Oldest operational computer was Re: cctalk Digest, Vol 54, Issue

Tube technology: - DeForest was hacking around looking for a non-infringing (on other's patents) detector for radio waves, not an amplifier, when he developed the audion (not 'audiotron'). I'm using the word 'hacking' in the pejorative sense here: some of his earlier attempts involved trying to send currents through the flame of a bunsen burner. Even when he arrived at the idea of a three-electrode vacuum device (he disavowed any influence by the Fleming valve), his first attempts didn't even have the control electrode ('grid') between the cathode and anode (the control electrode was not in the electron stream). I don't think I'm out of line in saying he had no idea what he was doing at a theoretical level. - The ability of the audion to amplify would not be realised/implemented for yet another few years after 1906/7. - The laws of physics and chemistry haven't changed for billions of years. The knowledge of them most certainly has changed since 1900, even as they relate to the principles of vacuum tubes. Thomson's discovery of the electron was in just 1897, Rutherford's model of the atom as a +charge nucleus with orbitting -charge electrons wasn't until 1911. How the audion worked was not well understood at the time of it's development, even by a physicist. - The characteristics of a vacuum tube will vary with the remnant gas pressure, getting a high vacuum was still a problem in 1900. (re: Will's mention of lack of uniformity/variation between tubes in the early years). - Even if you coul get a good vacuum when the tube was initially built, the seals were an issue in the early years. IIRC, it wasn't until much later (the 20's?, where are my refs) that a metal alloy that had a thermal expansion coefficient matching glass would be developed. -- The 'need' for a 'computer': - It most certainly was there, well before 1900. Babbage's work was inspired/driven by need: to reliably calculate function tables (in part for navigation). -- The possibility of Magnetostrictive Delay Lines around 1930: - Need to look up when the magnetostrictive principle was discovered. It's a pretty subtle characteristic exhibited only by a few materials, it may not have been discovered till quite late. (Also needs sensitive reasonably low-noise amplifiers.)