Today, we look for perpetual motion. The University
of Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
created them.
When we talk about a
perpetual motion machine, we usually mean a machine
that produces power without being fed an even
greater amount of power in a different form -- say
an engine that produces electrical energy without
eating up even more energy in the form of coal. For
140 years we've all agreed on thermodynamic laws
that tell us that that sort of machine can't exist.
But think for a moment like a medieval engineer.
For years you've harnessed the motions of wind and
water. You've harnessed a lot of power, and you're
hungry to harness still more. You watch a water
wheel turn, and turn, and turn. You watch a wind
mill turn, and stop for a while, and then turn some
more.
Your eyes tell you that perpetual motion obviously
is possible. Besides, the science of your day
doesn't discriminate very clearly between physics
and magic. The medieval engineer saw more magic
than physics in the way windmills induced breezes
to grind grain for him. And maybe we're the losers
today for failing to see more magic than we do in
such a process.
In any event, the Hindu mathematician Bhaskara
suggested a machine that would produce continuous
power in AD 1150. It was simple enough -- a wheel
with weights mounted around its rim in such a way
that they swung radially outward on one side and
inward on the other. This wheel was supposed to
stay forever out of balance and to turn forever.
The Moslems picked the idea up around AD 1200, and
it showed up again in France by 1235. For the next
500 years many writers recommended the use of this
ingenious -- if impossible -- little device. You
wonder, did they ever try to make one? Well, yes
they did, but it always seemed that they'd failed
to get the proportions just quite right.
17th and 18th-century science eventually made it
clear that the overcentered wheel wouldn't work.
But then, after that, as each new physical
phenomenon was discovered, people invented new ways
of using it to produce power without consuming
energy. People suggested perpetual motion machines
based on static electricity, surface tension,
magnetism, hydrostatic forces, and so on.
Today we still look for perpetual motion. Some
people do it in the face of the physics that says
it's impossible, but others look for
as-yet-unthought-of ways to keep producing power.
But whatever we concoct, I think that we -- like
the medieval engineer -- should be willing to see
some element of magic in what we do.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Ord-Hume, A.W.J.G., Perpetual Motion: the
History of an Obsession. London: George Allen
& Unwin Ltd., 1977.
For more on perpetual motion, see Episodes 438, 527,
528, and 614.
Image courtesy of the University of
Kentucky's Special Collections Library
A late 17th-century version of Fludd's perpetual
motion machine grinding grain as shown in
Böckler's Theatre of New Machines
Image courtesy of the University of
Kentucky's Special Collections Library
A late 17th-century pump driven by an "overcentered
wheel perpetual motion machine" as shown in
Böckler's Theatre of New Machines
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
Lienhard.
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