Why does a spinning skater speed up by pulling in?
The Spin Trade
Why does a spinning skater speed up by pulling in?
You've seen it: an ice skater spins slowly with arms stretched wide, then tucks in tight and suddenly whips into a blur. How does pulling in make them faster? They didn't push off anything. They didn't add energy. They just… got fast.
Here's the secret: when something spins, it wants to keep spinning at the same total "amount." That amount has a name — angular momentum — and it stays constant unless something from outside interferes. The skater isn't adding speed from nowhere. They're reshaping how that spinning-amount is distributed.
