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1,389 cards. Each one is a 40-second story with a five-minute read behind it. Page 17 of 24.

961. Fibre optics on the 1969 Moon cameras were a classified secretWhen NASA sent television cameras to the Moon, their use of optical fibres was classified, and anyone handling the cameras had to be watched by someone with security clearance. Ju…
962. Light microscopes hit a wall at about 200 nanometres, however much they magnifyYou can keep cranking up a light microscope's magnification, but past a certain point the picture just gets bigger and blurrier. Because visible light diffracts, details closer to…
963. Reflecting telescopes took over a century to catch on after Newton built oneIsaac Newton built a practical mirror telescope in 1668, avoiding the colour fringes that plagued lens telescopes. Yet his speculum metal mirrors were hard to make and performed p…
964. Early photographic film could only see blue lightUntreated silver halide crystals, the light-catching heart of photographic film, respond only to the blue end of the spectrum, so early photographs rendered some colours strangely…
965. Britain still treated photography as a mere craft as late as 1960Photographers were making deliberate art from the 1850s, yet as recently as 1960 a British enthusiast founding a fine-art photography association complained that his country saw t…
966. Cut a hologram in half and each piece still shows the whole sceneTear a photograph in two and you get two halves of a picture. Split a hologram and each fragment still contains the entire scene, seen through a smaller window. That is because ev…
967. Lord Rayleigh found tarnished old glass let through more light than newIn 1886 Lord Rayleigh noticed something odd: slightly tarnished pieces of old glass transmitted more light than clean new ones. The dull film sat between air and glass in refracti…
968. Why roof-prism binoculars must be aligned 300 times more precisely than Porro onesThe two numbers stamped on binoculars, like 10×50, mean magnification and the width of the front lenses in millimetres. Hidden inside is a harder problem: flipping the upside-down…
969. From darkened room to phone: how the camera shrank over two centuriesEvery camera ever made, from a wooden box of 1839 to the one in your pocket, follows one recipe: a lens bends light into a sealed chamber, a shutter decides how long it stays, and…
970. The failed memory idea that became the eye of digital camerasIn 1969 two Bell Labs engineers were trying to build a new kind of computer memory based on magnetic bubbles. They realised a packet of electric charge could stand in for a bubble…
971. A feather, some hairs and a CD: the story of the diffraction gratingTilt a CD under a lamp and rainbows slide across it. The disc's tightly packed spiral of data tracks splits white light into its colours, the same trick a Scottish mathematician s…
972. The first portable digital camera weighed 8 pounds and took 23 seconds per pictureIn December 1975 a Kodak engineer named Steven Sasson pressed the button on a boxy prototype and waited 23 seconds while it wrote a black-and-white picture of 10,000 pixels onto c…
973. Who invented the electron microscope? A patent office and a Nobel committee disagreeLight microscopes hit a wall at about 200 nanometres, because visible light waves are simply too long. Swapping light for electrons, whose wavelength can be over 100,000 times sho…
974. America's stealth bombers owe their shape to a Soviet physicist's equationsIn 1962 the Soviet physicist Pyotr Ufimtsev published equations showing how an object's shape governs the radar echo it returns. The US Air Force translated the work in 1971, Lock…
975. The first working submarines were rowed, cranked by hand, or powered by airIn 1620 a Dutch inventor serving James I of England built a submersible propelled by oars. Over the next two and a half centuries, inventors tried leather ballast bags, hand-turne…
976. Early swords stayed short because long bronze blades simply bentFor centuries, sword makers could not make a practical blade much longer than 60 centimetres. The problem was physics: bronze is not stiff enough, so longer blades flexed and bent…
977. Most of a hydrogen bomb's power actually comes from fission, not fusionThe hydrogen bomb takes its name from the fusion of heavy hydrogen isotopes, yet in typical American designs more than 80 percent of the energy comes from splitting uranium in the…
978. The torpedo is named after a fish that stuns its prey with electricityLong before it meant a weapon, torpedo was the name of the electric ray, from a Latin word for sluggishness. David Bushnell reportedly borrowed it for his submarine, Robert Fulton…
979. Chandragupta Maurya reportedly fielded 9,000 war elephants at his heightAncient Indian writers said an army without elephants was as contemptible as a forest without a lion or a kingdom without a king. At the peak of the Maurya Empire, Chandragupta re…
