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When most people think of a rocket, they think of a tall round vehicle that flies into space. But the word "rocket" can mean two different things. The word can describe a type of engine. The word rocket also is used to talk about a vehicle that uses a rocket engine. Most rocket engines turn the fuel into hot gas. Pushing the gas out of the back of the engine makes the rocket move forward.  A rocket is different from a jet engine. A jet engine requires oxygen from the air to work. A rocket engine carries everything it needs. That is why a rocket engine works in space, where there is no air.

Rocket move forward, In the vacuum of space, an engine has nothing to push against. Rockets work by a scientific rule called Newton's third law of motion. English scientist Sir Isaac Newton listed three Laws of Motion more than 300 years ago. The third law says that for every action, there is an equal and opposite reaction. When the rocket pushes out its exhaust, the exhaust also pushes the rocket. The rocket pushes the exhaust backward. The exhaust makes the rocket move forward. This rule can be seen on Earth. If a person stands on a skateboard and throws a bowling ball, the person and the ball will move in opposite directions. Because the person is heavier, the bowling ball will move farther.