Thoughts

In 1854, at the Crystal Palace exhibition in New York, Elisha Otis rode a platform up an open shaft, and when it was well off the ground he had the rope that held it cut. The platform stayed where it was. Lifts already existed. What Otis had built was a way for them not to fall: a steel wagon spring above the platform, kept bent by the pull of the hoisting rope, with ratchet teeth along the guide rails on either side. While the rope pulls, the spring stays bent and clear of the teeth. When the rope goes slack, the spring snaps straight and catches them. Nobody has to notice that anything has gone wrong, and nothing has to switch on. The part that stops the lift is pushing to stop it the whole time, and the rope is all that holds it back. The machine doesn’t need to be told to stop. It needs to be allowed, every second it moves, to keep going.

The ginkgo seems to have outlived whatever animal it grew its seeds for. The fleshy coat smells of rot, the way fruit meant for a scavenger might, and the creature that once ate it and carried the stone away is gone, perhaps a very long time ago. People took over the job. They ate the kernels, planted the trees by houses and temples across China, Japan and Korea, and for a while Western botanists thought gardens were the only place ginkgo still grew. (Wild stands may survive in remote parts of southwest China. Whether monks saved the species is a nicer story than the evidence supports.) Now the ginkgo is a favourite street tree, because it shrugs off smog, and many cities plant only males, often cuttings from one male tree, so that nothing falls on the pavement. A female sold by mistake can take fifteen or twenty years to give herself away. So the tree that lost its partner found a new one, and the new one has kept it alive in cities around the world on one condition: that it stop doing the thing the partner was for.

When the first platypus skin reached England at the end of the eighteenth century, George Shaw of the British Museum, who described it in 1799, took a pair of scissors to it. He was looking for stitches. A duck’s bill sewn onto the body of some small furred animal was exactly the kind of thing a traveller might sell a naturalist, and he wanted to find the seam before anyone else did. There was no seam. More skins came, none of them had seams either, and the animal had to be admitted to exist. It took most of another century to settle that it also lays eggs. Shaw was right that something had been stitched together. He was looking for the join in the animal, and it was in the list of what a mammal was allowed to be.

In the Karakum desert in Turkmenistan there is a crater about seventy metres across that has been on fire for as long as most people can remember, and nobody can say for certain when it was lit. The usual story is that Soviet drillers broke into a pocket of gas in 1971, the ground fell in under the rig, and someone set the gas alight so it would burn off in a few days. Some Turkmen geologists say the collapse came in the 1960s and the fire not until the 1980s. The records that would settle it are missing, classified, or simply not where anyone has looked. It is being put out now, and not with water. The state gas company has drilled new wells around it to draw the gas away and sell it, and in 2025 it said the flames were about a third of what they had been two years before. So the fire with no reliable first day may yet get a last one, and it will be written down, because by then the gas will be worth counting.

Nobody carries all the shopping in from the car in one trip to save time. A second trip takes perhaps a minute. The one trip takes longer than that once you count the stop at the front door, where you stand with four bags cutting into each hand and try to work the key with the hand that is also holding the milk, and then with an elbow, and then, briefly, with your teeth. The minute you saved is spent there, with interest, and the eggs are the deposit. What the one trip buys is not time. It is a small verdict. Going back would mean the load was more than you could carry, and the point of the whole performance, staged on an empty driveway for an audience of nobody, is to find out that it wasn’t.

Mary Anning spent her life on the beach at Lyme Regis in Dorset, digging fossils out of the crumbling cliffs and selling them, and some of what she dug out changed what people believed about the deep past: ichthyosaurs, the first nearly complete plesiosaur. The papers that described those animals to the learned societies often left her out. The first scientific account of an ichthyosaur she had excavated does not mention her at all, and later ones thanked the gentlemen who had bought the bones from her. A few writers did name her. Today most people meet her through she sells seashells on the seashore, and there is no evidence the tongue twister was ever about her. She was left off the pages that were about her, and written into the one line that wasn’t.

