History of science

86 cards about History of science, with explanations, methods and source links.

Cards about History of science

• How did meteorites make it possible to measure the age of the Earth?

  Measuring the age of the Earth directly is hard, because rock at the surface melts, erodes and is replaced without pause. The oldest stone you can find here is younger than the planet. So where do you get material that never changed?

  Source: Patterson, Geochimica et Cosmochimica Acta

• The bowerbird lays out stones in front of its bower. Why do they get smaller?

  A male bowerbird builds an avenue of sticks with a court in front of it covered in stones, bones and shells, and arranges them by size: small ones near, large ones far. When researchers shuffled them, he restored the order within days. Why does it matter to him?

  Source: Kelley & Endler, PNAS

• How did knots in a cord hold numbers with no written digits?

  A quipu is built from a main cord with colored strings hanging off it, tied with knots. There are no digits there, no ink and no page. And still an exact number can be recorded in it. How does that work?

  Source: Ascher & Ascher, Nature

• Why did a purple cloak in antiquity take thousands of sea snails?

  Several species of sea snail carry a gland that secretes the precursors of a dye, and after exposure to air and light they turn purple. Each snail yields a minute quantity. How many snails does one cloak take?

  Source: Wolk & Frimer, Molecules

• How did lead left in mud reveal when Naples repaired its water supply?

  Roman water pipes left particles of lead in the sediment piling up in the harbour of Naples, and the ratios of isotopes in them carry a signature that distinguishes one source of lead from another. Which means the mud kept a chronological record. What can be read in it?

  Source: Delile et al., PNAS

• The rock looks like a stack of cushions. How did tiny organisms build it layer by layer?

  A stromatolite is a rock that looks like a stack of cushions, built from thin layers laid one on another. Rock does not pile up that way by itself. Who built it?

  Source: Dupraz et al., Earth-Science Reviews

• Lightning strikes sand and is gone in an instant. What does it leave below the surface?

  A lightning current entering the ground heats a narrow path at enormous speed, and then vanishes within a fraction of a second. Above the surface almost nothing remains. What remains below?

  Source: McCloy, Journal of Non-Crystalline Solids: X

• How does a cloud of dry ash throw lightning with no rainstorm?

  Lightning forms in a thunderstorm when ice and water move about and separate charge inside a cloud. In a volcanic eruption there is no rain and no ordinary cloud, and lightning appears inside the ash column anyway. What makes it there?

  Source: Cimarelli & Genareau, Journal of Volcanology and Geothermal Research

• Did a giant eruption bring down a kingdom in East Asia?

  The Changbaishan volcano on the border of China and Korea erupted violently in the tenth century, and the kingdom of Bohai fell in 926. The pairing is tempting, and for years a link between them was proposed. Then the eruption was dated precisely. What came out?

  Source: Oppenheimer et al., Quaternary Science Reviews

• How can shards of Roman glass hint at ancient recycling?

  A shard of glass looks too small to tell a commercial story, and the materials it is made of leave a clear chemical signature. Glass can also be remelted, so recycling should leave a trace. Dozens of finds from Roman cities around the Black Sea were compared with known types of glass. What came out of the composition?

  Source: Bugoi et al., Materials

• How did a color experiment in Berlin create a blue painters had never known?

  Before Prussian blue, a deep and durable blue was hard and expensive to obtain, so it was saved for important details alone. Then a new pigment appeared in Berlin, out of a reaction between iron salts and ferrocyanide compounds. What did that change?

  Source: Guichard et al., Art History

• Can a transparent crystal find a sun that is hiding behind clouds?

  The light of the sky is polarized in a pattern that depends on where the sun is, even when the sun itself is hidden by cloud. Our eyes cannot see polarization. But there is a crystal that responds to it. What can be done with that?

  Source: Ropars et al., Contemporary Physics

• Why did a good storyteller matter to a group of hunters?

  A story sounds like entertainment, which makes it hard to explain why hunter-gatherer communities invest time and respect in it. Researchers worked with Agta people in the Philippines, examined the content of the stories, and measured cooperation in an experimental game. What was linked to what?

