Ask an Explainer

Rub your hands together. Do you feel them heating up? This is called friction, which is caused when two things rub together.

Now imagine what would happen if your hands could move 25,700 kilometers per hour (16,000 mph). That's how fast re-entry speeds are. As meteors, shuttles, or capsules hit the atmosphere, they rub against the air at very high speeds, which makes them burn. This is why spacecraft use heat shields to stop them from combusting.