Today, we go back 2200 years to North Africa. 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.
Alexander the Great fell ill
and died in 323 BC, after 12 years of conquest --
but not ordinary conquest. He'd worked very hard at
mixing the cultures of East and West -- at
stimulating trade, cultural exchange, and
intermarriage. His empire fell apart after his
death, but the effects of the mixing remained.
He'd founded some fifteen cities named Alexandria,
but the one just west of Cairo emerged as the
center of Mediterranean culture. A new dialect of
Greek called the Koinia became the common language
of the Eastern Mediterranean basin. And Alexandria
drew talent like a magnet. Euclid, Archimedes, and
the astronomer Ptolemy all worked there. Alexandria
remained the intellectual center of the world for
three centuries -- until Rome took it over after
the death of Cleopatra in 30 BC.
The much-praised technology of the Romans was built
on the inventions of the great Alexandrian
engineers. Plumbing, gearing, and water wheels, for
example, all came from Alexandria. These engineers
were less famous than Euclid and Archimedes. They
had names like Ktsebios, Heron, Vitruvius, and
The most remarkable Alexandrian invention was
feedback control. A feedback device automatically
corrects the way a machine functions. Present-day
feedback devices include thermostats, speed
controllers, and pressure regulators. The
Alexandrian engineers invented all sorts of float
valves and other liquid-level regulators. The most
important machine that used these gadgets was the
water clock. The Alexandrian water clock was the
basic time-keeper for about 1500 years -- until the
mechanical clock replaced it in the 14th century.
Alexandria was free-wheeling, open, polycultural,
and wonderfully inventive. After the authoritarian
Romans took it over, invention dried up in
Alexandria. It's interesting that the development
of feedback also stopped dead-cold in its tracks
and didn't resurface until a new craving for
freedom swept Europe in the middle of the18th
century; but that's another story.
Alexandria re-emphasizes a familiar message -- one
that good educators understand. The people who
really invent things are people who expose
themselves to a lot of different influences and can
let their minds run free.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
Clough, S., A History of the Western World,
Vol. I, Ancient Times to 1725. Boston: D. C. Heath,
1964. Mayr, O., The Origins of Feedback Control.
Cambridge, MA: MIT Press, 1970. 29
George, B., Reaping the Wind, American Heritage
of Invention & Technology, Vol. 8, No. 3,
Winter 1993, pp. 8-14.
Kealey, E., Harvesting the Air: Windmill
Pioneers in Twelfth-Century England. Berkeley:
University of California Press, 1987, Chapter 7.
This episode has been substantially revised as
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
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