. The problem is that almost all fundamental particle reactions produce exact numbers of matter and antimatter particles, which then go on to annihilate each other in flashes of energy. But the universe has an abundance of matter and very little antimatter. So why didn't everything just disappear in the early universe?

The problem is known as baryogenesis, and the leading hypothesis is that some unknown process led to an imbalance of matter over antimatter in the first moments of the Big Bang. But what could that process have been?

New research suggests that the answer may lie in ghostly little particles known as neutrinos. The research was published Dec. 18 on the preprint server arXiv and has not yet been peer-reviewed.

Related: 32 physics experiments that changed the world

There are three varieties of neutrinos, and they all have bizarre properties. For one, they have just a tiny bit of mass, far smaller than even the mass of electrons. They are also all "left-handed," which means their internal spins orient in only one direction as they travel, unlike all other particles that can orient in both directions.

This has led to speculation that there may be more neutrino varieties out there that we haven't detected yet — the right-handed counterparts to the known neutrinos. That's because interactions between the left- and right-handed varieties of neutrinos could cause them to have mass.

A shattered universe

In their recent paper, the researchers proposed a model in which there are two right-handed neutrino species that have very high masses. The model showed that in the earliest moments of the universe, the left- and right-handed neutrinos were in perfect balance. But as the cosmos expanded and cooled, that balance broke, leading to a breaking of symmetries that caused the left-handed neutrinos to acquire their mass and the right-handed neutrinos to disappear from view.

But the researchers' model found that this cataclysmic shift also had other consequences. For one, because neutrinos interact with other particles, their broken symmetry triggered a chain reaction that threw off the delicate balance between matter and antimatter. Second, the right-handed neutrinos mixed together to create an altogether new particle, dubbed the Majoron. The Majoron is a hypothetical particle that is its own anti-particle, and the researchers' calculations showed that this particle would have been made in abundance in the chaos of the early universe.

The Majoron would then survive as a relic of those ancient times, making up the bulk of the mass of every galaxy but remaining invisible and elusive. In other words, it would be a candidate for dark matter, the mysterious hidden substance that fills the cosmos.

It's an audacious proposal, but a comprehensive one. According to the researchers, a single mechanism could explain the strange properties of neutrinos, the baryogenesis that led to the dominance of matter in the universe, and the appearance of mysterious dark matter.

To date, there has been no experimental evidence for the existence of any right-handed neutrinos, let alone something even more exotic like the Majoron. But the researchers predict that if the Majoron exists, it could be within the detectability range of a number of neutrino experiments, like Super-Kamiokande and Borexino — two underground neutrino detectors based in Japan and Italy, respectively. Only time will tell if one of these experiments will find a new signal that lines up with this hypothesis — but if that happens, we may be on the path to solving a number of cosmological mysteries.

Editor's note: This article was updated on Jan. 11 to correct a spelling error. A previous version of the article called the proposed particle the "Majoran"; the correct name is the "Majoron."

For more than a century, scientists have been fascinated by the possibility that hidden, minuscule spatial dimensions could be influencing the physics of our familiar three-dimensional world. Despite decades of experimental searches, however, there has yet to be concrete evidence of these extra dimensions. Now, a recent study proposes a way to advance this search: using the upcoming Deep Underground Neutrino Experiment (DUNE) to probe these hidden dimensions through neutrino behavior.

Neutrinos are among the universe's most elusive particles, earning them the nickname "ghost particles." There are three known types — or "flavors" — of neutrinos, each with a mass billions of times smaller than an electron's. These particles are remarkable in their ability to transform — or oscillate — into different flavors as they travel through space, even without interacting with other particles.

Studying neutrinos with DUNE

DUNE is a forthcoming neutrino oscillation experiment based in Illinois and South Dakota. "In this experiment, neutrinos are generated by a particle accelerator at Fermilab [in Illinois], travel a distance of 1,300 kilometers [800 miles], and are observed using a massive underground detector in South Dakota," Mehedi Masud, a professor at Chung-Ang University in South Korea and co-author of the study, told Live Science via email.

The experimental setup is ideal for studying neutrino oscillations. Neutrinos created in Fermilab's collisions — primarily muon neutrinos (one of the three flavors) — will traverse Earth to reach the South Dakota detector. Along the way, some of these particles are expected to transform into the other two flavors: electron neutrinos and tau neutrinos.

By observing how the different flavors evolve during their journey, DUNE scientists hope to unravel several fundamental questions in neutrino physics, such as the hierarchy of neutrino masses, the precise parameters governing oscillation, and the role neutrinos may have played in creating the matter-antimatter imbalance in the universe.

Related: Our universe is merging with 'baby universes', causing it to expand, new theoretical study suggests

Probing extra dimensions with neutrino oscillations

The study, published in the Journal of High Energy Physics in November, proposes that the enigmatic behavior of neutrinos could be explained if, in addition to the familiar three dimensions of space, there exist extra spatial dimensions on the scale of micrometers (millionths of a meter). While tiny by everyday standards, such dimensions are remarkably large compared with the femtometer (one-quadrillionth of a meter) scales typical of subatomic particles.

"The theory of large extra dimensions, first proposed by Arkani-Hamed, Dimopoulos, and Dvali in 1998, suggests that our familiar three-dimensional space is embedded within a higher-dimensional framework" of four or more dimensions, Masud explained. "The primary motivation for this theory is to address why gravity is vastly weaker than the other fundamental forces in nature. Furthermore, the theory of large extra dimensions offers a potential explanation for the origin of the tiny neutrino masses, a phenomenon that remains unexplained within the Standard Model of particle physics."

If extra dimensions exist, they could subtly alter neutrino oscillation probabilities in ways detectable by DUNE, according to the study authors. These distortions could appear as a slight suppression of expected oscillation probabilities and as small oscillatory "wiggles" at higher neutrino energies.

Simulating DUNE data to hunt for extra dimensions

In this study, the authors considered the case of a single additional dimension. The effects of an extra dimension are determined primarily by its size. This dependence creates an opportunity for researchers to investigate the presence of such dimensions by analyzing how neutrinos interact with matter within the detector. The extra dimension influences the oscillation probabilities of neutrinos, which, in turn, can reveal valuable clues about its potential existence and properties.

"We simulated several years of neutrino data from the DUNE experiment using computational models," Masud said. "By analyzing both the low-energy and high-energy effects of large extra dimensions on neutrino oscillation probabilities, we statistically assessed DUNE's ability to constrain the potential size of these extra dimensions, assuming they exist in nature."

The team's analysis suggests that the DUNE experiment will be capable of detecting an extra dimension if its size is around half a micron (one-millionth of a meter). DUNE is currently under construction and is expected to begin data collection around 2030. After several years of operation, the accumulated data will likely be sufficient for a comprehensive analysis of the theory of large extra dimensions. The team expects the results of this analysis to be available roughly a decade from now.

Additionally, they think that, in the future, combining data from DUNE with other experimental methods — such as collider experiments or astrophysical and cosmological observations — will enhance the ability to investigate the properties of extra dimensions with greater precision and accuracy.

"In the future, incorporating inputs from other types of data could further tighten these upper bounds, making the discovery of large extra dimensions more plausible, should they exist in nature," Masud said. "Beyond being an exciting avenue for new physics, the potential presence of large extra dimensions could also help DUNE measure standard unknowns in neutrino physics more precisely, free from the influence of unaccounted-for effects."

The world's most massive science experiment has done it again, detecting hints of the heaviest antimatter particle ever found.

This means the Large Hadron Collider (LHC), the most powerful particle accelerator ever built, has given scientists a glimpse into conditions that existed when the universe was less than a second old. The antimatter particle is the partner of a massive matter particle called hyperhelium-4, and its discovery could help scientists tackle the mystery of why regular matter came to dominate the universe, despite the fact that matter and antimatter were created in equal amounts at the dawn of time.

This imbalance is known as "matter-antimatter asymmetry." Matter particles and antimatter particles annihilate on contact, releasing their energy back into the cosmos. That implies that if an imbalance between the two hadn't arisen early in the universe, then the cosmos may have been a much emptier and less interesting place indeed.

The LHC is no stranger to paradigm-shifting discoveries about the early universe. Running in a 17-mile (27-kilometer) long loop beneath the Alps near Geneva, Switzerland, the LHC is most famous for its discovery of the Higgs Boson particle, the "messenger" of the Higgs Field responsible for giving other particles their mass at the dawn of time.

The collisions that occur at the LHC generate a state of matter called "quark-gluon plasma." This dense sea of plasma is the same as the "primordial soup" of matter that filled the universe around one-millionth of a second after the Big Bang.

Exotic "hypernuclei" and their antimatter counterparts emerge from this quark-gluon plasma, allowing scientists a glimpse at the conditions of the early universe.