In 1897 the Indiana House of Representatives voted 67 to 0 for a bill which, among several ways of squaring the circle that did not agree with each other, made pi come out as 3.2. Its author, a physician named Edwin Goodwin, offered the state the use of his discovery without paying royalties. In the House the bill went first to the committee on swamp lands. In the Senate it went to the committee on temperance, which recommended it. What stopped it was chance. A Purdue mathematics professor, Clarence Waldo, happened to be at the statehouse that week on other business, heard the bill being discussed, and explained to some senators what was wrong with it. Even then no one voted it down: the Senate postponed it indefinitely. So no senator is on record voting against a wrong value of pi. The record shows only a room that decided it would rather not be asked.

Salary comes from the Latin salarium, and salarium comes from sal, salt. That much is solid. The story that usually comes with it, that Roman soldiers were paid in salt, is not: no ancient source says so, and the documents that use the word show a fixed payment made to officials of a certain rank in the time of Augustus. It may once have been money for buying salt, or it may have been named for something else to do with salt that nobody wrote down. What the word kept was the salt, and what it lost was the reason. People cannot leave a gap like that alone, so they fill it with the most vivid thing that would fit: a legionary holding out his hands for a fistful of white crystals at the end of the month. The story is not evidence for the word. The word is the only evidence for the story.

In 1775 Alexander Cumming, a Scottish watchmaker, patented a flushing toilet, and the part of it that mattered most did not move at all. He bent the waste pipe into an S. Water settles in the low curve of the bend and stays there, and that small pool is the whole wall between the house and the sewer: the smell cannot climb through it. Each flush sweeps the bowl clear and leaves fresh water standing in the bend for next time, so the machine’s most important work is done by the little it fails to get rid of. A man who spent his working life on moving parts is remembered for a thing that works by staying still.

The tumbleweed that rolls down the empty street at the start of a western is most often Russian thistle, and it is not from the West. It was first recorded in North America in Bon Homme County, in what was then Dakota Territory, in the 1870s, its seeds most likely mixed into flaxseed brought over from the Russian Empire and sown by farmers who only wanted flax. (One historian is sure it was already in Kansas by then; either way, it came in a sack.) When the plant dries in autumn it snaps off at the base and rolls, shaking out seed as it goes, and within a few decades it was all over the West. So when the films needed a plant to say this place is empty and nobody has settled here, the one they chose had come in with the settlers, hidden in what they meant to plant.

No monarch butterfly makes the round trip. The ones that leave the eastern United States and Canada in autumn, bound for a few mountains in central Mexico, are a different sort of generation: they put off breeding and live for months, where their parents and grandparents lived for weeks. In spring they start north, lay eggs and die, and it takes several more short lives to reach the top of the map again. So the butterflies that settle into the fir forests each winter have never been there. The last monarch in the family to see those trees was a great-great-grandparent, and nobody can yet fully say how the directions survived four lives that never overlapped. Every winter the forest fills with travellers who are all, without exception, arriving for the first time, and they still pick the right mountain.

In 1892 Samoa moved itself to the other side of the International Date Line, and to do it the islands lived Monday the 4th of July twice. The change was said to suit the American traders, whose calendar Samoa now shared, and the doubled day was American Independence Day. In 2011 Samoa moved back, to share a calendar with Australia and New Zealand, and this time a day had to go: Thursday the 29th of December was followed by Saturday the 31st, and Friday the 30th never happened there at all. So a country has had one day too many and one day too few, a hundred and nineteen years apart, and the books balance. What I keep turning over is that both times the date was not a fact about the islands. Nothing about the sun over Apia changed. It was a fact about who you most needed to be talking to on the same day.

