Re: [time-nuts] How many seconds in a year?
Neville Michie <[EMAIL PROTECTED]> wrote: > If leap seconds are applied to keep the meanderings of the planet in > phase with our mean time > clocks, then what about our leap year days which are applied to keep > the seasons in phase with our > calendars? Applying a whole day every so many years may keep the > civil authorities happy, > but when we all celebrate a new year we are not counting down the > completion of a planetary cycle > but the civil approximation to a new year. I have developed an alternate calendar which fixes this problem: http://ivan.Harhan.ORG/RT/calendar/spec.txt Today is SE 47 Vnd 29, which means day 29 of Vendemiaire of year 47 of Space Era. MS ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
Hi Neville: Leap Years do not occur once every 4 years but are on a more complex schedule. There's an exception for years that are exact multiples of 100 years. There's an exception to the exception for years that are exact multiples of 400 years. So on a very long term average there are 365.2425 days per year. See: http://en.wikipedia.org/wiki/Leapyear There have been proposals to add a 4000 or 8000 year exception, but that's so far in the future and the Earth's rotation has enough variation that these have not been made part of the leap year calculations. The Earth used to be the definition of time but once it was demonstrated that Cesium clocks kept much better time they became the definition of the time. At first the length of the second was going to be changed each year "rubber seconds", but that was soon discarded and replaced with the leap second. There are a couple of related areas. If you have read about or seen the movie about Harrison, his clocks and the longitude you know part of the story. The other is the search for the latitude. This turns out to be a much more complex problem and took a lot longer before there was an understanding of it. After I moved to Ukiah, CA I discovered there was a street called Observatory Ave. Doing some research at the local Historical house determined it was one of six of the Latitude Observatories all located very close to 39:08 deg N. http://www.prc68.com/I/UkiahObs.shtml Have Fun, Brooke Clarke http://www.prc68.com/P/Prod.html Products I make and sell http://www.prc68.com/Alpha.shtml All my web pages listed based on html name http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Web Cam Neville Michie wrote: > Thanks Jim, > you told me what I wanted. > We can listen to WWV to hear the stroke of midnight each day, and we > know it is UTC and > subject to the equation of time but otherwise it represents an exact > rotation of the planet. We know a day is about > 86400.00X seconds long, but a year is rounded to the nearest day, > what is its real length, as > it is not an integral multiple of days. > Now 12:00:00 is only the end of the civil and legal year and there > are errors of around 6 hours > each year in rounding it off to the nearest day. > Jim has given the length of a real year (the inverse of the frequency > of the planet orbit) and > I would be pleased to ask him another question as to the phase of > the annual turnover, > what time of day the next annual solstice? occurs. > That is the time for my new year chime to sound, > and Jim has already given the number of seconds to the next chime. > I was not really thinking of leaving an unattended clock running for > 200 years, but it would be nice > to think that I had used the precision available to observe the real > milestones in time. > I am sorry that this question has been so difficult to ask, but there > are so many arbitrary distortions > of the observation of time that it has become a very fuzzy concept. > cheers, Neville Michie > > > > On 15/10/2008, at 4:19 PM, Jim Palfreyman wrote: > >> Hi Neville, >> >> There are a few inaccuracies in your summary but the figure you >> want for >> J2000.0 is 365.242 190 419 SI days=31556925.252202 SI seconds. >> However we >> cannot give you an average over the next 200 years because it is >> steadily >> dropping by 5.324 ms per year. So in 200 years time it will be a >> second out. >> >> However, for your purposes if you use the number above you will get >> very >> close to what you want. >> >> Regards, >> >> Jim >> >> >> 2008/10/15 Neville Michie <[EMAIL PROTECTED]> >> >>> I have been thinking about my problem, the major part of the problem >>> is finding the right question. >>> If leap seconds are applied to keep the meanderings of the planet in >>> phase with our mean time >>> clocks, then what about our leap year days which are applied to keep >>> the seasons in phase with our >>> calendars? Applying a whole day every so many years may keep the >>> civil authorities happy, >>> but when we all celebrate a new year we are not counting down the >>> completion of a planetary cycle >>> but the civil approximation to a new year. >>> Now, having thought about it a bit more, the year is the completing >>> of an orbit of our elliptical orbit around the sun. >>> The start and finish of an orbit is defined by the inclined axis of >>> rotation of the Earth crossing the plane of its orbit which is what >>> causes the seasons. >>> The elliptical orbit is moving, hence the precession of the >>> equinoxes. As we can not measure a year >>> by looking at a particular star crossing our meridian, >>> we measure the year by watching a fictitious star crossing our >>> meridian. This star (which used to be at the first point of Aries >>> on the vernal equinox) is slowly orbiting around our solar system as >>> our tilted ecliptic precesses. >>> >>> Which now g
Re: [time-nuts] How many seconds in a year?
