On April 9, 1982, a doctor at the University of California, San Francisco, published a paper in the journal Science showing that infectious proteins caused a degenerative nerve disease in sheep. In doing so, he transformed our understanding of how some diseases are transmitted.

Dr. Stanley Prusiner had been studying the disease scrapie, which affects sheep and goats. It had long been a mystery exactly how scrapie was transmitted from animal to animal. He had also long been haunted by seeing a patient die rapidly of the degenerative brain disorder Creutzfeldt-Jakob disease (CJD) a decade earlier. The patient had no fever or other signs of immune system activation nor any evidence of a bacterial or viral infection. Yet Prusiner was told the patient was infected by a "slow virus," or one that progressed on longer time scales than is typically seen with viruses.

"At that time, I was beginning a residency in neurology and was most impressed by a disease process that could kill my patient in two months by destroying her brain while her body remained unaffected by this process," he said in a speech he later gave about his discovery.

In the 1950s, the term "slow virus" had been coined to describe the diseases scrapie in sheep and goats. By the 1960s, scientists had started applying the term to certain human disorders, noting that the disease "kuru" that ravaged the Fore tribe in Papua New Guinea seemed to be transmitted when tribal members ate the brains of those who previously died of the disease.

Research in chimpanzees in the 1960s definitively showed that Creutzfeld-Jakob disease ‪—‬ a fatal, relentless brain disease that seemed to run in families ‪—‬ could also be transmitted by feeding the chimpanzees brain tissue from affected animals. Under a microscope, brain tissues affected by kuru, scrapie or CJD all looked remarkably similar, showing a characteristic "spongiform" appearance. In other words, the brain tissue became riddled with holes, like a sponge.

Yet there was a puzzle: CJD seemed to be passed on in families. So how could viruses or bacteria be both heritable and infectious?

Prusiner was initially studying CJD but switched his focus to scrapie when he looked at data from a team led by Tikvah Alper, a radiobiologist. Alper had found that scrapie could still be transmitted when infected tissue was irradiated with ultraviolet light, which damages DNA.

So Prusiner began studying scrapie in mouse spleens and brains. But he quickly switched to hamsters because they developed disease symptoms within 70 days, as opposed to one to two years for mice. He then systematically worked to isolate and identify the chemical nature of the "infectious agent" driving the disease.

Ultimately, he pinpointed a protein as the culprit.

"Six separate and distinct lines of evidence show that the scrapie agent contains a protein that is required for infectivity," Prusiner wrote in the seminal 1982 study. All of those showed that breaking down the protein structure short-circuited the transmission of scrapie. He went on to show that there was no evidence for any nucleic acids, such as DNA or its cousins, in the samples. He proposed the name "prion" to describe the infectious protein, which he suggested could "code for its own biosynthesis," adding that "this hypothesis contradicts the 'central dogma' of molecular biology."

Prusiner's proposal was not widely accepted at first. But over the next 15 years, scientists elucidated the protein structure of prions and showed that they could take multiple conformations, even when encoded by the same DNA sequence. Researchers also showed how the prion's shape resisted degradation,and that it could "convert" the healthy versions of the protein into the pathological form.

Follow-up work in familial cases of CJD showed certain genes could also predispose people to the disease and that DNA damage determined how long it took for the disease to incubate.

Prusiner won the Nobel Prize in physiology or medicine in 1997 for his work on prions.

Prusiner's hypothesis was validated when the mad cow disease epidemic struck the U.K. in the early 2000s. Scientists would eventually determine that people became infected after eating beef from cows that had been fed the brain tissue of cows sick with bovine spongiform encephalopathy (BSE). After consuming meat from cows with BSE, humans develop a version of CJD known as "variant CJD."

On a cold day in February, an Augustinian friar described his experiments breeding garden-variety plants — and gave rise to the field of modern genetics.

Gregor Mendel was an Austrian priest who had spent eight years cultivating and crossbreeding more than 28,000 pea plants (Pisum sativum) in the garden of Monastery of St. Thomas in Brno (formerly known as Brünn), painstakingly recording details of the plants' progeny.

Mendel was actively discouraged from pursuing his research. His bishop giggled whenever Mendel told of his scientific experiments, according to a letter his abbot Cyril Napp wrote to him in 1859.

"He asked if I though [sic] it seemly for a man of your intellectual attainments to be plodding in a pea patch, prying into the germinal proclivities of peas. He suggested that pea propagation was a subject less worthy of your curiosity than, say, the writings of the Church Fathers or the Doctrine of Grace. My dear Brother Mendel, as sympathetic as I am to your researches [sic], we can ill afford to have the monastery made the laughingstock of the diocese."

But Mendel was undeterred from his research — not because of a deep-seated interest in plants, but because he wanted to reveal the principles of inheritance.

He had chosen to study the plants of this unassuming legume for a number of reasons. First, pea plants reproduced quickly and well in both pots and in the ground, according to an 1866 monograph he wrote about his research. Second, they seemed to have clear traits they passed along to their offspring — such as pink, white or red flowers — and the hybrids were perfectly fertile.

Finally, "accidental impregnation by foreign pollen, if it occurred during the experiments and were not recognized, would lead to entirely erroneous conclusions," he wrote.

He identified several distinct traits to track — such as the color of the peas and their pods, the positions of the flowers, and the lengths of the stems — and then crossbred those with differing characteristics. Then, he let each distinct type of plant "self-breed" for two years, showing that the traits continued to be passed along to offspring.

Next, he crossbred those plants and crossbred the resulting hybrids. He painstakingly tallied all of the ways traits were inherited, denoting different traits from each parent with simple labels like Aa, Bb and Cc.

By analyzing the mathematical patterns in each subsequent generation, he deduced the basic principles of inheritance. First, he noted that some traits were transmitted in discrete units, or "particles" — if you cross a green-pea plant with a yellow-pea plant, you get either green or yellow offspring, not yellowish-green ones.

He also concluded that some traits were inherited in a "dominant" pattern. For instance, if plants bred for generations to have only smooth seeds were bred with those that had wrinkly seeds, the offspring would always have smooth seeds.

When Mendel crossbred hybrids, he noticed something strange: Most of the plants would look smooth, but about a quarter would look wrinkled. He deduced that the wrinkly trait was instead passed on in a "recessive" manner and that the trait actually came from the grandfather plant's generation.

Mendel wasn't content to study one "particle" at a time. He also crossbred plants that were hybrids for two different traits and learned that each trait was transmitted separately, which is now known as the principle of segregation.

Mendel's work wasn't recognized in his lifetime. And although Mendel is often known as the "father of genetics," the term "genetics" was not coined until the early 1900s, when English biologist William Bateson rediscovered Mendel's forgotten work and realized its overarching significance.

Soon after, some argued Mendel's data was "too good to be true," and that he must have fabricated his results. A 2020 study put that idea to rest, showing that given the seeds available then, what Mendel knew, and how seeds were classified then, his results were in fact what you'd expect.

Decades later, research would reveal that inheritance isn't as simple as Mendel's pea plants would suggest — some genes are inherited in a sex-linked manner, and other traits have incomplete "penetrance," meaning they don't always manifest the same way. And in early 2026 research revealed that some disease-causing genes we believed were dominant don't operate like we thought, which may challenge some of the fundamental tenets of Mendelian inheritance.

In January 1816, the secretary general of the Paris Academy of Sciences sent Marie-Sophie Germain a strange letter.

In it, he acknowledged that she had won the institute's prestigious "Grand Mathematics Prize" for her mathematical work describing how sound waves travel across 2D surfaces. And yet, the letter offered no congratulations, noted condescendingly that she was the only entrant, and admitted that she had not received tickets to attend the prize ceremony set to occur two days later. He grudgingly acknowledged that, if needed, handwritten tickets could be hastily produced.

Germain did not attend the ceremony.

"The class of mathematical and physical sciences of the Institute held its public session today, a very large assembly that attracted without doubt those desiring to see virtuoso of a new kind, Miss Sophie Germain, to whom the prize for elastic membranes was to be awarded. The expectation of the public was disappointed: the young lady did not go to take the trophy that no one of her gender has ever received in France," the newspaper Journal des Débats reported about the event that day.

The award was the culmination of a decade of work by Germain, a self-taught polymath. Born to a wealthy merchant's family, she became interested in math while reading books in her father's library during a period of seclusion during the French revolution.

Her parents were not pleased with her "unladylike" pursuit. They banked the fires that kept the house toasty and took away her warm clothes, hoping that she'd be too cold and uncomfortable to study. But when they went to sleep, she'd grab candles and cover herself in quilts to continue her math research. She taught herself number theory and calculus that way.

When the École Polytechnique opened in 1794, women were barred from attending, but the notes from lectures were publicly available. She began reading those notes and submitting answers to problems from the lectures under the pseudonym "Antoine August LeBlanc." Under her pseudonym, Germain also began corresponding with some of the leading mathematicians of her day, including Carl Friedrich Gauss and Joseph-Louis Lagrange.

Around 1806, she became intrigued by the physics behind a perplexing experiment. In his 1787 book, physicist and musician Ernst Chladni, often called the "father of acoustics," described a phenomenon in which a person can sprinkle sand across a glass plate and then drag a violin bow across various surfaces and edges. Not only could the plate be played like a violin, but varied geometric patterns formed in the sand depending on how the plates were bowed.

The French institute had offered a prize three years running to mathematically describe the "Chladni figures" that formed. No one else bothered to attempt a solution, with most believing the existing math of the day insufficient to explain the phenomenon.

Germain, however, submitted her proposed solutions all three years. Her third proposal, submitted in 1816, was titled "Research on the Vibrations of Elastic Plates." Though "awkward and clumsy" given the math available at the time, it was still a brilliant insight into the subject of 2D harmonic oscillation, or stably moving waves.

Germain ultimately decided to skip the ceremony because she felt the committee didn't sufficiently respect her work. For instance, her leading rival, Siméon Poisson, was part of the award committee and refused to discuss the problem with her or talk with her in public. Not all of Germain's contemporaries were so dismissive, however; Lagrange and Gauss strongly supported her work.

"But when a woman, because of her sex, our customs and prejudices, encounters infinitely more obstacles than men in familiarizing herself with their knotty problems, yet overcomes these fetters and penetrates that which is most hidden, she doubtless has the most noble courage, extraordinary talent, and superior genius," Gauss wrote when he discovered her gender.

Germain would continue with her solitary math research for decades.

Her work with French mathematician Adrien-Marie Legendre was a major advance in the proof of Fermat's Last Theorem, which states that no three positive integers (a, b, c) can satisfy the equation aⁿ + bⁿ = cⁿ for any integer value of n greater than 2.

Germain showed that Fermat's Last Theorem held for a special class of prime numbers, now called Germain primes, in which both p and 2p+1 are prime. Her work formed the foundation for the eventual, complete solution produced by Andrew Wiles in 1994. Nonetheless, Germain's theorem was mentioned only in a footnote in Legendre's work.

In 1831, her longtime correspondent and mentor Gauss pushed for the University of Göttingen to give Germain an honorary degree. She died of breast cancer a few weeks before she could be given the award.

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.

In late December 1985, a worker opened the door to a remote cabin in the Virunga Mountains of Rwanda and encountered a horrific scene: Gorilla researcher Dian Fossey, whose aggressive approach to conservation had pitted her against the local community, had been hacked to death with a machete, and her cabin had been ransacked.

Fossey had been working with an endangered gorilla population in Rwanda's Volcanoes National Park since the late 1960s. Along with Jane Goodall and Biruté Galdikas, she was one of the three "trimates" chosen by Louis Leakey to study primates in their natural habitat.

Fossey had no formal training in ethology, the science of animal behavior, when she set out for Africa. She began her field work in Kabara, Congo, living in a tiny tent and venturing out to study mountain gorillas (Gorilla beringei beringei) there. After civil war broke out in 1967, she escaped to the Rwandan portion of the mountains and set up a new research project near Mount Karisimbi in Rwanda.

Fossey was inspired by the work of George Schaller, a biologist who, in 1959, had also studied the gorillas of the Virunga Mountains.

