Today, the invention of the pipe organ. 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.

A lexander the Great stirred together the peoples of Greece, Africa, and the Middle East before his death in 323 BC. Out of that cultural mixing, a new free-wheeling, cosmopolitan world replaced the conservative, isolationist Greek city-states. That world was centered on Alexandria, Egypt. Alexandria remained the center of intellectual ferment for most of the next seven centuries.

In the very first years after Alexander, people like Euclid and Archimedes worked in Alexandria. So, too, did one of the greatest engineers who ever lived -- a man named Ktesibios.

Ktesibios was fascinated by fluid flow -- the movement of water and air. He revolutionized the measurement of time when he invented a new water clock. The flow of water into it was held steady by the first feedback-controlled water supply valve.

He invented a piston-powered water pump and used it to force water into a closed reservoir where it trapped air. That compressed air could then expel water through, say, a fire-fighting nozzle.

Ktesibios was also interested in music. Writer Thomas Levenson tells how Ktesibios solved the problem of supplying air to a set of pipes. He used his water-powered air-reservoir to fill a box that fed the pipes. He created a keyboard that let performers open individual pipes to the air box. In one stroke he'd given us the pipe organ, close to its modern form, over 2200 years ago.

The organ quickly took root. The Romans were quite taken with it. They called it the hydraulis . If Nero played anything while Rome burned, it wasn't the fiddle. Nero was an organist.

But after Rome adopted Christianity, the organ died out. St. Augustine was troubled by music. It could, no doubt, provide us with a wink of Heaven, but it was too seductive -- more likely to break our concentration on God than enhance it. And organs produced the most powerful musical sound available. In the end, the early Church of Rome came down against organs.

Only when the Church found a new home in medieval Europe did theologians once again take the view that the arts, including music, were acceptable aids to worship. The organ entered that world in AD 757 when the Byzantine court presented a Ktesibios type of water organ to Charlemagne's father. From then on, organs became an integral part of Northern European culture.

Augustine, I suppose, would be no less concerned today. The teeth-rattling rumble of a 32-foot pipe, the blast of trumpets of state, feathery flute sounds barely floating above the mass -- they all affect our thoughts and our meditations.

Today, we expect that. And it came about because the brilliant Ktesibios saw air and water as material motive forces. In that, he was the spiritual father of the steam engine and the Saturn rocket -- as well as the pipe organ.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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