system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 If there is no matter in space, what do the rockets push on to accelerate a ship?

We were talking about space vacuums and stuff and physics and the teacher danced around my question. So what do they push on? Since there is no air or land in space (duh).
gpt
That's not how rockets work. Rockets don't "push on" anything. They're not sneakers. By igniting a chemical reaction, they cause an action, i.e., projecting a stream of expanding gas in a particular direction. The reaction is moving the rocket in the opposite direction. Whether the surrounding environment is a vacuum or not is entirely irrelevant to that analysis. Indeed, rockets work *better* in a vacuum, as there is no atmosphere to resist the motion of the engine.