Today, we just begin to invent the steam engine. 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.
Read any book on steam engines, indeed almost any book on
invention, and there you'll run into Hero's Turbine. Its creator, Heron
of Alexandria, made very sophisticated machines during the first century BC. His
so-called Turbine was a steam-powered whirligig device. It delivered no
useable power and was only one of many steam-powered gadgets that came out of Alexandria.
We wouldn't actually have steam engines for another seventeen centuries. First,
science itself had to overcome a big conceptual hurdle -- the recognition that gases
(of which steam is one) have substance and can transmit large forces. Until that time,
most people would continue to regard any gas as flimsy nothingness.
Hero jumped that hurdle. So did an earlier Alexandrian, a profoundly clever inventor
and engineer named Ktesibios. He was born in 270 BC. He was the son of a barber, from
whom he apparently derived much of his ability. His father was known to have contrived
an adjustable mirror with a counterbalance that used a compressed air plunger. Young
Ktesibios understood how such a device implied that air had corporeal solidity. And,
he went on to create all kinds of air-powered machinery.
Ktesibios invented the earliest known water organ
-- a regular organ with a kind of water piston forcing air through its pipes. He invented
an air pump and compressed air catapults. He did much more, but that makes another story
for another day. The very name Ktesibios means He who lives as a maker of things.
Very shortly after Ktesibios, a Byzantine engineer named Philon worked for a time in
Alexandria, and he left behind a book titled Pneumatics. In it, he described a
dazzling variety of pneumatic devices, including many that'd been invented by Ktesibios.
So Hero's Turbine was only a late step in a long progression of Hellenistic devices that
put steam and air to use. It also marked the end of a profoundly inventive age -- an era
that seemed poised to give us a true steam engine, long before such machines finally appeared
in the eighteenth-century. The question that bothers me is not,
"How were we clever enough to invent the steam engine?" but rather
"Why on earth did it take so long?"
I can only guess, but I'll bet it goes back to the Aristotelian belief that all matter was
made from the alchemical essences of earth, air, fire, and water. That led us to see gases
as ephemeral. The Hellenistic engineers, however, picked up on the even older Greek concept
that matter was made of atoms. They recognized the material nature of air. They saw it as
made of solid elements that could exert large forces.
But the tidal wave of alchemy swept atoms aside. An atomic conception of matter didn't
reassert itself until the scientific revolution in the 1600s. And it was only then that
could we finally finish inventing the steam engine.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Clear and precise articles by A. G. Drachmann on Ctesibios (Ktesibios), Philo of Byzantium, and
Hero of Alexandria are given in the Dictionary of Scientific Biography (C.C. Gilespie, ed.)
New York: Charles Scribner's Sons, 1970-1980.
For more on these inventors, see O. Mayr, The Origins of Feedback Control. Cambridge, MA:
The M.I.T. Press, 1969. See Part One, Section II.
For more on Hero, see Episode 1038.
The working end of a 1788 Watt steam engine on display at the
London Science Museum. This is from ninety years after the first
working steam engine and about 1750 years after Hero. (Photo by John Lienhard)
The Engines of Our Ingenuity is
Copyright © 1988-2004 by John H.
Lienhard.