"I knew that animals try to stay out of your way. If you go quietly near them, they come to accept your presence. That's what I did with gorillas. I just went near them day after day, which was fairly easy because they form cohesive social groups. Soon, I knew them as individuals, both their faces and their behavior, and I just sat and watched them," Schaller said in a 2006 interview.

Fossey operated on this same principle of patient, unobtrusive observation. Still, the gorillas initially fled from her, and she spent hours tracking and trailing them across the misty forest.

After a year, they stopped fleeing at her presence and started beating their chests and vocalizing. It was a bluff meant to scare her off, but it was still far from their ordinary, natural behavior, she said in a 1973 lecture. After two years, she received two young gorillas, Coco and Pucker; rehabilitated them; and learned about gorilla young by observing them.

"I came to know the gorillas' need for love and affection, and the young gorillas' need for constant play," she said.

It would take three years before the gorillas came to accept her presence and reveal more naturalistic behavior, she said in the lecture.

During her decades in Virunga, Fossey described and learned to mimic the vocalizations of gorillas, including the "belch vocalization" that signifies contentment. She also elucidated their tight-knit family structures, courtship and mating rituals, as well as documented the occasional murder of infant gorillas by rival males.

Although she would eventually earn her doctorate in zoology from the University of Cambridge, Fossey spent her first years studying the gorillas with no formal training. Perhaps because of her initial lack of training, she formed close bonds with individual animals and tended to ascribe more humanlike motivations and descriptions to their actions than is typically accepted in formal zoology. She often described gorillas as more altruistic than humans.

"You take these fine, regal animals,'' she told an interviewer, as reported by The New York Times. ''How many fathers have the same sense of paternity? How many human mothers are more caring? The family structure is unbelievably strong.''

She formed a particularly close bond with a gorilla she nicknamed Digit — so named for his damaged finger — who did not have playmates his age. Digit was killed by poachers in 1977.

The last years of Fossey's life were increasingly focused on conserving the gorillas' dwindling habitat and combating poachers. She used confrontational methods, such as burning snares, wearing masks to scare poachers, and spray-painting cattle to prevent herders from bringing them into the national park, according to the Dian Fossey Gorilla Fund.

She also shot over the heads of tourists to scare them away and told her graduate students to carry guns, according to The Washington Post.

Given that many of the people living on the fringes of the park lived in poverty and resorted to expansion and herding to survive, this did not earn her good will with many of the locals.

Fossey's murder was never solved. Many think poachers were responsible for the killing, but other theories have been floated as well.

On this day, chemists discovered a substance 900 times more radioactive than uranium. Their research led to unprecedented medical breakthroughs and worldwide fame — but it would also kill one of them.

Marie Curie was a medical student at the Sorbonne, a university in Paris, when she decided to study the new field of radiation for her thesis. In 1895, Wilhelm Röntgen discovered powerful "Röntgen rays," which would eventually be dubbed X-rays. The following year, Henri Becquerel accidentally discovered much weaker rays emitted by uranium salts would fog up photographic plates just like light rays did — even in the absence of light.

Curie realized that she wouldn't have to read a long list of prior papers on the newfangled subject before diving into experimental work, according to the American Institute of Physics. Curie's husband, Pierre, found her a workspace in a musty, crowded storeroom at his institution, the Paris Municipal School of Industrial Physics and Chemistry. He soon became so fascinated with her research that he abandoned his own to pursue hers.

Key to Marie Curie's research was the piezoelectric quartz electrometer. The device, invented by her brother-in-law, Jacques Curie, measured the weak electrical currents produced by radioactivity.

"Instead of making these bodies act upon photographic plates, I preferred to determine the intensity of their radiation by measuring the conductivity of the air exposed to the action of the rays," Curie wrote in a 1904 article for Century magazine.

The damp storeroom messed with her results, but she ultimately discovered that the intensity of this radiation depended on the concentration of uranium in the minerals she studied. She speculated that something intrinsic to the atomic structure of uranium must be at play.

Working with her husband Pierre and Gustave Bémont, the head of chemistry at the Higher School of Industrial Physics and Chemistry of the City of Paris, they began to study pitchblende, a black mineral rich in uranium often found in deposits alongside silver.

Curie noticed that it could be much more radioactive than uranium ore itself.

"How could an ore, containing many substances which I had proved inactive, be more active than the active substances of which it was formed? The answer came to me immediately: The ore must contain a substance more radioactive than uranium and thorium, and this substance must necessarily be a chemical element as yet unknown," Marie Curie wrote in Century magazine in 1903.

Marie Curie deduced that whatever this mysterious substance was, it had to exist only in small quantities yet have a remarkable level of what she had dubbed "radio-activity." The trio decided to try to separate pitchblende, which can be composed of up to 30 minerals, into its constituent parts to identify the radioactive substance. They used the light spectra of different substances to try to isolate and identify the ingredients.

In July, they pinpointed one mineral that was around 60 times more "radio-active" than uranium, which they named polonium. And on Dec. 21, they found another — called radium — that was an unprecedented 900 times more radioactive than uranium. They described both new substances during a talk at the French Academy of Sciences on Dec. 26.

The Curies would go on to isolate the radioactive elements over the next several years, while working in a poorly ventilated shed in the courtyard across from the original storeroom.

Their research on radiation earned the Curies and Becquerel the Nobel Prize in Physics in 1903. (Marie was originally going to be passed over, but she received the prize only after her husband, Pierre, insisted the committee credit her work.) Marie would earn another Nobel Prize in 1911, this time in chemistry, for her work on radium.

Pierre was killed by a horse-drawn carriage in 1906, but Marie would go on to advocate for the use of X-rays in medicine — including developing vehicles that could provide mobile X-rays for soldiers on the battlefield during World War I. She also noted that radium killed off diseased cells faster than healthy ones, a principle that would later inspire the development of radiotherapy for cancer treatment.

Radium caused frequent radiation sickness and burns in both Curies. Marie's radiation exposure likely killed her; she died in 1934 at age 66 due to aplastic anemia, a type of leukemia that can be caused by radiation damage to bone marrow. The notebook she used to document her 1898 discovery is still radioactive and is stored in a lead box.

On a cloudy winter's day, in the Amazon jungle, a shuttle blasted off into space — and changed our view of the universe forever.

The James Webb Space Telescope (JWST) left Earth aboard an Ariane 5 rocket at 25,000 mph (40,000 km/h) "from a tropical rainforest to the edge of time itself," according to a live broadcast from NASA.

About a month later, it reached its orbiting parking place in space, a gravitationally-stable Lagrange point 930,000 miles (1.5 million kilometers) away, in perfect equilibrium between Earth and the sun's gravity. The telescope would beam back its first, spectacular pictures in July 2022. And the firehose of data it has sent back since has transformed our understanding of the cosmos.

JWST has been so pivotal in part because it can peer back to the "cosmic dawn," a period a few hundred million years after the Big Bang, when the first stars were winking on.

"The James Webb Space Telescope has proven itself capable of seeing 98% of the way back to the Big Bang," Peter Jakobsen, an affiliate professor of astrophysics at the University of Copenhagen in Denmark, previously told Live Science in an email.

Yet Webb, which was first conceived at Lockheed Martin in the late 1990s, almost didn't launch at all. The now-iconic, $10 billion project was catastrophically over budget, plagued by years' worth of delays and snarled by "stupid mistakes."

That was in part because, when it launched, it was by far the most complex telescope ever built.

It took more than 20,000 engineers and hundreds of scientists to design, build and launch the eye in the sky. That 21.3 feet (6.5 meter) mirror had to be folded into a honeycomb shape to be lofted on a rocket, then unfolded once in space. Yet despite being foldable, it also had to be so smooth that if it were as big as a continent, "it would feature no hill or valley greater than ankle height," according to Quanta Magazine.

To see the earliest epochs of cosmic history, Webb needed infrared vision. That's because ancient light has been stretched, or red-shifted, into infrared wavelengths as it travels across space-time. On Earth, humans and every other living thing give off heat in the form of infrared radiation, and that would drown out the faint infrared signals from the most distant, ancient starlight. So JWST needed to be lofted into the cold dark of outer space to use its infrared instruments.

Once JWST started imaging the cosmos, it promptly began breaking our existing models of the universe. It rapidly confirmed the Hubble tension — the discrepancy between the universe's expansion rates depending on where and what astronomers measure. It has found hints of potentially life-sustaining atmospheres shrouding distant exoplanets. And it has spotted shockingly bright galaxies and seemingly "impossible" black holes at the dawn of time. All these clues are pointing to new understandings of the universe.

Some of the questions JWST is raising, such as whether other planets harbor life, it will probably not be able to answer in its planned 10-year lifespan. But future telescopes — such as the currently operational Vera C. Rubin Observatory, meant to create a real-time "movie of the universe"; the recently completed Nancy Grace Roman Telescope, set to launch in 2027 and resolve questions about dark matter and energy; the Extremely Large Telescope, set to turn on in 2029; or the recently announced Habitable Worlds Observatory, which may come online in the 2030s — could start to answer the questions that Webb is raising.

At the end of 1924, an anthropologist began chipping away rock around an old primate skull — and rewrote the story of human evolution.

The diminutive skull — about the size of a coffee mug — clearly belonged to a creature very different from us and yet also quite distinct from other apes and monkeys.

But the man credited with its discovery, Raymond Dart, a professor of anatomy and anthropology at the University of Witwatersrand in Johannesburg, hadn't actually excavated the skull.

Rather, it came to Dart because his student had brought another skull from a quarry to his class. Local workers at the Buxton Limeworks in Taung had previously blasted a baboon skull out of the rock and had brought it to the attention of the company. From there, the baboon skull landed with Dart's student, Josephine Salmons. She recognized it for what it was and brought it to his class.

Dart was excited about the possibility that other ancient primate fossils would be embedded in the same sediments, and he showed the baboon skull to his geologist colleague Robert Young. Young knew the quarry and made contact with the quarryman, a Mr. de Bruyn, and asked him to keep an eye out for more skulls. In late November, de Bruyn identified a brain cast in a piece of rock and set it aside for Young, who then hand-delivered the cranium to Dart.

In his 1959 memoir, "Adventures with the Missing Link," Dart makes no mention of Young hand-delivering the skull. Instead, he implies that he had pulled the skull out of rubble in crates that were delivered from Buxton Limeworks.

In Dart's telling, he immediately recognized what he had found.

"As soon as I removed the lid a thrill of excitement shot through me. On the very top of the rock heap was what was undoubtedly an endocranial cast or mold of the interior of the skull," Dart recounted in his memoir. "I stood in the shade holding the brain as greedily as any miser hugs his gold … Here, I was certain, was one of the most significant finds ever made in the history of anthropology."

On Dec. 23, "the rock parted. I could view the face from the front, although the right side was still embedded," Dart wrote in his 1959 memoir.

Over the next 40-odd days, he feverishly analyzed the skull. In a paper published in the journal Nature on Feb. 7, 1925, he described a newfound human ancestor and named it Australopithecus africanus, or "The Man-Ape of South Africa."

The "Taung Child" would rocket Dart to fame and confirm Charles Darwin's hypothesis that humans and nonhuman apes shared a common ancestor that evolved in Africa.

The discovery of the "Taung Child" was the first time scientists had ever found a near-complete fossil skull of an ancient human ancestor. It was longer than other primate skulls, and the molars in the skull suggested "it corresponds anatomically with a human child of six years of age," according to the study, though later estimates would suggest the child died at around age 3 or 4. We don't know for sure, but most researchers think the Taung Child was a girl.

Because the skull was taken out of its "context," it was difficult to peg its age. Over the years, some researchers have estimated it to be 3.7 million years old, but more recent research suggests it was around 2.58 million years old.

For nearly 50 years, A. africanus was thought to be our direct human ancestor. Then, in 1974, scientists digging in Afar, Ethiopia, unearthed another fossil skull from a related species. This one, dated to 3.2 million years ago, was the iconic "Lucy," and her species, Australopithecus afarensis, wound up dethroning the Taung Child as our direct common ancestor.

But there's a twist ending to this story, as scientists found a few fossil fragments that raise the possibility that Lucy's species isn't our direct ancestor after all, with some even suggesting A. africanus could regain its title.

