atomic_fungus (atomic_fungus) wrote,

#893: No. Just no.

Steven Den Beste comments today on a thread he found on MetaFilter. The gist of the thread: amateur scientist thinks he's found an "over unity" device--a perpetual motion machine.

Problem: that's fricking impossible.

The basis of the "invention" is that the guy puts a magnet next to a motor running at a certain speed. The motor then speeds up, apparently turning faster for a given input of electricity.

Anyone who's ever studied motor theory--even casually--knows why this is BS: if you increase the strength of the magnetic field in which the rotor turns, the rotor will turn faster. It will also consume more power; there is no free lunch here. The voltage across the motor won't change--at least not once it regains homeostasis--but the current drawn by the motor will increase.

Several of the soi disant "intellectuals" commenting in the MeFi thread, however, seem to think that the laws of thermodynamics are a "construct" of "patriarchal Western civilization". But there's a reason why we call them the laws of thermodynamics, not the "hypotheses" or "theories" of thermodynamics.

Pretty much the same reason we call it the law of gravitation: it has never been wrong. EVER.

The laws of thermodynamics have never been wrong. Not ever, not once, not even a little bit. Physicists have used the laws of thermodynamics as building blocks for theories which have turned out to be correct (such as the theories surrounding nuclear decay, to cite an example cited by Steven).

It's pretty safe to say that when you think you've got a way around the laws of thermodynamics, you're wrong. In fact, I'd say it's damn certain you're wrong.

"But," you say, "what about a nuclear reactor? What about the Sun? Those are over-unity devices!"

No, they're not.

The energy output of the sun comes from E=mc2. Nuclear fusion ends up converting some of the mass of the fused atoms into energy.

The energy output of a nuclear reactor comes from E=mc2. Nuclear fission converts some of the mass of the U-235 in the core into energy. (The U-235 itself was generated in supernova explosions billions of years ago.)

Come to think of it, E=mc2 isn't even considered a law. Very few things in physics are considered laws, and most of those are centuries old.

The real irony of the comments in the MeFi thread is that the same people who are contending that we don't know everything about the laws of thermodynamics probably argue that man-made global warming is "proven". *sigh*

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