Field observers keep finding fish holding station in churning water when calmer flow is available a body length away. Behind an obstacle a trout adopts the , swinging its body wide and beating its tail in time with the vortices coming off the cylinder. The obvious reading is that it is hiding in the slack water. Liao put electrodes in the swimming muscles to see what they were doing. How much work is the fish putting in?
Every tissue in the body has a to carry waste away, and the brain has none, although it burns about a fifth of the body’s energy. To see how it clears anyway, researchers injected a glowing tracer into the of mice and filmed the living brain awake and asleep. What changed between the two?
Knowledge of how to read and write hieroglyphs disappeared soon after the fourth century, and the script then sat unreadable for fourteen hundred years. In July of seventeen ninety-nine, French soldiers digging foundations for a fort near Rashid, on the Nile delta, turned up a broken slab built into an old wall. Their officer saw at once that it mattered. What made it the key?
Two numbers about the same city trees sound like they are arguing. One says the trees cancel close to half of the urban heat effect. The other says they pull the thermometer down by a fraction of a degree. Both are correct, so how do they fit together?
What is a good predictor that someone will be recorded as 110 years old?
On 19 September 1991 two German hikers found a human corpse at 3,210 meters near , in the Schnalstal valley, with only the upper body protruding from the ice. The obvious reading was a mountaineering accident. Everything that followed over the next days was run on that assumption.
was presented for years as the textbook case of a , one that lost its job. Except that it is unusually rich in , which does not suit an organ with nothing to do. So what is it doing?
Moonlight is reflected sunlight, so it carries the same spectrum, and a water droplet does not care which direction its illumination arrived from. Rainbows do occur at night, made by the moon rather than the sun. They are rare, and they need a and low moon, a dark sky and water droplets opposite it. To the naked eye they look white.
An extraordinary disease outbreak hit the Soviet city of Sverdlovsk in April of nineteen seventy-nine, serious enough that the authorities imposed a and did not get the situation under control until late May. The Soviet Union announced nothing, which was unlike its handling of natural epidemics. The Weapon and Space Systems Intelligence Committee reviewed what was known. What did it find?
Three separate groups of insects supplied red dye for most of recorded history: the cochineal dyes, the dye and the lac dye. All three share a chemistry and differ in which acid carries the color. Cooksey reviewed the structures, the histories and what became of each of them. Which one survived into industry?
The effect says familiarity breeds liking, and it is one of the most repeated findings in social psychology. If it were simply true, more exposure would always mean more liking. A meta-analysis pulled 268 out of 81 articles to see what shape the relationship actually has.
Tile a floor with squares or hexagons and the design repeats: slide the whole pattern far enough and it lands on itself. For a long time that looked like what tiling meant. Penrose produced a pair of shapes for which it is impossible.
When a mammal is injured the body closes the wound fast with scar tissue, which saves lives and blocks any rebuilding. In an something else entirely happens at the cut. What gets built there?
An audience at a concert hears the same music at the same moment, and each person experiences it alone in their own head. To find out whether the body responds together, heart rate, , and movement were recorded in a hundred and thirty-two listeners. What synchronized?
Dark matter is a central element of modern cosmology, and the standard model of the universe does not work without it. The story of how it got there is usually told as an anecdote about a few pioneering scientists. Bertone and Hooper set out to check that telling against the record.
Advice to parents about fussy eating usually arrives as information: a leaflet, a word about nutrition, an explanation of why vegetables matter. A trial put that against something far duller. 156 parents of two to six year olds picked a vegetable their child already disliked, then drew one of three groups: taste it daily for a fortnight, receive nutrition advice, or do nothing at all. Whose children changed?
Topics, collections and studies worth meeting.
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Four friends, one WhatsApp group, and far too many years of sending each other things at odd hours.
It started the way these things usually do. Someone reads something, can’t believe it, and sends it along. Someone else checks and finds out it’s true. A third person discovers that the familiar version of the story is wrong, and the truth is more interesting.
After years of this, we learned two things. The best moment isn’t just learning a new fact. It’s watching something you were sure of fall apart. And most things passed around online as “amazing facts” simply aren’t true.
So we built the place we wished we had.
It’s an inside joke, and we’ll own that upfront.
Old cartoons have a moment everyone knows: a wolf chases a bird, runs straight off a cliff, then stops. He looks down and realizes there’s been nothing beneath him for several seconds. Only then does he fall.
That look on his face is the whole app.
One of us used to answer every fact like that with one word: “wat.” No question mark, no extra letters. When it was really good, twice.
We don’t write cards from memory. We check every claim against a named source, and link to it so you can read it yourself. We say when something is disputed, and every card tells you what we still don’t know. Every image is a real photograph someone opened and checked; none are computer-generated.
That’s how this always starts: someone finds something and shares it. If you’ve come across a fact that made you rethink what you knew, send it our way.
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Every photograph here is freely licensed, from Wikimedia Commons, NASA and ESA, and public research labs, with full credit in /aha/CREDITS.json.