In 1910, a fierce competition began between Norwegian explorer Roald Amundsen and British captain Robert Falcon Scott. Each explorer wanted to be first to reach the geographic South Pole, thereby vanquishing the last unexplored continent on Earth. The race was destined to end in tragedy.

Scott previously attempted to conquer the southernmost continent in 1902, but he had to turn back due to ill health and unfavorable temperatures. His crew, most of whom came from Ernest Shackleton's recently returned Nimrod, set sail from Cardiff, Wales, on June 15, 1910.

Amundsen, meanwhile, played his cards close to the vest. He, too, wanted to be the first to reach a pole, and he had originally set his sights on the North Pole. He quietly changed plans in 1909 after Matthew Henson and Robert Peary, along with four Inuit assistants, beat him to it.

Amundsen set sail from Norway on Aug. 9, 1910, aboard the Fram, which had previously been used on two key expeditions — one drifting over the Arctic Ocean and another exploring what is now Nunavut, Canada. Amundsen kept his plans secret from all but three of his crew members until he reached the Portuguese island of Madeira in September.

At that point, he told the crew and messaged his rival. "Beg leave to inform you Fram proceeding Antarctic. Amundsen," he said in his telegram to Scott, according to the Antarctic Heritage Trust. The message was waiting for Scott when he arrived in October in Melbourne, Australia.

By early 1911, Scott had set up his base in McMurdo Sound, while Amundsen sailed into the Bay of Whales and established his base, Framheim, on the Ross Ice Shelf. This put Amundsen a crucial 60 miles (100 kilometers) closer to the geographic South Pole.

After an initial, unsuccessful exploratory foray, Amundsen returned to Framheim and regrouped. He split up his team, with one group setting off for the South Pole and another exploring a separate region. On Oct. 21, Amundsen and crew members Olav Bjaaland, Oscar Wisting, Helmer Hanssen and Sverre Hassel set off from Framheim on four sleds, each of which was pulled by 13 dogs.

On Dec. 14, at 3 p.m. local time, Amundsen shouted "Halt!"

They believed they'd reached the South Pole, and they soon set up a tent and planted the Norwegian flag.

Scott arrived 35 days later to find Amundsen's tent and Norwegian flag. He and his crew would perish on the return journey, due to starvation, dehydration and exposure to extreme cold.

In his last journal entry on March 29, Scott wrote, "I do not think we can hope for any better things now. We shall stick it out to the end, but we are getting weaker, of course, and the end cannot be far. It seems a pity, but I do not think I can write more." They were just 11 miles (17 km) from their next supply cache. Their bodies were found in November, 1912.

Why did Amundsen's crew succeed where Scott did not? A few details may have made a difference. Amundsen took a shorter route over the Axel Glacier. He also dressed his crew in the traditional Inuit garb, whereas Scott's team wore wool clothes. They also ruthlessly reduced the weight of their sleds and organized their supplies so they could reach them with minimal exposure to cold temperatures.

Finally, Amundsen devised a plan to shoot and eat the sled dogs along the way to supplement their relatively meager food supplies, and they ate raw penguin meat, which provides the vitamin C crucial to staving off scurvy. All of these factors may have helped him arrive more quickly and return safely.

Early accounts painted Scott's failure as one of ineptitude, but recent evidence suggests he may have simply fallen prey to unusually severe weather — and possibly the malfeasance of his crew. A 2017 article in the journal Polar Record suggested that crew member Edward Evans may have contributed to the team's failure by taking more than his fair share of food, leaving shortages at key depots. He also may have failed to pass on orders, such as the placement of sled dogs at critical junctures, which could have led to the team's demise.

Just a few years later, Shackleton helmed the Endurance as part of an attempt to cross the coldest continent on foot. The effort famously failed; the ship sank, and its crew became stranded on Elephant Island. But incredibly, all of the crew members survived for four months and were rescued in August 1916 after Shackleton left to seek help.

Nowadays, the South Pole is home to the Amundsen-Scott South Pole Station, as well as the IceCube Neutrino Observatory and the South Pole Telescope.

In 1954, researchers described a new drug that sent children with acute leukemia into remission. It would become one of the first chemotherapy drugs and would later form the basis for a new, "rational" approach to designing drugs.

Gertrude Elion had earned a master's degree in chemistry in 1941, but she was turned down for many graduate research posts, which were not available to women. So she worked as a high school chemistry teacher and a food quality tester for a supermarket company, according to an autobiographical sketch she wrote in 1988.

But by 1944, she had found a job in the lab of George Hitchings at the Burroughs-Wellcome pharmaceutical company (now GSK). Hitchings was developing a novel way to make new drugs that eschewed the trial-and-error approach that had previously dominated drug design.

"One of the deciding factors may have been that my grandfather, whom I loved dearly, died of cancer when I was 15. I was highly motivated to do something that might eventually lead to a cure for this terrible disease," Elion wrote in 1988.

Hitchings and Elion reasoned that, because all living cells need nucleic acids, which make up DNA, to reproduce, then fast-growing cells, like invasive bacteria and tumor cells, would need even more of these compounds to fuel their insatiable growth. So, they rationalized, finding compounds that inhibit the synthesis of nucleic acids could squelch cancer growth.

In 1950, when Elion was 32, the team discovered a compound derived from purine, called 6-mercaptopurine (6-MP), which could inhibit the growth of both bacterial cells and leukemia cells in a lab dish. Over the next two years, they tested the drug in tumors in animals, finding that it slowed tumor growth. In 1952, researchers began trials in 107 patients with various types of cancer, including 45 children and 18 adults with acute leukemia. Prior to this, there was no good treatment for these children, who would usually die months after their diagnosis.

There had been a few earlier chemotherapy drugs, but many were based on highly toxic compounds, such as war gases. By contrast, the children who took 6-MP seemed to tolerate it fairly well, and 15 children went into complete remission for a few weeks to a few months. It wasn't a huge increase, but it was more than had been possible before. Elion was elated when the children got better, and crushed when they got sick again.

Hitchings and Elion were determined to pursue other, related compounds that could create a more durable remission. In the late 1950s, they hit upon a regimen that combined methotrexate — another chemotherapy drug, developed by Dr. Jane Wright and colleagues — with 6-MP to create a longer-lasting, stable remission in some kids with acute leukemia.

Over a decades-long career, Elion would go on to develop many more drugs, including azathioprine, a rheumatoid arthritis and transplant anti-rejection drug; acyclovir, an antiviral that treats genital herpes, chickenpox and shingles; and AZT, the first drug that worked against HIV/AIDS. In 1988, she earned the Nobel Prize in physiology or medicine, along with Hitchings and James Black for her work on "important principles in drug design," including her work on 6-MP.

At a low-key talk for a local professional society in 1964, computer scientist and chemist Gordon Moore laid out a prediction that would define the world of technology for more than 50 years.

In the presentation for The Electrochemical Society, titled, "The Evolving Technology of the Semiconductor Integrated Circuits," Moore predicted that the number of transistors on an integrated circuit would double every year.

The final version of this prediction would become known as "Moore's law," and it would drive progress in the semiconductor industry for decades.

Although it's called a law, it was a prediction based more on economic dictates and industry trends than on the physical laws of nature.

Moore was a director of research and development at Fairchild Semiconductors when he gave the talk, and his goal was ultimately to sell more chips. At the time, computers were gigantic machines that took up a whole room, and integrated circuits, known as microchips, had somewhat limited practical applications.

The silicon transistor, the workhorse that does calculations in a computer, had been invented just a decade earlier, and the integrated circuit, which allowed computers to be miniaturized, had been patented just five years earlier. In 1961, the electronics company RCA had built a 16-transistor chip, and by 1964, General Microelectronics had built a 120-transistor chip.

Moore witnessed this dramatic progress and noticed that a mathematical rule seemed to be governing that progress. This mathematical correlation was later given the name "Moore's law" by other people.

Although Moore laid out the principle to The Electrochemical Society in 1964, it gained widespread traction in April of the following year, when he was asked to write an editorial in Electronics magazine. In it, he boldly predicted that as many as 65,000 components could be squeezed onto a single chip — an unheard-of number at the time. It's a charmingly small-potatoes number now, given that in 2024, a company unveiled a 4 trillion-transistor chip.

In 1968, Moore would co-found the chipmaker Intel, where his doubling law would go from a casual observation to a motivation for innovation.

Despite its name, Moore's law was never an ironclad rule. In 1975, Moore downgraded the pace of progress to transistor doubling every two years, rather than every year. That more modest doubling rate would become the official Moore's law, which would hold for years after. This relentless drive toward more computing power and miniaturization is what enables virtually all modern electronics, from the personal computer to the smartphone.

For years, people predicted that the law would become outdated, but it proved remarkably resilient for quite some time.

"The fact that we've been able to continue [Moore's law] this long has surprised me more than anything," Moore said in an interview with The Electrochemical Society in 2016. "There always seems to be an impenetrable barrier down the road, but as we get closer to it, people come up with solutions."

However, eventually, the principle would no longer hold. It's not clear exactly when Moore's law became defunct. In its canonical form, the standard likely died in 2016, as it took Intel five years to go from the 14-nanometer-size technology to 10 nanometers. Moore saw this happen, as this was years before he died at the ripe old age of 94 in 2023.

Eventually, Moore's "law" had to peter out because it runs up against the actual laws of physics. As transistors became ever smaller, quantum mechanics, the physics that governs the very small, began to play an outsize role. The world's smallest transistors can face problems with "quantum tunneling," wherein electrons in one tiny transistor can tunnel into another, thereby allowing current to flow in transistors that should be in the "off" position.

As a result, chipmakers are looking at designing chips with new materials and new architecture. The next Moore's law may apply to quantum computers, which harness quantum mechanics as a feature, not a bug, of calculations.

An astronomy graduate student in England was scouring more than 100 pages of data per day from a radio telescope when she noticed a strange, repeating signal that she dubbed "LGM" — short for "little green men."

The doctoral student, Jocelyn Bell Burnell (then Jocelyn Bell), had helped build the radio telescope, called the Mullard Radio Astronomy Observatory. The "observatory" was an inelegant mishmash of wires and cables strung from posts, spanning a space about the size of 57 tennis courts, and it looked a bit like a frame you'd use to grow pea plants, Bell Burnell said in a Q&A with the University of Cambridge in 2018.

Bell Burnell was solely responsible for operating the observatory and analyzing the data, and for weeks, the grad student had seen a strange "bit of scruff" in a sea of radio data from the observatory.

"From one particular piece of the sky an unclassifiable signal sometimes recurred and my brain started to say: 'You’ve seen something like this before, haven't you? You've seen something like this before from this bit of the sky, haven't you?" she said in the Q&A.

She nicknamed the recurring blip "little green men" because that was what she dubbed an unclassifiable signal that wasn't tied to an obvious source of interference, like car noise or glitches in the wiring.

She took out earlier recordings and noticed the same signal, which she took to her adviser, Antony Hewish. Hewish noted that the squiggle made up only 1 part in 10 million of the data and suggested she needed a faster recorder.

For a month, she heard nothing. Then, on Nov. 28, she found a string of pulses 1.3 seconds apart. She notified Hewish, but when he came to observe on a separate telescope, nothing showed up.

"It was a horrible moment,” Bell Burnell said “And suddenly there it was, five minutes later because we had miscalculated when the telescope would see it."

The duo tried to figure out what it was coming from. It didn't originate from ordinary sources of interference, and it was too fast to be coming from any known type of star.

Then, Bell Burnell noted another bit of scruff with a regularly repeating signal from a different patch of the sky. All told, over the next month, they found four such signals. Hewish, Bell Burnell and colleagues submitted their discovery to the journal Nature. Soon after, Hewish gave a talk at Cambridge about the discovery, which sparked a media frenzy about the possibility of aliens.

That media attention came with a big dose of silliness and sexism.

"Journalists were asking relevant questions like was I taller than or not quite as tall as Princess Margaret, and how many boyfriends did I have at a time?” Bell Burnell recalled.

Bell Burnell and Hewish quickly ruled out aliens, and by the following year, scientists had found dozens of these strange cosmic repeaters.