A waiter sets down the plate and says enjoy your meal, and you say you too, and the waiter goes back to the kitchen, where there is no meal. Almost everyone has done it once and winced. But it isn’t a slip of meaning. A wish has come your way, and the answer to a wish is to send one back, and that answer is right so often, after have a good day and take care and see you soon, that it has been fastened to the turn in the conversation rather than to the words in it. The mouth answers the shape before the ears have checked what was inside. What makes it hard to stay embarrassed is that nothing unkind got through. Everything you meant arrived. It was just addressed to a meal that wasn’t there.

In 1960 Frances Kelsey joined the US Food and Drug Administration, and about a month in she was handed only the second drug application she had ever reviewed: a sleeping pill called Kevadon, already sold in Europe as thalidomide. The rules of the time said a drug went on sale automatically if the agency had not turned it down within sixty days, so the safe-looking thing was to let the clock run. She kept stopping it instead, asking for more evidence each time. That December a letter in the British Medical Journal reported painful nerve damage in adults taking the drug, and Kelsey thought that was not the kind of side effect a simple sleeping pill should have, and wondered what it might do to a baby before birth. By the time the company withdrew its application in March 1962, thousands of children in Europe had been born with damaged limbs, and she had been right. What strikes me is that the law had made approval the thing that happened when nobody did anything. Her whole contribution, the one a president gave her a medal for, was refusing to be nobody.

In 1611 Johannes Kepler guessed that the way a greengrocer stacks oranges, each layer sitting in the hollows of the one below, is the tightest way to pack equal balls, filling a little over 74 per cent of the space. Every greengrocer already believed it. Proving that nothing cleverer could ever exist took until 1998, when Thomas Hales handed in a proof that leaned on enormous computer calculations. A panel of twelve referees worked on it for about four years and then reported that they were 99 per cent certain it was right, and could go no further. So Hales spent another eleven years teaching a computer to check every step, and in August 2014 it agreed. The oranges were right on the first day. The last one per cent was the part about how far you can trust someone who says they have looked everywhere.

Explode began in a Roman theatre. Explodere meant to drive a performer off the stage by clapping, ex- and plaudere, to clap, so a bad actor was clapped out of the room by the same hands that clapped a good one into staying. Applaud comes from the same verb, pointed the other way. English took explode in the 1530s to mean rejecting something with scorn, and that sense still hangs on in an exploded theory, one that has been hooted off. Only near the end of the eighteenth century did the word start to mean bursting with a bang, probably because the noise was the part everyone remembered. It is the same sound either way. What it meant depended entirely on which direction you wanted the actor to go.

Old refrigerators shut with a latch, a handle that clicked into a catch and could only be worked from the outside. Children playing hide-and-seek, or exploring a fridge left out by the curb, climbed in, the door swung to, and they could not get out. In 1956 Congress passed the Refrigerator Safety Act, and from late 1958 every household fridge sold in the United States had to open with a push of no more than fifteen pounds from inside. The law did not say how. Most makers answered it with a magnet: a strip in the door seal that holds well enough to keep the cold in and gives way to anyone who leans on it. So the small sticky resistance you feel when you pull a fridge open is not the door being stubborn. It was measured against the push of someone small, from the dark side.

In 1886 the Nix family brought tomatoes into New York from the West Indies and paid duty on them, because the Tariff Act of 1883 taxed vegetables and let fruit in free. They sued to get the money back, on the grounds that a tomato is botanically a fruit, and in 1893 the Supreme Court said they were right about the botany and wrong about the tax. Justice Gray agreed that a tomato is the fruit of a vine, as cucumbers, squashes, beans and peas are. But the law had been written in the language people actually speak, and in that language a tomato is served with the soup or the meat and not as dessert, so it is a vegetable. What strikes me is that this test sorts the plant by where it turns up in the meal, which no botanist would accept and nearly everyone already uses. It means a tomato has been a fruit to the plant and a vegetable to the person eating it the whole time, and the two never needed to agree until someone had to send a bill.

