I'm a bit of a physics noob, but I am always curious about everything in the world. I concluded from Newton's third law that when you exert a force on a wall it exerts a force back on you. But I want to know from where does that force actually come? I mean ok you as a person might have a mass and an acceleration, but the wall doesn't though, so how come it has a force that it exerts on you? Does the wall accelerate to begin with?