980. For centuries, half a war fleet might be borrowed merchant shipsUntil the seventeenth century, navies routinely pressed trading vessels into service, and more than half a fleet could be merchant ships, because a cargo carrier and a fighting sh…
981. Early iron swords were no better than bronze; horses changed war insteadWhen ironworking reached Greece around 1300 BC, the first iron swords were no improvement on bronze ones. The bigger military shift had come centuries earlier, around 2000 BC, whe…
982. An archbishop coined weapons of mass destruction years before the atom bombThe phrase weapons of mass destruction first appears on record in 1937, spoken by Cosmo Gordon Lang, Archbishop of Canterbury, as he reflected on the bombing of Guernica and the w…
983. The shotgun began as a bird hunter's fowling piece with a six-foot barrelBefore it was called a shotgun, the weapon was a fowling piece, built in sixteenth-century Europe for shooting birds on the wing, with barrels that later stretched to six feet. Th…
984. The humble sling outranged Persian stones when Rhodians switched to leadTwo cords and a pouch can hurl a stone far beyond any human arm, sometimes over 400 metres on a high arc. Ancient armies relied on the sling for thousands of years, yet surviving …
985. Humans have made spears for 400,000 years, and chimpanzees make them tooWooden spears from Schöningen in Germany and Clacton in England show people hunting with sharpened shafts at least 400,000 years ago. Humans are not alone in this: western chimpan…
986. Clearing a naval minefield can take 200 times longer than laying itA naval mine can cost as little as 2,000 dollars, and laying one typically costs between 0.5 and 10 percent of removing it. Clearing a minefield may take up to 200 times as long a…
987. Full plate armour peaked after the Middle Ages, not during themThe shining knight in full plate is usually pictured in the medieval era, yet complete suits only appeared around 1420 and reached their peak in the 15th and 16th centuries. Much …
988. The rapier began as a Spanish 'dress sword' worn with everyday clothesSpaniards called it the espada ropera, the dress sword, because gentlemen wore it as part of their outfit. The long, slender thrusting blade became a badge of nobility across 16th…
989. Spiral grooves turned a wobbly musket ball into an accurate rifle shotA musket ball sat loosely in its smooth barrel, rattling against the sides and leaving the muzzle in an unpredictable direction. Cutting spiral grooves inside the barrel made the …
990. The small buckler shield gave English the word 'swashbuckler'A buckler was a round metal shield just 20 to 40 centimetres across, light enough to hang from a belt and used for both blocking and striking at close quarters. Carried by knights…
991. The word battleship is shorthand for 'ship of the line of battle'Twentieth-century battleships got their name from a sailing-era tactic. Fleets in the 17th century began forming single-file lines to trade broadsides, and only the strongest ship…
992. Ming dynasty engineers built pressure-triggered mines centuries before EuropeA 14th-century Chinese manual, the Huolongjing, describes buried bamboo mines set off when enemies stepped on hidden boards, dropping a weight that spun steel wheels against flint…
993. Hiram Maxim made guns reload themselves using their own recoilThe Gatling gun of 1862 fired fast, but a person still had to turn its crank. Hiram Maxim's breakthrough was to capture each shot's recoil energy and use it to reload, creating a …
994. Military aviation began with a French observation balloon in 1794Just eleven years after the first practical balloons rose in 1783, the French Aerostatic Corps sent one up to watch the Battle of Fleurus, the first major battle observed from the…
995. China's bamboo fire lance evolved into the first metal gunsA Buddhist mural at Dunhuang from around 950 shows a fire lance, a bamboo tube that spat flame and debris. Within two centuries bamboo gave way to cast iron, and the oldest surviv…
996. Missiles descend from rocket-powered arrows flown in tenth-century ChinaChinese archers were strapping rockets to arrows by the 10th century. Iron-cased rockets from Mysore and the Maratha Empire later inspired Britain's Congreve rocket, and today's g…
997. Benin City's moats and ramparts stretched some 16,000 kilometresThe walls of Benin, in present-day Nigeria, combined ditches and earth ramparts across more than 500 linked settlement boundaries. Journalist Fred Pearce put their length at four …
998. The mortar takes its name from the kitchen bowl it resembledThe first mortars were squat iron bowls, so like the apothecary's mortar and pestle that they borrowed the name. Early ones lobbed stones so high that, at Belgrade in 1456, lookou…
999. 'Lock, stock and barrel' comes from the three main parts of a musketThe phrase lock, stock and barrel names a musket's firing mechanism, wooden body and tube. The weapon itself began around 1521 as an arquebus so heavy it rested on a forked stick,…
1000. War horses came in three sizes, each trading speed for carrying powerA horse can carry roughly 30 percent of its own weight, but pulling a wheeled load on a paved road it can shift about eight times its weight. That simple gap shaped millennia of w…
