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Why a treatment can win in every group and still lose overall: Simpson's paradox Treatment B beats Treatment A overall, yet A wins for small stones and for large stones. That is Simpson's paradox, and it is real data from a kidney-stone… Maths4 min read3 Nov Why honey never spoils: it isn't the sugar, it's the missing water Honey is rich, sweet and nutritious, so why don't bacteria and moulds move in? Because microbes need free water, and honey's sugar holds almost all of it… Food Science4 min read29 Oct Why a sentence can nest forever on paper but not in your head: centre-embedding The rat the cat the dog chased killed ate the malt. It is perfectly grammatical, and almost nobody can read it. English lets you tuck one clause inside another… Language4 min read23 Oct Why you hear a note that isn't there: the missing fundamental Play only 220, 330 and 440 hertz and most people hear a note at 110 hertz — a frequency that is not in the sound at all. This is the missing fundamental: the… Music & Sound5 min read23 Oct Why English plurals say s, z or iz: the wug test Say 'cats' and 'dogs' out loud and listen to the last sound. One is a hiss, the other a buzz, and 'buses' adds a whole extra syllable. English spells all three… Language4 min read13 Oct Why 0.1 + 0.2 isn't 0.3: flip the 64 bits a computer uses for decimals Type 0.1 + 0.2 into almost any programming language and you get 0.30000000000000004. Nothing is broken. Computers count in powers of two, and a tenth is an… Computing3 min read6 Oct Why salt makes ice cream freeze: the cold that ice and salt create Ice is already cold, so why does salt make ice cream freeze? Because salt does not add cold. It stops the ice and water from staying in balance at 0 °C… Food Science3 min read5 Oct Why you hear bass from a speaker too small to make it: the missing fundamental Your phone speaker is far too small to produce a deep bass note, yet you still hear the bass. The trick is that pitch is not a frequency in the air. It is a… Music & Sound3 min read3 Oct 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 seven shuffles are enough to mix a deck of cards A 52-card deck can be put in about 8 × 10^67 different orders, yet a few quick shuffles leave a lot of the old order behind. In 1992 Dave Bayer and Persi… Maths4 min read27 Sep Why English spelling doesn't match how words sound Around 1400, English spelling roughly matched speech. Bite sounded close to "beet", meet roughly like "mate", and house like "hoose". Then, over about three… Language5 min read26 Sep