I saw someone post a question or a comment about relative motion and acceleration. It got me thinking about the spaceship in deep space with rocket boosters. Well, when that guy or girl hits the booster, he or she accelerates, but the person is not necassarily moving relative to anything. Is that correct? I have another question, but I just want to make sure I have this correct. To clarify: when I say "deep space", I'm talking about a point in space where there is no matter (stars, planets, humans, whatever) that you can see. When you hit that rocket booster, you are accelerating into dark space.