Talk:Perpetual motion machine

Perpetual motion machine

I'm sorry, but I think you're just wrong about the meaning of the phrase "perpetual motion" as used in discussions of thermodynamics, statements about the impossibility of perpetual motion, etc.

    The perpetual motion, then, which has been the subject of such anxious and laborious search, is not a mere motion which is continued indefinitely. If it were, the diurnal and annual motion of the earth, and the corresponding motions of the other planets and satellites in the solar system, as well as the rotation of the sun upon its axis, would be all perpetual motions....

    In short, a perpetual motion would be a watch or clock which would go for so long as its mechanism would endure without being wound up: it would be a mill which could grind corn or work machinery without the action upon it of water, wind, steam, animal power, or any other moving force external to it.

—Dionysis Lardner, 1857, Natural Philosophy for Schools, p. 70

    Perpetual motion is of course possible, as is stated in the first law of motion, "Motion continues in a straight line undiminished in velocity unless acted on by some external force." A top set spinning under conditions where there is no friction will never cease to spin. These conditions are very nearly realized in the motions of the planets and stars. The statement that energy cannot be destroyed asserts this possibility.

    But by "perpetual motion" is generally meant a machine which will do work and keep going though energy equivalent to the work done is not supplied to it. Many attempts have been made to construct such a machine. They have all failed. The statement that energy cannot be created denies the possibility of such a machine.

—S. Lawrence Bigelow (1912), "Theoretical and Physical Chemistry," Theoretical and Physical Chemistry By S Lawrence Bigelow p. 26

Dpbsmith 18:20, 1 January 2007 (EST)

Retrieved from "http://www.conservapedia.com/User_talk:Aschlafly"

Dpsmith, I moved this discussion to the talk page for perpetual motion, so others can benefit and contribute as desired to this.

Your quotes are helpful, and I agree that there are different definitions for a perpetual motion machine. But everyone agrees that a machine that does work without energy is impossible. So the above definitions do not lead to productive discussion. Besides, the earth is not really a perpetual motion machine. Our orbit would eventually become unstable, and presumably we would slow down eventually.

What is a fascinating question is whether motion can continue indefinitely in a closed system. One quote above implies it can, but I doubt most would agree. I wouldn't. --Aschlafly 18:59, 1 January 2007 (EST)

He's right Mr. Schlafly; the impossibility of perpetual motion is proven by the 1st law of thermodynamics, not the second.

Ben

OK, Ben, but define perpetual motion machine in a trivial away and it only results in a trivial answer.

How about this, let's define "perpetual motion machine II" that simply means a machine capable of perpetual motion (without a perpetual energy supply).

Now that's an interesting question that is difficult to answer fully! --Aschlafly 19:05, 1 January 2007 (EST)

Theoretically it is possible (the first law of motion), but practically it is impossible just because you wouldn't be able to eliminate all outside forces. I also have a comment on your proof using the 2nd law of thermodynamics:

"The only argument that a perpetual motion machine is impossible is based on an interpretation of the Second Law of Thermodynamics. If entropy is always increasing, even in closed (and isolated) systems, then indefinite motion is impossible because an increase in the disorder of the system will inevitably disrupt the motion"

Firstly, as Dpbsmith has demonstrated, this is not the only argument against perpetual motion.

Secondly, though it is almost inevitable that increaced disorder will disrupt motion, it still isn't logically proven; it is always possible that it might go on just a little bit longer.

Ben