Related: World's smallest particle accelerator is 54 million times smaller than the Large Hadron Collider, and it works

ALICE through the looking glass

Hypernuclei contain protons and neutrons like ordinary atomic nuclei and also unstable particles called "hyperons." Like protons and neutrons, hyperons are composed of fundamental particles called "quarks." Whereas protons and neutrons contain two types of quarks known as up and down quarks, hyperons contain one or more so-called "strange quarks."

Hypernuclei were first discovered in cosmic rays, showers of charged particles that rain down on Earth from deep space around seven decades ago. However, they are rarely found in nature and are difficult to create and study in the lab. This has made them somewhat mysterious.

The discovery of the first evidence of the hypernuclei that is an antimatter counterpart of hyperhelium-4 was made at the LHC detector ALICE.

While most of the nine experiments at the LHC, each with its own detector, generate their results by slamming together protons at near the speed of light, the ALICE collaboration creates quark-gluon plasma by slamming together much heavier particles, usually lead nuclei, or "ions."

The collision of iron ions (try saying that ten times fast) is ideal for generating significant amounts of hypernuclei. Yet until recently, scientists conducting heavy-ion collisions had only succeeded in observing the lightest hypernucleus, hypertriton, and its antimatter partner, antihypertriton.

That was until earlier in 2024 when scientists used the Relativistic Heavy Ion Collider (RHIC) in New York to detect antihyperhydrogen-4, which is composed of an antiproton, two antineutrons, and a quark-containing particle called an "antilambda."

Now, ALICE has followed this with the detection of a heavier anti-hypernuclei particle, antihyperhelium-4, composed of two antiprotons, an antineutron, and an antilambda.

The lead-lead collision and the ALICE data that yielded the detection of the heaviest antimatter hypernucleus yet at the LHC actually date back to 2018.

The signature of antihyperhelium-4 was revealed by its decay into other particles and the detection of these particles.

ALICE scientists teased the signature of antihyperhelium-4 out of the data using a machine-learning technique that can outperform the collaboration's usual search techniques.

In addition to spotting evidence of antihyperhelium-4 and antihyperhydrogen-4, the ALICE team was also able to determine their masses, which were in good agreement with current particle physics theories.

The scientists were also able to determine the amounts of these particles produced in lead-lead collisions.

They found these numbers consistent with the ALICE data, which indicates that antimatter and matter are produced in equal amounts from quark-gluon plasma produced at the energy levels the LHC is capable of reaching.

The reason for the universe's matter/antimatter imbalance remains unknown, but antihyperhelium-4 and antihyperhydrogen-4 could provide important clues in this mystery.

Researchers in Birmingham have created the first image of a photon, a lemon-shaped particle of light emitted from the surface of a nanoparticle. The theory that made this image possible, reported Nov. 14 in the journal Physical Review Letters, enables scientists to calculate and understand various properties of these quantum particles — which could open up a range of new possibilities across fields such as quantum computing, photovoltaic devices and artificial photosynthesis.

Light's quantum behavior is well established, with over 100 years of experiments showing it can exist in both wave and particle form. But our fundamental understanding of this quantum nature is much further behind, and we only have a limited grasp of how photons are created and emitted, or of how they change through space and time.

"We want to be able to understand these processes to leverage that quantum side," first author Ben Yuen, a research fellow at the University of Birmingham in the U.K., told Live Science. "How do light and matter really interact at this level?"

However, the very nature of light means the answer to this question has almost limitless possibilities. "We can think of a photon being a fundamental excitation of an electromagnetic field," explained Yuen. These fields are a continuum of different frequencies, each of which could potentially become excited. "You can split up a continuum into smaller parts and between any two points, there's still an infinite number of possible points you could pick," Yuen added.

The result is that the properties of a photon are heavily dependent on the properties of its environment, leading to some incredibly complex math. "At first glance, we would have to write down and solve an infinite number of equations to reach an answer," Yuen said.

Related: High school students who came up with 'impossible' proof of Pythagorean theorem discover 9 more solutions to the problem

To tackle this seemingly impossible task, Yuen and co-author Angela Demetriadou, professor of theoretical nanophotonics at the University of Birmingham, employed a clever math trick to dramatically simplify the equations.

Introducing imaginary numbers — multiples of the impossible square root of -1 — is a powerful tool when handling complex equations. Manipulating these imaginary components allows many of the difficult terms in the equation to cancel each other out. Provided all imaginary numbers are converted back to real numbers before reaching the solution, this leaves a much more manageable calculation.

"We transformed that continuum of real frequencies into a discrete set of complex frequencies," explained Yuen. "By doing that, we simplify the equations from a continuum into a discrete set which we can handle. We can put those into a computer and solve them."

The team used these new calculations to model the properties of a photon emitted from the surface of a nanoparticle, describing the interactions with the emitter and how the photon propagated away from the source. From these results, the team generated the first image of a photon, a lemon-shaped particle never seen before in physics.

Yuen stressed, however, that this is only the shape of a photon generated under these conditions. "The shape changes completely with the environment," he said. "This is really the point of nanophotonics, that by shaping the environment, we can really shape the photon itself."

The team's calculations provide a fundamental insight into the properties of this quantum particle — knowledge that Yuen believes will open up new lines of research for physicists, chemists and biologists alike.

"We could think about optoelectronic devices, photochemistry, light harvesting and photovoltaics, understanding photosynthesis, biosensors, and quantum communication," Yuen said. "And there will be a whole host of unknown applications. By doing this kind of really fundamental theory, you unlock new possibilities in other areas."

From the most distant stars in the sky to the screen in front of your face, light is everywhere. But the exact nature of light, and how it travels, has long puzzled scientists. One question in particular has vexed thinkers from Issac Newton to Albert Einstein: Is light a particle or a wave?

"Whether light is a particle or a wave is a very old question," Riccardo Sapienza, a physicist at Imperial College London, told Live Science. As a species, we seem driven to understand the fundamental nature of the world around us, and this particular puzzle kept 19th-century scientists busy.

Today, there's no doubt about the answer: Light is both a particle and a wave. But how did scientists reach this mind-bending conclusion?

The starting point was to scientifically distinguish between waves and particles. "You would describe an object as a particle if you can identify it as a point in space," Sapienza said. "A wave is an object that you don't define as a point in space and you need to give a frequency of oscillation and distance between maximum and minimum."

The first conclusive evidence of the wave nature of light came in 1801, when Thomas Young performed his now-famous double-slit experiment. He placed a screen with two holes in front of a light source and observed the behavior of the light after it had passed through the slits. The light hitting the wall showed a complicated pattern of bright and dark bands, known as interference fringes.

As the light waves passed through each hole, they generated partial waves that radiated spherically, intercepting each other and adding or subtracting to the final intensity.

"If the light was a particle, you would have ended up with two bunches on the other side of the screen," Sapienza said. "But we have interference, and we see light everywhere after the screen, not just at the position of the holes. That's proof that light is indeed a wave."

Eighty-six years later, Heinrich Hertz became the first to demonstrate the particle nature of light. He noticed that when ultraviolet light shone on a metal surface, it generated a charge — a phenomenon called the photoelectric effect. However, the significance of his observation wasn't fully understood until many years later.

Related: What is the speed of light?

Atoms contain electrons in fixed energy levels. Shining light on them is therefore expected to give the electrons energy and enable them to escape from the atom, with brighter light liberating electrons faster. But in experiments following Hertz's work, several unusual observations seemed to completely contradict this classical understanding of physics.

It was Einstein who finally solved this puzzle, for which he was awarded a Nobel prize in 1921. Rather than absorbing light continuously from a wave, atoms actually receive energy in packets of light called photons, explaining odd observations such as the existence of a cutoff frequency.

But what determines whether light behaves as a wave or as a particle? According to Sapienza, this isn't the right question to be asking. "Light is not sometimes a particle and sometimes a wave," he said. "It is always both a wave and a particle. It's just that we highlight one of the properties depending on which experiment we do."

In day-to-day life, we mostly experience light as a wave, and it's this form that physicists find most useful to manipulate.

"There's a full field called metamaterials — by shaping a material with the same features as light, we can enhance the interaction of light with the material and control the waves,” Sapienza said. "For example, we can make solar absorbers that can absorb light more efficiently for energy generation or metamaterial MRI probes which are much more effective."

However, light's double nature, known as wave particle duality, is absolutely fundamental to the existence of the world as we know it. This strange twinned behavior also extends to other quantum particles, like electrons.

"You could not have an atom be stable if you didn't have quantum mechanics with the electrons in specific states," Sapienza said. "If you remove the fact that it is a particle, you remove the fact that it has a specific energy and life could not exist."

Primordial black holes (PBHs), which are thought to have formed right after the Big Bang, may be heating up and exploding throughout the universe.

These black hole explosions, powered by Hawking radiation — a quantum process where black holes generate particles from the vacuum due to their intense gravitational fields — could be detected by upcoming telescopes, physicists suggest in a new study. And, once spotted, these exotic explosions could reveal whether our universe contains previously undiscovered particles.