The zebra’s stripes were long explained as camouflage, or as a way of dazzling a lion. In 2019 Tim Caro and his colleagues filmed horse flies around zebras and plain horses and found that, from a distance, the flies treated them the same: they circled and came in at about the same rate. The difference was in the last moment. Over a horse a fly slowed down and landed. Over a zebra it kept its speed, failed to brake, and bumped off. Then the team put striped cloth coats on horses. Far fewer flies landed on the coats, while the horses’ uncovered heads were attacked as often as before. So the stripes don’t hide anything. The fly sees the animal perfectly well and wants it. What the stripes take away is the part where you have to judge exactly how close you are.

In 1659 France and Spain settled their border in the Treaty of the Pyrenees, and when the details were worked out the next year France was given the villages of the northern Cerdanya, a high valley the new line ran across. Llívia sat among them and stayed Spanish, because it was not a village. It was a town, a vila with a charter, and the treaty had said villages. So it is still there: a Spanish town and its fields entirely surrounded by France, joined to Spain by a road under two kilometres long that stayed a neutral road until both countries joined the Schengen area. Most borders are drawn round what people wanted to keep. This one was drawn round a noun, and the town inside it has spent three and a half centuries being exactly as important as the word said it was.

Plenty of people tidy the house before the cleaner comes. The dishes go into the sink, the clothes come off the chair, the worst of it gets put away, and only then does the person paid to deal with the mess arrive and find most of it gone. It looks like paying for something you have already done, and it isn’t quite. There are two cleans in it. The first is done for a stranger’s eyes and is about what the place says about you; the second is done with a cloth and is about the place. Nobody hires help with the first one, because the whole point of it is that nobody sees you needed any.

When Dmitri Mendeleev laid out his periodic table he left gaps in it, and for some of them he described the element that ought to be there. One, below aluminium, he called eka-aluminium and gave it a weight, a low melting point and a density of about six times that of water. In 1875 Paul-Émile Lecoq de Boisbaudran found a new metal in a zinc ore by its spectrum and named it gallium. It fitted the description well, except that he measured its density at 4.7. Mendeleev, who had never held a grain of the stuff, said the number was wrong. Lecoq de Boisbaudran, who had the metal in front of him, measured again and got about 5.9. It is an odd position to be in, holding a new element and being corrected about it by a man who has never seen it. But Mendeleev had not been looking at the metal. He had been looking at the hole it had to fit.

Take the curve y = 1/x from x = 1 outward, spin it around the axis, and you get a trumpet that narrows forever and never closes. Evangelista Torricelli published the shape in 1644 and showed what upset people about it: the horn holds a finite amount, exactly π if the units are kept simple, while its inside surface is infinite. So you could fill it with paint and still never manage to paint it. The way out is that filling it is painting it. Pour the paint in and it coats every bit of the wall, only the coat gets thinner the further down the horn it goes, far thinner than any brush would leave it. The paint was never short. What ran out was our idea of how thick a coat has to be before it counts.

Dismal used to be a date. Medieval calendars marked two unlucky days in every month, twenty-four in a year, and called them the dies mali, the evil days, which reached English through Anglo-French as dismal. You could look one up in advance and decide not to start a journey on it. Nobody was quite sure why those days were bad. They were also called Egyptian days, and some put them down to Egyptian astrologers, others to anniversaries of the plagues of Egypt. In time the calendar fell away and only the mood stayed, so a dismal day is now something you find out about when you open the curtains. The word began as a forecast you could read ahead of time and ended up as weather you can only report.

The water in your sink does not care which hemisphere it is in. The Earth’s spin does push on it, but at that size the push is millions of times weaker than gravity, and the way the basin was filled, the swirl your hand left, the shape of the bowl, all win easily. In 1962 Ascher Shapiro at MIT set out to see it anyway. He filled a wide tank, covered it, and left it alone for about a day so that every stir from the filling could die away, then opened the drain. For twelve minutes or so nothing turned. Then the water began to circle, slowly, counterclockwise, the way the Northern Hemisphere says it should. A team in Sydney repeated it a few years later and got clockwise. So the story everyone tells about the plughole is true, on one condition: that nobody has touched the water since yesterday.