1001. Where a katana's signature sits reveals which way up it was wornJapanese smiths carved their signature on the side of the tang that faced outward when worn. Because the older tachi hung edge-down and the katana was thrust through the sash edge…
1002. Knives are at least 2.5 million years old and still evolvingStone cutting tools from the Oldowan culture show that people have been making knives for at least 2.5 million years. Blades have since moved from flint and obsidian through coppe…
1003. From straw and bramble to Kevlar, helmets kept reinventing themselvesSome eighteenth-century British gamekeepers protected their heads with straw bound together by cut bramble. Their successors wear aramid fibre, and so do soldiers. In between came…
1004. Chinese city walls grew so thick they held back cannon developmentJericho had a wall around it in the eighth millennium BC, making walls one of humanity's oldest large projects. For thousands of years nearly every city needed one. In China they …
1005. Fighter planes went from fabric biplanes to stealth jets in a centuryThe first fighters were wooden frames wrapped in fabric that topped out near 160 kilometres an hour. Today's fighters are bigger and heavier than Second World War medium bombers, …
1006. Firearms began as bamboo tubes of gunpowder strapped to spearsThe ancestor of every rifle and pistol was a Song dynasty invention: a bamboo tube packed with gunpowder and pellets, lashed to a spear so one soldier could carry it. This fire la…
1007. Every new weapon forced fortresses to reinvent themselvesFortifications have always chased weapons. Tall medieval walls fell to fourteenth-century cannon, so builders went low, sinking walls into ditches behind earth slopes. Nineteenth-…
1008. Oar-driven galleys ruled Mediterranean seas for over two thousand yearsPhoenicians, Greeks and Romans all fought in long, slim rowing ships, and the design refused to die. Galleys carried pilgrims, guarded precious cargo, pioneered ship-killing canno…
1009. The grenade takes its name from the pomegranateByzantine soldiers hurled jars of Greek fire, Song Chinese troops packed gunpowder into iron shells they called thunder crash bombs, and in 1433 a Catalan fleet sailed for Sicily …
1010. The word gun may come from a giant crossbow named Lady GunildaIn the fourteenth century Windsor Castle housed an enormous mechanical bolt-thrower nicknamed Domina Gunilda. Her name, likely from the Old Norse Gunnhildr, built from two words f…
1011. Gunpowder was an accident of the search for eternal lifeChinese alchemists hunting for an elixir of immortality kept mixing sulfur, saltpeter and other ingredients, and one ninth-century Daoist text warns that such experiments burned p…
1012. Korea's tiny se-chongtong was an early handgun carried by spiesIn 1432, under Sejong the Great, Joseon Korea introduced the se-chongtong, a gun under 14 centimetres long that fired small arrows. Officials first wrote it off as a failure becau…
1013. The cannon began as a Chinese fire-lance and conquered EurasiaThe oldest cannon with its production date inscribed on it, the Xanadu Gun of 1298, is only about 35 centimetres long and weighs just over 6 kilograms. Within two centuries its de…
1014. Castles were private homes built to fight from, not just hide inHistorians define a castle narrowly: a lord's private fortified residence. That rules out walled cities, Anglo-Saxon burhs and most things crusaders called castles. It also explai…
1015. Greek catapults grew from bows, and turned engineering into scienceA catapult hurls things without any gunpowder, storing energy slowly in bent bows, springs or twisted rope and releasing it all at once. Greek engineers began by beefing up the hu…
1016. Mail armour guarded warriors for two millennia and now stops sharksLink enough small metal rings together and you get mail, armour that protected European soldiers from the third century BC into the 1500s. It is far from obsolete. Butchers wear m…
1017. The spoked wheel made the war chariot possibleA chariot was barely more than a floor on two wheels with a waist-high rail, pulled by horses harnessed side by side. What made it fast enough to reshape Bronze Age warfare was a …
1018. The humble club has had a surprisingly long careerA stick swung hard may be the simplest weapon ever made, and people have used one since prehistory. Yet the club never really retired. It evolved into the metal mace, became a bad…
1019. The crossbow traded speed for patience, and changed who could shootA longbow demands years of practice and serious muscle, because the archer must draw and loose almost in one movement. The crossbow sidestepped both problems. A trigger holds the …
1020. Tutankhamun was buried with a dagger forged from a meteoriteWhen archaeologists opened Tutankhamun's tomb in 1924, they found two daggers: one with a golden blade and one of iron, a metal Egypt had no ore for. In 2016 x-ray analysis confir…

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