Black holes from the dawn of time

There's already plenty of evidence for the existence of black holes ranging from a few times the mass of the sun to billions of times the sun's mass. These black holes have been directly detected through the gravitational waves they emit during the mergers that help them grow. Some black holes, such as the Milky Way's Sagittarius A*, have even been directly imaged as "shadows" by the Event Horizon Telescope.

PBHs, first proposed by Yakov Zeldovich and Igor Novikov in 1967, are thought to have formed within the first fractions of a second after the Big Bang and may have been as small as subatomic particles, according to NASA. Unlike their larger counterparts, which form from the collapse of massive stars and galaxies, PBHs might have emerged from the collapse of ultradense regions in the extremely hot "primeval soup" of particles in the early universe.

If they exist, these compact objects could provide a natural explanation for dark matter, the invisible entity that makes up about 85% of the matter in the universe. However, PBHs remain elusive. Their theoretical existence is supported by a combination of cosmological models, but they have yet to be directly observed.

The Hawking radiation effect

One of the most interesting aspects of PBHs is their connection to Hawking radiation. According to quantum theory, black holes aren't completely "black"; they can emit radiation and slowly lose mass through a process first theorized by Stephen Hawking. This emission, known as Hawking radiation, occurs when virtual particle pairs pop in and out of the vacuum of space near a black hole's edge — its "event horizon." While these pairs normally annihilate each other, if one falls into the black hole, the other particle can escape as radiation. Over time, this leads to the black hole's gradual evaporation.

"For black holes with masses larger than a few times that of the Sun, Hawking radiation is nearly undetectable," Marco Calzà, a theoretical physicist at the University of Coimbra in Portugal and co-author of the study, told Live Science in an email. "But lighter black holes — such as PBHs — would be much hotter and emit far more radiation, potentially allowing us to detect this process. This radiation can include a variety of particles, from photons to electrons to neutrinos."

Related: Stephen Hawking's black hole radiation paradox could finally be solved — if black holes aren't what they seem

As the PBH evaporates, it loses mass, becoming hotter and emitting more radiation in a feedback loop. Eventually, the black hole should explode in a powerful burst of radiation — a process that existing gamma-ray and neutrino telescopes are actively searching for. Although no definitive PBH explosions have been detected yet, the new study suggests these rare events could be the key to unlocking new physics.

Probing the final moments of a PBH

In their recent study, published in the Journal of High Energy Physics, Calzà and study co-author João G. Rosa, also a theoretical physicist at the University of Coimbra, introduced innovative methods for studying PBHs during their final stages of evaporation. By analyzing the properties of their Hawking radiation, the duo developed tools to estimate a PBH's mass and spin.

"Tracking a PBH's mass and spin as it evaporates could provide valuable clues about its formation and evolution," Rosa told Live Science in an email.

Their work has significant implications for fundamental physics. In a previous study, Rosa, Calzà and collaborator John March-Russell of the University of Oxford explored how string theory — an attempt to unify the fundamental forces of nature within a single quantum theory — could affect an evaporating PBH. String theory predicts the existence of numerous low-mass particles called axions, which have no intrinsic spin. Their research suggested that axion emission could actually spin up a PBH, contrary to Hawking's predictions.

"A spinning PBH would provide compelling evidence for these exotic axions, potentially revolutionizing our understanding of particle physics," Calzà said.

Furthermore, the study suggests that analyzing the evolution of a PBH's mass and spin in its final moments could reveal the existence of other new particles. By tracking the spectrum of Hawking radiation, scientists might be able to distinguish between high-energy particle physics models. Neutrino telescopes, such as IceCube, could even help uncover these new particles as PBHs explode in space.

"If we can catch just one exploding PBH and measure its Hawking radiation, we could learn a tremendous amount about new particles and potentially guide the design of future particle accelerators," Rosa said.

Although no exploding PBH has been detected yet, the tools and methods developed by Calzà and Rosa's team could pave the way for future discoveries. The researchers emphasized that dedicated experiments may not be necessary, as several new gamma-ray and neutrino telescopes with unprecedented sensitivity are already in development.

"Upcoming telescopes could easily spot one if it explodes nearby. If we're lucky enough to detect an exploding PBH, it could change everything we know about the fundamental laws of nature," Rosa said.

Physicists at the world's largest atom smasher have observed two quarks in a state of quantum entanglement for the first time.

The observation, made at the Large Hadron Collider (LHC) at CERN, near Geneva, revealed a top quark — the heaviest fundamental particle — quantumly linked to its antimatter counterpart in the highest-energy detection of entanglement ever made. The researchers published their findings Sept. 18 in the journal Nature.

The ATLAS experiment (A Toroidal LHC Apparatus) is the largest detector at the LHC, and picks out the tiny subatomic particles created after beams of particles crash into each other at near light speeds.

"While particle physics is deeply rooted in quantum mechanics, the observation of quantum entanglement in a new particle system and at much higher energy than previously possible is remarkable," Andreas Hoecker, a spokesperson for the ATLAS experiment, said in an email statement. "It paves the way for new investigations into this fascinating phenomenon, opening up a rich menu of exploration as our data samples continue to grow."

Particles that are entangled have their properties connected to each other, so that a change to one instantaneously causes a change to another, even if they are separated by vast distances. Albert Einstein famously dismissed the idea as "spooky action at a distance," but later experiments proved that the bizarre, locality-breaking effect is indeed real. 

Related: Heaviest antimatter particle ever discovered could hold secrets to our universe's origins

But there are many aspects of entanglement that remain unexplored, and the one between quarks is one of them. This is because the subatomic particles cannot exist on their own, instead fusing together into various particle "recipes" called hadrons. Mixtures of three quarks are called baryons — such as the proton and the neutron — and combinations of quarks and their antimatter opposites are called mesons. 

When individual quarks are ripped from hadrons, the energy used to extract them makes them immediately unstable, and they decay into branching jets of smaller particles in a process known as hadronization. 

This means that to observe the entanglement of a top quark and an antiquark, scientists at the LHC's ATLAS and Compact Muon Solenoid (CMS) detectors had to pick out the distinct particles that they decayed into from billions of others. In particular, they looked for particles whose decay products were emitted at a distinct angle that occurs only between entangled particles. 

By measuring these angles and correcting for experimental effects that may have changed them, the team observed entanglement between top particles with a large enough statistical significance to be considered real. Now that the entangled particles have been spotted, the scientists say they want to study them to further probe unknown physics. 

"With measurements of entanglement and other quantum concepts in a new particle system and at an energy range beyond what was previously accessible, we can test the Standard Model of particle physics in new ways and look for signs of new physics that may lie beyond it," Patricia McBride, a spokesperson for the CMS experiment, said in the statement.

Scientists have spotted the heaviest antimatter nucleus ever detected lurking in a particle accelerator.

The antimatter heavyweight, called antihyperhydrogen-4, is made up of an antiproton, two antineutrons and one antihyperon (a baryon that contains a strange quark). Physicists found traces of this antimatter among particle tracks from 6 billion collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in New York.

By studying the strange particle, physicists hope to discover some key differences between matter and antimatter, which may help explain why our universe is now filled with matter given that antimatter was created in equal amounts at the beginning of time. The researchers published their findings Aug. 21 in the journal Nature.

"Our physics knowledge about matter and antimatter is that, except for having opposite electric charges, antimatter has the same properties as matter — same mass, same lifetime before decaying, and same interactions," study co-author Junlin Wu, a graduate student at the Joint Department for Nuclear Physics, Lanzhou University and Institute of Modern Physics, China said in a statement. "Why our universe is dominated by matter is still a question, and we don't know the full answer."

According to the standard model of cosmology, after the Big Bang the young cosmos was a roiling plasma broth of matter and antimatter particles that popped into existence and annihilated each other upon contact.

Related: 'Ghostly' neutrinos spotted inside the world's largest particle accelerator for the first time

Theory predicts that the matter and antimatter inside this plasma soup should have annihilated each other entirely. But scientists believe that some unknown imbalance enabled more matter than antimatter to be produced, saving the universe from self-destruction.

To investigate what could have caused this imbalance, the researchers behind the new study produced antimatter particles from a mini-Big Bang simulator. The RHIC collider hurls billions of heavy ions (atomic nuclei stripped of their electrons) at each other, creating a plasma soup from which the primordial elements of our cosmos briefly emerge, combine and then decay.

To fish out new particles from the plasma sea, the physicists searched for the telltale tracks made as the ions decay, or transform into other particles. By retracing the trajectories of these particles from billions of collision events, the researchers found roughly 16 antihyperhydrogen-4 nuclei.

Both hyperhydrogen-4 and its antimatter counterpart antihyperhydrogen-4 seem to wink out of existence very quickly, the researchers found. But the physicists didn't find a significant difference between their lifetimes — indicating that our best models describing the two types of particles are correct.

"If we were to see a violation of [this particular] symmetry, basically we'd have to throw a lot of what we know about physics out the window," study co-author Emilie Duckworth, a doctoral student at Kent State University, said in the statement.

The scientists' next step will be to compare the masses of the antiparticles and their particle opposites, which they hope could reveal some clues as to how our matter-heavy universe came to be.

