Three thousand tubes of what?

I'm currently reading Arthur C. Clarke's Prelude to Space, written in 1947 and set in 1978, which describes a first mission to the Moon. Clarke points out in his introduction to the 1977 reprinting of the novel that, "On July 20, 1969, all the countless science-fiction stories of the first landing on the Moon become frozen in time, like flies in amber. We can look back on them now with a new perspective...for we know how it was really done and can judge the accuracy of the prediction."

Clarke's description of the mission varies considerably from the final result, but not so much that the novel has the anachronistic feel of Jules Verne or H.G. Wells. (Actually, I find that Wells holds up much better than Verne over time, but that's another topic.) However, the part that really jumped out at me, sixty years in Clarke's future, was the following conversation after a tour of the ship's cockpit:

"It's a bit overwhelming, but not so very much worse than a transcontinental jet's cockpit."

"It is if you know what goes on behind all those panels," said Matthews grimly. "Arnold Clinton - that's the electronics king - once told me that there are three thousand tubes in the computing and control circuits alone. And there must be a good many hundreds on the communications side."

Three thousand vacuum tubes? I almost laughed out loud - relying on a system like that to go to the Moon would be like having someone say that a battleship would only be able to sail if none of the light bulbs on board burned out. Now, admittedly, when Clarke was writing the book, state-of-the-art computing was represented by ENIAC, which had close to 18,000 vacuum tubes and weighed 27 tons. The next time that you have a problem with your computer, remember the gentleman in the image at the left of this paragraph, who is troubleshooting a problem in ENIAC by looking for a dead tube - see, Vista's not that bad after all, is it.

Coincidentally, the needs of the Apollo program for a more reliable system for use in the Apollo Guidance Computer led to concentrated research into the development of the integrated circuitry that replaced the vacuum tube and which is now used in virtually every piece of electronics in existence. Sadly, the AGC crashed five times - only in the computer sense, fortunately - during the landing approach to the Moon by the Eagle module.

- Sid