The earth rotates, because of the sun's gravity, and because the polar caps are drawn to and from the earth, which enables the earth to have different seasons, as when the certain area is farther away from the sun, it is winter, and when closer, it is summer. Other planets actually affect us more then we affect them more, for if they are to close, we would have a greater chance to collide. However, if they are too far, then we wouldnt have gravitational from other planets that hold us in our 'circle', (basically it means that without them, we would fly out into space). If you need more, send me a message hope this helps