Although our universe may seem stable, having existed for a whopping 13.7 billion years, several experiments suggest that it is at risk — walking on the edge of a very dangerous cliff. And it's all down to the instability of a single fundamental particle: the Higgs boson.

In new research by me and my colleagues, just accepted for publication in Physical Letters B, we show that some models of the early universe, those which involve objects called light primordial black holes, are unlikely to be right because they would have triggered the Higgs boson to end the cosmos by now.

The Higgs boson is responsible for the mass and interactions of all the particles we know of. That's because particle masses are a consequence of elementary particles interacting with a field, dubbed the Higgs field. Because the Higgs boson exists, we know that the field exists.

You can think of this field as a perfectly still water bath that we soak in. It has identical properties across the entire universe. This means we observe the same masses and interactions throughout the cosmos. This uniformity has allowed us to observe and describe the same physics over several millennia (astronomers typically look backwards in time).

RELATED: Antimatter detected on International Space Station could reveal new physics

But the Higgs field isn't likely to be in the lowest possible energy state it could be in. That means it could theoretically change its state, dropping to a lower energy state in a certain location. If that happened, however, it would alter the laws of physics dramatically.

Such a change would represent what physicists call a phase transition. This is what happens when water turns into vapour, forming bubbles in the process. A phase transition in the Higgs field would similarly create low-energy bubbles of space with completely different physics in them.

In such a bubble, the mass of electrons would suddenly change, and so would its interactions with other particles. Protons and neutrons — which make up the atomic nucleus and are made of quarks — would suddenly dislocate. Essentially, anybody experiencing such a change would likely no longer be able to report it.

Constant risk

Recent measurements of particle masses from the Large Hadron Collider (LHC) at Cern suggest that such an event might be possible. But don't panic; this may only occur in a few thousand billion billion years after we retire. For this reason, in the corridors of particle physics departments, it is usually said that the universe is not unstable but rather "meta-stable", because the world's end will not happen anytime soon.

To form a bubble, the Higgs field needs a good reason. Due to quantum mechanics, the theory which governs the microcosmos of atoms and particles, the energy of the Higgs is always fluctuating. And it is statistically possible (although unlikely, which is why it takes so much time) that the Higgs forms a bubble from time to time.

However, the story is different in the presence of external energy sources like strong gravitational fields or hot plasma (a form of matter made up of charged particles): the field can borrow this energy to form bubbles more easily.

Therefore, although there is no reason to expect that the Higgs field forms numerous bubbles today, a big question in the context of cosmology is whether the extreme environments shortly after the Big Bang could have triggered such bubbling.

However, when the universe was very hot, although energy was available to help form Higgs bubbles, thermal effects also stabilised the Higgs by modifying its quantum properties. Therefore, this heat could not trigger the end of the universe, which is probably why we are still here.

Primordial black holes

In our new research, we showed there is one source of heat, however, that would constantly cause such bubbling (without the stabilising thermal effects seen in the early days after the Big Bang). That's primordial black holes, a type of black hole which emerged in the early universe from the collapse of overly dense regions of spacetime. Unlike normal black holes, which form when stars collapse, primordial ones could be tiny — as light as a gram.

the universe blew up hugely in size after the Big Bang.

However, proving this existence comes with a big caveat: Stephen Hawking demonstrated in the 1970s that, because of quantum mechanics, black holes evaporate slowly by emitting radiation through their event horizon (a point at which not even light can escape).

Hawking showed that black holes behave like heat sources in the universe, with a temperature inversely proportional to their mass. This means that light black holes are much hotter and evaporate more quickly than massive ones. In particular, if primordial black holes lighter than a few thousands billion grams formed in the early universe (10 billion times smaller than the Moon's mass), as many models suggest, they would have evaporated by now.

In the presence of the Higgs field, such objects would behave like impurities in a fizzy drink — helping the liquid form gas bubbles by contributing to its energy via the effect of gravity (due to the mass of the black hole) and the ambient temperature (due to its Hawking radiation).

When primordial black holes evaporate, they heat the universe locally. They would evolve in the middle of hot spots that could be much hotter than the surrounding universe, but still colder than their typical Hawking temperature. What we showed, using a combination of analytical calculations and numerical simulations, is that, because of the existence of these hot spots, they would constantly cause the Higgs field to bubble.

But we are still here. This means that such objects are highly unlikely to ever have existed. In fact, we should rule out all of the cosmological scenarios predicting their existence.

That's of course unless we discover some evidence of their past existence in ancient radiation or gravitational waves. If we do, that may be even more exciting. That would indicate that there's something we don't know about the Higgs; something that protects it from bubbling in the presence of evaporating primordial black holes. This may, in fact, be brand new particles or forces.

Either way, it is clear that we still have a lot to discover about the universe on the smallest and biggest scales.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Since the discovery of the proton and the electron in the 20th century, a mystery persists at the core of the atom: Despite belonging to completely different particle families and being radically different in size, the charges of these two particles completely balance each other out — enabling a universe where gravity dominates. But why?

To explore the clues, Live Science sat down with Frank Close, an author and emeritus professor of particle physics at Oxford University, to discuss his new book "Charge" (Oxford University Press, 2024). In it, Close traces out the conundrum through a concise history of particle physics, including the strong, weak and electromagnetic forces that operate over short distances, the discovery of the Higgs boson, and the hints of a yet-to-be-discovered grand unified theory.

Ben Turner: Your book provides a fascinating summary of the current state of particle physics, and the remaining mysteries in it — most importantly the electrical neutrality of matter. What motivated you to write it? And why now?

Frank Close: It's been a puzzle that's been with me for a long time.

Why is it that, every breath you take, your hair doesn't stand on end, given that you're breathing in a billion billion billion atoms of oxygen and nitrogen in the air, each of which has got all this electricity in it? The negative charge on the electrons of all these atoms is triflingly small, but there are so many of them together that a single breath is like breathing in roughly 15,000 coulombs — that's enough to spark 1,000 bolts of lightning.

The answer is that the atom is electrically neutral. The negative charge of the electron outside is precisely balanced by the positive charge of the nucleus in the middle.

It's one of the unanswered questions in science, and it strikes me, perhaps, as the most immediate one. You don't have to have a huge theoretical background to notice it.

BT: "Why" is always one of the more fraught questions to ask in physics, but I'll do it. Why might charges be perfectly balanced?

FC: It's a solid question you might ask a really smart PhD student doing their exam. You know that you don't know the answer and they don't either, but it might terrify them for a moment.

It's the puzzle at the heart of the book. If we had this discussion a century ago, the only particles that were known were the negatively charged electrons and the positively charged protons. I would probably have told you that I don't know quite what charge is, but it is something that you can take away or add and that in the case of the electron it's had it removed and the proton has had it added.

The problem is that we now know much more. In the 1960s we discovered that the proton has a structure, it's made up of things called quarks. Up quarks have two thirds of positive charge, and down quarks negative charge of one third. The simplest way to make a proton is out of three quarks — two up quarks and one down. If you want to make a [neutrally charged] neutron you use two down quarks and one up.

So the equality between the plus one charge of the proton and the minus one charge of the electron is a remarkable conspiracy. Is that a coincidence? I don't believe in coincidences. But it shows the conundrum is not simply a matter of painting charge onto the proton and removing it from the electron.

BT: I'm asking why again, but why do quarks clump in threes? What causes it? And what's its relationship to electrical charge?

FC: Quarks carry another sort of charge, which we call color. This color charge occurs in three different varieties: red, blue and green. They're not real colors, but there are three of them and they follow the same rules as electrostatic charges — with like charges repelling and unlike ones attracting. So it's this 'threeness' of the color charges that help them clump powerfully to form the proton. The fact that each of them, on average, carries one-third electrical charge is what makes the conspiracy work.

There's something tantalizing going on. Color charges follow the same rules of attraction and repulsion as electric charges do. You feel that, on some level, these things are profoundly related, even though you don't quite know how. You feel like you're on the edge of something. If only we could just see a little bit more clearly, it would all fall into place.

BT: And that's possibly that they're all connected, or branchings of the same thing at different energies, a so-called grand unified theory of everything?

FC: They must be fossil relics of something much more significant, powerful and unified, from which the idea of a unified theory begins to emerge. We've clearly stumbled upon something here: the 'threeness' of these [short range] forces as we know them in the cold universe today.

We know from very precise experiments over the last 30 or 40 years that, as you go to higher energies at the Large Hadron Collider, that the relative strength of these [fundamental] forces does change slightly. If you extrapolate that, it means that at some unimaginably high energy these three forces [the strong force via color charge, the electromagnetic force via electrostatic charge, and the weak force via the W and Z bosons] have roughly the same strength.

BT: You used the word tantalizing to describe these hints. If that's the case, how close might we be to finding a grand unified theory? When did physicists begin to chase this idea?

FC: Mathematically, there's no difficulty in creating grand unified theories.The frustration of being a theoretical physicist is that experiment keeps showing you that you're wrong.