  Source: Smith et al., Nature Communications

• What happens to an investment strategy after research publishes it?

  If a paper finds a pattern predicting which shares will rise, it stands to reason that investors will exploit it. It also stands to reason that the exploitation will eat the pattern itself. Ninety-seven published variables were examined before publication and after. What happened to them?

  Source: McLean & Pontiff, The Journal of Finance

• Why do people choose to visit a place tied to disaster or death?

  Dark tourism is a visit to sites connected with death, disaster or suffering, such as a battlefield or a memorial. It is easy to assume morbid curiosity or social pressure. A thousand visitors were asked themselves. What moved them?

  Source: Lewis et al., International Hospitality Review

• How did a quiet lake release a lethal cloud in a single night?

  Villagers in Cameroon woke in the night struggling to breathe, with no fire and no smoke on the horizon. What had reached them from the lake next door?

  Source: U.S. Geological Survey

• Where do the oldest people in the world live? Where there are no birth certificates

  Regions where many people live past a hundred have drawn enormous attention, with explanations about diet, social ties and genes. One researcher examined an entirely different variable: the quality of civil registration. What did he find?

  Source: Newman, bioRxiv

• Tulip prices in Holland collapsed in a single week. What exactly happened that week?

  The familiar story of the Dutch tulip mania comes almost entirely from a 19th-century book rather than from the data. What is known: the bulbs were traded while buried in the ground, and nobody could see what would grow from them. What happened in the week the prices collapsed?

  Source: McClure & Thomas, Financial History Review

• Was Cahokia, the largest city in North America, really abandoned?

  Cahokia was the largest population center in pre-Columbian North America, with enormous earthen mounds where St. Louis stands today. Around 1400 it emptied, and ever since it has been told as a civilization that vanished. Then researchers measured chemical traces of human beings in the bed of a nearby lake, layer by layer. What did those show?

  Source: White et al., American Antiquity

• Why is a ship that survived three hundred years in water falling apart on land?

  The Vasa sank in Stockholm harbour on her maiden voyage in 1628 and was raised almost intact after 333 years. The cold, brackish water preserved the wood better than any storehouse, and the ship was dried, treated and put in a museum of her own. Then, after years in a climate-controlled hall, salt stains appeared on the timbers and the acidity jumped. What is happening to the wood?

  Source: Sandström et al., Nature

• How did the great stone city of Africa secure its water?

  Great Zimbabwe was built entirely in dry stone, block on block with no mortar at all, and its central wall is the largest ancient structure on the continent south of the Sahara. Generations of archaeologists studied the walls, and less the more everyday question: where did thousands of people drink in an arid region? Then round depressions in the ground around the city were examined. What were they?

  Source: Pikirayi et al., Anthropocene

• Which problem sank whole ships until one clock was invented?

  Latitude can be worked out fairly easily from the height of the sun. Longitude required knowing exactly what the hour was back in the home port at that very moment, and pendulum clocks did not survive the motion of a ship or the damp. How was it solved?

  Source: Royal Museums Greenwich

• Whose carelessness on holiday saved millions of lives?

  In 1928 Alexander Fleming came back from holiday and found that one of the Petri dishes he had left out was contaminated with a mold. Around the patch of mold no bacteria grew, while the rest of the dish went on filling with them. What did he manage to do with that, and what did he not?

  Source: Nobel Prize in Physiology or Medicine 1945

• What does milking cows have to do with the first vaccine in history?

  Before 1796 the only defense against smallpox was variolation, deliberately giving a healthy person material from a smallpox sore and hoping for a mild case. A country doctor named Edward Jenner noticed that milkmaids who had caught a mild disease from cattle seemed to escape the epidemic. What did he do with the observation?

  Source: History of Vaccines, The College of Physicians of Philadelphia

• The stuff in the funnel shatters like a solid. So why does a drop fall from it once a decade?

