Why Do Figure Skaters Spin Faster With Their Arms In? | The Mary Sue

### Why Do Figure Skaters Spin Faster With Their Arms Held in Than Out? Our Friend Bill Nye Explains– With Science!

#### If we're going to talk about sports then we're talking about angular momentum and Bill Nye.

The Olympics are happening, and are apparently all anyone wants to talk about. But if we’re going to talk about the Olympics then we’re going to find a way to cram some science into it. Why do figure skaters spin faster when they pull their arms in? Because science. Let our friend Bill Nye demonstrate.

Spinning takes energy. The momentum built up by a spinning figure skater is that same whether they have their limbs extended or pulled in towards their body, but with their arms extended, their mass extends further from their center and their speed decreases to compensate. With their limbs pulled into their body, their momentum is conserved and they spin faster than with their arms extended.

If you look at a spinning figure skater from above, it helps illustrate the point. The circle made by holding one’s arms out is larger than the one made by holding them in. That means that the mass of the skater’s arms has a longer distance to travel using the same momentum. Shorten the distance, increase the speed.

Now, focus on sticking the landing.

(via Sophia.org, image via The Forest Historical Society)