Saturday, January 5, 2008

What Time Is It? Why, It's Perpetual Motion Time Again!

Ok, let's all look at the video below:



Got that? Ok, great.

Brief primer: Perpetual motion refers to a system that, once placed in motion, generates its own energy to sustain the motion indefinitely.

Briefer primer: it's pseudo-science.

Every 20 years or so - for, like, the last 4000 years - some joker pops up with an "invention" or paper that professes to maintain a system in motion without outside influence. (For the past few hundred years, it almost always involves magnets...excuse me..."loadstones") Some of these people even try and pull one off on the US Patent Office. Ironically, several of the inventors seem to believe their own a-think-I-went-to-high-school-but-I'm-not-certain theories.

The Perpetual Motion Lunatic Fringe (or, the PMLF) like to point out that a system that generates enough energy to maintain its own motion doesn't violate Newton's First Law of Motion: basically that any nudged into motion will stay in motion until acted upon by another force. Well, you know what? They're right. Perpetual motion doesn't violate Newton's 1st law. Sadly for the PMLF, though, there are more laws to physics than Mr. Newton could conceive of under his apple tree, and perpetual motion violates most of them...the most egregious abuse being against the Conservation of Energy, which states that even though the total amount of energy in a closed system cannot be added to or subtracted from, it is completely free to change forms.

As a matter of fact, it changes forms all the time... actually, constantly. Take our weird little magnet video above - which is getting a disturbing amount of Diggs, by the way. The magnets seem to be doing a good job of maintaining that spin, aren't they? Sure, but give it time, and it will stop. Everything that system is doing is transferring energy around - the spin around the axis causes friction which translates the spin into heat, the magnets themselves are transferring electromagnetic energy into rotational velocity, the whizzing sound you hear is noise energy created by the disc frictioning with the surrounding air, etc. (Uh, and the whole "speeding up" thing - implying that this system is actually generating more energy than it is consuming? I'm betting on a motor powered by an energizer battery...but I digress.)

This is true for every contained system - including the good ol' universe. It's a closed system too - all those stars? All that gravitational energy? The Big Bang? Surely we are in a giant PM machine, aren't we? Nope. Sorry. Depending on which theory you subscribe, the universe is either slowing down to collapse in upon itself (my personal fav), or expanding forever. In either case, entropy (which is the measure of the unavailability of the amount of work a system can do) is increasing. Entropy is, basically, a measure of the decay of energy available to do work -- the energy is there, but it migrates to a form that is, for all intents and purposes, useless. Entropy is king. Everything decays. Including the grand ol' universe...and, especially, that stupid magnet-on-a-pinwheel thing above.

So, moral of the story:

  • Diggers: just stop giving that guy any cred, please.
  • VC community: Don't put your cash into a PM machine, no matter how whizzy the Power Point presentation is...

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