  In 1927 the physicist Thomas Parnell heated pitch and poured it into a sealed glass funnel, and three years later he cut the stem open and waited. At room temperature pitch shatters under a hammer, the way brittle glass does. What happens if you simply wait?

  Source: University of Queensland, Explainer: the pitch drop experiment

• The sky looks like a rough sea seen from below. Is that really a new kind of cloud?

  Asperitas looks like a dark, rumpled surface of chaotic waves hanging under the cloud base. Photographs of it arrived from all over the world, until the World Meteorological Organization put it into the official atlas in 2017. It is not a kind of cloud, though. So what is it?

  Source: World Meteorological Organization, International Cloud Atlas

• Why is a tennis ball yellow, when the game was played with white ones?

  For decades tennis balls were black or white, chosen against the background color of the court, and that worked perfectly well for anybody sitting in the stands. Then the audience moved to the living room and the television set turned color. What did that change?

  Source: International Tennis Federation, History of Tennis Balls

• What happened in Hawaii when a missile alert went out by mistake?

  At 8:07 in the morning on 13 January 2018, every phone in Hawaii received a warning of an inbound ballistic missile, ending with the words THIS IS NOT A DRILL. There was no missile. An internal exercise at the state emergency agency had gone out to the public instead. What happened over the next half hour?

  Source: US Federal Communications Commission

• Why does an old book have a smell you can actually archive?

  Everybody recognizes the smell of an old book, and nothing in conservation practice preserves it. Paper, glue, ink and board release a shifting mixture of volatile molecules as they age, so the smell is information that leaves the building. Researchers sampled the air itself, in a historic book and a historic library. What can you do with that?

  Source: Bembibre and Strlic, Heritage Science

• Did the numbers ever support Semmelweis in his own lifetime?

  Semmelweis is the standard case of a man who was right and was rejected. He noticed that the clinic staffed by doctors and students killed more mothers than the one staffed by midwives, and he blamed the autopsy room. Nobody ever ran the statistics on his own data. What happens when you do?

  Source: Noakes et al., Epidemiology and Infection

• What can a medieval book tell you besides what it says?

  A manuscript is read for its text, and the page it is written on is an animal. Parchment carries biological material from the herd it came from, from the people who made the book and from everyone who has handled it since. A field guide exists for getting at it. What is in there?

  Source: Fiddyment et al., Heritage Science

• How did the world find out about X-rays?

  Wilhelm Röntgen had little time for publicity. He rarely appeared at conferences, rarely wrote papers, and never promoted his work outside his field. Then one evening in his laboratory a screen glowed when nothing should have reached it, and within weeks his X-rays were a press sensation.

  Source: The Nobel Prize, Physics 1901

• What finally convinced geologists the continents move?

  Continental drift was debated for decades after Wegener died, then largely dismissed as eccentric, preposterous and improbable. From the 1950s a wealth of new evidence revived it, and one strand of that evidence came from instruments built in wartime to find submarines.

  Source: United States Geological Survey

• How do you prove that life does not arise from broth?

  Spontaneous generation goes back to the ancient Greeks and held through the Middle Ages. By the nineteenth century the argument was specific: boiled broth in a sealed flask stayed sterile because sealing also kept out a life force. Air was the thing in dispute. How do you let air in and nothing else?

  Source: OpenStax Microbiology

• Did Vikings wear horned helmets?

  The popular image is of fearsome warriors in horned helmets, and many depictions of Vikings carry that attribute. Depictions are not the same as helmets, and the archaeological record is thinner than the iconography. Only one helmet survives from the whole Viking Age.

  Source: National Museum of Denmark

• How long did the first photograph take to expose?

  Nicéphore Niépce had been producing legible but fleeting camera pictures since 1816, which is the problem with them: they did not stay. He spent the next decade trying chemicals, materials and techniques for a process he called héliographie, sun writing. The surviving plate dates from 1827.

  Source: Harry Ransom Center, University of Texas

• What carves a canyon into thousands of stone spires?