Thanks Jim, you told me what I wanted. We can listen to WWV to hear the stroke of midnight each day, and we know it is UTC and subject to the equation of time but otherwise it represents an exact rotation of the planet. We know a day is about 86400.00X seconds long, but a year is rounded to the nearest day, what is its real length, as it is not an integral multiple of days. Now 12:00:00 is only the end of the civil and legal year and there are errors of around 6 hours each year in rounding it off to the nearest day. Jim has given the length of a real year (the inverse of the frequency of the planet orbit) and I would be pleased to ask him another question as to the phase of the annual turnover, what time of day the next annual solstice? occurs. That is the time for my new year chime to sound, and Jim has already given the number of seconds to the next chime. I was not really thinking of leaving an unattended clock running for 200 years, but it would be nice to think that I had used the precision available to observe the real milestones in time. I am sorry that this question has been so difficult to ask, but there are so many arbitrary distortions of the observation of time that it has become a very fuzzy concept. cheers, Neville Michie On 15/10/2008, at 4:19 PM, Jim Palfreyman wrote: > Hi Neville, > > There are a few inaccuracies in your summary but the figure you > want for > J2000.0 is 365.242 190 419 SI days=31556925.252202 SI seconds. > However we > cannot give you an average over the next 200 years because it is > steadily > dropping by 5.324 ms per year. So in 200 years time it will be a > second out. > > However, for your purposes if you use the number above you will get > very > close to what you want. > > Regards, > > Jim > > > 2008/10/15 Neville Michie <[EMAIL PROTECTED]> > >> I have been thinking about my problem, the major part of the problem >> is finding the right question. >> If leap seconds are applied to keep the meanderings of the planet in >> phase with our mean time >> clocks, then what about our leap year days which are applied to keep >> the seasons in phase with our >> calendars? Applying a whole day every so many years may keep the >> civil authorities happy, >> but when we all celebrate a new year we are not counting down the >> completion of a planetary cycle >> but the civil approximation to a new year. >> Now, having thought about it a bit more, the year is the completing >> of an orbit of our elliptical orbit around the sun. >> The start and finish of an orbit is defined by the inclined axis of >> rotation of the Earth crossing the plane of its orbit which is what >> causes the seasons. >> The elliptical orbit is moving, hence the precession of the >> equinoxes. As we can not measure a year >> by looking at a particular star crossing our meridian, >> we measure the year by watching a fictitious star crossing our >> meridian. This star (which used to be at the first point of Aries >> on the vernal equinox) is slowly orbiting around our solar system as >> our tilted ecliptic precesses. >> >> Which now gets me back to my question. If I want to make a clock that >> chimes once per solar year when we have completed a cycle it will >> count down a >> number of seconds then chime. So I want to know the number of seconds >> in a Mean Year, accurate enough so that in 200 years time >> it will still be right. >> It should be fun to see the time the new year really starts as we >> head around the orbit again. The time will not be midnight >> but will jump around in the day with different years. >> There are so many interference's in time keeping by accountants and >> politicians I was thinking of making a clock that >> showed real time as determined by sun and stars. >> Although that brings up the equation of time, and mean time is so >> convenient if you have an atomic clock. >> I might just try to make a clock that shows the mediaeval "Italian >> Hours", where every day has 24 hours with sunrise at 6 AM with sunset >> at 6PM. >> The old clocks had dials marked so that you read off the elastic >> Italian hours. >> cheers, Neville Michie >> >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ >>> time-nuts >>> and follow the instructions there. >> >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