For 2,000 years we've been searching for what matter is made of, and we've found deeper layers of structure by going to higher and higher energies. Around 1970, the idea emerged that at extremely high energies things might be simple and that the early universe was also very hot.

At CERN, we started doing experiments that initially annihilated electrons and their antimatter counterparts, positrons, so that their light-speed kinetic energy was converted instantly into a flash of pure energy. In a very small region, for a brief moment, you've got the sort of energy density that would have been present in the universe about a billionth of a second after the Big Bang.

Observing what emerged from that 'mini bang', we began to understand not so much what matter is made of today, but how matter came to be in the first place. That began a psychological transition from particle physics to experimental cosmology — it was no longer just stamp collecting, we were replicating the aftermath of creation.

BT: At the present time, particle physics is slowly moving into higher energies and cosmology is getting a lot better at looking back into the hotter, earlier years of the universe — peering into the primordial particle collider. What are the big open questions that remain?

FC: I think probably the first one is to go back 10 years to the discovery of the Higgs boson. What does its discovery actually mean and where should we go from here?

There's something very profound about the Higgs boson. It confirms that, if you took everything away — all the particles, all the sources of charge and gravity and everything else in the universe — there'd still be something left. Some weird essence that we call the Higgs field. What it is, we have no clue, but it's there.

We and everything are immersed in the Higgs field, and we need it just like a fish needs water. We know it's there because (much like an electromagnetic field does with photons) if you add a bit of energy to the Higgs field it will bubble up as Higgs bosons. This means that, in the heat of the Big Bang, Higgs bosons were everywhere.

It's as if a very clever goldfish had discovered a molecule of H2O. It now knows it's immersed in water, but what it really wants to know is what water is like: "What's water? What's ice? What's steam?"

In a similar way, we want to know if the Higgs field has different phases and how it operates. At the moment we can produce one Higgs boson periodically, but could we produce two at the same time in a single collision and see how they interact? That's the immediate goal at CERN, and in the next decade or so I'm sure that answer will begin to emerge.

Editor's note: This interview has been condensed and edited for clarity.

Antimatter particles detected on the International Space Station (ISS) may be evidence for unknown physics, new research suggests.

The particles, antimatter versions of helium nuclei, may have been produced by cosmic fireballs, — and physicists can't explain how those fireballs formed using the Standard Model, the theory which describes the zoo of subatomic particles.

All elementary particles have corresponding antiparticles with opposite electric charges, which annihilate each other on contact. Theory suggests half the matter in the universe should have been antimatter, which would mean the universe would have destroyed itself soon after the Big Bang.

Yet antimatter in the universe is scarce and fleeting. While particle accelerators can generate antiparticles through collisions of protons and electrons, and special detectors observe antiparticles from high-energy space collisions, such as those from supernova explosions, these usually yield only single antiparticles like positrons (antielectrons) and antiprotons.

Related: Mysterious 'unparticles' may be pushing the universe apart, new theoretical study suggests

However, about eight years ago, the Alpha Magnetic Spectrometer (AMS-02) aboard the ISS detected around 10 antihelium nuclei. These nuclei consisted of two antiprotons and either one or two antineutrons (for antihelium-3 and antihelium-4 versions, respectively). If confirmed through further analysis, the discovery would challenge the Standard Model of particle physics

According to the Standard Model, making antihelium-4 requires that at least three or four antiprotons and antineutrons be near enough to each other and be moving slowly enough to stick together, study co-author Michael A. Fedderke, a postdoctoral researcher at the Perimeter Institute for Theoretical Physics in Canada, told Live Science in an email. Based on these requirements, one antihelium-4 would be produced for every 10,000 antihelium-3.

"The really interesting thing about the AMS-02 candidate events is that the data seem to be consistent with about one antihelium-4 event for every two to three antihelium-3 events," Fedderke said., That's far above what the Standard Model predicts.

In the new study, published June 21 in the journal Physical Review D, the team tried to explain this discrepancy using hypothetical objects called fireballs. These fireballs could result from currently unobserved phenomena, such as the collision of extremely dense clumps of dark matter — a mysterious substance that makes up about 80% of the universe's matter but does not interact with light so can't be directly observed.

"A fireball is a dense, energetic region of space containing large numbers of antiparticles," study co-author Anubhav Mathur, a doctoral student at Johns Hopkins University, told Live Science. "Once formed, it expands at close to the speed of light, releasing antiprotons, antineutrons, and antihelium into the surrounding environment. The antinuclei subsequently travel outward, and some of them reach the Earth where they can be detected."

The researchers modeled fireballs of various sizes and behavior. They found that if the fireballs were large, "composite" objects made of many dark matter particles, then the amount of antihelium nuclei they produced matches well with the preliminary results detected aboard the ISS, Fedderke said.

While these findings are promising, they are still preliminary and require further validation. Follow-up studies will help determine if their hypothesis is correct.

"On the observational side, we're looking forward to AMS-02 completing their analysis of their candidate antihelium events, as well as to them taking more data in future which may shed further light on this puzzle," Fedderke said.

The General AntiParticle Spectrometer (GAPS) project, which will launch a balloon over Antarctica later this year to detect antimatter cosmic rays, including antihelium nuclei, could also shed light on the matter, Fedderke added.

The Google Doodle released today (July 11) is a tribute to César Lattes, a pioneering Brazilian physicist who would have celebrated his 100th birthday today.

Born to Italian immigrants in 1924 in Curitiba, Brazil, Lattes is widely credited with the discovery of the subatomic particle known as the pion, or pi meson — which is produced in the shockwaves from star explosions and rains down on Earth in the form of cosmic rays.

"Happy birthday César Lattes, thank you for paving the way for experimental physics in Latin America and around the world!" Google representatives wrote in a blog post honoring Lattes.

Lattes’ induction to advanced experimental physics began in 1934 at the recently founded University of São Paulo, where he was the only student enrolled in a course run by the then-famous Italian experimental physicist Giuseppe Occhialini. Occhialini taught Lattes to develop photographic film exposed to radiation.

In 1944 Occhialini went to the University of Bristol to work with the English physicist Cecil Frank Powell on the development of nuclear emulsion plates that could detect traces of highly energetic particles. Consisting of photosensitive silver salt suspended inside gelatin, the plates, upon development, clearly showed the tracks of charged particles that had passed through them.

Related: Who was J. Robert Oppenheimer? Biographer Kai Bird delves into the physicist's fascinating life and legacy

After obtaining one of the plates sent by Occhialini, Lattes realized that it was missing a key ingredient: boron.

"Lattes correctly suspected that adding boron to photographic plates would give him a clearer image of particles breaking down," according to the Google blog post. "It worked so well, he could see each proton."

In April 1947, at 23 years old, Lattes climbed 17,060 feet (5,200 meters) to a weather station atop Bolivia’s Mount Chacaltaya with two of his photographic plates. There, clear as day inside the tracks preserved in the plates, Lattes discovered a particle that had been predicted but never seen — the pion.

Consisting of a quark and an antiquark glued together by the strong nuclear force, the pion (or pi meson) can come in three distinct types. The discovery earned Powell — but neither Lattes nor Occhialini — the 1950 Nobel Prize.

In fact, Lattes was nominated seven times for the Nobel Prize — despite never having earned a doctorate — but never won.

Lattes later returned to Brazil to teach, and died in 2005 from a heart attack in the suburbs near his São Paulo campus. Despite his rockstar status across Brazil and Latin America, Lattes was characteristically nonchalant about his fame.

"I was dragged along by history, and I did my best," Lattes told the Brazilian science and culture magazine Superinteressante in 1997. "If I had to choose, today I would be a veterinarian."

Physicists have taken one small-but-consequential step toward measuring the mass of an elusive "ghost particle" called a neutrino — an achievement that could poke a significant hole in the Standard Model of particle physics. 

A precise measurement of the neutrino’s mass would enable physicists to delve deeper into the evolution of our universe and potentially find new, undiscovered physics lurking beyond the Standard Model.But measuring this mass is not easy. The particles' spooky nickname is well-earned: they lack an electrical charge and have almost no mass, meaning they fly straight through regular matter at close to the speed of light. 

So, to approach the most precise upper limit on the neutrino's mass yet, the researchers had to devise an experiment with unprecedented sensitivity. They reported their findings in a paper published April 19 in the journal Nature Physics.

"With an Airbus A-380 with a maximum load, you could use this sensitivity to determine whether a single drop of water has landed on it," Christoph Schweiger, a doctoral student at the Max Planck Institute for Nuclear Physics in Germany and the study's first author, said in a statement.

Every second, about 100 billion neutrinos pass through each square centimeter of your body. The tiny particles are everywhere — produced in the nuclear fire of stars, in enormous supernova explosions, by cosmic rays and radioactive decay, and in particle accelerators and nuclear reactors on Earth.

In fact, neutrinos, which were first discovered zipping out of a nuclear reactor in 1956, are second only to photons (light particles) as the most abundant subatomic particles in the universe.