In May 1968, astrophysicist Thomas Gold showed that the mysterious signals came from pulsars — rapidly rotating neutron stars that, like cosmic lighthouses, consistently sweep beams of radio waves across the cosmos. (Neutron stars are ultradense, collapsed cores of stars that have gone supernova.)

Pulsars send out regular beams of radiation because their powerful magnetic fields are misaligned with the remnant star husks' rotational axes, according to the American Physical Society.

In 1974, Hewish shared the Nobel Prize in physics for his discovery of pulsars with Martin Ryle, one of the key creators of the radio telescope. Bell Burnell was snubbed, prompting some to dub the awards the "No-Bell Prizes."

Bell Burnell, for her part, took the snub philosophically. She noted that it was always up for debate whether an adviser or mentee gets credit for research, and thought the Nobel shouldn't be bestowed on students except in rare cases.

"I am not myself upset about it — after all, I am in good company, am I not?" she joked about not receiving the award.

Bell Burnell later left radio astronomy to work in X-ray and gamma-ray astronomy. But her legacy was eventually honored. In 2018, she was awarded the $3 million Breakthrough Prize for her part in the discovery of pulsars. She donated her prize winnings to fund a scholarship.

More than 50 years ago, two anthropologists were digging in Hadar, Ethiopia, when they spotted something glinting in a gully. What they found would transform the story of human evolution.

Donald Johanson, then a curator at the Cleveland Museum of Natural History, was leading an excavation in the Awash Valley because of some millions-of-years-old stone tools that had been found there. He and graduate student Tom Gray had set out early that morning to hunt for fossils. The object they'd spotted turned out to be a fossil of a human ancestor, and when they looked around the site, they found others from the same individual.

Later that night, the team excitedly discussed the find as the Beatles song "Lucy in the Sky with Diamonds" played in the background. Team member Pamela Alderman suggested the fossil be named "Lucy."

"And it just became iconic," Johanson told Live Science in 2024. "A moniker that everybody knew."

Over the next several weeks, the team would dig up parts of the skull, rib cage, pelvis and limb bones of a 3.2 million-year-old human ancestor — at the time, the oldest and most complete skeleton of a human ancestor ever found. It would become known as Australopithecus afarensis — and would transform our knowledge of human evolution.

"Lucy" was so complete that you could almost see her staring out at you across the eons. We've learned much about her life over the years: that she had massive leg muscles for walking and climbing trees; that she would have been a bad runner due to differently shaped tendons and muscles in her calf; and that she likely used tools.

"Lucy" also settled a debate that had been brewing in the field. Lucy lived at the "halfway point" in human evolution — about equidistant in time from both apes and modern Homo sapiens. At the time, many anthropologists thought big brains evolved before upright walking. But the diminutive, small-headed "Lucy" was clearly adapted to walking on two legs. Most anthropologists now think A. afarensis represents a direct human ancestor.

Lucy's discovery set the stage for the identification of even older archaic hominins, including the famous Ardipithecus ramidus fossil known as "Ardi."

"The discovery of Lucy really hit the start button for looking in older and older sediments in Africa," John Kappelman, a paleoanthropologist at the University of Texas at Austin, previously told Live Science.

Over the years, scientists have unearthed more than 500 A. afarensis fossils spanning a million years of evolutionary history, from sites in Tanzania, Kenya and Ethiopia. And we have learned a lot about how Lucy herself lived and died, and can even re-create her last day on Earth.

We have also discovered that Lucy's kind lived in a world teeming with other human ancestors and relatives. Thus far, anthropologists have identified several Australopithecus species, as well as other related genera.

Thanks to fossils like Lucy and her relatives, anthropologists are now realizing that human evolutionary history is more like a braided stream than a family tree.

In 1943, a physicist and a biologist published a paper that confirmed one of the central pillars of Darwin's theory of evolution.

The paper, by Max Delbrück of Vanderbilt University and Salvador Luria of Indiana University, described a simple experiment, called the "fluctuation test," that showed that mutations arose spontaneously in bacteria, rather than emerging in response to "selection pressures."

The question had been debated since Darwin published his classic "On the Origin of Species" in 1859. Darwin proposed that natural variation occurs randomly in all creatures and environmental pressures then make some of those variations better or worse for certain organisms in their "struggle for existence." Over time, those traits become more common as the fittest organisms survive and multiply. In contrast, French naturalist Jean-Baptiste Lamarck proposed in the early 1800s that variation could be induced by environmental pressures.

When Delbrück and Luria did their experiments, Darwin's theory was thought to be correct for plants and animals, but some scientists believed that interactions between bacteriophages — viruses that attack bacteria — and their bacterial hosts could somehow induce bacterial resistance to the phages.

Delbrück came into the field by accident. The disaffected physicist had emigrated to the U.S. from Germany due to the hostility of the Nazi regime and became interested in the idea of modeling genetics using ideas derived from quantum mechanics and atomic theory.

While researchering in California, he met a researcher who was studying a newly characterized bacterium called Escherichia coli, which had been cultured from Los Angeles sewage. The researcher had identified a phage that preyed on the E. coli. Delbrück was blown away by how easy it was to identify and count individual phage particles under a microscope.

"You could put them on a plate with a lawn of bacteria, and the next morning every virus particle would have eaten a macroscopic 1 mm [0.04 inch] hole in the lawn," Delbrück recounted in an oral history taken in the 1970s. "This seemed to me just beyond my wildest dreams of doing simple experiments on something like atoms in biology."

In December 1940, at Cold Spring Harbor Laboratory in New York, Delbrück met Luria, an Italian-Jewish doctor. Like Delbrück, Luria had fled the Nazis, and like Delbrück, he had been bored with his chosen specialty.

Luria had seen some early work on phages and had also become enamored with the idea of using phages to investigate genes as if they were a collection of atoms. At the time, people understood the idea of genes but had little understanding of what they were made of.

About nine months after they met, the duo decided to test whether phages could induce resistance in E. coli. They were stuck on how to proceed, until Luria chatted with a colleague who was playing the slots. He realized statistics could be used to distinguish between random mutations and ones induced by the phages — in other words, to determine the direction of the cause and effect.

They filled a bunch of tubes with E. coli and then exposed the bacteria to phages and serially cultured them on plates. If mutations were acquired, they reasoned, all of the plates would develop E. coli with resistance mutations at roughly the same proportions, and only after the phage was introduced to the plates. By contrast, if mutations arose randomly, there would be more variation in the number of resistant bacteria between cultures; some would be "jackpot plates" with many more resistant E. coli because they happened to evolve resistance genes early in culture growth, as opposed to later on.

This became known as the "fluctuation test," and the duo published their findings confirming that mutations arise randomly in bacteria in 1943.

That same year, they began collaborating with Alfred Hershey, a microbial chemist then at Washington University in St. Louis. The trio would go on to show that phages contained more than one gene and that the viruses could swap genetic information with each other within the same bacteria, known as genetic recombination. Later, Hershey and collaborator Martha Chase showed that DNA was the carrier of that genetic information. Hershey, Luria and Delbrück would earn the 1969 Nobel Prize in physiology or medicine for their contributions to genetics.

Interestingly, while their work cemented the Darwinian hypothesis that natural selection acts upon random variation, some newer research suggests that not all mutations are completely random. Mutation rates in "essential genes" occur at lower rates than in more incidental ones, at least in certain plants. And recent research suggests that if the team had chosen a different bacterium and phage system to study — such as one that used the bacterial immune system CRISPR to fight off phages — the statistical results would not have been so clear-cut.

In January 2003, epidemiologists in China identified two cases of "atypical pneumonia" in patients who had visited health care workers in Guangdong province. Teams initiated contact tracing and eventually discovered that the germ responsible for the illnesses had been circulating since a patient fell ill Nov. 16, 2002.

Those early cases in November were in "food handlers" — those who either worked as chefs in restaurants or as vendors at "wet markets," where live animals, such as poultry and more-exotic animals like civet cats and raccoon dogs, were held in crowded conditions.

By the time Chinese disease investigators realized an outbreak might be unfolding, the disease had already been circulating for two months and had spread to health care workers.

The disease reached Hong Kong in February and then exploded when a nephrologist from southern China traveled to the region for a wedding on Feb. 21, 2003. He was unwell during his trip and later died of the disease.

In March, a case investigator for the World Health Organization (WHO), Dr. Carlo Urbani, came to investigate a case observed in a businessman who had traveled to Hong Kong before arriving in Hanoi, Vietnam, and being hospitalized there. Urbani ultimately acquired the disease himself and died that same month.

By March 12, the WHO had issued an alert about a severe form of pneumonia of unknown origin in people from China, Hong Kong and Vietnam. By March 15, the Centers for Disease Control and Prevention (CDC) had officially named the disease severe acute respiratory syndrome (SARS), and by March 24, they had identified a novel coronavirus as the cause.

By that time, the outbreak had neared its peak. The pandemic lasted for months, spread to 28 countries beyond China —with 29 cases in the U.S. — and affected more than 8,000 people, 774 of whom died. The disease's case-fatality rate was estimated to be around 9.6%.

In early 2004, SARS briefly flared up again, but its spread was quickly squelched through an aggressive and rapid contact-tracing-and-containment strategy.

That second flare-up enabled scientists to trace the SARS virus to palm civets and raccoon dogs sold at markets. The next year, scientists proposed that horseshoe bats were the pathogen's original animal host, but it wasn't until 2017 that researchers found the smoking gun: bats carrying a rich pool of SARS-like viruses living in remote caves in China's Yunnan province. The caves were just a mile away from villages.

"The risk of spillover into people and emergence of a disease similar to SARS is possible,” authors warned in their paper at the time.

The SARS epidemic, as scary as it was at the time, was ultimately just a dress rehearsal for the COVID-19 pandemic that swept across the globe from March 2020 to May 2023, after early cases started to emerge in November 2019. The two viruses belong to the same general family of coronaviruses and likely emerged from a similar animal host.

Scientists and public health officials successfully applied some of the lessons of SARS to the COVID pandemic. For instance, when SARS first emerged, China had a very rudimentary infectious-disease surveillance system. While they did report cases of infectious and food-borne diseases, communication was by telephone call, there was no standardized case reporting system, and they had no system in place to track contacts or collect lab results. After the SARS epidemic, China quickly implemented a thorough contact-tracing and disease-surveillance system.

That would prove crucial when SARS-CoV-2, the coronavirus that causes COVID-19, emerged in China. The country logged hundreds of thousands of cases of infections during the first wave, which ended in China by mid-February — just a few months after investigators first reported a cluster of pneumonia cases of unknown cause in Wuhan. (A draconian lockdown also likely helped contain the virus's spread within the country.)

Whereas it took months to identify the cause of the SARS pandemic, the SARS-CoV-2 virus was identified less than two weeks after the first cases were noticed. And SARS had no specific treatment, whereas by mid-March 2020, vaccines against the newly identified virus were in clinical trials, thanks to mRNA technology that had been in the works for decades.

Other lessons the world could have taken from SARS were only partially learned. In 2017, when the SARS source was identified, Dr. Kwok-Yung Yuen, a virologist at the University of Hong Kong who co-discovered the virus, told Nature News that the finding "reinforces the notion that we should not disturb wildlife habitats and never put wild animals into markets." He told Nature News that respecting nature "is the way to stay away from the harm of emerging infections." Yet the practice continued.

In some ways, the SARS epidemic also gave public health agencies a false sense of security. SARS and related coronavirus diseases, such as Middle East respiratory syndrome (MERS), were much deadlier than SARS-CoV-2 but also much easier to contain. Outbreaks were relatively easy to control using contact tracing and other public health measures, rather than requiring the distribution of vaccines.

That's because SARS had a shorter infectious window than COVID-19. It was most infectious during the second week of the illness, when people were seriously ill, whereas SARS-CoV-2 was easily transmitted from the early phases of disease, sometimes even before symptoms emerged.

Over a feverish 10-day period in 1985, scientists conceived of a new molecule of perfect symmetry — and named it after one of the 20th century's most famous inventors and futurists.

The hunt started in the 1970s when Harry Kroto, a lab chemist at the University of Sussex in the U.K., was puzzling over the discovery of a primordial soup of organic molecules in the "vast dark clouds that lie between the stars," Kroto said in his Nobel Prize speech.

