Peter Galison wrote a fascinating book, "Einstein's Clocks, Poincare's Maps," in 2003, subtitled "Empires of Time."
>From the bottom of page 92, "But if France could lock space and mass in the protected basement of Bretuil [kilogram and meter], time proved more elusive. At the beginning of the 1880s, one French review lamented that clocks were extraordinarily recalcitrant, each one's own "personality" repelling any attempt to regularize it . . ." "Not that French astronomers and physicists had not tried. All over Europe, neighborhoods, cities, regions, and countries were struggling to standardize and unify their clocks. In Paris and Vienna during the late 1870s, industrial steam plants injected subterranean pipes with compressed air, then modulated that pressure to set clocks pneumatically around the city." [There are no details of the modulator or the regulating mechanism in the clocks, probably for the same reason that equations are not used in books for wide audiences. There is a drawing of the control room at the Rue du Telegraphe, circa 1880, but the operation remains obscure.] "At first the fifteen-second delay caused by the time it took the pressure pulse to race under the streets of Paris seemed like nothing. Yet time sensitivity had sufficiently mounted by 1881 that even this tiny delay (. . .) became visible. Astronomers caught the problem, so did the engineers of bridges and roads. Soon the public did as well." "At first the engineers tried to shrug off the discrepancy: "this small discordance, indisputable in theory, has little practical importance since we are dealing with clocks that display minutes, and where the minute hands jump in steps and do not permit further divisions, even approximately between that division of time."" "The clock minders hastened to add that they would offset the Observatory's clock by the fifteen seconds the pulse took to reach the outermost reaches of the network. To be exact, they then mounted retarding counter-weights on each pneumatic clock based on its distance from the center." "Two striking features of time coordination emerge from this little vignette. First, time awareness had become acute. Before the nineteenth century, clocks normally did not even have minute hands. . . . Second, the transmission time - even of a pressure wave traveling at the speed of sound - looked to professionals and the public like a problem demanding correction." [Of course, electrical transmission soon solved the problem, but certainly not overnight.] IMHO, a little history helps to put today's problems in perspective. Google provides some useful hits. An 1881 article in the London Times (reprinted by the NY Times) reveals that the system runs on pulses at one minute intervals that index the minute hand. Paris had 16 miles of clock air piping to over 2000 clocks and 14 public clocks at that time. There is no mention of time synchronization, just the pulse from a pendulum oscillator. The US had pneumatic clocks made by Hals and Wenzel. NAWCC has some articles - need to follow up on that. Would like to see one of those pneumatic clocks. If I owned one, I'd build a GPS disciplined pneumatic oscillator for it. Bill Hawkins -----Original Message----- From: Tom Van Baak Sent: Tuesday, March 10, 2009 12:52 PM 1pps = 1 puff per second? _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
