Every Action has an Equal and Opposite Reaction?
This is the third of Sir Issac Newton's laws of physics, and one that is very important to space flight. Here's how it works. If you push on anything, it pushes back on you. That's why if you lean against the wall, you don't just fall through it. The wall pushes back on you as hard as you push on it, and you and the wall stay in place. If you throw something, you put more force behind it than just leaning on it, so it pushes back with more force. This is hard to observe, because usually, if you throw something away from you, the friction between you and the floor makes resistance to keep you in place.