Re: [time-nuts] Absolute time accuracy pre-Cesium?
Bob, Physicists are still debating whether time is continuous or granular. One current theory of granularity uses the Planck Time, the time required for a photon traveling at c, the speed of light in a vacuum, to travel a Planck Length. This turns out to be 5.39x10^-44 seconds. This is small enough that, for the moment at least, even Time Nuts can treat time as continuous. Francis Grosz - Original Message --- Message: 1 Date: Tue, 26 Mar 2019 15:46:55 + (UTC) From: Bob Albert To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Absolute time accuracy pre-Cesium? Message-ID: <1289017299.10285197.1553615215...@mail.yahoo.com> Content-Type: text/plain; charset=UTF-8 I have been pondering something somewhat related to all of this. We know that the smallest unit of a substance is a molecule.? The smallest unit of charge is maybe an electron.? So what could one imagine the smallest unit of time to be?? Is time digital in the nanoscale, or is it always an analog measurement?? Or, more fundamentally, is is just a concept rather than a reality? Bob ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
Hi TIme is “just a number”, it has no inherent granularity. If you need to measure at the 10^-?? level, the units will not be the problem. Coming up with a device that provides 10^-15 or 10^-18 sort of stability (let alone accuracy …. yikes ….) would take a pretty big limit on your charge card. Bumping the number an order of magnitude is the sort of thing that keeps an entire generation of staff at some pretty big national labs employed. That said, there have been some papers over the years about “what will you run into and when will you run into it?”. At some point gravity noise from “stuff” moving around gets into the picture and you need to move your clock into deep space ….. there *is* a number and for how much you walking across the room changes the gravity on your clock …. Needless to say, there are a lot of other things to worry about before that is the limit you worry about. Bob > On Mar 26, 2019, at 11:46 AM, Bob Albert via time-nuts > wrote: > > I have been pondering something somewhat related to all of this. > We know that the smallest unit of a substance is a molecule. The smallest > unit of charge is maybe an electron. So what could one imagine the smallest > unit of time to be? Is time digital in the nanoscale, or is it always an > analog measurement? Or, more fundamentally, is is just a concept rather than > a reality? > Bob >On Tuesday, March 26, 2019, 7:00:45 AM PDT, Kevin Birth > wrote: > > It all depends on how far back you want to go. With mechanical > timepieces, even before the pendulum there was Jost Burgi¹s astronomical > clock which achieved a precision of a second, and is reported to have been > accurate to that level based on astronomical measurements. Tycho Brahe > tried to achieve accuracy through using multiple clocks. This technique > actually seems to have been developed before Brahe with potentates like > Charles V having large numbers of clocks that he tried to synchronize. > There is at least one case of a Holy Roman Emperor with a bundle of clocks > getting angry at a clockmaker for having sold him a poor performing > clock‹that was Rudolf II. > > Before that you have some of the great Islamic observatories that measured > time with very large instruments. Here is a link, even without a > knowledge of Arabic, one can get a sense from the pictures how these > Muslim astronomers used scale to achieve great accuracy and precision. > What limited them were their materials‹at a certain scale their > instruments started to warp under their own weight. Many of the > principles in these instruments were based on Ptolemy¹s ALMAGEST, which > takes things back to the 3rd century AD or so. > > Here¹s the link: > https://gallica.bnf.fr/ark:/12148/btv1b8414999t.r=taqi%20al-din%20instrumen > ts?rk=21459;2 > > Before that the most detailed account of time measurement equipment is in > Vitruvius¹ work on architecture, but Vitruvius¹ descriptions are often > garbled, so there is no good way to judge their accuracy in relationship > to their claims of precision. > > Less well documented are Persian and South Asian methods in which the > smallest unit translates to something like the duration of a blink of an > eye. I do not know enough about those traditions to know what > observational methods or instruments they used to measure such a unit > (other than blinking a lot). > > Best, > > Kevin > > > -- > Kevin K. Birth, Professor > Department of Anthropology > Queens College, City University of New York > 65-30 Kissena Boulevard > Flushing, NY 11367 > telephone: 718/997-5518 > > "Tempus est mundi instabilis motus, rerumque labentium cursus." --Hrabanus > Maurus > > "We may live longer but we may be subject to peculiar contagion and > spiritual torpor or illiteracies of the imagination" --Wilson Harris > > > > > On 3/26/19, 7:30 AM, "time-nuts on behalf of John Ackermann. N8UR" > wrote: > >> EXTERNAL EMAIL: please report suspicious content to the ITS Help Desk. >> >> >> All -- thanks much for all the great references! I am giving the preso >> this afternoon (to a bunch of university space science students) so this >> will be a big help. And it looks like there's a lot of great reading for >> when I have time to breathe. >> >> Thanks again. >> John >> >> On Mar 25, 2019, 10:03 PM, at 10:03 PM, Ben Bradley >> 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
Re: [time-nuts] Absolute time accuracy pre-Cesium?
