Definition
A gravity-assist (or slingshot effect) is a technique used in space exploration to change a spacecraft's speed and direction by using the gravity of a planet or other celestial body. The spacecraft approaches a planet, swings around it, and gains or loses energy from the planet's motion. This can significantly reduce the amount of fuel needed for long-distance space missions. Think of it like a slingshot, where the planet's gravity is the rubber band. However, the spacecraft doesn't actually 'steal' energy from the planet; it exchanges momentum. It’s a clever way to get a boost in space.