  Bryce Canyon sits at up to 9,115 feet, and its rocks formed near sea level in a lake and floodplain system around 50 million years ago. Getting them up there took plate tectonics. Turning a plateau into spires took something far smaller and more repetitive.

  Source: U.S. National Park Service, Bryce Canyon

• Why does lava erupting underwater come out in lumps?

  Lava on land runs in sheets and ropes. On the seafloor it arrives as bulbous, spherical or tubular lobes, stacked into mounds, and the shape is consistent enough to have its own name. The difference is not the lava. It is how fast it leaves the vent.

  Source: NOAA Pacific Marine Environmental Laboratory

• Did Watson and Crick solve DNA by stealing one photograph?

  The familiar story says the double helix came from Photograph 51, an X-ray image of DNA shown to Watson without Rosalind Franklin’s knowledge, which she had supposedly failed to understand. Two biographers went through her archive at Churchill College with an overlooked letter and an unpublished 1953 news article in hand. What they found rearranges who knew what.

  Source: Cobb and Comfort, Nature

• Why does a library protect its visitors from the manuscripts?

  Archives normally work the other way round, with gloves and climate control defending fragile paper from the people who come to read it. The Pierre and Marie Curie collection at France’s Bibliothèque Nationale inverts that. The reason is in what the Curies handled daily, and where they kept it.

  Source: Christian Science Monitor

• What did geologists do to the man who proposed continental drift?

  On Christmas of nineteen ten, a meteorologist browsing a friend’s new atlas noticed that the Atlantic coast of Brazil looked as though it had once been tucked against West Africa. Others had seen the same thing and let it pass. Alfred Wegener cut the continents out, fitted them on a globe, and gathered fossils and rock layers that matched across oceans. Then he published. What did the field make of it?

  Source: Smithsonian Magazine

• When Japanese food went onto the heritage list, what was actually listed?

  In two thousand thirteen, washoku was inscribed on UNESCO’s Representative List of the Intangible Cultural Heritage of Humanity. The obvious reading is that a cuisine was honored: a set of dishes, with sushi somewhere near the front. The inscription itself describes something narrower and stranger. What did the listing actually protect?

  Source: UNESCO Intangible Cultural Heritage

• Why did one broken slab unlock a language nobody had read for centuries?

  Knowledge of how to read and write hieroglyphs disappeared soon after the fourth century, and the script then sat unreadable for fourteen hundred years. In July of seventeen ninety-nine, French soldiers digging foundations for a fort near Rashid, on the Nile delta, turned up a broken slab built into an old wall. Their officer saw at once that it mattered. What made it the key?

  Source: British Museum

• What turned an ordinary London fog into one that killed thousands?

  Fog was routine in London, and smoky fog had been part of the city since the Industrial Revolution, with the death rate climbing after the worst of them. December of nineteen fifty-two began very cold, with heavy snow, so households burned more coal than usual. On the fifth the sky was clear, the wind light, the air near the ground moist. What turned that into the Great Smog?

  Source: UK Met Office

• Who worked out that the uranium atom had split?

  Otto Hahn and Lise Meitner worked together in Berlin for three decades, beginning in a remodeled carpenter’s shop because the university did not yet accept women officially. By nineteen thirty-eight she had to leave Germany. Hahn and Fritz Strassmann then bombarded uranium with neutrons and found barium, far lighter than anything they had expected, and could not account for it. Who worked out what had happened?

  Source: Science History Institute

• Why does cooling lava crack into columns?

  The Giant’s Causeway in Ireland and the Devil’s Postpile in California look built rather than cooled, rank on rank of near-regular columns. Nothing arranged them. A thick basalt flow simply loses its heat, and losing heat is not usually a shaping process. The Hawaiian Volcano Observatory describes what happens inside a flow as it solidifies. Where does the pattern come from?

  Source: U.S. Geological Survey, Volcano Watch

• What was a box of precision gearwheels doing on a Greek shipwreck?