But radio and light-based data from this interstellar medium suggested there were many more long carbon-chains than should have been possible given the astrophysical molecular synthesis theories of the time. Scientists began to wonder whether cooling red giant stars were pumping the interstellar medium full of these six to eight carbon chains.

The eureka moment for Kroto was a visit to the Rice University laboratories of chemists Robert Kurl and Richard Smalley. Smalley had a special apparatus in which a laser beam vaporized atoms on the surface of a metal disk, then swept them up into a helium cloud and a vacuum to cool them, finally analyzing their makeup using another laser.

Kroto began to wonder if they could simulate the outer shells of cool red giants by swapping out the metal disk for one made of graphite, a form of carbon.

Over the first 10 days of September, the trio, along with graduate students Sean O'Brien, and Jim Heath, produced the six-to-eight-carbon chains that supported the red giant theory.

But there were some interlopers: strange forms of carbon made up of 60 carbon atoms, and a smaller concentration of an even-larger byproduct made up of 70 carbon atoms. These "uninvited guests," as Kroto called them, had actually been found in an experiment from Exxon Corporate Research Science Laboratory in New Jersey about a year earlier, but no one had paid them much attention.

After days of working, on Sept. 9, the team came to a conclusion about its structure. "C60 appeared to be really quite unreactive, а behavior difficult to reconcile with a flat hexagonal graphene sheet-the most obvious first thought," Kroto said.

In theory, a flat graphene sheet would have had tons of dangling bonds that would make it more reactive.

For many days, the scientists worked with toothpicks and jellybeans, paper cutouts of hexagons and pentagons, and other "low-tech" modeling solutions to try to puzzle out the structure of this 60-carbon molecule.

Kroto thought back to the 1967 Expo in Montreal, where 20th-century futurist and inventor Buckminster Fuller was showcasing a geodesic dome, a spherical structure with a network of triangles on its surface, which he had patented in the 1950s. Smalley went to his office to grab a book detailing Fuller’s work, and they figured out the proposed structure.

The resulting compound, which they named buckminster fullerene, was a molecule of incredible symmetry. The paper describing their new molecule was published Nov. 14, 1985 in the journal Nature, and they were soon nicknamed buckyballs.

Over the next few years, the team deduced the properties of the class of closed molecules, called fullerenes. And by 1990, scientists had figured out that by putting an electric arc between two sticks of carbon, they could produce scads of buckyballs.

Kroto, Smalley and Curl won the 1996 Nobel Prize in Chemistry for their discovery and characterization of buckyballs.

Fullerenes as a class have proven useful, and chemical relatives of buckyballs, called nanotubes, are super strong and have high thermal and electrical conductivity. These nanotubes have become crucial in atomic force microscopes, batteries, coatings and biosensors. But though scientists have proposed using buckyballs in everything from quantum computing to drug delivery, they have yet to find their niche in mainstream applications.

On a cold day in November, a man living quietly in Russia posted a paper to a public server.

Published by "Grisha Perelman" and titled "The entropy formula for the Ricci flow and its geometric applications," it was the foundation for one of the most important math proofs.

The paper was the first of three published over the next year solving the long-standing Poincaré conjecture, a hypothesis posed nearly a century earlier by Henri Poincaré.

In simple terms, Poincaré hypothesized that if you were to take any kind of 3D space — from a cat to the Empire State Building — and draw a 2D loop on it, if you can shrink that loop down to a point without breaking either the loop or the shape, then the space is mathematically equivalent to a sphere.

Proving this conjecture was crucial to topology, the mathematical study of shapes. Mathematician Stephen Smale had solved the conjecture in five dimensions in 1961, earning math's prestigious Fields Medal in the process. But the 3D case proved the most intractable.

In the 1980s, Richard Hamilton, a mathematician at Columbia University, proposed solving the conjecture using a math technique called Ricci flow, which had been useful for Einstein's theory of general relativity, as well as string theory.

In 2006, New York Times reporter Dennis Overbye likened the Ricci flow technique to using heat from a hair dryer to smooth out shrink-wrap. Similarly, the Ricci flow could smooth out wrinkles and curvature and reduce a complicated shape to a more fundamental one.

Ricci flow worked to simplify roundish shapes to spheres, but singularities — points of infinite density — kept cropping up in more complicated shapes. Topologists can perform a kind of "surgery" to excise these singularities, but there was still a possibility that the singularities would keep emerging forever. Researchers were stuck.

Perelman's work solved the singularity problem. Perelman (whose first name is Grigori, also spelled Grigory; Grisha was a nickname) had spent the prior decade doing postdoctoral research in the U.S. at several institutions. In the mid-1990s, he turned down very prestigious math fellowships in the U.S. and Europe, returned to St. Petersburg, and took a position at the Steklov Institute of Mathematics.

The friendly-but-shy and "unworldly" mathematician "looked like Rasputin, with long hair and fingernails," and he told colleagues he enjoyed hiking in the woods around St. Petersburg, hunting for mushrooms, Robert Greene, a mathematician at UCLA, told Overbye in 2006. He seemed completely uninterested in wealth or material success, his colleagues reported.

Perelman receded into obscurity after he returned to Russia in the mid- to late 1990s, and many of his colleagues thought he had left mathematics altogether.

Then Perelman published his 2002 paper. Over the next year, he published two more papers and gave a series of talks at several East Coast colleges, explaining his process. Then, he receded into the background once more.

Perelman's work showed that all of the singularities actually reduced to simple shapes, like spheres or tubes, and that if you could follow the Ricci process to its end, you would find the 3D shape reduced to a sphere. He had proved the Poincaré conjecture, but it would take another few years for mathematicians to wade through his brilliant, original and highly technical proofs and confirm that the great topographical problem had, indeed, been solved.

In 2006, mathematicians John Morgan and Gang Tian published a 473-page paper showing that Perelman's work, building on Hamilton's, did in fact prove the elusive conjecture.

Perelman was offered the prestigious Fields Medal and the Clay Millennium math prize, which came with a $1 million award. He turned them down, reportedly due to objections about how credit was given for solving the problem.

Perelman resigned from his position at the Steklov Institute in 2005 and has since ferociously avoided the limelight. It's unclear whether he is still working on math in his St. Petersburg apartment, where as of the early 2010s, his neighbors said he cared for his elderly mom.

When a reporter tried to contact him in 2010, he rejected an interview, saying, "You are disturbing me. I am picking mushrooms."

The winds were blowing at 40 mph (64 km/h) across the Tacoma Narrows strait when "Galloping Gertie" began to bounce.

The Tacoma Narrows Bridge, which connected Tacoma, Washington, with the Kitsap Peninsula, had opened to great fanfare just a few months earlier, in July 1940. The elegant and flexible structure — at the time, the third-longest suspension bridge in the world — had been designed by world-renowned bridge engineer Leon Moisseiff, who also helped design the Golden Gate Bridge.

Yet, from the beginning, workers noticed the bridge's oscillation in the wind, nicknaming it "Galloping Gertie."

"We knew from the night of the day the bridge opened that something was wrong. On that night, the bridge began to gallop," said F. Bert Farquharson, an engineer at the University of Washington who had been hired by the Toll Authority to figure out the source of the oscillation, according to the Washington Department of Transportation (WSDOT).

When Farquharson's team contacted Moisseiff, he acknowledged that two of his other bridges also oscillated, but with much lower amplitude.

Farquharson's team commissioned a 1:200 scale model that was 54 feet (16.5 meters) long, as well as an 8-foot-long (2.4 m) 1:20 scale version of one of the bridge sections to try to pinpoint the problem. They also used a wind tunnel in an attempt to replicate the issue.

Meanwhile, the Toll Authority immediately began trying to remedy the problem. Soon after the bridge's opening, engineers installed four hydraulic jacks to act as shock absorbers, but Gertie kept galloping. In October, the team affixed temporary cables to tie the bridge to the ground across the bridge's span. Although the tie-down cables reduced oscillations at the bridge's ends, the center still moved up and down. In any case, one cable snapped during high winds on Nov. 1, and the bridge began galloping again.

On Nov. 2, Farquharson's team finished their modeling, which revealed that the bridge began twisting when winds gusted up from the sides. The team suggested either cutting holes in the girders or blocking the wind with deflectors. They began making fixes. In 10 days, some of those deflectors would have given the bridge enough stability to be safe, they argued, and the full bridge retrofit would have been completed in 45 days.

But they never got a chance to see if those fixes would work. On the morning of Nov. 7, Leonard Coatsworth, a copy editor at the Tacoma News Tribune, was driving to the family's summer cottage on the peninsula with Tubby, his daughter's three-legged cocker spaniel, when the bridge began to undulate up and down and tilt side to side. He called his newspaper, which sent along reporter Bert Brintnall and staffer Howard Clifford as a photographer.

Prior to this, Coatsworth said, he'd experienced the bridge moving up and down, but the tilting was new.

"Before I realized it, the tilt from side to side became so violent I lost control of the car and thought for a moment it would leap the high curb and plunge across the sidewalk of the bridge and into the railing," Coatsworth wrote in an account the same day for the Tacoma News Tribune.

He abandoned the car part way across the bridge.

Clifford, for his part, was the last man off the bridge.

"The roadway was bouncing up and down, falling beneath me and literally leaving me running in air. It would then bounce back, forcing me to my knees. I continued for what seemed like ages, but probably was only a couple of minutes and finally reached stable ground. Bert [Brintnall] was waiting there for me, leaving me to be the last person off the bridge," Clifford said in a later story for the newspaper.

There was a loud noise, like a shot, when the 57 foot (17.5 m) cable snapped, and at 11:02 a.m., the center of the bridge fell into the water. Clifford and Brintnall and a cameraman captured the bridge's fall.

Tubby the dog did not make it, but he was the only casualty of the day.

The catastrophic collapse seriously tarnished the reputation of Moisseiff, who died of a heart attack just three years later.

But the bridge collapse also provided unprecedented engineering insights.

A team eventually determined that the collapse was caused by torsional flutter. After a cable midspan slipped, it separated into two unequal lengths. This, in turn, allowed the bridge to start twisting. Twisting changed the angle of the wind relative to the bridge's main plate girders so that it absorbed more energy, thus raising the amplitude of the motion. At some point, the twisting synchronized with the wind vortex, and the twisting became self-sustaining.

"In other words, the forces acting on the bridge were no longer caused by wind. The bridge deck's own motion produced the forces. Engineers call this "self-excited" motion," according to the WSDOT.

In all, the bridge was too long, its deck was too light, and its roadway was too skinny to provide sufficient resistance to aerodynamic forces, a report on the failure concluded.

As a result of the collapse, all engineers must test a 3D-scale version of any bridge in a wind tunnel before building begins. The failure also meant that "deflection theory" — a notion that only vertical motion in suspension bridges was relevant — was amended to include other modes of motion. And after a great windstorm threatened the Golden Gate Bridge in 1951, the iconic Bay Area landmark was strengthened to improve its "torsional stability."

On a sunny morning, Egyptian workers were clearing the sands at the Valley of the Kings, when they uncovered the hint of stone steps about 13 feet (4 meters) below the tomb of Ramesses VI.

This sunken staircase would lead to the unlooted tomb of King Tutankhamun, a pharaoh who died as a teenager more than 3,200 years earlier.

The excavation team, helmed by British archaeologist Howard Carter but composed almost exclusively of Egyptians, had been clearing away sand near huts in the Valley of the Kings. Some stories hold that a water boy, Hussein Abd el-Rassul, may have been the first to spot the staircase.

When they found the steps, the group knew they had uncovered something important. The team worked feverishly until they reached the 12th step, where they discovered a small doorway covered with plaster, Carter wrote in his diary. On the door, they could partly make out the seal of the Royal Necropolis, which depicted the god Anubis as a king standing over the vanquished bodies of nine foes.

"Here before us was sufficient evidence to show that it really was an entrance to a tomb, and by the seals, to all outward appearances that it was intact," Carter wrote in his diary on Nov. 5.

As they explored further, the team found that the entryway had been filled with rubble — likely by priests intending to block the tomb, which was further evidence the tomb had not been looted.

