I have a feeling someone is gonna be like "Duhhh" on this one. But I got to thinking. I recall reading somewhere that the guy that came up with the rocket engine for use in space got an F on his paper because "I think" the professor said that there would be nothing to push back on the rocket in space. So I got to thinking, I know Einstein said for every action there is an equal and opposite reaction... well.. for example I push a wall, it's pushing back on me with equal force. However a rocket in space pushes on well.. a vaccuum, a vaccuum can push back? In the same way I know that if I was surrounded by air and waved my arms around in a gravityless room with air inside I would move. But if I was in a space suit in space and did this I feel that I wouldn't move, because their is nothing to push back.