In recent decades crackpot inventors have focused on a variant of perpetual-motion machines known as free-energy devices or over-unity generators. These contraptions supposedly output more power than they take in, generally by drawing on an implausible font of energy hitherto unknown to science. The motionless electromagnetic generator discussed last month is a good example [see "There's No Stopping Them," by Graham P. Collins; Staking Claims]. At first it appears to be based on misconceptions about magnets, but it turns out the inventors have published a physics paper describing a "higher symmetry electrodynamics" that would allow infinite energy to be extracted from the vacuum by their device.

Limitless energy is more marketable than mere perpetual motion. Many over-unity promoters are outright scam artists, putting on public appearances to drum up investment money or to sell franchises and making it onto TV news shows with gullible hosts.

   
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