For the next few weeks, the team excavated the steps and the doorway until they uncovered a seal bearing the cartouche — an oval filled with hieroglyphs depicting a ruler's name — of King Tutankhamun on Nov. 24. But the team still wasn't sure who was buried inside, because the rubble filling the entryway had a confusing mélange of pottery shards and broken boxes that bore signs of other ancient Egyptian monarchs, including Akhenaten, Tut's father.

On Nov. 25, they opened the first door to the tomb. The next day, they found a second door and cut a tiny hole inside to see what lay beyond it. No Egyptian officials were permitted to view the tomb, but Carter had brought along Lord Carnarvon, who had financed the tomb excavation; Lady Evelyn Herbert, Carnarvon's daughter; and Arthur Callender, an engineer with the dig. All waited anxiously to see what lay inside.

"It was sometime before one could see, the hot air escaping caused the candle to flicker, but as soon as one's eyes became accustomed to the glimmer of light the interior of the chamber gradually loomed before one, with its strange and wonderful medley of extraordinary and beautiful objects heaped upon one another," Carter wrote in his diary.

King Tut's tomb was the first unlooted pharaoh's tomb discovered in the modern era, and it was teeming with rich treasure. One of the most famous artifacts discovered was his ornate death mask, a 22-pound (10 kilograms) solid-gold face covering inlaid with semiprecious stones. But Tutankhamun was also buried with board games, several beds, and even a mannequin to try on outfits in the afterlife.

Tutankhamun was laid to rest in three nesting coffins — two made of gilded wood and the third (and smallest) of solid gold — and his body was soaked in oil that turned it black before he was mummified.

About a month after the tomb was opened, Lord Carnarvon died after a mosquito bite became infected following a shaving accident. And, in 1923, Pearson's Magazine published a fictional story called "The Tomb of the Bird," in which Carter's canary was found dead in the mouth of a cobra soon after the tomb was opened. The rumor mill and media reports spun these and a handful of other flimsy coincidences into evidence of a mummy's curse, the notion that whoever opened a pharaoh's tomb would face an early or unnatural death. However, a 2002 study found that the 25 Westerners exposed to the tomb (and thus the "mummy's curse") lived about as long as would be expected for the time.

In September 1994, a pair of Swiss astronomers at a little observatory nestled in the south of France began training their telescopes on a star about 50 light-years from Earth — and created the field of exoplanet research.

The duo, Michel Mayor and Didier Queloz, had finally found something they'd spent 18 months searching for: a planet orbiting a star like our own.

The discovery was the first step in a much more ambitious goal: to prove we are not alone in the universe. Carl Sagan and other astronomers had begun searching for intelligent life as early as the 1960s, but many of those efforts were focused on finding radio signals or other deliberate communications from intelligent, technological life-forms.

But by the 1980s, astronomers realized they could find potentially habitable planets by looking at the light from their companion stars. Astronomers had found hints of a planet circling a pulsar — an ultradense, magnetized star that beams radiation like a lighthouse. But the extreme, destructive conditions surrounding a pulsar made it highly unlikely that life could exist there.

And back in 1987, a Canadian team of astronomers thought they had spotted a planet around another star, only to conclude five years later that the signal did not indicate a planet. (Their first hypothesis was ultimately confirmed in 2003.)

So Queloz and Mayor, who were astronomers at the Geneva Observatory at the time, began looking for anomalies in the trajectories of nearly 150 smaller, more ordinary stars.

After months of observations, they noticed a handful of stars with significant deviations, or wobbles, in their trajectories. They zeroed in on one of those stars: Pegasi 51, located about 50 light-years from Earth in the constellation Pegasus. The middle-age, main sequence star looked a lot like our sun, and the wobble of the star's velocity suggested it was being tugged back and forth by a planet.

An analysis of the star's light unmasked the planet, which scientists dubbed 51 Pegasi b, or Dimidium. The astronomers found that the planet was likely a "hot Jupiter" — a giant gas planet that orbits very close to its star. Dimidium, the team found, was a gas giant bigger in diameter than Jupiter with about half its mass. It orbited just 5 million miles (8 million kilometers) from its star. That close orbit meant the planet completed a revolution around its star every 4.2 days. Soon after, scientists at the Lick Observatory in California confirmed the discovery.

On Nov. 1, 1995, Queloz and Mayor described their findings in the journal Nature — and opened the floodgates to exoplanet discovery. Soon after, dozens of exoplanets were found, setting off a race to search for planets that could harbor life and ushering in new techniques to discover them. In 2004, astronomers using the Very Large Telescope in Chile captured the first photographic evidence of an exoplanet orbiting a distant star, with hundreds of others soon to follow.

In 2019, Mayor and Queloz won the Nobel Prize in physics for their work on Dimidium, sharing their prize with Canadian physicist James Peebles, who helped quantify how much of the universe was made of dark energy and dark matter.

Over the next three decades, astronomers would find many more hot Jupiters, hell planets, super-Earths, water worlds and desert planets in the cosmos. To date, we know of at least 6,000 exoplanets — and though none has been found to harbor life so far, we've had a few promising candidates.

Late one evening, UCLA graduate student Charley Kline sat in front of a refrigerator-sized computer and sent the message "lo" to a rack of computers operated by systems engineer Bill Duvall at the Stanford Research Institute (SRI), hundreds of miles away.

This message itself was nothing special; it was meant to be the word "login," but the system crashed before it could be completed. However, the transmission was revolutionary, because it formed the foundation for the internet.

The two computers were part of a four-computer network that made up the first Advanced Research Projects Agency Network (ARPANET).

The notion of computers communicating was part of a grand vision to "augment human intellect," but ARPANET was ultimately funded for a more practical purpose: to enable the U.S. government to communicate in the wake of a nuclear attack. Although telephone lines would likely be intact in that case, the major switching centers could be destroyed, the military worried.

In 1964, RAND Corp. scientists Paul Baran and Sharla Boehm sent a memo proposing a solution: a "distributed network" that involved "hot potato" switching so that no single node would be crucial to the system's functioning.

From there, the military agency funded a project to create such a network. For the system to work, it needed a way to break up messages from a sender into smaller portions that were then reassembled at the destination. Boehm and Baran simulated this process, which would eventually become known as packet switching, using a program written in the computer language Fortran.

Even before ARPANET was realized, however, the scientists involved in the project clearly saw the potential of the concept. Baran, for instance, envisioned that by the year 2000, people would be able to do their shopping from home using a TV.

In 1968, ARPANET was approved, and by the summer, scientists at the University of California, Santa Barbara; SRI; UCLA; and the University of Utah began building the infrastructure to allow their computers to communicate using these packets.

For the first transmission, each computer at these locations had a separate, "mini-computer" called an interface message processor (IMP), which would evolve into the routers of today. The IMPs were meant to break up the messages into smaller chunks and send them to the IMP at the receiving end, which would then reassemble them and echo them to the receiving terminal.

On the storied evening the message was sent, Kline and Duvall were on the phone with each other, confirming when each letter arrived. But the system crashed because the Stanford computer was expecting the data to be transmitted at 10 characters per second, while ARPANET had an unprecedented speed of 5,000 characters per second. This overloaded the "buffer" in the Stanford computer, according to BBC Future.

"It was like filling a glass with a fire hose," Duvall told BBC Future.

Duvall identified the problem and got the system up and running an hour later.

Almost immediately, researchers realized the potential of the system.

"As of now, computer networks are still in their infancy, but as they grow up and become more sophisticated, we will probably see the spread of 'computer utilities,' which, like present electric and telephone utilities, will service individual homes and offices across the country," Leonard Kleinrock, a computer science professor who was in charge of that UCLA node, said in a statement at the time.

ARPANET would be tied to its military roots until 1981, when the military spun off its own MILNET. And while the term "internetwork" was coined in a 1970s paper to describe a standardized protocol for transmitting and receiving data, the internet itself technically wasn't born until 1983, when ARPANET switched over to that protocol.

In 2007, scientists published a paper that laid out a recipe for a new type of biochemistry. The method would allow scientists to see what was happening in organisms in real time.

Carolyn Bertozzi, then a biochemist at the University of California, Berkeley, and her research lab had spent years trying to visualize glycans, special carbohydrate molecules that dot cell surfaces.

Glycans are one of the three major classes of biomolecules (alongside proteins and nucleic acids) and had been implicated in inflammation and disease, but scientists had found them challenging to visualize. To do so, Bertozzi built upon a chemical approach pioneered by biochemists K. Barry Sharpless, of Scripps Research, and Morten Meldal, of the University of Copenhagen.

Sharpless had laid out a vision for "click chemistry" — a way to rapidly build complex biological molecules by snapping smaller subunits together.

Biological molecules often have backbones of bonded carbon atoms, but carbon atoms aren't keen to link up. That meant that historically, chemists had to use painstaking, multistep processes that employed multiple enzymes and left unwanted byproducts. That was fine for a lab but bad for mass-producing biomolecules for pharmaceuticals.

Sharpless realized that they could simplify and scale up the process if they could snap together simple molecules that already had a complete carbon frame. They just needed a quick, powerful, reliable connector.

Separately, Sharpless and Meldal happened upon the critical connector: a chemical reaction between the compounds azide and alkyne. The trick was the addition of copper as a catalyst.

The reaction was extremely powerful and quick, and it occurred more than 99.9% of the time, without producing any byproducts.

But for Bertozzi, there was a problem: Copper is highly toxic to cells.

So Bertozzi combed the literature to devise click chemistry that was safe in living cells. She found the answer in decades' old work: Azide and alkyne would react "explosively," without the need for a catalyst, if the alkyne was forced to take on a ring shape.

In 2004, her team demonstrated that this reaction could be used to attach azide molecules to living cells without harming them. And in 2007, Bertozzi and colleagues used her method to visualize glycans within living hamster cells.

Her process involved incorporating a carbohydrate molecule modified with azide into glycans in living cells. When they added a ring-shaped alkyne molecule that was bound to a green fluorescent protein, the azide and alkyne clicked together and the glowing green protein revealed where the glycans were in the cell.

Bertozzi dubbed the process "bioorthogonal" click chemistry — so named because it would be orthogonal to — that is, would not interfere with — the biological processes occurring in the cell. Her work has proved crucial in understanding how small molecules move through living cells. It has been used to track glycans in zebrafish embryos, to see how cancer cells mark themselves safe from immune attack using the sugar molecules, and to develop radioactive "tracers" for biomedical imaging. And click chemistry more broadly has supercharged the process of drug discovery.

In 2022, Sharpless, Meldal and Bertozzi earned the Nobel Prize in chemistry for their work on click chemistry.

On the afternoon of Oct. 9, 1876, Alexander Graham Bell was in Boston when he had a three-hour chat with his assistant and fellow inventor, Thomas Watson. It would not have been noteworthy — except that Watson was across the Charles River, in Cambridgeport.

This was the first two-way telephone call transmitted across outdoor wires, and it would eventually pave the way for a global network that would transform how people communicate.

Bell and Watson had spoken via their device as early as March of that year, soon after Bell's improved "telegraphy" device was patented. But the crackly command — "Mr. Watson, come here; I want to see you," was issued over only a short distance.

In contrast, the call that October day lasted a few hours and was transmitted via long telegraph wires.

Bell was in a crowded field of inventors who were dreaming up new ways to transmit sound via electricity. A few decades earlier, Antonio Meucci created — and took preliminary steps to patent — a "telectrophone" to communicate with his bedridden wife in another room. In 1861, German inventor Johann Philipp Reiss coined the term "telephon" to describe a device of his own, which converted sound waves to an electrical signal and back. His transmissions faithfully reproduced melodies, but words were too garbled to be understood. And around the same time as Bell, Elisha Gray developed a similar water-microphone-based design.

Key to Bell's ability to transmit a voice was the notion of transmitting multiple frequencies simultaneously, which he did by using what he called an "undulatory" — or variable — current, rather than the pulses of intermittent current that Samuel Morse had used for his telegraph.

"The rate of oscillation in the electrical current corresponds to the rate of vibration of the inducing body — that is, to the pitch of the sound produced," Bell's patent states. "The intensity of the current varies with the amplitude of the vibration — that is, with the loudness of the sound." In short, the features of the current encode features of the sound.

