Hi: I have a some what related question. I'm just curious how far back in time do the current time scales extend ? (Ie. When was the first "second hack / synchronization" that can be related to our current time.)
Thanks in advance for any answers. Mark Spencer [email protected] 604 762 4099 > On Mar 26, 2019, at 2:58 AM, Ben Bradley <[email protected]> wrote: > > For independent standards (not quite what you asked) I recall from > "The Science of Clocks and Watches" (a book with much technical info > if you're interested in these mechanical devices) that the most > accurate mechanical/pendulum clock was the Shortt Clock that used a > pendulum in a vacuum chamber for its standard. Mechanical clocks were > replaced by more stable electronic quartz crystal oscillators, and > then finally by atomic clocks. > > Perhaps closer to your question: I recall in my readings about > clockmaker John Harrison (likely either in "The Quest for Longitude" > or Dava Sobel's "Longitude") that he would look from the edge of his > window at a particular star each night and note (while counting the > ticks he heard from his clock) the exact moment it would disappear > behind a nearby chimney, and knowing the Earth's rotation takes four > minutes and some (I forget) seconds off from a day, he used this to > calibrate and test the precision and accuracy of his long clocks. It > was suggested he could get within less than second with this method. > This was around age 21, so the year would be about 1714. Looking > online for PZT (photographic zenith tube), I didn't find much about > it, but it was surely first made a couple centuries after this. > > The Sobel book (all about how Harrison won the Longitude prize) is > more a popular book and less technical, but "Quest" has many > mostly-technical articles, mostly about Harrison, as well as beautiful > photos of his clocks. One or two of the articles is by the man who > made (or made the parts for it, the story is complicated) the > one-second-in-100-days "Clock B" pendulum clock, built from Harrison's > writings and claims of just that accuracy in the book he wrote shortly > before his death. > >> On Mon, Mar 25, 2019 at 7:00 PM John Ackermann N8UR <[email protected]> wrote: >> >> Does anyone have a pointer to information about the absolute time >> accuracy (not stability) that was available via PZT or other techniques >> prior to the Cesium definition? I'm doing a presentation and want to >> show the evolution of accuracy. My Google-fu has failed me in finding >> anything pre-Atomic. >> >> Thanks! >> John >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
