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Why 23 people are enough for two to share a birthday Put 23 people in a room and there's a better-than-even chance that two of them share a birthday. That sounds wrong, because 23 is tiny next to 365. The catch… Maths4 min read29 Sep Earth is closest to the Sun in January. So why is that winter? Summer can't be caused by being closer to the Sun: Earth makes its closest pass around 3 January and is farthest around 4 July. The distance changes by only… Earth & Space4 min read29 Sep Why Spanish sounds faster than Vietnamese yet says just as much Listen to Spanish or Japanese and it seems to rush past; Vietnamese or Thai can sound almost unhurried. Yet when researchers timed 170 people reading the same… Language5 min read29 Sep Why guitar frets get closer together as you go up the neck Guitar frets crowd together toward the body because of one fact about hearing: we hear pitch by ratio, not by difference. Each fret has to raise the note by… Music & Sound5 min read28 Sep Why some notes sound sweet together and others seem to fight Play C and E together and they sound sweet. Play C and C sharp and they buzz. The notes aren't the problem: the clash only happens when they meet. Every… Music & Sound5 min read28 Sep Chilli isn't hot: capsaicin trips the heat alarm on your tongue A chilli is exactly as warm as the room. There is no heat in it at all. The burn comes from capsaicin, a molecule that pries open TRPV1, the gate in your… Food Science5 min read28 Sep Why soap bubbles swirl with colour, then turn black just before they pop Soap has no dye, yet bubbles shimmer with magenta, gold and green. The colour comes from thickness: light bounces off both the front and the back of the film… Physics5 min read28 Sep How chameleons change colour: they stretch a mirror made of crystals A chameleon doesn't change colour by mixing pigments. Under its skin sit cells packed with tiny guanine crystals, arranged in a lattice that works like a… Biology4 min read28 Sep Why October 1582 lost ten days: a calendar year 11 minutes too long In 1582, Thursday 4 October was followed by Friday 15 October. Ten dates were simply deleted across Catholic Europe. The reason was an error of about 11… History5 min read28 Sep Why turning a wobbly table can stop it rocking: the quarter-turn proof Your café table rocks. Before you wedge a folded napkin under a leg, try turning the whole table on the spot. On most floors, somewhere within a quarter-turn… Maths5 min read28 Sep Why astronauts float: the space station never stops falling Astronauts on the International Space Station look weightless, but at 400 km up, Earth's gravity is still about 90% as strong as on the ground. The trick is… Earth & Space4 min read28 Sep Why everyone agrees which blob is 'bouba' and which is 'kiki' Show people a soft blob and a spiky star and ask which one is bouba and which is kiki. The words are made up, yet in the classic version of the test about 95%… Language5 min read27 Sep