Bell's first prototype used a diaphragm, an inductor (an iron core encircled by a coil of wires), a permanent magnet, and connecting wires. When a sound wave hit the diaphragm, the pressure waves caused that diaphragm to vibrate. These vibrations moved the inductor, altering the magnetic field it produced, which, in turn, caused current to flow in the coiled wire. That current was then transmitted via wires to the receiver, which had the same elements in reverse.

That first long-distance conversation was galvanizing, but the first telephone line, which was laid in April 1877, only connected a merchant's shop with his home. Phone lines were initially rented in pairs and were used to connect discrete locations. But the opening of "central exchanges" and switchboards around a year later enabled calls to be routed between locations, dramatically improving the usefulness of the invention.

It would be decades before the first transcontinental and cross-continental calls were made, and the first undersea trans-Atlantic phone cables were laid in 1956.

The telephone industry helped spur a number of other modern innovations, including switches, the transistor that would usher in the computing era, fiber-optic cables for data transmission, and communications satellites.

On the night of Oct. 5 to 6, 1923, Edwin Hubble discovered a new star — and revealed the utter vastness of the universe.

Hubble was looking at the cosmos with the 100-inch Hooker telescope at the Mount Wilson Observatory near Pasadena, California, when he homed in on a faint smudge of light. He took a series of photographic plates of the object. The rather fuzzy, unimpressive images would go on to revolutionize our understanding of the cosmos.

At first, Hubble thought the object was a nova, a type of exploding star, but a closer look revealed the star's light varied in intensity over the course of the night, brightening, dimming and brightening again in a predictable pattern. On one photographic plate, he crossed out the "N" for nova and replaced it with "VAR!" for variable star.

Named M31-V1, it was a cepheid variable star, a type of star that fluctuates in intensity with striking regularity. Hubble wasn't the first to discover these cosmic "standard candles." In 1912, Harvard observatory astronomer Henrietta Swan Leavitt had cataloged the luminosity and period (pattern of brightening and dimming) of 25 cepheids in the small magellanic cloud, a nearby dwarf galaxy. The brighter a cepheid, the slower it flickered, she found.

But Hubble's observations proved to be pivotal to a great debate raging at the time. Astronomer Harlow Shapley thought the Milky Way constituted the entire universe, while his rival Heber Curtis had done a rough measurement of the distance to neighboring Andromeda, also known as Messier 31, that suggested we lived in an "island universe," teeming with large and staggeringly distant galaxies.

On a dark night, our neighboring galaxy had always been visible to the naked eye, but over the years, skywatchers had debated whether it was a constellation, a nebula or another galaxy.

Hubble's discovery of the cepheid next door buttressed Curtis' argument that Andromeda was a separate galaxy from our own. Hubble would go on to measure M31's cepheid on several nights over the year. The flickering star's variable light intensity enabled Hubble to calculate that Andromeda was a vast 900,000 light-years away.

Leavitt's work on cepheids proved invaluable for Hubble's other great finding: the expansion of the universe. While others, such as Georges Lemaître, had theorized that the universe was expanding by using Einstein's theory of general relativity, Hubble confirmed it with precise calculations.

He combined Leavitt's cepheid distance data with data from Milton Humason and others that showed galaxies' "red shift" — in which wavelengths of light are stretched, or shifted toward the redder end of the spectrum, by the Doppler effect as they move away from us. More-distant objects had a higher red shift, showing they were moving away faster than objects nearby.

Hubble's calculated expansion rate would come to be called the Hubble constant. Since cepheid M31-V1's discovery, multiple lines of evidence have confirmed that we live in an ever-expanding universe, and with the discovery of dark energy in the 1990s, we now know that expansion is accelerating. But modern measurements of the universe's expansion rate don't line up with each other. Determining the source of the discrepancy could pave the way for us to discover new physics, and upend accepted cosmological models once more.

On Oct. 3, 1950, three scientists at Bell Labs in New Jersey received a U.S. patent for what would become one of the most important inventions of the 20th century — the transistor.

John Bardeen, Walter Brattain and William Shockley had submitted the patent application for a "three-electrode circuit element utilizing semiconductor materials" two years earlier, and it would be another few years before the full significance of this technology became clear.

The transistor was initially designed because AT&T wanted to improve its telephone network. At the time, AT&T amplified and transmitted phone signals using triodes. These devices encased a positive and negative terminal and a wire mesh in a vacuum tube, which ensured electrons could flow without bumping into air molecules.

But triodes were power hogs that often overheated, so by the 1930s, Bell Labs President Mervin Kelly began to look for alternatives. He was intrigued by the potential of semiconductors, which have electrical properties between those of insulators and conductors. In 1925, Julius Lilienfeld had patented a semiconductor precursor to the transistor, but it used copper sulfide, which was unreliable, and the underlying physics were poorly understood.

At the end of World War II, as the lab shifted its focus from war technology, Kelly recruited a team, led by Shockley, to find a replacement for vacuum-tube triodes. The team conducted a number of experiments, including plunging silicon into a hot thermos, with limited success. The problem was that they didn't get much amplification.

Then, in 1947, Brattain and Bardeen switched from silicon to germanium and helped clarify the physics at play in the semiconductor. Their work led to a "point-contact" transistor that used a little spring to press two thin slips of gold foil into a germanium slab. Notably, this early transistor took some finessing to work, requiring Brattain to wiggle things "just right" to get the impressive 100-fold amplification in signal.

In 1948, Shockley iterated on that design with what would later be termed the junction transistor, the subject of the patent that would go on to form the basis of most modern transistors.

The key to the technology is that when a voltage is applied to a semiconductor, electrons migrate within the material, leaving positively charged "holes" behind, according to the patent.

Thus, it's possible to create "N-type" or "P-type" semiconductors — areas that carry an excess of either negative or positive charges. When a metal electrode contacts a semiconductor, the current flow would go one way if touching an N-type material and the opposite direction in a P-type material, the patent noted.

The junction transistor takes advantage of this property with a semiconductor with three attached electrodes. By modifying the voltage applied and the properties of the electrodes and the semiconductor, it's possible to reliably amplify the current. This amplification would soon prove invaluable in radios, televisions and telephone networks.

But amplification isn't what ushered in the era of modern computing. Rather, the junction transistor was a tiny, reliable, low-power, "on-off" switch that didn't heat up much. Vacuum tubes were the switches in the first computers, and the transistor was just a much better on-off switch.

Shockley was a notoriously bad boss (and a eugenicist and racist). The key researchers went their separate ways, with Bardeen moving to the University of Illinois and Shockley helping to found the modern Silicon Valley semiconductor industry. The trio would win the 1956 Nobel Prize in physics for their work on the "transistor effect."

A few years later, physical chemist Morris Tanenbaum, who worked briefly under Shockley at Bell Labs, would invent the first silicon transistor. In 1959, Jack Kilby of Texas Instruments filed a patent for the first integrated circuit, which would form the basis for the modern computer chip. And by the early 1960s, the vacuum-tube computer was functionally extinct.

In 1968, Gordon Moore, the founder of Intel, noted in a talk that transistors were being miniaturized and chips were getting twice as powerful at a predictable rate, ushering in the era of Moore's law, which would continue for another four decades.

But with Moore's law now obsolete and AI demanding ever-more-powerful computing, scientists are banking that quantum computers — which can encode multiple quantum states in a qubit, or "quantum bit" — will usher in the next era of computing.

On Sept. 28, 1928, Alexander Fleming woke up to check on his experiments investigating bacterial growth — and accidentally discovered the world's first antibiotic.

The Scottish physicist and microbiologist had been doing experiments in a cramped, roughly 12-square-foot (1 square meter) room in a turret inside London's St Mary's Hospital. The famously untidy scientist would culture bacteria from infected hospital patients; he would leave those cultures around for two or three weeks until his bench was crammed with 40 to 50 plates. Then, he would inspect each plate to see if anything interesting had grown in it, before tossing it out.

The discovery of penicillin occurred when Fleming returned from a two-week break. He looked at his plates of Staphylococcus aureus that had been cultured from an infected wound. On one of the plates, Fleming noticed a patch of green mold intersecting the golden-yellow bacterial colonies, according to an account from his assistant, V.D. Allison. Near the green patch, the bacteria were translucent, colorless and dead. The substance that killed the bacteria would form the basis of the first antibiotic, though the term wasn't coined until 1941.

"When I woke up just after dawn on September 28, 1928, I certainly didn't plan to revolutionize all medicine by discovering the world's first antibiotic, or bacteria killer," Fleming later said. "But I suppose that was exactly what I did."

Fleming determined that the "mold juice" came from a fungal species he eventually identified as Penicillium. When he described the discovery to his fellow doctors at a meeting the next year, he was met with almost total disinterest. Isolating the elusive "mold juice" also proved challenging, so the discovery languished for a decade, Allison wrote in personal recollections.

Then, in 1939, scientists Howard Florey and Ernst Chain took an interest in the substance. They created a research team and, along with scientists such as Margaret Jennings, Edward Abraham and Norman Heatley, managed to isolate penicillin from the mold, test it and use the yellowy, powdery substance to cure a handful of patients. However, the compound was still relatively impure.

In 1942, Fleming was treating a young patient who was seriously ill with meningitis. He found the powder killed the patient's bacterial infection, and he phoned Florey and Chain for some of their stash, even though it was not purified. After Fleming injected it into the boy's spinal cord, the patient recovered.

After this miraculous recovery, Fleming was convinced that penicillin needed to be mass-produced. He pitched it to the government, and soon there was a joint effort between the U.S. and the U.K. to mass-produce the substance. By 1945, the first antibiotic was widely available.

Fleming, Florey and Chain would win the 1945 Nobel Prize in medicine for their work on the discovery, isolation and production of penicillin. In 1964, Dorothy Hodgkin would earn the Nobel Prize in chemistry for elucidating its crystal structure, which helped chemists design later antibiotics.

It's estimated that since its discovery, penicillin has saved 500 million lives and, along with its derivatives, is still a mainstay in the treatment of myriad illnesses, including ear infections, strep throat, and urinary tract infections.

Penicillin also led to the development of hundreds of different antibiotics. But widespread use and misuse of these wonder drugs have meant that many bacterial strains have evolved resistance against common antibiotics, including penicillin. In the arms race against superbugs, scientists are now finding totally new ways to fight bacteria, from harnessing the power of viruses to attack bacteria to using the gene-editing tool CRISPR to design new drugs.

On Sept. 27, 1822, French philologist Jean-François Champollion announced that he had deciphered the text on the Rosetta stone, opening a window into ancient Egyptian civilization.

The stone had been discovered by French forces in 1799, during Napoleon's first foray into Egypt. The soldiers were building fortifications in the town of Rashid, which had been ancient Rosetta, when officer Pierre François Bouchard noticed the granite-like stone built into an old wall.

The 44-inch-tall (112 centimeters), 1,680-pound (760 kilograms) slab of granodiorite was inscribed in Greek, hieroglyphics and demotic, a kind of cursive Egyptian script. Bouchard immediately realized its significance and surmised that the text was identical in all three languages. That meant the ancient Greek could potentially be used to decrypt the other two scripts, which had been indecipherable for centuries.

Ottoman and British forces defeated the French, and in 1801, the Rosetta stone was taken by the British as part of the Treaty of Alexandria and moved to the British Museum.

Based on the Greek inscription, scholars quickly deduced that the text was a royal decree from 196 B.C. that was written in honor of boy king Ptolemy V Epiphanes on the first anniversary of his coronation. The aim of the decree was to assert the Macedonian Greek pharaoh's authority at a tumultuous time, soon after rebellion by the native Egyptians had roiled the Hellenistic hierarchy and the nearby Seleucid Empire had invaded parts of the western Mediterranean.

The inscribed stone slab, or stela, pronounces that Ptolemy, "the god who maketh himself manifest," will fund temples and animal cults, increase priestly income, lighten the tax burden and pardon prisoners. In exchange, statues of him would be placed in all of the temples and priests would tend to those statues thrice daily. Similar stelae were placed throughout the country.

