I'm not sure if I'm questioning gravity here, but I was thinking about the movement of the planets around the sun and couldn't explain something. I know they say that gravity and the speed of the planets keep them going around the sun, but...how. I mean this sounds awfully like a system of perpetual motion. Everything seems to be held fairly constant. In the process of revolutions, it seems like either the planets should be pulled towards the sun faster and faster, like water circling down a drain or the should be fast enough to escape the gravitational field. What made me think of this was Hailey's Comet. How can an object be pulled in by the suns gravity, get very close to it, then escape again, only to return and do this systematically over time? The orbiting path seems to be in near direct opposition to the suns gravitational force. It almost comes straight in and straight back out. This is like a paper ball being sucked close to a vacuum, escaping to a very long distance, and then inexplicably being pulled back by the very same force it escaped. I hope that came out clear enough because I've been tangling with that one for a while. I was also wondering if gravity was considered an energy because it seems to be another questionable thing since it almost seems infinite as well as proportional to mass, meaning a certain mass will create a certain amount of gravity without end. As a force or energy, it doesn't seem to run out. Any clarity would be awesome.