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Start swiping — it's freeShown a spiky shape and a rounded blob and asked which is 'bouba' and which is 'kiki,' around 95% of people across many different languages pick the same match — round shape 'bouba,' spiky shape 'kiki.' First observed in the 1920s and renamed and popularised by Ramachandran and Hubbard in 2001, it suggests some sound-to-shape associations may be close to universal rather than arbitrary.
In Smullyan's Transylvania, every inhabitant is a human (always truthful) or a vampire (always lying) — and separately, either sane (correct about what's true) or insane (convinced every true thing is false). Two sisters, one human and one vampire, sanity unknown. The first says, 'We are both insane.' The second says, 'That's not true!' Which sister is the vampire?
The first sister is the vampire. Working through both possible truth-values of her claim shows the two are only ever mutually consistent when she is the vampire — the second sister's contradiction is forced into being true in every consistent scenario, which only a human or an insane vampire could state truly, and elimination fixes the first sister as the liar. From Raymond Smullyan's What Is the Name of This Book?
The Silk Road was never one single road but a changing network of overland and maritime routes linking China, Central Asia, the Middle East and Europe for roughly 1,500 years. It carried silk and spices west and glass and horses east, but also religions, papermaking technology, and eventually the Black Death. The name itself is modern — coined only in 1877 by the German geographer Ferdinand von Richthofen.
— Valerie Hansen, The Silk Road: A New History — Oxford University Press, 2012
In 1905, an irrigation canal built to tap the Colorado River breached during floods, and the river poured uncontrolled into the desert for nearly two years before crews could plug the break. The runaway flood filled an ancient dry basin and created the Salton Sea, still California's largest lake today.
— Wikipedia contributors, Salton Sea — Wikipedia, Colorado Desert entry
Arthur Laffer argued that tax revenue is zero at both a 0% and a 100% tax rate, so somewhere between them lies a rate that maximises what governments actually collect — raise taxes past that point and revenue can fall. The idea predates Laffer by centuries, but a napkin sketch at a 1974 dinner with future officials Cheney and Rumsfeld made it famous; the napkin now sits in the Smithsonian.