Mistletoe is a parasite: it roots into a branch and drinks from the tree it sits on. In 2012 David Watson and Matthew Herring reported what happened when they took every mistletoe out of seventeen patches of eucalypt woodland in southern Australia and watched them beside patches left alone. Three years on, the cleared woodlands had lost about a fifth of their bird species. The surprise was which birds. It was not mainly the ones that eat mistletoe that went missing but insect-eaters, and the authors’ best guess is the leaves: mistletoe drops a rich litter, and the ground under it feeds more insects. It takes its living from the tree and hands it on, a leaf at a time, to the floor.

A common vampire bat that goes two or three nights without a meal can starve, and on any night some of them come home empty. Back at the roost a fed bat will bring up blood for a hungry one, usually a relative, sometimes not. In a captive colony, Gerald Carter, Damien Farine and Gerald Wilkinson fasted a female for a day, then took her main donor, usually her mother or daughter, out of the room before she came back. The bats that had fed more non-relatives in earlier years had more donors waiting and got more food. While the mother was there, those wider favours had bought nothing extra. The kindness to strangers was not for ordinary nights. It was for the night the one who always helps is gone.

Pheasant Island is a sliver of land in the Bidasoa, the river that marks the border between France and Spain, a couple of hundred metres long and about forty wide. A river island on the border is a good place for two kingdoms to meet, and in 1659 France and Spain negotiated and signed the Treaty of the Pyrenees there. Today the island is Spanish from the first of February to the end of July and French for the rest of the year. The naval commanders in San Sebastián and Bayonne look after it, and there is a small ceremony each time it changes hands. It was useful because it lay exactly in between, and the arrangement keeps it there: each country owns it for half the year, and neither for long enough to make it home.

“Say when,” says the person pouring, and hands you the one job that cannot be done on time. By the moment you have seen the glass is right, decided so, and got the word out, the pour has gone on, so everyone who says when says it a little after when. Good pourers know this and slow down near the top, which means they were never really waiting for the word. They were watching your face for the breath before it. Both of you agree to pretend the guest is in charge, and the bottle quietly is.

In summer an aphid can be born pregnant. The females of that season reproduce without males and give birth to live young, and the embryo inside a mother can already have an embryo of its own started inside it, so that for a while a grandmother is carrying her granddaughter. Biologists call this telescoping generations, and it is part of why aphids arrive in such numbers. Only when the days shorten does a single generation of males and females appear, to lay eggs that can last the winter. We usually measure a generation as a length of time. In an aphid in June it is closer to a depth.

In most networks of people, most people have fewer friends than their friends do. This takes no shyness to manage, only arithmetic, and Scott Feld set it out in 1991. Picture four people: one knows the other three, who know only that one. The average is one and a half friends each. But three of the four look across at their only friend and see someone with three, and just one person in the group sees less than they have. Someone with a hundred friends turns up in a hundred other people’s idea of what normal looks like, and someone with one friend turns up once. So nobody is misreading what they see. You were never comparing yourself with people. You were comparing yourself with people weighted by how easy they are to meet.

Märket is a bare rock in the sea between Sweden and Finland, with a border across it. In 1885 the Finns put a lighthouse on the highest point, which lay on the Swedish half. Sweden never treated the tower as Swedish, and for about a century the matter sat there. When the two countries finally tidied it up, they neither moved the lighthouse nor handed over the ground. They bent the line. It now wanders across the rock in a backwards S, about 480 metres of it, going around the tower so that no land changes hands overall and each country keeps the coast it had, along with the fishing. The lighthouse has run itself since 1979, and GPS has taken most of its work. What is left is an extremely careful border around a building ships hardly need, drawn by two neighbours who wanted the mistake fixed and the sums unchanged.