By 1802, a Swedish diplomat had made progress in deciphering some of the words in demotic by relying on its similarity with Coptic, an Egyptian language that, like Latin, wasn't spoken but was still understood.

But it wasn't until 1819 that the key breakthroughs were made. British scholar Thomas Young published an article in the Encyclopedia Britannica in which he defined 218 demotic words and linked them to around 200 associated hieroglyphics. He also deciphered the phonetic hieroglyphs for the word "Ptolemy." However, he suspected only names and foreign words were likely to be phonetic and that other hieroglyphs were symbolic.

When Champollion looked at Young's work, he disagreed. Hieroglyphs, he was convinced, were a decryptable alphabet. He systematically matched the ancient Greek and Coptic words against the hieroglyphs, slowly chipping away at the sounds. Lore has it that when he first realized he'd deciphered the whole text, he fainted for a week. Though that's likely a myth, soon after, he announced his discovery at the Académie des Inscriptions et Belles-Lettres in Paris, where rival Young would hear his discovery.

The translation of the Rosetta stone essentially created the field of Egyptology and allowed scholars to understand the sophisticated civilization that emerged on the banks of the Nile more than 5,000 years ago and persisted for millennia.

Thanks to the Rosetta stone, we have uncovered the elaborate rituals and religious beliefs that governed life and death in the Book of the Dead, have re-created the complex embalming recipes the ancient Egyptians used to mummify the dead, have a detailed picture of day-to-day life for royals and commoners alike, and have untangled the histories of dynasties that ruled for thousands of years.

The Rosetta stone was taken as a spoil of war and is still housed at the British Museum, but it remains a central piece of Egypt's heritage. For many years, Egypt has called for the artifact to be returned to its homeland.

On Sept. 26, 2022, at 7:14 p.m. EDT, NASA smashed a pint-sized spacecraft into an asteroid — and changed the course of both the space rock and planetary defense forever.

The purpose of that mission, dubbed the Double Asteroid Redirection Test (DART), was to see whether an "impactor," or a heavy, fast craft, could deflect a dangerous asteroid from a potential collision course with Earth.

As early as 1968, students at MIT had proposed a thought experiment to commandeer NASA rockets to deflect an earthbound asteroid. But it wasn't till 1980, when geologist Luis Alvarez and colleagues found a global band of iridium in Earth's crust dating to the end of the Cretaceous period, that the potential stakes of such a strike became clear.

The layer of iridium, rare on Earth but common on asteroids, suggested that a massive space rock had struck our planet 66 million years ago, triggering a mass extinction event that wiped out the dinosaurs. In 1992, scientists found the "smoking gun:" the roughly 120-mile-wide (200 kilometers) Chicxulub crater off of Mexico's Yucatan peninsula.

In the 1980s and 1990s astronomers identified a bevy of potentially dangerous space rocks — sometimes only after they had passed worryingly close to Earth. So they began to seriously consider proposals to neutralize asteroids: by nuking them , shooting lasers at them, shoving them off course with steam clouds, or smashing something big into them. (The “smashing” scenario is now known as the kinetic impactor method.)

Then in 2013, a meteor the size of a semitrailer breached the atmosphere over Chelyabinsk, Russia. Exploding with 30 times the energy of the Hiroshima blast, it blew out the windows on more than 7,000 buildings and caused instant ultraviolet burns and injuries to 1,600 people on the ground. No one saw it coming.

Chelyabinsk "was a cosmic wake-up call," then NASA Planetary Defense Officer Lindley Johnson said about the event.

In 2017, NASA approved funding for a project to test a kinetic impactor against Dimorphos, a moonlet that orbited the larger asteroid Didymos. The duo posed little threat to Earth, but because they skim relatively close to our planet, they presented a good test bed for the kinetic impactor method.

Over the next few years, scientists with NASA and Johns Hopkins' Applied Physics Laboratory built a 6.2-foot-long (1.9 meters), 1,280 pound (580 kilograms) spacecraft whose sole purpose was to slam into Dimorphos.

DART launched on Nov. 23, 2021, and smashed into the moonlet's rocky heart, just shy of center, on Sept. 26, 2022, using a special onboard camera to record its last moments. A tiny cube camera had split off from the main rocket days earlier, and lingered to record the chaotic aftermath of the collision.

DART shortened Dimorphos' orbit by 32 minutes, more than astronomers expected and far more than the 73 seconds needed for the project to be considered a success. The impact also created a swarm of boulders, Hubble revealed.

Follow-up studies have raised concerns about the unintended consequences of future deflection missions. One found that rogue boulders from the rubble pile could hit Earth and trigger a spectacular meteor shower in 30 years, while another study predicted that boulders could crash into Mars.

And earlier this year, scientists determined that the boulders aren't behaving as expected, traveling faster and in non-random configurations that hint at physics not yet accounted for. The findings suggest we still have more to learn before we can rely on such technology to save us from a true killer space rock.

"If an asteroid was tumbling toward us, and we knew we had to move it a specific amount to prevent it from hitting Earth, then all these subtleties become very, very important," Jessica Sunshine, a University of Maryland scientist who worked on DART, said at the time. "You can think of it as a cosmic pool game. We might miss the pocket if we don’t consider all the variables."

DART remains the first and only planetary defense mission to be tested on a real space rock. But China has announced that its space agency will mount its own DART-like mission to strike the roughly 100-foot-wide (30 meters) asteroid 2015 XF261, with the launch window opening as soon as 2027.

Twenty-six years ago today, on Sept. 17, a teenager who had received an experimental gene therapy died. His death led to needed changes in the clinical trial process while also spurring skepticism that would ultimately stall the field of gene therapy for years.

Jesse Gelsinger was an 18-year-old with ornithine transcarbamylase (OTC) deficiency, a genetic disease that affects about 1 in 40,000 newborns. The condition makes the body unable to make an enzyme that would normally break down ammonia, a natural waste product of metabolism. Without this enzyme, ammonia builds up in the body and poisons the blood.

About 90% of babies with the most severe form of OTC deficiency die. But Gelsinger — who had a milder, "late-onset" form of the disease — had reached adulthood by strictly adhering to a low-protein diet and a regimen of 50 pills a day, to help reduce the amount of ammonia in his blood and offset its effects. Although Gelsinger was small for his age and experienced a dangerous ammonia crisis when he stopped taking his pills, he was otherwise healthy.

Gelsinger wanted to help newborns with the disease, so he enrolled in a trial to test the safety of a gene therapy aimed at correcting the defective OTC gene. The treatment used a weakened form of an adenovirus, a type of cold virus, to deliver the corrected form of the OTC gene into Gelsinger's cells.

Gelsinger flew to the University of Pennsylvania, where the trial was being run, and had the treatment infused into the artery feeding the liver on Sept. 13, 1999. He had flu-like symptoms that day, as was expected. But by the next day, he was jaundiced, he developed a severe inflammatory reaction and a blood clotting disorder, and his organs began to fail. He was taken off life support around 2:30 p.m. on Sept. 17. Investigations revealed that his death was caused by a severe immune reaction to the virus used to deliver the treatment.

A Food and Drug Administration (FDA) investigation found numerous problems with Gelsinger's enrollment in the trial, according to The New York Times. First, his liver function was too poor and ammonia levels were too high when he started the trial. Second, the team did not disclose to patients that, prior to the trial, lab animals had died from higher doses of the therapy. Additionally, other human participants had experienced serious side effects. Meanwhile, Dr. James Wilson, the lead investigator, owned stock in Genovo, the company developing the therapy, and stood to gain millions if the therapy was successful.

"We don't know what the impact of these deviations are," Dr. Kathryn Zoon, then-director of the FDA's Center for Biologics Evaluation and Research, said at the time, The New York Times reported. "But they're important."

Gelsinger's father, Paul Gelsinger, launched a wrongful-death suit against parties involved in the trial; it was eventually settled for an undisclosed sum.

Gelsinger's death led to several changes in how gene therapy clinical trials are run and to stronger informed-consent requirements. All of the gene therapy trials underway at the University of Pennsylvania were halted. The FDA also started requiring greater monitoring for gene therapy trials.

The death cast a pall over the field, and as public and private funding for the approach dried up, gene therapy stalled. Eventually, however, with progress in understanding the viral vectors used to deliver gene therapy, and later, with the advent of the cut-and-paste gene editing tool CRISPR, the field has rebounded.

Scientists have now used gene therapy to treat many rare genetic disorders, including severe combined immune deficiency and multiple forms of blindness. The first CRISPR-based gene therapy, which treats sickle cell anemia by disabling a specific gene, was approved in January 2024. And in 2025, scientists announced that they'd used a customized CRISPR treatment designed for his particular gene mutation to treat a baby with a rare and devastating genetic syndrome.

Right now, the number of approved gene therapy products is still small. Many of those approved therapies use cells that are edited in the lab and then returned to the body to fight or treat cancer, rather than changing the genes in the nucleus of a patient's own cells.

But the field has come a long way since Gelsinger's death, and in 2021, scientists used gene therapy to successfully treat OTC deficiency.

Ten years ago today, on Sept. 14, physicists detected gravitational waves rippling through the cosmos for the first time.

The roots of this discovery date back a century. Albert Einstein's general relativity predicted that massive objects would warp space-time. When such massive objects accelerate — such as when two black holes collide — they would send ripples through the cosmos, called gravitational waves, he posited.

Einstein never thought we could detect them, because the distortion of space-time caused by these waves would be far tinier than a single atom.

However, in the 1970s, MIT physicist Rainer Weiss, who died in August, proposed it might be possible to detect these tiny ripples from colliding massive black holes.

Key to his scheme was the interferometer, which would split a beam of laser light. From there, the light would travel down two separate paths before bouncing off hanging mirrors and recombining at their source, where a light detector would measure their arrival. Ordinarily, if the paths were the same lengths, these two beams would return at the same time.

But if a gravitational wave was passing by, Weiss reasoned, these beams would be ever-so-slightly out of phase. That's because gravitational waves temporarily smoosh and stretch space-time, thereby creating fluctuations in the length of the passageways through which the laser beams travel.

Weiss, along with Caltech physicist Kip Thorne, proposed the idea of trying to measure these elusive waves. The detector pathways, they argued, needed to be very long to detect such tiny signals. And the project would need two widely spaced detectors to eliminate the possibility that signals came from local disturbances, and to help localize the source of cosmic collisions.

By 1990, the Laser Interferometer Gravitational-Wave Observatory (LIGO) project had been approved, and two identical L-shaped detectors, with arms 2.5 miles (4 kilometers) long, were built in Hanford, Washington and Livingston, Louisiana, respectively.

For years, the detectors found nothing. So LIGO was upgraded to become more sensitive to ever-tinier signals. Much of that entailed protecting the equipment from vibrations caused by nearby traffic, planes or distant earthquakes, which could obscure the signals from the distant universe.

In September 2015, the scientists turned on the upgraded instruments.

Overnight on Sept. 14, researchers at both LIGO sites detected something interesting.

"I got to the computer and I looked at the screen. And lo and behold, there is this incredible picture of the waveform, and it looked like exactly the thing that had been imagined by Einstein," Weiss said in a documentary about the discovery.

It was a strong "chirp," or a fluctuation in the length of the detector arms, and it was a thousand times smaller than the diameter of a nucleus.

On Feb. 11, 2016, scientists announced that the event they'd detected came from the smashup of two massive black holes that collided about 1.3 billion years ago. Europe's gravitational wave experiment, called Virgo, detected the same event.

The discovery ushered in a whole new way to study the universe's most extreme events. Since that first detection, LIGO's detectors, along with its European counterpart experiment Virgo and the Japanese Kamioka Gravitational Wave Detector (KAGRA), have detected around 300 collisions, including triple black hole mergers and the collision of black holes and neutron stars. In June 2023, a team of scientists announced that a faint "gravitational wave background" permeates the universe thanks to pairs of black holes veering toward collision all across space and time. And in September 2025, scientists from the LIGO Collaboration validated Stephen Hawking's decades-old theory about black holes, linking quantum mechanics and general relativity.

Weiss and Thorne, along with their colleague Barry Barish, were awarded the 2017 Nobel Prize for their work.