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No. 1319:
Differential Analyzer

Today, a eulogy for a 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.

It sometimes feels as though the computer came into being only yesterday. No doubt, it has come into its own during the lifetimes of today's college students. But serious attempts to do complicated machine calculation were under way well before WW-II. The most important pre-war effort was started in the 1920s by Vannevar Bush -- Bush who went on to be a presidential advisor and the great technological visionary of fifty years ago.

Bush's work culminated in 1942 with the dedication of his huge Rockefeller Differential Analyzer at MIT -- a one-hundred-ton machine with 2000 vacuum tubes and 150 motors. Bush's Analyzer was an analog computer. Analog computers follow physical processes that obey the equations we're trying to solve -- in this case, mixed electrical and mechanical processes. Digital computers break computations down into sequences of additions and subtractions. They solve equations by doing a whole lot of simple arithmetic.

Bush's Analyzer quickly fell under the pall of WW-II secrecy, but only after the head of electrical engineering at MIT had proclaimed it would "mark the beginning of a new era in mechanized calculus," and MIT president Compton had announced it would be "one of the great scientific instruments of modern times."

When this wonderful device emerged from secrecy after the war, it'd gone from triumph to obsolescence in only five years. The government had secretly been pouring huge sums of money into developing the ENIAC digital computer to solve artillery fire control problems. The new breed of high-speed digital computers had simply brushed Bush's Analyzer aside.

Historian Larry Owens looks at this fall from grace and asks sadly, "How does one tell the story of a machine?" Owens concludes that the real importance of the fall is that it so clearly illustrates a change in the character of engineering after the war.

Bush, he says, represented a kind of engineering still in contact with the workshop. His computer was made of complex mechanical and electrical elements. It thought the way prewar engineers thought -- in physical, graphical terms. The modern digital computer speaks in a totally different mathematical language to the more abstract and mathematical breed of postwar engineers.

We didn't realize it then, but the failure of Bush's machine served notice that our work as engineers had changed. We're only now beginning to see that it was almost a kind of android, incorporating those human values of physical intuition and intimacy with process -- values we're trying to rediscover in our work today.

The best comes back in technology. The best finds new forms, and it resurfaces. So if Bush's Analyzer is dead, I certainly hope that what it represents is not.

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

(Theme music)

Owens, L., Vannevar Bush and the Differential Analyzer: The Text and Context of an Early Computer, Technology and Culture, Vol. 27, No. 1, January 1986, pp. 63-95.

This is a revised and extended version of Episode 27.

For more on Vannevar Bush, see Episode 685.

See also, this MIT page about the Differential Analyser.