system
Given the following post, respond as if you're commenting on Reddit:
human
When you hear about a space craft “slingshotting” off of a planet, does that really increase speed? Wouldn’t the craft just slow down again as it moves away from the planet?
gpt
It does increase their speed. When the smaller object turns around the larger object, it steals a little bit of energy from the larger object, and leaves with a higher kinetic energy. It still slows down as it moves away from the larger object, but the net result is still a higher kinetic energy than it had initially.

Gravity is a conservative force, so if the larger body was fixed in space, the smaller body would lose as much energy as it gained, and there would be no net change in its speed. But since the larger body is not fixed in space, its motion is perturbed by the smaller body, and some of its energy is stolen.