  In nineteen hundred, sponge divers sheltering from a storm off the tiny island of Antikythera found a wreck full of Greek treasures. One recovered lump, about the size of a large dictionary, drew no attention beside the marble sculptures. Months later, in Athens, it broke apart. Inside were bronze gearwheels the size of coins. What is it?

  Source: Scientific American

• How fast can a treaty move once the evidence is in?

  The ozone layer is the planet’s sunscreen, holding back the ultraviolet-B that drives skin cancer, cataracts and damage to crops and ecosystems. In May of nineteen eighty-five, three scientists at the British Antarctic Survey published something nobody was expecting about the layer above Antarctica. What they found was that it vanishes each spring. What happened next?

  Source: British Antarctic Survey

• How do you prove what is causing an epidemic before anybody can see a germ?

  In eighteen fifty-four nobody could see a cholera bacterium, and the respectable explanation was miasma: bad air rising from filth. John Snow, better known as an anesthetist, backed the unpopular alternative that cholera travels in water. When an epidemic broke out in London on the thirty-first of August, he suspected one particular pump on Broad Street. How could he test that?

  Source: Centers for Disease Control and Prevention

• Why did Mount St Helens flatten a forest sideways instead of upward?

  A volcano is supposed to go up. On the eighteenth of May, nineteen eighty, the north flank of Mount St Helens slid away as a debris avalanche, and the climactic eruption began within seconds of it. Trees lay flattened in parallel rows as far as nineteen miles out, pointing away from the mountain. What direction did the explosion travel, and why?

  Source: U.S. Geological Survey

• How did a tank of molasses kill twenty-one people?

  At about one in the afternoon on the fifteenth of January, nineteen nineteen, people out enjoying unseasonably warm weather in Boston’s North End heard a low rumble and took it for an approaching elevated train. A fifty-foot tank of industrial molasses had ruptured. Local residents already knew the tank leaked, and children had collected pails of it from the seams. How bad was it?

  Source: Boston City Archives

• Why can a plant starve in an atmosphere that is mostly nitrogen?

  Nitrogen is one of the most important plant fertilizers, and air is mostly nitrogen, which ought to settle the matter. It does not. Plants can use nitrogen only when it is already part of a chemical compound, and the nitrogen overhead is not. Around nineteen thirteen Fritz Haber built an apparatus to address that. What does it do?

  Source: Nobel Prize Outreach

• Who was allowed to tell the public what tomorrow’s weather would be?

  Robert FitzRoy led the Meteorological Office from its founding in eighteen fifty-four, collecting daily readings telegraphed in at nine in the morning from stations around the British and Irish coasts. After the Royal Charter Gale of eighteen fifty-nine he built a national Storm Warning Service, which the government had approved. For forecasting on land he had no permission at all. What did he do about that?

  Source: UK Met Office

• What did geologists see in nineteen oh six that they could not explain?

  At twelve minutes past five on the morning of the eighteenth of April, nineteen oh six, a foreshock was felt across the San Francisco Bay area. The great earthquake broke twenty to twenty-five seconds later, with violent shocks through forty-five to sixty seconds of strong shaking. Afterward, fences and roads across northern California no longer lined up. What had the ground done?

  Source: USGS

• What changed for a diabetic child in nineteen twenty-two?

  Doctors had long suspected the pancreas secreted something that controlled carbohydrate metabolism, and several groups early in the twentieth century prepared pancreatic extracts that lowered blood glucose. None was safe to give a person. Impurities nobody could remove produced toxic reactions. A fourteen-year-old in Toronto named Leonard Thompson weighed sixty-five pounds and was drifting in and out of consciousness. What was there to try?

  Source: Nobel Prize

• What was a hollow bronze unicorn for?

  A copper alloy unicorn, cast in Nuremberg around fourteen twenty-five to fifty, stands about fifteen inches long and weighs nearly seven pounds. It is hollow. There is a flap on top of it and a spigot set into its chest, and its tail curls up in a flame shape. The horn is a replacement. What was it made to do?

  Source: The Metropolitan Museum of Art

• Who carried an axe with a gun built into the handle?