Related: Ghostly neutrino particles are blasting out of a nearby galaxy, and scientists aren't sure why

In the past, physicists assumed that neutrinos (much like photons) had no rest mass — a fact that would make their existence compatible with the Standard Model of particle physics. But this assumption was challenged by the discovery of neutrinos streaming out of the sun, which can switch at random between the three "flavors" of neutrinos — electron, muon and tau neutrinos, which refer to the different particles the neutrinos interact with.

Such a transformation should be possible only if neutrinos have some mass, leading physicists to design complex experiments to gauge it.

A ghost on the scales

Technically, the weirdness of the quantum mechanical mixing among the three neutrino flavors means that none of them have a well-defined mass. Instead, they are combinations of three different "mass states." This means that physicists don't look for an exact reading of a neutrino's mass but for an upper limit of how big this mass could be.

Nearly 99% of the mass of any object, including our own bodies, comes from the binding energy holding elementary particles together inside atoms. The remaining 1% of the mass, however, is intrinsic to those particles.

To find this intrinsic mass, physicists look for something called the Q value — the difference between the sum of the masses of the initial reactants and the sum of the masses of the final products. With this value in hand, further measurements can extract the intrinsic mass from the overall mass of the atom.

One neutrino-mass-measuring experiment, the Karlsruhe Tritium Neutrino experiment (KATRIN) in Germany, found a precise estimate for the neutrino's mass by measuring the energy — and, therefore, by Einstein's E = mc2, the mass difference — as superheavy hydrogen decayed into helium, emitting an electron and a neutrino in the process.

The KATRIN experiment’s best result found an upper neutrino mass limit of 0.8 electronvolts, making it roughly 500,000 times smaller than the mass of an electron.

This measurement can also be made in reverse by observing an electron being captured by the artificial isotope holmium-163, transforming it into dysprosium-163 and releasing a neutrino. But to do so, the isotope must be surrounded by gold atoms.

"However, these gold atoms could have an influence on holmium-163," Schweiger said. "It is therefore important to measure the value of Q as precisely as possible using an alternative method" and to compare it with the mass value determined through the KATRIN method in order to detect possible sources of error.

To get closer to a separate measurement of the neutrino's elusive mass, the researchers designed an experiment known as a Penantrap — a combination of five "Penning traps," which can capture atoms inside a combination of an electric field and a magnetic field, in which they swing in an intricate motion known as a "circle dance."

By placing charged holmium-163 and dysprosium-163 ions inside the Penning traps and measuring the subtle differences in their swing rates, the physicists gauged the difference in their energies caused by the additional neutrino.

The result was a measurement of a Q value that the researchers say is 50 times more precise than the result of any previous experiment. With this result in hand, an even better upper limit for the neutrino's mass is one tiny — but consequential — step closer.

Peter Higgs, the theoretical physicist who predicted the existence of the Higgs boson, has died at the age of 94.

The University of Edinburgh confirmed the Nobel Prize-winning physicist's April 8 death following a short illness in a statement released Tuesday (April 9). Higgs was a professor emeritus at the university, where he worked beginning in 1960 until his retirement in 1996.

Higgs is best known for his pioneering work in predicting the masses of subatomic particles. He was awarded the Nobel Prize in physics in 2013 alongside Belgian physicist François Englert for their 1960s work predicting the existence of a particle that, by interacting with other particles, gives them mass. This particle became known as the Higgs boson. Following a 50-year search, the Higgs boson was finally detected in 2012. It was discovered using the Large Hadron Collider, the world's largest particle accelerator, which sits on the border of France and Switzerland.

Related: What is the Higgs boson?

Higgs was born in Newcastle upon Tyne, England, on May 29, 1929. He earned his doctoral degree from King's College London in 1954. A bedeviling question in physics at the time was how elementary particles such as the electron and quark have mass. In a 1964 paper, Higgs posited that these particles gain their mass through an interaction with a field, now known as a Higgs field, and that this Higgs field should give rise to a detectable particle, the Higgs boson.

Actually detecting the Higgs boson was a massive challenge, however, because these particles are vanishingly rare and decay within fractions of a second. It took decades of effort to finally detect the Higgs boson, finally proving Higgs' theory correct. The particle is 130 times more massive than a proton, but it has no charge and no spin (or angular momentum). Without it, no other particle would have mass.

Higgs reacted to the news of the Higgs boson discovery by welling up — an emotional reaction he later explained to science writer Ian Sample. "I was knocked over by the wave of the reaction of the audience," Sample quoted Higgs as saying in a 2013 article. "Up until then I was holding back emotionally," Higgs added, "but when the audience reacted, I couldn't hold back any more."

The ever-accelerating expansion of the universe may be driven by a mysterious form of matter called "unparticles," which do not obey the Standard Model of particle physics, a new theoretical paper suggests.

Scientists widely acknowledge that the universe is expanding, though the cause of that expansion remains elusive. One of the most popular proposed explanations is a mysterious entity called dark energy in the form of a cosmological constant, which leads to expansion at a rate independent of the age of the universe and the temperature of matter and radiation. However, recent astronomical observations challenge this hypothesis, prompting physicists to explore alternatives to what dark energy could be.

Now, in a new paper, researchers analyzed the idea that dark energy is instead made of a theoretical form of matter called unparticles. They found that this theory aligns better with observations than the prevalent standard cosmological model, which assumes a cosmological constant.

"Observationally, discrepancies arise in the values of the universe's expansion rate and the growth of large-scale structures [galaxies and galactic clusters] between measurements," study co-author Utkarsh Kumar, a cosmologist at Ariel University, told Live Science in an email. "Various observations, including Cosmic Microwave Background measurements, dimming of supernovae and many others, contribute to this tension."

Related: There may be a 'dark mirror' universe within ours where atoms failed to form, new study suggests

Quantities such as the Hubble constant, which determines the rate of expansion, and the so-called S8, which contains information about the formation of large-scale structures, are not measured directly. Instead, they are calculated from observations of the cosmic microwave background (leftover radiation from the Big Bang) and distant stars and galaxies, using mathematical  theories. However, different theories yield different values of these parameters from the same data, posing a huge tension in cosmology.

To address this problem, the authors of the new study, published in December 2023 in the Journal of Cosmology and Astroparticle Physics, suggest that the expansion of the universe is driven not by a cosmological constant but by unparticles, which had previously been considered in the context of particle physics.

"The idea of unparticles was introduced by [theoretical physicist Howard] Georgi over a decade ago," lead study author Ido Ben-Dayan, also of Ariel University, told Live Science in an email. "In fundamental physics, we usually discuss fields, like the electric field, where particles are excitations of that field. In the electric field case, these are the photons," or packets of light. In almost all cases, Ben-Dayan added, particles are excitations with a well-defined mass and momentum.

However, "unparticles are the result of a set of fields that their excitations do not have a well-defined momentum and mass," Ben-Dayan said. "Thus, at the macroscopic level, they behave as a fluid. A special outcome of this property is that their equation of state, describing the ratio between the pressure they exert and their energy density, depends on temperature."

This equation of state strongly resembles the equation for the cosmological constant. Moreover, the very weak interaction of unparticles with “regular” matter, which is predicted by all theoretical models of the substance, makes it an excellent candidate for dark energy.

Unparticles untangled

In their work, Ben-Dayan and Kumar used the unparticle hypothesis instead of the cosmological constant and combined it with observational data collected from many experiments. They found that, unlike the values calculated using the standard cosmological model, the values of the Hubble constant and the S8 parameter deduced from these experiments were consistent with each other when they used the unparticle theory.

"Moreover, their model reduced the discrepancy between the measurements of the Hubble constant and S8, thus restoring the agreement between the different measurements, Kumar said. 

For now, there is no empirical evidence to back up this theory.  However, the authors are confident that, in the next decade or so, the accuracy of astronomical measurements will improve enough to determine whether the unparticle theory is correct.

"Our model is tested by constantly improving cosmological observations," Ben-Dayan said. "If it is correct, future Cosmic Microwave Background experiments should [confirm it]."

Experiments to measure the nature of dark energy are currently being developed, but will require telescopes to "probe further back in time" than they currently do, Ben-Dayan added.

Moreover, the physicists plan to increase the accuracy of their calculations and look for possible manifestations of unparticles in more familiar experiments with elementary particles in accelerators, which could be affected by the presence of unparticles.

"We plan to consider interactions between unparticles and the Standard Model of elementary particles," Kumar said. "This can further test our model. We will further study some extensions of our model and their cosmological consequences."

Researchers at the world's biggest particle accelerator have put forward proposals to build a new, even larger atom smasher.

The $17 billion Future Circular Collider (FCC) would be 57 miles (91 kilometers) long,  dwarfing its predecessor, the 16.5-mile-long (27 kilometers) Large Hadron Collider (LHC), located at the European Organization for Nuclear Research (CERN) near Geneva.

