The first stored-program electronic computer capable of doing useful work was the EDSAC, built at Cambridge University and commissioned in 1949. It supported research in several scientific disciplines as well as the development of software techniques until being scrapped as obsolete in 1958. There is now a project to rebuild this pioneering computer: the reconstructed version will be made as close as possible to the original, with one exception…and the reasons for the exception, I think, are perhaps more related to social history than to the history of technology.
EDSAC used vacuum tubes (valves, in Britspeak) for its arithmetical and logical functions; for memory, it used something called a mercury delay line, an idea borrowed from WWII radar technology. (EDSAC=Electronic Delay Storage Automatic Calculator.) information to be stored was introduced at one end of a tube of mercury, down which it traveled in the form of pulses of sound. About 1 millisecond later, at the other end of the tank, the pulses were picked up, amplified, and emitted again at the starting point, with the whole train of information bits in the line thereby being kept in continuous circulation as long as the power was on.
Can you guess how the reconstructed EDSAC is going to differ from the original version?
That’s right…no mercury. “Health and safety regulations” have led to a decision that mercury cannot be used in the rebuild.
Certainly, mercury can be hazardous when not handled carefully–see the material safety data sheet. But it’s not plutonium. It’s not even nitroglycerin. Is it perhaps an overreaction to ban the use of this substance, which would be contained in metal tubes, in a one-of-a-kind museum piece?
Now, much of the EDSAC rebuild work will be done by volunteers–maybe even in the absence of government and/or insurance regulations, the team would have preferred to avoid the cumbersomeness of working with mercury. And I’m sure they’ll do as good a job as possible in coming up with an alternative non-mercury approach to the machine’s memory. (Maybe gin for a delay medium, as was suggested by Alan Turing for the original machine.)
My concern here isn’t really mainly with the rebuild project per se, but rather a more general one–the growing timidity of our western societies, often enforced by regulations of one kind or another. A couple of years ago, I wrote about the Congressional suppression of passenger service on the historic steamboat Delta Queen, on fire-safety grounds–despite the fact that the vessel has been outfitted with fire detection and suppression systems, is never more than a mile or so from shore, and surely provides a vacation experience which is significantly safer than most other things people could do with the same amount of time. And throughout the US, many kinds of playground equipment…swings, jungle gyms, merry-go-rounds, for example…have been removed on safety grounds. See the boys and girls in the plastic bubble…see also, via a commenter at that post, this story about the fate of space-program-themed playgrounds constructed in the 1960s.
The pros and cons of safety-related tradeoffs can of course be debated for individual cases, whether we’re talking about playground equipment or a computer reconstruction. But it’s hard to escape the conclusion that the general level of timidity in our societies has increased substantially, and that there is some level of such timidity that leads to individual psychological harm and to social dysfunction.
Some countervailing forces to the drift toward timidity have arisen…see for example the free-range kids movement created by Lenore Skezany. But I’m afraid the general trend is much in the other direction.
The EDSAC rebuild project site is here.