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Start swiping — it's freeWhen a tax or price control pushes a market away from its free equilibrium, some mutually beneficial trades simply stop happening. Economist Arnold Harberger showed this lost value forms a small triangle on a supply-and-demand graph, and used it to estimate how much monopolies and tariffs actually cost an economy. Unlike a transfer, that loss benefits no one at all.
Three prisoners, A, B and C, are told one of them has been picked at random for pardon. Prisoner A asks the warden — who knows the answer but can't reveal it — to name one of the other two who will definitely be executed. The warden names C. Has A's own chance of pardon improved from 1 in 3?
No — it's still exactly 1 in 3, though it feels like it should rise to 1 in 2. The warden's answer only ever eliminates a prisoner who wasn't A, so it carries no information about A specifically; the freed-up probability shifts entirely onto the unnamed prisoner, B. Martin Gardner published the puzzle in 1959, decades before an equivalent version, the Monty Hall problem, made the same logic famous.
— Martin Gardner, Mathematical Games column — Scientific American, October 1959
Verlan is a French word game that disguises ordinary words by inverting their syllables - 'femme' (woman) becomes 'meuf', 'louche' (shady) becomes 'chelou'. It grew out of working-class and immigrant neighborhoods as a way to speak without being fully understood by outsiders. Some verlan words have since slipped so completely into mainstream French that most speakers no longer notice they're backwards.
In 1494, Spain and Portugal signed a treaty dividing all lands outside Europe along a north-south meridian in the Atlantic — everything west belonged to Spain, everything east to Portugal. Neither side had any real idea what they were dividing, and it's a large part of why Brazil speaks Portuguese while the rest of Latin America speaks Spanish.
— Kingdoms of Castile and Portugal, Treaty of Tordesillas — 7 June 1494
Jean Piaget showed young children two identical glasses of water, then poured one into a taller, thinner glass. Children under about seven typically insist the taller glass now holds more — they haven't yet grasped that quantity stays constant despite a change in shape.