Physicists want to use the FCC's increased size and power to probe fringes of the Standard Model of particle physics, the current best theory that describes how the smallest components of the universe behave. By smashing particles at even higher energies (100 tera electron volts, compared with the LHC's 14), the researchers hope to find unknown particles and forces; discover why matter outweighs antimatter; and probe the nature of dark matter and dark energy, two invisible entities believed to make up 95 percent of the universe.

Related: Our universe is merging with 'baby universes,' causing it to expand, new theoretical study suggests

"The FCC will not only be a wonderful instrument to improve our understanding of the fundamental laws of physics and nature," Fabiola Gianotti, CERN's director-general, said at a news conference Monday (Feb. 5). "It will also be a driver of innovation, because we will need new advanced technologies, from cryogenics to superconducting magnets, vacuum technologies, detectors, instrumentation — technologies with a potentially huge impact on our society and huge socioeconomic benefits."

Atom smashers like the LHC collide protons together at near light speed while looking for rare decay products that could be clues to new particles or forces. This helps physicists scrutinize their best understanding of the universe's most fundamental building blocks and how they interact, described by the Standard Model of physics.

Though the Standard Model has enabled scientists to make remarkable predictions — such as the existence of the Higgs boson, discovered by the LHC in 2012 — physicists are far from satisfied with it and are constantly looking for new physics that might break it.

This is because the model, despite being our most comprehensive one yet, includes enormous gaps, making it totally incapable of explaining where the force of gravity comes from, what dark matter is made of, or why there is so much more matter than antimatter in the universe.

To unlock these new frontiers, physicists at CERN will use the sevenfold increase in beam energy of the FCC to accelerate particles to even higher speeds.

But the detector, despite having taken a promising step forward, is far from built. The proposals put forward by CERN are part of an interim report on a feasibility study set to be finished next year. Once it's complete and if the detector plans go ahead, CERN — which is run by 18 European Union member states, as well as Switzerland, Norway, Serbia, Israel and the U.K. — will likely look for additional funding from nonmember states for the project.

Despite the high hopes for what the new collider could find, some scientists remain skeptical that the expensive machine will encounter new physics.

"The FCC would be more expensive than both the LHC and LIGO [Laser Interferometer Gravitational-Wave Observatory] combined and it has less discovery potential," Sabine Hossenfelder, a theoretical physicist at the Munich Center for Mathematical Philosophy, wrote in a 2019 post on the platform X, formerly Twitter. "It would, at the present state of knowledge and technology, not give a good return on investment. There are presently better avenues to pursue than high energy physics."

Member states will meet in 2028 to decide whether to greenlight the project. Then, the first phase of the machine — which would collide electrons with their animatter counterparts, positrons — would come online in 2045. Finally, in the 2070s, the FCC would begin slamming protons into one another.

Scientists recently fired up the world's smallest particle accelerator for the first time. The tiny technological triumph, which is around the size of a small coin, could open the door to a wide range of applications, including using the teensy particle accelerators inside human patients.

The new machine, known as a nanophotonic electron accelerator (NEA), consists of a small microchip that houses an even smaller vacuum tube made up of thousands of individual "pillars." Researchers can accelerate electrons by firing mini laser beams at these pillars.

The main acceleration tube is approximately 0.02 inch (0.5 millimeter) long, which is 54 million times shorter than the 16.8-mile-long (27 kilometers) ring that makes up CERN's Large Hadron Collider (LHC) in Switzerland — the world's largest and most powerful particle accelerator, which has discovered a range of new particles including the Higgs boson (or God particle), ghostly neutrinos, the charm meson and the mysterious X particle. 

The inside of the tiny tunnel is only around 225 nanometers wide. For context, human hairs are 80,000 to 100,000 nanometers thick, according to the National Nanotechnology Institute.

Related: Why a physicist wants to build a particle collider on the moon

In a new study, published Oct. 18 in the journal Nature, researchers from the Friedrich–Alexander University of Erlangen–Nuremberg (FAU) in Germany used the tiny contraption to accelerate electrons from an energy value of 28.4 kiloelectron volts to 40.7 keV, which is an increase of around 43%.

It is the first time that a nanophotonic electron accelerator, which was first proposed in 2015, has been successfully fired, the researchers wrote in a statement. (Researchers from Stanford University have already repeated the feat with their mini accelerator, but their results are still under review).

"For the first time, we really can speak about a particle accelerator on a [micro]chip," study co-author Roy Shiloh, a physicist at FAU, said in the statement.

The LHC uses more than 9,000 magnets to create a magnetic field that accelerates particles to around 99.9% of the speed of light. The NEA also creates a magnetic field, but it works by firing light beams at the pillars in the vacuum tube; this amplifies the energy in just the right way, but the resulting energy field is much weaker.

Related: Black holes could become massive particle accelerators

The electrons accelerated by the NEA only have around a millionth of the energy that particles accelerated by the LHC have. However, the researchers believe they can improve the NEA's design by using alternative materials or stacking multiple tubes next to one another, which could further accelerate the particles. Still, they will never reach anywhere near the same energy levels as the big colliders.

That may be no bad thing, given the main goal of creating these accelerators is to utilize the energy given off by the accelerated electrons in targeted medical treatments that can replace more damaging forms of radiotherapy, which is used to kill cancer cells.

"The dream application would be to place a particle accelerator on an endoscope in order to be able to administer radiotherapy directly at the affected area within the body," study lead author Tomáš Chlouba, a physicist at FAU, wrote in the statement. But this is still a long way off, he added.

The strong force or strong nuclear force is one of the four fundamental forces of nature, along with gravity, electromagnetism and the weak force. As the name suggests, the strong force is the strongest force of the four. It binds fundamental particles of matter, known as quarks, to form larger particles.

But in August 2023, a new discovery called the strong force into question. By smashing an isotope of oxygen with a beam of fluorine atoms, physicists have finally created oxygen-28 — a rare form of oxygen long-predicted to be ultrastable. The only problem is that it isn’t. Oxygen-28 decays within a zeptosecond, or a trillionth of a billionth of a second. This has left physicists baffled, and the Standard Model (the five-decade-old theory of how particles should behave) open to doubt.

The strong force in the Standard Model

The reigning theory of particle physics is the Standard Model, which describes the basic building blocks of matter and how they interact. The theory was developed in the early 1970s and, over time and through many experiments, has become established as a well-tested physics theory, according to CERN, the European Organization for Nuclear Research. 

Under the Standard Model, one of the smallest, most fundamental elementary particles, or those that cannot be split up into smaller parts, is the quark. These particles are the building blocks of a class of massive particles known as hadrons, which include protons and neutrons. Scientists haven't seen any indication that there is anything smaller than a quark, but they're still looking.

The strong force was first proposed to explain why atomic nuclei do not fly apart. It seemed that they would do so due to the repulsive electromagnetic force between the positively charged protons located in the nucleus. Physicists later found that the strong force not only holds nuclei together but is also responsible for binding the quarks that make up hadrons. 

"Strong force interactions are important in … holding hadrons together," according to "The Four Forces," physics course material from Duke University. "The fundamental strong interaction holds the constituent quarks of a hadron together, and the residual force holds hadrons together with each other, such as the proton and neutrons in a nucleus."

Quarks and hadrons

Quarks were theorized in 1964, independently by physicists Murray Gell-Mann and George Zweig, and physicist first observed the particles at the Stanford Linear Accelerator National Laboratory in 1968. According to The Nobel Foundation, Gell-Mann chose the name, which is said to have come from a poem in the novel "Finnegans Wake," by James Joyce: 

"Three quarks for Muster Mark! Sure he has not got much of a bark, And sure any he has it's all beside the mark."

"Experiments at particle accelerators in the '50s and '60s showed that protons and neutrons are merely representatives of a large family of particles now called hadrons. More than 100 [now more than 200] hadrons, sometimes called the 'hadronic zoo,' have thus far been detected," according to the book "Particles and Nuclei: An Introduction to the Physical Concepts" (Springer, 2008). 

Scientists have detailed the ways quarks constitute these hadron particles. "There are two types of hadrons: baryons and mesons," Lena Hansen wrote in "The Color Force," a paper published online by Duke University. "Every baryon is made up of three quarks, and every meson is made of a quark and an antiquark," where an antiquark is the antimatter counterpart of a quark having the opposite electric charge. Baryons are the class of particles that comprises protons and neutrons. Mesons are short-lived particles produced in large particle accelerators and in interactions with high-energy cosmic rays. 

Quark flavors and colors

Quarks come in six varieties that physicists call "flavors." In order of increasing mass, they are referred to as up, down, strange, charm, bottom and top. The up and down quarks are stable and make up protons and neutrons, Live Science previously reported. For example, the proton is composed of two up quarks and a down quark, and is denoted as (uud).

The other, more massive flavors are produced only in high-energy interactions and decay extremely quickly. They are typically observed in mesons, which can contain different combinations of flavors as quark-antiquark pairs. The last of these, the top quark, was theorized in 1973 by Makoto Kobayashi and Toshihide Maskawa, but it was not observed until 1995, in an accelerator experiment at the Fermi National Accelerator Laboratory (Fermilab). Kobayashi and Maskawa were awarded the 2008 Nobel Prize in physics for their prediction. 

