Everything in the universe is in motion relative to everything else. In that respect you could say that everything is in perpetual motion, but not the same type as the definition of it that you are thinking about. For instance, if you get a bit of matter to be totally at rest the question is at rest in reference to what? The same is true with motion. Perpetual motion machines deal with closed systems, or little local systems. A local system, over time will even out so that everything is the same. In that way, things always run down. Temperature rises or falls in relation to everything else around it. I know this sounds a little complicated but for the type of thing you are talking about you have to take all things, all types of energy and forces into account. An object "floating" in space will be subject to many different things including even the pressure from photons hitting its surface. It will continue to move, but its motion will be relative to all other objects, particles, and whatever. And according to relativity its actual velocity depends on who measures it. We might measure it as having one velocity but someone on it would have a completely different measurement. Remember, nothing is ever alone in the universe. Is the object you are looking at moving away from you or is it you that is moving "backwards"? That is the point of relativity, you can't really tell. An even better question is that if the other object is moving away from you does it then actually impart energy to you, the observer, since it could just as easily be you that is moving instead? Indeed, is movement really the increasing and decreasing of distance between objects and therefore both objects are seen as accelerating and gaining energy? Once you get out of a closed system, the concepts change. A space craft that has been launched from earth will continue to move in its course, unless acted upon by something else. But keep in mind that it was already in motion with respect to the solar system and universe before it was ever launched. All we did was change its direction, we did not actually put it into motion. So, in that respect you could even try to make an argument that the earth is in a state of perpetual motion already. Well, it is and its not. In reference to the sun and the galaxy its slowing down a little all the time. But in reference to the rest of the universe , ??