  The wheel lock arrived early in the sixteenth century and gave firearms an ignition system that was reliable if complex and expensive, which set off a rapid development of pistols and long arms. By mid-century a new genre appeared: a wheel-lock pistol combined with a sword, a dagger, an axe or a mace. The obvious reading is insecurity, a backup for a missed shot. Is that what they were for?

  Source: The Metropolitan Museum of Art

• Why did medieval locks get so elaborate?

  Gothic iron locks and keys were decorated to the highest standard of workmanship, with motifs drawn straight from Gothic architecture: tracery patterns reproduced at miniature scale, and sometimes tiny statuettes. All of that is visible on the outside. The interesting part of some of these locks is what cannot be seen. What were they built to do?

  Source: The Metropolitan Museum of Art

• What exactly did Ada Lovelace write that people call the first program?

  Charles Babbage began designing his Analytical Engine in the mid-eighteen thirties, a calculating machine meant to pause mid-calculation and use what it had already worked out to choose between two next steps. It was never built. In eighteen forty-three Ada Lovelace published a translation of a French account of it, with appendices of her own running to forty-one of the paper’s sixty-six pages. What is in the last one?

  Source: BBC Science Focus

• Did Alfred Nobel really found the prizes after reading his own obituary?

  Nobel signed his will in Paris in November of eighteen ninety-five, devoting almost all his estate to prizes for those who had conferred the greatest benefit on mankind. He was an unlikely source for a peace prize, holding three hundred and fifty-five patents, having invented dynamite, and owning nearly a hundred explosives factories. He never explained himself publicly. So where does the story come from?

  Source: HISTORY

• Why is one square in Lucca a perfect oval?

  Piazza Anfiteatro in Lucca is an ellipse of pale houses with cafes under them, and no architect of the eighteen thirties would have chosen that shape from nothing. A Roman amphitheatre stood on the spot, built outside the walls in the first or second century. It fell into ruin during the barbarian invasions and was stripped. So how did its outline survive?

  Source: Turismo Lucca

• What do you have to invent to draw the Roman road network as a subway map?

  A subway diagram works by throwing away geography. It keeps which line connects to which, and discards distance, direction and everything else. Alexandr Trubetskoy applied that logic to the major Roman roads of the empire around one hundred and twenty-five, pulling on Stanford’s ORBIS model, the Pelagios Project and the Antonine Itinerary. What does the form cost?

  Source: Sasha Trubetskoy, Roman Roads

• What did American intelligence conclude about the Sverdlovsk outbreak?

  An extraordinary disease outbreak hit the Soviet city of Sverdlovsk in April of nineteen seventy-nine, serious enough that the authorities imposed a quarantine and did not get the situation under control until late May. The Soviet Union announced nothing, which was unlike its handling of natural epidemics. The Weapon and Space Systems Intelligence Committee reviewed what was known. What did it find?

  Source: U.S. State Department Historical Documents

• Why were so many people standing at the dock watching?

  Fires around the docks were fairly common in Texas City, and residents were in the habit of going down to watch them and to watch the firemen work. On the morning of the sixteenth of April, nineteen forty-seven, the SS Grandcamp was burning, producing a dense and brilliantly colored smoke visible all over town. Her cargo included ammonium nitrate. What happened at twelve minutes past nine?

  Source: City of Texas City

• Who burned the Library of Alexandria?

  The picture everyone carries is a single fire and a single culprit, with Julius Caesar usually cast in the part. In forty-eight BCE he was in Alexandria defending Cleopatra against her brother, and his men set the ships and wharves alight to trap the enemy fleet. The flames did reach the Mouseion. Is that how the library ended?

  Source: National Geographic

• What happened to the first man to receive another person’s heart?

  On the third of December, nineteen sixty-seven, Christiaan Barnard performed the first human-to-human heart transplant at Groote Schuur Hospital in Cape Town. The donor was a twenty-five-year-old woman fatally injured in a car accident. The recipient was Lewis Washkansky, a fifty-three-year-old grocer dying of chronic heart disease. How long did he live?