Quarks have another property, also with six manifestations. This property was labeled "color," but it should not be confused with the common understanding of color. The six manifestations are termed red, blue, green, antired, antiblue and antigreen. The anticolors belong, appropriately, to the antiquarks. The color properties explain how the quarks can obey the Pauli exclusion principle, which states that no two identical objects can occupy the same quantum state, Hansen said. That is, quarks making up the same hadron must have different colors. Thus, all three quarks in a baryon are of different colors, and a meson must contain a colored quark and an antiquark of the corresponding anticolor.

Gluons and the strong force

Particles of matter transfer energy by exchanging force-carrying particles, known as bosons, with one another. The strong force is carried by a type of boson called a "gluon," so named because these particles function as the "glue" that holds the nucleus and its constituent baryons together. A strange thing happens in the attraction between two quarks: The strong force does not decrease with the distance between the two particles, as the electromagnetic force does; in fact, it increases, more akin to the stretching of a mechanical spring. 

As with a mechanical spring, there is a limit to the distance that two quarks can be separated from each other, which is about the diameter of a proton. When this limit is reached, the tremendous energy required to achieve the separation is suddenly converted to mass in the form of a quark-antiquark pair. This energy-to-mass conversion happens in accordance with Einstein's famous equation E = mc2 — or, in this case, m = E/c2 — where E is energy, m is mass, and c is the speed of light. Because this conversion occurs every time we try to separate quarks from each other, free quarks have not been observed and physicists don’t believe they exist as individual particles. In his book "Gauge Theories of the Strong, Weak and Electromagnetic Interactions: Second Edition" (Princeton University Press, 2013), Chris Quigg of Fermilab states, "The definitive observation of free quarks would be revolutionary."

Residual strong force

When three quarks are bound together in a proton or a neutron, the strong force produced by the gluons is mostly neutralized, because nearly all of it goes toward binding the quarks together. As a result, the force is confined mostly within the particle. However, a tiny fraction of the force does act outside the proton or neutron. This fraction of the force can operate between protons and neutrons, collectively known as nucleons. 

According to Constantinos G. Vayenas and Stamatios N.-A. Souentie in their book "Gravity, Special Relativity and the Strong Force" (Springer, 2012), "it became evident that the force between nucleons is the result, or side effect, of a stronger and more fundamental force which binds together quarks in protons and neutrons." This "side effect" is called the "residual strong force" or the "nuclear force," and it is what holds atomic nuclei together in spite of the repulsive electromagnetic force between the positively charged protons that acts to push them apart. 

Unlike the strong force, though, the residual strong force drops off quickly at short distances and is significant only between adjacent particles within the nucleus. The repulsive electromagnetic force, however, drops off more slowly, so it acts across the entire nucleus. Therefore, in heavy nuclei, particularly those with atomic numbers greater than 82 (lead), while the nuclear force on a particle remains nearly constant, the total electromagnetic force on that particle increases with atomic number to the point that, eventually, it can push the nucleus apart. "Fission can be seen as a 'tug-of-war' between the strong attractive nuclear force and the repulsive electrostatic force," according to the Lawrence-Berkeley National Laboratory's ABC's of Nuclear Science. "In fission reactions, electrostatic repulsion wins." 

The energy released by the breaking of the residual strong force bond takes the form of high-speed particles and gamma-rays, producing what we call radioactivity. Collisions with particles from the decay of nearby nuclei can precipitate this process, causing a nuclear chain reaction. Energy from the fission of heavy nuclei, such as uranium-235 and plutonium-239, is what powers nuclear reactors and atomic bombs.

Limitations of the Standard Model

In addition to all the known and predicted subatomic particles, the Standard Model includes the strong and weak forces and electromagnetism, and explains how these forces act on particles of matter. However, the theory does not include gravity. Fitting the gravitational force into the framework of the model has stumped scientists for decades. But, according to CERN, at the scale of these particles, the effect of gravity is so minuscule that the model works well despite the exclusion of that fundamental force.

The Standard Model also predicts that the isotope oxygen-28 should be stable. As fermions, protons and neutrons cannot overlap with each other. Intead, they stack into discrete shells inside the atomic nucleus. 

When these shells are filled, atoms become ultra-stable or "magic" and have no need to decay into more stable forms. Yet oxygen-28 decays incredibly quickly in the tiniest fraction of a second. 

What this means for our understanding of subatomic forces is unclear but it could suggest that deeper, unknown physics is dictating the behavior of the bizarre isotope. Because the strong force is what holds an atom together, as well as ruling their actions at these short timescales, it is this force that the new findings call into question. 

Additional resources

CERN created a rich website describing all the intricacies of our efforts to understand the strong force, which you can see here. You can also check out interactive demos either on the web or via an app courtesy of The Particle Adventure. If you're in more of a listening mood, check out this podcast episode digging into the strong force.

Bibliography

Constantinos, G. et al. Gravity, Special Relativity, and the Strong Force (Springer Science & Business Media, 2012)

Quigg, C. Gauge Theories of the Strong, Weak, and Electromagnetic Interactions (Princeton University Press, 2013)

Povh, B. et al. Particles and Nuclei: An Introduction to the Physical Concepts (Springer Science & Business Media, 2008)

Thacker, T. (1995, Jan 29) The Four Forces https://webhome.phy.duke.edu/~kolena/modern/forces.html#005

Hansen, L. (1997, Feb 27) The Color Force https://webhome.phy.duke.edu/~kolena/modern/hansen.html

A tiny wobbling particle may be about to reveal a fifth force of nature, scientists behind one of the biggest particle physics experiments say.

Physicists at the Fermi National Accelerator Laboratory, or Fermilab, near Chicago have found more evidence that the muon, a subatomic particle, is wobbling far more than it should — and they think it's because an unknown force is pushing it.

The results build on a previous experiment made in 2021 but produced four times the data with the experimental uncertainty reduced by a factor of two. If the findings are true, and the theoretical controversies around these measurements can be overcome, they represent a breakthrough in physics of a kind that hasn't been seen for 50 years, when the dominant theory to explain subatomic particles was solidified. 

In other words, the muon's minute wobbling — known as its magnetic moment — has the potential to shake the very foundations of science. 

"We're really probing new territory," Brendan Casey, a senior scientist at Fermilab who works on the experiment, known as Muon g-2, said in a statement. "We're determining the muon magnetic moment at a better precision than it has ever been seen before." 

Related: Bizarre particle that can remember its own past created inside quantum computer

Occasionally referred to as "fat electrons," muons are similar to electrons but are 200 times heavier and radioactively unstable — decaying in mere millionths of a second into electrons and tiny, ghostly, chargeless particles known as neutrinos. Muons also have a property called spin, which makes them behave as if they were tiny magnets, causing them to wobble like mini gyroscopes when inside a magnetic field.

To investigate the muon's wobbling, physicists at Fermilab sent the particles flying around a  minus 450 degree Fahrenheit (minus 268 degrees Celsius) superconducting magnetic ring at nearly the speed of light — a speed that, due to relativistic time dilation, extends the muons' short lifetimes by a factor of about 3,000. 

By looking at how muons wobbled as they made thousands of laps around the 50-foot-diameter (15 meters) ring, the physicists compiled data suggesting that the muon was wobbling far more than it should be.

The explanation, the study scientists say, is the existence of something not yet accounted for by the Standard Model — the set of equations that explain all subatomic particles, which has remained unchanged since the mid-1970s. 

This mysterious something could be a completely unknown force of nature (the known four are gravitational, electromagnetic and the strong and weak nuclear forces). Alternatively, it could be an unknown exotic particle, or evidence of a new dimension or an undiscovered aspect of space-time. 

But whichever way they slice it, the physicists' data suggests that something unknown is nudging and tugging at the muons inside the ring.

Full confirmation will take a little while longer, however. To be as certain as possible, physicists will use all of the data collected during the g-2 experiment's 2018 to 2023 run: The current result only takes data from 2019 and 2020. Secondly, they will need to wait for theoretical predictions from the Standard Model to catch up.

There are currently two theoretical methods for calculating what the muon's wobble should be under the Standard Model. These two methods produce conflicting predictions. Some of these calculations, including one published the same week as the 2021 g-2 experiment findings, give a much larger value to the theoretical uncertainty of the muon's magnetic moment — threatening to rob the experiment of its physics-breaking significance.

Another experiment, using data from the CMD-3 accelerator in Novosibirsk, Russia, also appears to find the muons wobbling within normal bounds, but the experiment directly contradicts a previous run of the accelerator that hinted at an opposite result.

Fermilab researchers hope that the full results, which they expect to be ready in 2025, could be precise enough to give a clear reading.

The scientists have submitted their work for publication in the journal Physical Review Letters; a preprint of the findings can be found here.