Read Book IV of Aristotle’s PHYSICS, take two aspirin then use all the instructions in the Islamic Hadith to know when it is really morning in order to call me in the morning :) Aristotle worried a lot about whether the measurement of time is conflated with time itself. We can reckon time using both analog and digital representations, but once we start wondering what the relationship of our representations are to what time is, we’re in deep philosophical waters. That said, Western metrology has tended toward emphasizing the usefulness of uniform units of measure. This has encouraged a trend towards viewing time as digital. Other cultural traditions view time as analog, and instead of reckoning time in terms of units of duration, reckon it in terms of points on a continuum of time. Hence my reference to the Hadith (the commentaries on the Qur’an). In the Hadith, it is very important to identify particular moments when one absolutely may not pray (e.g., the exact moment of sunrise). Its techniques for reckoning time are focused on knowing when particular moments are approaching. So I guess I’m saying that whether time is analog or digital depends on culture. But then again, I’m a cultural anthropologist, so that’s what I get paid to say. Best, Kevin -- Kevin K. Birth, Professor Department of Anthropology Queens College, City University of New York 65-30 Kissena Boulevard Flushing, NY 11367 telephone: 718/997-5518 "Tempus est mundi instabilis motus, rerumque labentium cursus." --Hrabanus Maurus "We may live longer but we may be subject to peculiar contagion and spiritual torpor or illiteracies of the imagination" --Wilson Harris On 3/26/19, 11:46 AM, "time-nuts on behalf of Bob Albert via time-nuts" wrote: >EXTERNAL EMAIL: please report suspicious content to the ITS Help Desk. > > > I have been pondering something somewhat related to all of this. >We know that the smallest unit of a substance is a molecule. The >smallest unit of charge is maybe an electron. So what could one imagine >the smallest unit of time to be? Is time digital in the nanoscale, or is >it always an analog measurement? Or, more fundamentally, is is just a >concept rather than a reality? >Bob >On Tuesday, March 26, 2019, 7:00:45 AM PDT, Kevin Birth > wrote: > > It all depends on how far back you want to go. With mechanical >timepieces, even before the pendulum there was Jost Burgi¹s astronomical >clock which achieved a precision of a second, and is reported to have been >accurate to that level based on astronomical measurements. Tycho Brahe >tried to achieve accuracy through using multiple clocks. This technique >actually seems to have been developed before Brahe with potentates like >Charles V having large numbers of clocks that he tried to synchronize. >There is at least one case of a Holy Roman Emperor with a bundle of clocks >getting angry at a clockmaker for having sold him a poor performing >clock‹that was Rudolf II. > >Before that you have some of the great Islamic observatories that measured >time with very large instruments. Here is a link, even without a >knowledge of Arabic, one can get a sense from the pictures how these >Muslim astronomers used scale to achieve great accuracy and precision. >What limited them were their materials‹at a certain scale their >instruments started to warp under their own weight. Many of the >principles in these instruments were based on Ptolemy¹s ALMAGEST, which >takes things back to the 3rd century AD or so. > >Here¹s the link: >https://gallica.bnf.fr/ark:/12148/btv1b8414999t.r=taqi%20al-din%20instrume >n >ts?rk=21459;2 > >Before that the most detailed account of time measurement equipment is in >Vitruvius¹ work on architecture, but Vitruvius¹ descriptions are often >garbled, so there is no good way to judge their accuracy in relationship >to their claims of precision. > >Less well documented are Persian and South Asian methods in which the >smallest unit translates to something like the duration of a blink of an >eye. I do not know enough about those traditions to know what >observational methods or instruments they used to measure such a unit >(other than blinking a lot). > >Best, > >Kevin > > >-- >Kevin K. Birth, Professor >Department of Anthropology >Queens College, City University of New York >65-30 Kissena Boulevard >Flushing, NY 11367 >telephone: 718/997-5518 > >"Tempus est mundi instabilis motus, rerumque labentium cursus." --Hrabanus >Maurus > >"We may live longer but we may be subject to peculiar contagion and >spiritual torpor or illiteracies of the imagination" --Wilson Harris > > > > >On 3/26/19, 7:30 AM, "time-nuts on behalf of John Ackermann. N8UR" > wrote: > >>EXTERNAL EMAIL: please report suspicious content to the ITS Help Desk. >> >> >>All -- thanks much for all the great references! I am giving the preso >>this afternoon (to a bunch of university space science students) so this >>will be a big help. And it looks like there's a lot of great
Re: [time-nuts] Absolute time accuracy pre-Cesium?