  Source: HRSA, U.S. Health Resources and Services Administration

• How do you remove a disease from the world entirely?

  Smallpox is caused by the variola virus, is believed to have existed for at least three thousand years, and was fatal in up to thirty percent of cases. Edward Jenner made the first successful vaccine against it in seventeen ninety-six, after noticing that milkmaids who had caught cowpox did not catch smallpox. A vaccine is not the same as an end. What finished it?

  Source: World Health Organization

• What does it take to notice that your chocolate bar has melted?

  Percy Spencer left school in the fifth grade, taught himself electrical engineering from books while working at a paper mill, and ended up at Raytheon solving the hardest manufacturing problem of the radar war. Magnetron production ran at about twenty a day when he started on it. In nineteen forty-five, testing an active magnetron, he found a candy bar in his pocket had melted. What did he do next?

  Source: HISTORY

• How does a glue that does not stick properly become a product?

  In nineteen sixty-eight, Spencer Silver was at 3M Laboratories trying to develop super-strong adhesives. What he produced instead was a weak one, which stuck to surfaces without bonding tightly to them. That is a failure by the only measure the project had. Silver could not immediately see a use for it either. So what happened to it?

  Source: Inc

• How far does a tsunami from Alaska actually travel?

  At thirty-six minutes past three in the morning UTC on the twenty-eighth of March, nineteen sixty-four, a magnitude nine point two earthquake struck about one hundred and twenty kilometers east of Anchorage. It generated a major tsunami. Local runup exceeded thirty meters along Alaskan shorelines, and in Valdez harbor reports put it above sixty meters, possibly helped by a landslide. Where did the wave stop?

  Source: NOAA

• Why did a job painting watch faces kill the people who did it?

  Radioluminescent paint arrived with the discovery of radioactivity, made by combining radium with a phosphorescent material and an adhesive. Painting it onto dials and instruments was fine work, and the painters were primarily women. Until the mid to late nineteen twenties they shaped the brush by drawing it between their lips. What did that do?

  Source: Martinez et al., International Journal of Radiation Biology

• What flattens two thousand square kilometers of forest and leaves no crater?

  On a June morning in nineteen hundred and eight, something exploded over central Siberia with the force of up to fifteen megatons of TNT, a thousand times the Hiroshima bomb. Seismographs in western Europe picked it up. Trees fell outward for tens of kilometers. The first expedition reached the site nineteen years later and found no crater at all.

  Source: Britannica

• What happens when a comet is pulled apart and then swallowed by a planet?

  In nineteen ninety-three three astronomers found a comet beside Jupiter that looked wrong: at least a dozen nuclei strung out like glowing pearls, eventually twenty-one of them. Working out the orbit revealed what had happened to it, and what was going to. Every telescope that could point at Jupiter was waiting the following July. What did they see?

  Source: Britannica

• What held two copper bowls together against a team of horses?

  In sixteen fifty, the mayor of Magdeburg invented the air pump and began making partial vacuums with it, finding among other things that light crosses a vacuum and sound does not. Four years later he staged a demonstration in front of the Holy Roman Emperor using two copper bowls and nothing else to fasten them. Horses could not separate them. What was holding?

  Source: Britannica

• Whose cells are in almost every laboratory in the world?

  Cancer research in the nineteen fifties needed something nobody had managed to grow: a human cell line that would keep dividing outside the body. Samples came in and died. At Johns Hopkins, the head of tissue culture research was collecting them from patient after patient. In February nineteen fifty-one a biopsy came in from a woman with cervical cancer, and her sample did something the others had not.

  Source: Britannica

• How does a rock that never reaches the ground injure fifteen hundred people?

  In February two thousand and thirteen an object about seventeen meters across came apart in the atmosphere over the Chelyabinsk region of Russia. Nothing of consequence landed on anyone. More than one and a half thousand people were hurt anyway, and almost all of the injuries shared one cause, which says something uncomfortable about how modern buildings meet a shock wave.

