How Can a Rocket Fly in the Vacuum of Space?

Physics, Technology
Recently a friend told me he met a man who doesn’t believe in rockets flying in space. Why not? Because (he said) there’s nothing in space for a rocket to push against. There’s only vacuum—no air. A rocket fly in space? Nah. Rockets in space are products of film studios. A Stupid Thing to Say? That’s not really an entirely stupid statement. Imagine you’re on a chair with wheels. How can you move if you don’t push on something? But the man didn’t fully appreciate the rocket does push on something—or, rather, something pushes on the rocket—its fuel. To Illustrate Imagine one of those kids’ cherry bombs, a quarter-sized explosive kids set off on various occasions. Imagine a cherry bomb tied with a very sewing thread, suspended from a tree…
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