Perpetual Motion

[Eurox]

If you use that trick you where you balance a magnet above a super conductor and use it in a vaccuum. If you spin it, it would never stop because there really would be nothing stopping it so why not use it for a perpetual motion machine?

[dawkins]

how would you keep the super coductor cold and the magnet from losing its magnetism?

[jake-the-peg]

Because you have no Because when you extract energy from it it slows down.

Perpetual motion is a bit of a misnomer - there are many examples of what is effectively perpetual motion - stars and planets, space probes whizzing off forever (yes I know they'll eventually slow from impacts etc. but that's not the point)

The point is you cannot manufacture energy. Your spinning superconductor has a certain energy and if you connect it to a generator it will slow and stop as the kinetic energy is converted to electrical energy

[Bert]

For a perpetual motion machine to exist, you don't have to be able to draw energy out of it - it is sufficient that the motion be perpetual. Unless there is a simpler explanation , I would say that Eurox's suggestion would fail because a perfect vacuum is a theoretical thing that cannot be achieved in reality, so collisions with gas molecules would slow the spinning magnet down. Dawkins may have something, but we could imagine doing the experiment on a cold planet, where the superconductor would not need cooling. Have you heard the First Law of Thermodynamics stated as "You can't get something for nothing"? And the Second law stated as "Not only that, but you can't break even"?

[dawkins]

http://www.vias.org/feee/conduct_08.html

[Whickerman]

http://en.wikipedia.org/wiki/Steorn

This might be of interest. If it's real, it's the biggest discovery in history.

[jake-the-peg]

Yes and it would violate one of the most firmly established principles of Physics.

Not just a bit - totally - free-energy machines are simply nonsense but they have a great history in seperating fools from their money.

This also goes for internal combustion engines that run on water and all the other derivatives.

In principal you could have a eternal motion because if a body has a certain kinetic energy it will stay in motion and preserve that energy.

It's not the eternal motion but rather that in the real world you lose energy and you can't create that from nowhere.

The superconductor is a red herring because you could equally well consider a body spinning in free space

[Whickerman]

Jake, whilst I agree with you in principle, the water driven engine not only exists, it was demonstrated on TopGear last year. GM produced a motor that runs on Hydrogen, and you fill the tank with salt water. The power cells are currently prohibitively expensive (but so were computers 30 years ago...)