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Why a roast keeps getting hotter after you take it out: carryover cooking and the heat still on its way in You pull the roast at 60 °C, and five minutes later the probe says 66 °C. Nothing is heating it, so where did the heat come from? The answer is that an oven… Food Science4 min read8 Nov Why fair coin flips end with one person owning almost everything: the yard-sale model of wealth Give 60 people 100 coins each and let them trade by fair coin flips, with the stake a fixed share of the poorer person's wealth. Nobody has any skill or… Economics4 min read1 Nov Why a skater spins faster when she pulls her arms in: angular momentum and r squared A skater starts a slow spin with her arms wide, pulls them in, and blurs into a fast spin with no push from anything. The trick is a quantity that cannot… Physics4 min read31 Oct Why a dropped stick can find π: Buffon's needle Drop a stick on a floor of planks and count how often it lands across a seam. The count secretly contains π: for a needle as long as the plank width, the… Maths4 min read21 Oct Why 23 people are enough for a shared birthday: counting pairs, not people Put 23 people in a room and the chance that two share a birthday is already 51%. It feels far too low a number, because we picture one person matching our… Maths3 min read16 Oct Why mild preferences can build a segregated town: Schelling's chequerboard Nobody in this town wants it split into blue and orange districts. Each household only asks that a few of its neighbours look like it. Yet run the rule and the… Economics4 min read15 Oct Why switching doors wins twice as often: the Monty Hall problem Three doors, one car. You pick one, the host opens a goat door, and offers a swap. Most people say it's 50/50. It isn't: switching wins twice as often as… Maths4 min read10 Oct Why a tossed tennis racket flips: the intermediate axis theorem Spin a tennis racket about its handle or its face and it flies cleanly. Spin it about the third axis and it flips, even in orbit where nothing pushes on it… Physics3 min read5 Oct How a leopard gets its spots: Turing's two-chemical pattern machine A leopard's spots and a zebra's stripes start out as a smooth sheet of near-identical cells. In 1952 Alan Turing showed that two interacting chemicals, one… Biology3 min read5 Oct How dropping needles on a floor reveals the number π: Buffon's needle Toss a match onto a plank floor and ask: does it touch a crack? Do it thousands of times and the fraction that do will quietly spell out π, though no circle is… Maths3 min read4 Oct Why traffic jams appear out of nowhere Sometimes a motorway grinds to a halt and then clears up with no crash, roadworks or merge in sight. That's a phantom traffic jam, and it starts with one… Engineering4 min read26 Sep