There is something I don't fully comprehend. When I throw a ball into the air while I'm sitting in a train, I won't accelerate past the ball because the ball carries the momentum of the train just as well as I do. Furthermore, the ball, the train and I carry the momentum of the Earth, which is orbiting the sun. When we launch a spacecraft, assuming that we launch one normal to the ground, that craft does not carry the momentum of the Earth by the time it's reached orbit even if it is still subjected to the pull of gravity. By the time the spacecraft is pulled back down from orbit by the acceleration of Earth's gravity, it obviously lands in a completely different place on the surface of the Earth because it hasn't carried the momentum of Earth's rotation into space with it. Why not? If the ball conserves the train's momentum, shouldn't the space shuttle conserve the Earth's momentum?