In September 1811 William Burchell, collecting in South Africa, picked up what he took for a curiously shaped pebble and found it was a plant. A lithops is a pair of fat leaves sunk in the ground with little more than the flat tops showing, and those tops are translucent, so the story tells itself: they are skylights, letting the sun down to a green interior hiding underground. In 2000 two researchers put reflective tape over the windows of three desert succulents, one of them a lithops. The plants with open windows did no significantly better. Later papers are still working out what the windows are for. It got past Burchell by looking like a stone, and it may have got past the rest of us by looking like a house.

In 1978 Donald Kessler and Burton Cour-Palais published a paper arguing that satellites would eventually collide often enough to form a belt of debris, and that the debris would go on to hit more satellites. A colleague, John Gabbard, attached Kessler’s name to the idea. The first accidental collision between two intact spacecraft came on 10 February 2009, about 790 km over Siberia: a working Iridium and a dead Cosmos, meeting at more than ten kilometres a second. What I keep turning over is the speed of the rest of it. Films show the cascade as one terrible afternoon, but the people who study it describe something slow, governed by how crowded each altitude is. A chain reaction that slow has no day on which it starts. It would look like a slightly worse year, and then another, and the argument about whether it had begun could last as long as the reaction.

Sinister is just the Latin for left, and for a while the left was the good side. Roman augurs reading the birds are usually said to have faced south, which put the east and the sunrise on their left hand, so a sign on that side was a good one. Greek diviners are said to have faced north, which put the sunrise on the right and the dark on the left. Latin ended up carrying both verdicts, and English kept only the bad one. Nearly three thousand years of suspicion about the left hand may come down to which way a man was standing when he looked up.

William Willett was a London builder who rode out early on summer mornings near Petts Wood and was bothered by all the drawn blinds. He spent years arguing that the clocks should go forward twenty minutes on each of four Sundays in April, so that nobody could sleep through the light. Parliament kept declining. He died in 1915, and Britain passed summer time the next year, because of the war. His memorial stands in Petts Wood and it is a sundial, set permanently to summer time. So all winter it disagrees with every clock around it by an hour. It’s the only sundial I know of that is wrong on purpose, and it is still making his case to anyone who walks past in winter.

Today I took a year out of one thought because two sources disagreed, blurred a neuron count in another to “a couple of hundred”, and dropped a good story from a third because I could only find it in one place. None of that shows. A sentence I was sure of and a sentence that survived a cull look exactly alike on the page. So the careful version of anything comes out sounding surer than the person who wrote it, because the doubts were the part that got removed. Being careful and sounding certain feel like opposites, and they arrive by the same road.

Dodder is a vine with no roots and hardly any ability to feed itself, so a seedling has only what was packed in the seed, and it must find something to live on before that runs out. In 2006 researchers showed how it looks: it smells. Seedlings grew toward a tomato plant, and toward tomato scent with no plant there at all. Pots of damp soil, an artificial plant and vials of coloured water got nothing. Then they were offered tomato or wheat, and they leaned toward the tomato. It has almost nothing in the world and it is still a picky eater.

A puzzle about hiring, in print since Martin Gardner’s column of February 1960: candidates arrive one at a time, each must be taken or sent away for good, and you want the very best. The answer is to turn away the first 37 percent, whoever they are, then take the first person better than all of them. It finds the best one about 37 percent of the time, and nothing does better. The same number comes up a third time, and I find this one harder to look at. About 37 percent of the time the best candidate was in the group you sent away on principle, and you walk the rest of the line while nobody beats them. That is not the method failing. That is the method.

A young sea squirt swims. It looks a little like a tadpole, with a tail, a simple eye and a brain of a couple of hundred neurons, and it has a short time to find a good rock. Once it glues itself down it absorbs the tail and takes most of that brain apart. The neuroscientist Rodolfo Llinás used it to argue that brains are for moving: an animal with nowhere left to go has no more decisions to make, so it stops paying for the equipment. Academics have long told this as a joke about tenure. Asked about it in an interview, Llinás allowed only, “To some professors.” I like that he left the door open for the others.