> I have been pondering something somewhat related to all of this. JohnA started and then concluded this thread about pre-Cesium time accuracy. Musings about quantized time gets pretty far off-topic for time-nuts. A couple of delayed postings from the queue will follow. But please, lets not go down a Planck rabbit hole here on time-nuts. Unless someone really knows, we'll call the thread closed. /tvb - Original Message - From: "Bob Albert via time-nuts" To: "Discussion of precise time and frequency measurement" Cc: "Bob Albert" Sent: Tuesday, March 26, 2019 8:46 AM Subject: Re: [time-nuts] Absolute time accuracy pre-Cesium? > I have been pondering something somewhat related to all of this. > We know that the smallest unit of a substance is a molecule. The smallest > unit of charge is maybe an electron. So what could one imagine the smallest > unit of time to be? Is time digital in the nanoscale, or is it always an > analog measurement? Or, more fundamentally, is is just a concept rather than > a reality? > Bob ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
I have been pondering something somewhat related to all of this. We know that the smallest unit of a substance is a molecule. The smallest unit of charge is maybe an electron. So what could one imagine the smallest unit of time to be? Is time digital in the nanoscale, or is it always an analog measurement? Or, more fundamentally, is is just a concept rather than a reality? Bob On Tuesday, March 26, 2019, 7:00:45 AM PDT, Kevin Birth wrote: It all depends on how far back you want to go. With mechanical timepieces, even before the pendulum there was Jost Burgi¹s astronomical clock which achieved a precision of a second, and is reported to have been accurate to that level based on astronomical measurements. Tycho Brahe tried to achieve accuracy through using multiple clocks. This technique actually seems to have been developed before Brahe with potentates like Charles V having large numbers of clocks that he tried to synchronize. There is at least one case of a Holy Roman Emperor with a bundle of clocks getting angry at a clockmaker for having sold him a poor performing clock‹that was Rudolf II. Before that you have some of the great Islamic observatories that measured time with very large instruments. Here is a link, even without a knowledge of Arabic, one can get a sense from the pictures how these Muslim astronomers used scale to achieve great accuracy and precision. What limited them were their materials‹at a certain scale their instruments started to warp under their own weight. Many of the principles in these instruments were based on Ptolemy¹s ALMAGEST, which takes things back to the 3rd century AD or so. Here¹s the link: https://gallica.bnf.fr/ark:/12148/btv1b8414999t.r=taqi%20al-din%20instrumen ts?rk=21459;2 Before that the most detailed account of time measurement equipment is in Vitruvius¹ work on architecture, but Vitruvius¹ descriptions are often garbled, so there is no good way to judge their accuracy in relationship to their claims of precision. Less well documented are Persian and South Asian methods in which the smallest unit translates to something like the duration of a blink of an eye. I do not know enough about those traditions to know what observational methods or instruments they used to measure such a unit (other than blinking a lot). Best, Kevin -- Kevin K. Birth, Professor Department of Anthropology Queens College, City University of New York 65-30 Kissena Boulevard Flushing, NY 11367 telephone: 718/997-5518 "Tempus est mundi instabilis motus, rerumque labentium cursus." --Hrabanus Maurus "We may live longer but we may be subject to peculiar contagion and spiritual torpor or illiteracies of the imagination" --Wilson Harris On 3/26/19, 7:30 AM, "time-nuts on behalf of John Ackermann. N8UR" wrote: >EXTERNAL EMAIL: please report suspicious content to the ITS Help Desk. > > >All -- thanks much for all the great references! I am giving the preso >this afternoon (to a bunch of university space science students) so this >will be a big help. And it looks like there's a lot of great reading for >when I have time to breathe. > >Thanks again. >John > >On Mar 25, 2019, 10:03 PM, at 10:03 PM, Ben Bradley > 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
Re: [time-nuts] Absolute time accuracy pre-Cesium?
