Feynman on conservation of energy and perpetual motion

Carl Feynman (carlf@atg.com)
Wed, 30 Apr 1997 11:43:56 -0400

At 06:01 PM 4/28/97 -0700, Lee Daniel Crocker wrote:

>I'm sure a more thorough search might turn up something better, but
>I doubt our particular reporter would have been swayed by calmer heads
>anyway, as his credulity seemed unswayed by any of the replies, and I
>didn't think a suggestion to read the whole set of Feynmann Lectures
>on Physics would be very welcome, although that's really all there is
>to say.

Actually, all he would need to read is the chapter entitled "Conservation of
Energy", in either the Feynman Lectures on Physics, or in the new book Six
Easy Pieces, which collects six lectures from the big books that are
particularly easy for the public to understand. That chapter is amusing,
entirely clear, entirely convincing, and sufficiently simple for an
intelligent child to understand (I know this because I read it when I was an
intelligent child.) People who don't believe in the conservation of energy
should read this; if they still disagree, we can at least have an
intelligent debate.

Richard Feynman (who was also my father) divided perpetual motion machines
into Perpetual Motion Machines of the First Kind, which violate the first
law of thermodynamics (AKA conservation of energy), Perpetual Motion
Machines of the Second Kind, which violate the second law of thermodynamics
(entropy must increase), and Those Other Perpetual Motion Machines, which
purport to get their energy from other laws of physics.

CALYK's alternator-drives-electrolyzer-drives-engine-drives-alternator
machine is a typical example of the First Kind. They are the most common
kind, and usually pretty lame.

The Second Kind is rarer; the only example I'm familiar with is one that my
dad showed me the plans for. Once in a while, someone would come to him
with a perpetual motion machine prospectus and ask if it was a good
investment. One of these was a machine that claimed to extract heat energy
from the air and run a generator with it. They had built half the machine,
which worked as far as they could test it, and were looking for gullible
investors to pay for finishing it. By carefully going over the immensely
complex plans, my father and I found a "heat exchanger" that was supposed
to take warm freon and cool air, and produce hot freon and cold air.
Naturally, this heat exchanger was in the as-yet unbuilt portion.

Those Other Perpetual Motion Machines get their energy from heretofore
unknown physics, like cold fusion, vacuum fluctuations, or secret new
physical laws that will be disclosed only on the payment of $1,000,000.
These are worthy of much more serious physical investigation, since it is
entirely concievable that someone will discover a new easy way of making
energy. Cold fusion is the most famous recent example of this type. It's a
pity it doesn't actually seem to work.

Back around 1970, my father went to a public demonstration of one of Those
Other Perpetual Motion Machines. He discovered an electric cord running out
of the back of the machine, plugged into the wall. When he unplugged the
machine and pointed out to the inventor that a perpetual motion machine that
had to be plugged in wasn't really perpetual, the inventor pushed a button
on the control panel and the machine exploded. Several spectators were
severely injured; I believe one man lost an arm. The inventor sued my
father on the grounds that he had caused the explosion; my father suspected
that the explosion was deliberate. The trial ended up with my father not
having to pay.

--Carl Feynman