Today, we make an impossible machine. 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.
Perpetual-motion machines
have been an ongoing dream for about a thousand
years. Here's a strange windmill. It drives a
bellows that blows the air that turns it. There's a
water wheel that pumps its own water supply. Always
something for nothing!
Now I gaze at a photo of a beautiful machine. It is
exquisite. It's tall like a grandfather clock. The
polished wood and brass is a work of art. High up
is a clock face. The body contains a huge
blown-glass barometer. It has the noble lines of
classic architecture.
This is James Cox's perpetual-motion machine. Not
only is it beautiful, but it also works. This is no
sham. Of course, it isn't really a perpetual-motion
machine. But Cox, who built it in London during the
1760's, thought it was.
What it is is a clock that never has to be wound.
As the weather changes, the barometer drives a
ratchet mechanism. It keeps the clock wound. The
whole action runs on jewelled bearings. It's a
stunningly delicate and sophisticated heat engine.
Cox was a well-known clockmaker. He showed his
self-winding clock in a private museum along with
other fine clocks. When he died in 1788, a museum
owner named Thomas Weeks bought the clock. It
ticked away in his museum until the 1830s.
After that it was sold off again. This time, it
vanished until it turned up on public display in
1898. It finally came to rest in the Victoria and
Albert Museum.
Cox's clock writes an odd chapter in the history of
human ingenuity. For he seemingly succeeded in
creating that great will-o-the-wisp, perpetual
motion. 18th-century science hadn't yet written
laws that would tell us it was impossible. But Cox
saw where that science was going, and he worked
around it. He saw how nature could provide energy
and make it look like something for nothing.
A contemporary writer said Cox's engine was like a
water wheel. That, he said, was perpetual motion of
a similar kind. And he was right. Cox's clock was
actually kin to the windmill.
Like the windmill, it took energy from the sun. The
warming of air causes winds and pressure changes.
Machines that tap that reservoir don't violate
physical laws. What they do is create the illusion
of magic by accepting a gift from nature.
This strange clock is a fit reminder of the most
magical source of energy for our energy-hungry
world. That source is the sun. The sun brings us as
close as we'll ever get to realizing the age-old
hope -- of perpetual motion.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