Hi John: One of the papers from 1968 mentioned "continental drift" could be detected if two stations were at the same latitude, i.e. looking at the same set of stars. That was also the case for the Latitude Observatories which were all at 39:08. While they were setup with Zenith Telescopes optimized to measure the angle between plumb and a star near the Zenith, near the end some PZTs were tried and worked about the same. https://prc68.com/I/UkiahObs.shtml The observatory here in Ukiah, CA at first used a sidereal pendulum clock, but at the end it was using a Heathkit GC-100 clock. It was a big deal and so showed up in the local newspaper. https://prc68.com/I/HeathkitGC1000.shtml -- Have Fun, Brooke Clarke https://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html axioms: 1. The extent to which you can fix or improve something will be limited by how well you understand how it works. 2. Everybody, with no exceptions, holds false beliefs. Original Message All -- thanks much for all the great references! I am giving the preso this afternoon (to a bunch of university space science students) so this will be a big help. And it looks like there's a lot of great reading for when I have time to breathe. Thanks again. John On Mar 25, 2019, 10:03 PM, at 10:03 PM, Ben Bradley 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 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 -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
It all depends on how far back you want to go. With mechanical timepieces, even before the pendulum there was Jost Burgi¹s astronomical clock which achieved a precision of a second, and is reported to have been accurate to that level based on astronomical measurements. Tycho Brahe tried to achieve accuracy through using multiple clocks. This technique actually seems to have been developed before Brahe with potentates like Charles V having large numbers of clocks that he tried to synchronize. There is at least one case of a Holy Roman Emperor with a bundle of clocks getting angry at a clockmaker for having sold him a poor performing clock‹that was Rudolf II. Before that you have some of the great Islamic observatories that measured time with very large instruments. Here is a link, even without a knowledge of Arabic, one can get a sense from the pictures how these Muslim astronomers used scale to achieve great accuracy and precision. What limited them were their materials‹at a certain scale their instruments started to warp under their own weight. Many of the principles in these instruments were based on Ptolemy¹s ALMAGEST, which takes things back to the 3rd century AD or so. Here¹s the link: https://gallica.bnf.fr/ark:/12148/btv1b8414999t.r=taqi%20al-din%20instrumen ts?rk=21459;2 Before that the most detailed account of time measurement equipment is in Vitruvius¹ work on architecture, but Vitruvius¹ descriptions are often garbled, so there is no good way to judge their accuracy in relationship to their claims of precision. Less well documented are Persian and South Asian methods in which the smallest unit translates to something like the duration of a blink of an eye. I do not know enough about those traditions to know what observational methods or instruments they used to measure such a unit (other than blinking a lot). Best, Kevin -- Kevin K. Birth, Professor Department of Anthropology Queens College, City University of New York 65-30 Kissena Boulevard Flushing, NY 11367 telephone: 718/997-5518 "Tempus est mundi instabilis motus, rerumque labentium cursus." --Hrabanus Maurus "We may live longer but we may be subject to peculiar contagion and spiritual torpor or illiteracies of the imagination" --Wilson Harris On 3/26/19, 7:30 AM, "time-nuts on behalf of John Ackermann. N8UR" wrote: >EXTERNAL EMAIL: please report suspicious content to the ITS Help Desk. > > >All -- thanks much for all the great references! I am giving the preso >this afternoon (to a bunch of university space science students) so this >will be a big help. And it looks like there's a lot of great reading for >when I have time to breathe. > >Thanks again. >John > >On Mar 25, 2019, 10:03 PM, at 10:03 PM, Ben Bradley > 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 >>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 >>> >>> >>>
Re: [time-nuts] Absolute time accuracy pre-Cesium?
All -- thanks much for all the great references! I am giving the preso this afternoon (to a bunch of university space science students) so this will be a big help. And it looks like there's a lot of great reading for when I have time to breathe. Thanks again. John On Mar 25, 2019, 10:03 PM, at 10:03 PM, Ben Bradley 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 >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 -- time-nuts@lists.febo.com >> To unsubscribe, go to >http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > >___ >time-nuts mailing list -- time-nuts@lists.febo.com >To unsubscribe, go to >http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
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 m...@alignedsolutions.com 604 762 4099 > On Mar 26, 2019, at 2:58 AM, Ben Bradley 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 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 -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
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 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 -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