  Source: Britannica

• How do three people get home from the Moon with the power failing?

  Two days out from Earth, Apollo 13 was coasting toward the Moon on a trajectory so accurate that two planned course corrections had been cancelled. On the evening of the thirteenth of April nineteen seventy, with the crew checking the lunar module for a landing, there was a loud explosion. Within eight seconds one of the two cryogenic oxygen tanks had dropped to zero pressure.

  Source: Britannica

• What do you do when the computer flying you to the Moon says its memory is full?

  Eagle had separated from Columbia and dropped to within fifteen thousand meters of the surface before firing for the powered descent. Then, five separate times on the way down, the guidance computer raised an alarm: its memory was full. Somebody on the ground had to decide, in seconds, whether a landing could continue on a computer that kept complaining.

  Source: Britannica

• What exactly did Gutenberg invent, if printing already existed?

  Europe could already stamp letters onto surfaces and print whole pages from carved woodblocks. What it could not do was produce books in quantity. A craftsman in Mainz changed that in the middle of the fifteenth century, and the invention was not a single device but a set of things that had to work together. What were they?

  Source: Britannica

• What killed the Pony Express after eighteen months?

  In eighteen sixty, news took twenty-four days to cross the United States overland, and with the Civil War approaching that was no longer tolerable. The answer was the Pony Express, a relay of horses and riders covering nearly two thousand miles in about ten days. It ran from April eighteen sixty to October eighteen sixty-one and then stopped. Something had made it pointless.

  Source: Britannica

• What did one volcano do to the whole atmosphere in a single afternoon?

  The Hunga Tonga eruption of January two thousand and twenty-two was one of the most explosive volcanic events of the modern era, throwing a plume that peaked more than fifty kilometers above the Earth. The explosion and the plume set off atmospheric waves that went around the world several times. Nobody had recorded a global wave response like it from one source.

  Source: Wright et al., Nature

• What happens on a flight deck when nobody dares correct the captain?

  Flight data recorders and cockpit voice recorders changed what accident investigators could see. Many crashes turned out not to involve a technical malfunction, a failure of handling skill or missing knowledge. They involved crews unable to respond appropriately to the situation they were in, and the barrier was often inside the conversation.

  Source: SKYbrary Aviation Safety

• What did the Sun do to the only electrical network of eighteen fifty-nine?

  On the first of September eighteen fifty-nine a British amateur astronomer watched something anomalous happen on the Sun. Roughly seventeen hours later the Earth answered, with magnetic effects on a global scale. The only extensive electrical system anyone had built at the time was the telegraph, and the telegraph is where the effects landed. What happened to it?

  Source: Oliveira, Revista Brasileira de Ensino de Fisica

• What happened when a country detonated a nuclear weapon four hundred kilometers up?

  A month after Sputnik, a physicist at Livermore proposed intercepting incoming missiles with a cloud of electrons, produced by exploding a nuclear bomb in the upper atmosphere and trapped in the Earth’s magnetic field. The idea was tested in nineteen fifty-eight and then on a far larger scale in July nineteen sixty-two. What did the largest shot leave behind?

  Source: Gombosi et al., Space Science Reviews

• Why can one failure take down the power for fifty million people?

  The August two thousand and three blackout across the northeastern United States put energy transmission in the spotlight, and left an awkward problem behind it. The electric infrastructure is so complex and so interconnected that for a long time nobody could explain why certain events had happened at all. Albert, Albert and Nakarado tried a different approach: treat the grid as a network.

  Source: Albert et al., Physical Review E

• How high can a wave reach if the water has nowhere to go?

  Lituya Bay is a T-shaped tidal inlet on the northeast shore of the Gulf of Alaska, and it heads in the trench along the Fairweather fault. In July nineteen fifty-eight the fault moved. The arm at the head of the bay is deep, steep-sided and narrow, which turns out to be the worst possible shape for what happened next.

  Source: Miller, Bulletin of the Seismological Society of America

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