7 Strange Facts About Quarks

Teensy Particles

particle collisions inside the large hadron collider — Matter and antimatter particles are behaving differently inside the Large Hadron Collider, where particles smash together at near light-speed. Here, an illustration of particle collisions inside the atom smasher. (Image credit: MichaelTaylor | Shutterstock)

Quarks are particles that are not only hard to see, but pretty much impossible to measure. These teensy-tiny particles are the basis of subatomic particles called hadrons. With every discovery in this field of particle physics in the past 50 years, however, more questions arise about how quarks influence the universe's growth and ultimate fate. Here are seven strange facts about quarks.

Emerged just after Big Bang

Big Bang Theory: Universe Timeline — This graphic shows a timeline of the universe based on the Big Bang theory and inflation models. (Image credit: NASA/WMAP)

The first quarks appeared about 10^minus 12 seconds after the universe was formed, in the same era where the weak force (which today is the basis for some radioactivity) separated from the electromagnetic force. The antiparticles of quarks appeared around the same time.

Discovered in an atom smasher

Behind the Scenes at Humongous U.S. Atom Smasher — A computer simulation of a collision of two beams of gold nuclei in the STAR detector. The beams travel in opposite directions at nearly the speed of light before colliding. The resulting particles fly in all directions to be measured by the cylinder-shaped detector. (Image credit: Brookhaven National Lab)

A mystery arose in the 1960s when researchers using the Stanford Linear Accelerator Center found that the electrons were scattering from each other more widely than calculations suggested. More research found that there were at least three locations where electrons scattered more than expected within the nucleon or heart of these atoms, meaning something was causing that scattering. That was the basis for our understanding of quarks today.

Mentioned by James Joyce

James Joyce in Zurch around 1918. (Image credit: Cornell Joyce Collection, Public Domain)

Murray Gell-Mann, the co-proposer for the quark model in the 1960s, drew inspiration for the spelling from the 1939 James Joyce book "Finnegan's Wake," which read: "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." (The book came out well before quarks were discovered and so their name has always been spelled in this way.)

Come in flavors

Fundamental particles called quarks come in six different flavors. Protons are made of two up quarks and one down quark, while neutrons contain two down quarks and one up quark. (Image credit: MichaelTaylor | Shutterstock)

Physicists refer to the different types of quark as flavors: up, down, strange, charm, bottom, and top. The biggest differentiation between the flavors is their mass, but some also differ by charge and by spin. For instance, while all quarks have the same spin of 1/2, three of them (up, charm and top) have charge 2/3, and the other three (down, strange and bottom) have charge minus 1/3. And just because a quark starts out as a flavor doesn't mean it will stay that way; down quarks can easily transform into up quarks, and charm quarks can change into strange quarks. [Read more about quark flavors]

Tricky to measure

An ordinary proton or neutron (foreground) is formed of three quarks bound together by gluons, carriers of the color force. Above a critical temperature, protons and neutrons and other forms of hadronic matter 'melt' into a hot, dense soup of free quarks and gluons (background), the quark-gluon plasma. (Image credit: Lawrence Berkeley National Laboratory)

Quarks can't be measured, because the energy required produces an antimatter equivalent (called an antiquark) before they can be observed separately, among other reasons, according to a primer from Georgia State University. The mass of quarks is best determined by techniques such as using a supercomputer to simulate the interactions between quarks and gluons, with gluons being the particles that glue quarks together.

Teach us about matter

illustration of antimatter atom being weighed on a scale. — Do atoms of antihydrogen weigh the same as atoms of ordinary hydrogen? Could they even have 'negative' weight? To find out, physicists 'weighed' antimatter to understand how it interacts with gravity. (Image credit: Chukman So)

In 2014, researchers published the first observation of a charm quark decaying into its antiparticle, providing more information about how matter behaves. Because particles and antiparticles should destroy each other, one would think the universe should just have photons and other elementary particles. Yet antiphotons and antiparticles still exist, leading to the mystery of why the universe is made mostly of matter and not antimatter.

May set the universe's fate

Firing landscape. Planet Earth after Apocalypse concept. — The universe may end in another 10 billion years or sooner if the top quark, which is the heaviest of all the known elementary particles, is even heavier than previously thought. And if the particle is not heavier than thought, an even stranger fate may await us … disembodied brains. (Image credit: Irina Mos | Shutterstock)

Nailing down the mass of the top quark could reveal to researchers one of two ghastly scenarios: that the universe could end in 10 billion years, or that people could materialize out of nowhere. If the top quark is heavier than expected, energy carried through the vacuum of space could collapse. If it's lower than expected, an unlikely scenario called "Boltzmann brain" could see self-aware entities come out of random collections of atoms. (While this isn't a part of the Standard Model, the theory – framed as a paradox – goes that it would be more likely to see organized groups of atoms as the random ones observed in the universe.)