If I am reading the paper correctly they used the moon as the reference. I would have thought it was the sun. But the moon gives a very clean edge definition. And now I know how the 770 came about. One more bit in the knowledge bunker. Thanks Paul WB8TSL On Mon, Mar 25, 2019 at 8:03 PM Tom Van Baak 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 > > A nice example of how good astronomical timing was is how they calibrated > cesium atomic time against astronomical time. The original 1958 paper is > here: > > > http://leapsecond.com/history/1958-PhysRev-v1-n3-Markowitz-Hall-Essen-Parry.pdf > > What you see there is that they spent 4(!) years and took 4(!) data points > to precisely compare the best astronomical clock with the first cesium > clock. It appears they got millisecond accuracy in their timings. Compared > against the existing astronomical clock standard, the four measurements of > cesium frequency were: > > 9 192 631 761 > 9 192 631 767 > 9 192 631 772 > 9 192 631 780 > > Do the math: the mean is 9 192 631 770 +/- 8 Hz. That, literally, is where > the magic 9192.631770 MHz cesium number and definition of the SI second > comes from. That suggests the precision was 8 Hz / 9192631770 Hz, which is > 8.7e-10, the equivalent of 75 us/day, or 2 ms/month, or 27 ms/year. > > As a practical matter a more accurate value of 9192631770 would have been > useless because the earth is less stable than 8e-10 anyway. Here, for > example, is how different UTC and UT1 would be depending on how the cesium > SI second had been defined: > > http://www.leapsecond.com/pages/ut/cs9192-ut1-ani.gif > http://www.leapsecond.com/pages/ut/ > > In retrospect we would have had fewer leap seconds if they had chosen > 9192631950 Hz instead of 9192631770 Hz. But at the time it wasn't a choice; > it was just a measurement. > > /tvb > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
On Mon 2019-03-25T16:54:28-0700 Tom Van Baak hath writ: > In retrospect we would have had fewer leap seconds if they had > chosen 9192631950 Hz instead of 9192631770 Hz. But at the time it > wasn't a choice; it was just a measurement. And it was a measurement which was performed during an interval when everyone was surprised by the data they were seeing. Around the beginning of 1957 the rotation of the earth's crust shifted suddenly as seen in the USNO plot of UT2 at the bottom of https://www.ucolick.org/~sla/leapsecs/amsci.html At the time that the paper giving 9192631770 was published nobody was sure whether this was an actual change in the earth or some failure to understand cesium frequency standards. It was a few years before it had become clear that earth rotation has a power spectrum of random fluctuations. Over time the BIH had the opportunity to watch cesium vs. Ephemeris Time for more years than the original papers. In 1964 Anna Stoyko found a value of the cesium frequency 9192631799 Hz w.r.t. Ephemeris Time (Bulletin Horaire ser 6 no 7 p 186). -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
> 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 A nice example of how good astronomical timing was is how they calibrated cesium atomic time against astronomical time. The original 1958 paper is here: http://leapsecond.com/history/1958-PhysRev-v1-n3-Markowitz-Hall-Essen-Parry.pdf What you see there is that they spent 4(!) years and took 4(!) data points to precisely compare the best astronomical clock with the first cesium clock. It appears they got millisecond accuracy in their timings. Compared against the existing astronomical clock standard, the four measurements of cesium frequency were: 9 192 631 761 9 192 631 767 9 192 631 772 9 192 631 780 Do the math: the mean is 9 192 631 770 +/- 8 Hz. That, literally, is where the magic 9192.631770 MHz cesium number and definition of the SI second comes from. That suggests the precision was 8 Hz / 9192631770 Hz, which is 8.7e-10, the equivalent of 75 us/day, or 2 ms/month, or 27 ms/year. As a practical matter a more accurate value of 9192631770 would have been useless because the earth is less stable than 8e-10 anyway. Here, for example, is how different UTC and UT1 would be depending on how the cesium SI second had been defined: http://www.leapsecond.com/pages/ut/cs9192-ut1-ani.gif http://www.leapsecond.com/pages/ut/ In retrospect we would have had fewer leap seconds if they had chosen 9192631950 Hz instead of 9192631770 Hz. But at the time it wasn't a choice; it was just a measurement. /tvb ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
https://www.cambridge.org/core/services/aop-cambridge-core/content/view/FFA10ED6A784AA1E39637CC0CA93B750/S0074180900036007a.pdf/div-class-title-some-advantages-and-disadvantages-of-a-photographic-zenith-tube-div.pdf indicates a timing error of around 6 millisec Bruce > On 26 March 2019 at 12:15 Bruce Griffiths wrote: > > > John > http://adsabs.harvard.edu/full/1968JRASC..62..205T > indicates a timing accuracy of a few milliseconds was typical for the Calgary > PZT. > > Bruce > > On 26 March 2019 at 11:44 John Ackermann N8UR 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 -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
On Mon 2019-03-25T18:44:05-0400 John Ackermann N8UR hath writ: > 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. https://www.ucolick.org/~sla/leapsecs/annastoyko.html -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Absolute time accuracy pre-Cesium?
John http://adsabs.harvard.edu/full/1968JRASC..62..205T indicates a timing accuracy of a few milliseconds was typical for the Calgary PZT. Bruce > On 26 March 2019 at 11:44 John Ackermann N8UR 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 -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] Absolute time accuracy pre-Cesium?
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 -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
