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RandomUnder500

An index of explained things

Curious about everything.
Explained in under 500 words.

Clear, sourced explainers on how the world works and why we believe what we do. No filler, no hot takes. Just the facts that matter, in the time it takes to finish a coffee.

4 entries · 4 topics
Two stacks of worn gold coins on a dark wooden desk, the taller stack about twice the height of the shorter, beside a leather-bound book and a quill in a brass inkwell.Latest · No.004
● Money · 10 November 2026 · 2 min readThe Rule of 72: A 500-Year-Old Trick for Seeing How Fast Money GrowsDivide 72 by an interest rate and you get the years it takes to double. Here is where the shortcut came from, why it works, and three places it changes the picture.
The indexNewest first
  1. No.003The Year Ten Days Disappeared: How the Calendar Was FixedIn October 1582, millions of people went to bed on the 4th and woke up on the 15th. Here is why the calendar had to skip ahead, and what it still affects.● History9 November 2026 · 2 min
  2. No.002Tardigrades: The Toughest Animals on Earth Are Not IndestructibleTardigrades can survive space, deep freezing and decades without water. But the popular story of an unkillable animal leaves out the interesting part.● Biology9 November 2026 · 2 min
  3. No.001The Mandela Effect: Why Millions Remember Things That Never HappenedThousands of people share the same false memories, from a monocle that never existed to a movie line never spoken. Here is what the science says.● Psychology9 November 2026 · 2 min
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