Perpetual motion

[Colonel Sanders]

OK, so perpetual motion is impossible.

But what about water? Out in the ocean, the water evaporates, goes to clouds, then falls back down. Isn't that somewhat an example of perpetual motion, or at least a perpetual cycle?

L J

[M. A. Dockter]

The sun provides the energy for that evaporation

[Hi Ho]

It would be perpetual if the water evaporated on its own without any help from the sun.

[Colonel Sanders]

Yeah, forgot that "little detail" about the sun...

But I kinda wonder if perpetual motion(or at least a perpetual cycle) is really not possible. I thought energy can not be created or destroyed? By that it seems that a perpetual cycle might be possible.

L J

[ghost2003]

I saw a show once about a guy who has a perpetual machine. They say if its true and not all a scam most of what we know about physics and stuff can go down the toilet. It has something to do with giving a little power to the machine and comming out with motion that gives alot more.

EDIT: I dont know much about phisycs but I know this (I think ) If you had a cycle that passed 100% of the energy to the next stage then yes but a law of physics stops that from happening

[Colonel Sanders]

I'd be amazed if you could come out with more energy, but the idea of keeping a cycle going without gaining or loosing energy seems possible to me.

L J

[ghost2003]

when something moves it looses energy so its impossible. But we never know.

[Byte 2.0]

Perpetual motion is not possible. It is also true that energy is not created or destroyed. All energy we use/have is harvested in a sense.

There are some devices that are very efficient, such as sterling engines. These devices have been around for about a 200 years or so, but are little known. They can operate on very low amount of energy, but never the less, energy is used to make them work.


http://travel.howstuffworks.com/stirling-engine.htm

[HAL9000]

Perpetual motion is possible in a frictionless environment, but still requires some energy to start the motion. The example we were given in physics was a magnet suspened between two other magnets with like poles at each end... pull against the force to one magnet and it would repell the the other untill the repelling force of that one stopped it and forced it back.... but the only way for this to work would be a frictionless enviornment meaning in a complete vacuum, and even so you would need a way of keeping the moving magnet from spinning out of position.

[Byte 2.0]

For a science project once, I did something like what hal9000 talks about. I found some magnets that were made into rings, kinda like donuts. I used a plastic tube in the center and put like poles to each other. What i was showing was levitation but in my experience I needed the plastic tube to keep the magnets from flying away from each other.

But even if someone comes up with a perpetual motion device, the moment they trying to extract any energy from it, it will lose the perpetual motion effect.

[Kubie]

The closest thing I've seen to perpetual motion are 2 and 3 year old kids at Christmas.

Carl

[Byte 2.0]

yea, but they run on sugar.

[peter8d9]

Its not really physics that says perpetual motion machines are impossible. It is a thermodynamic law. The fifth part of the first law of thermodynamics states that Permetual motion machines of the first kind do not exist.