> Which now gets me back to my question. If I want to make a clock that > chimes once per solar year when we have completed a cycle it will > count down a number of seconds then chime. So I want to know the > number of seconds in a Mean Year, accurate enough so that in 200 > years time it will still be right. What does "right" mean? The traditional leap year calculation is good down to (roughly) 1 day per 400 years. That's 86400 seconds per 400 years or 216 seconds per year. Or perhaps significantly better. (Those old geezers had really good telescopes and knew how to drive them. One of the proposals fighting for the navigation prize that Harrison eventually won was getting time by watching Jupiter's moons. They even corrected for speed of light delays due to relative orbital positions.) Leap seconds happen every year or so, at least so far. Who knows what will happen tomorrow. Thats 1/2 % of the leap year corrections. So what do you mean my "right"? Do you want legal midnight? Sidereal midnight? Solar midnight? How close do you want to be? 200 years is halfway through the 400 year leap cycle, so if you do one obvious thing, you will be off roughly 1/2 day. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
> Which now gets me back to my question. If I want to make a clock > that chimes once per solar year when we have completed a cycle > it will count down a number of seconds then chime. So I want to > know the number of seconds in a Mean Year, accurate enough > so that in 200 years time it will still be right. Neville, I'm pretty sure no electronic clock ever made is accurate enough and reliable enough to meet your goal. But you might want to look at this one, though: http://www.longnow.org/projects/clock/ http://www.longnow.org/projects/clock/prototype1/ http://www.longnow.org/projects/clock/chimes/ /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
Hi Neville, There are a few inaccuracies in your summary but the figure you want for J2000.0 is 365.242 190 419 SI days=31556925.252202 SI seconds. However we cannot give you an average over the next 200 years because it is steadily dropping by 5.324 ms per year. So in 200 years time it will be a second out. However, for your purposes if you use the number above you will get very close to what you want. Regards, Jim 2008/10/15 Neville Michie <[EMAIL PROTECTED]> > I have been thinking about my problem, the major part of the problem > is finding the right question. > If leap seconds are applied to keep the meanderings of the planet in > phase with our mean time > clocks, then what about our leap year days which are applied to keep > the seasons in phase with our > calendars? Applying a whole day every so many years may keep the > civil authorities happy, > but when we all celebrate a new year we are not counting down the > completion of a planetary cycle > but the civil approximation to a new year. > Now, having thought about it a bit more, the year is the completing > of an orbit of our elliptical orbit around the sun. > The start and finish of an orbit is defined by the inclined axis of > rotation of the Earth crossing the plane of its orbit which is what > causes the seasons. > The elliptical orbit is moving, hence the precession of the > equinoxes. As we can not measure a year > by looking at a particular star crossing our meridian, > we measure the year by watching a fictitious star crossing our > meridian. This star (which used to be at the first point of Aries > on the vernal equinox) is slowly orbiting around our solar system as > our tilted ecliptic precesses. > > Which now gets me back to my question. If I want to make a clock that > chimes once per solar year when we have completed a cycle it will > count down a > number of seconds then chime. So I want to know the number of seconds > in a Mean Year, accurate enough so that in 200 years time > it will still be right. > It should be fun to see the time the new year really starts as we > head around the orbit again. The time will not be midnight > but will jump around in the day with different years. > There are so many interference's in time keeping by accountants and > politicians I was thinking of making a clock that > showed real time as determined by sun and stars. > Although that brings up the equation of time, and mean time is so > convenient if you have an atomic clock. > I might just try to make a clock that shows the mediaeval "Italian > Hours", where every day has 24 hours with sunrise at 6 AM with sunset > at 6PM. > The old clocks had dials marked so that you read off the elastic > Italian hours. > cheers, Neville Michie > > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > > time-nuts > > and follow the instructions there. > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
Neville Michie wrote: > I have been thinking about my problem, the major part of the problem > is finding the right question. > If leap seconds are applied to keep the meanderings of the planet in > phase with our mean time > clocks, then what about our leap year days which are applied to keep > the seasons in phase with our > calendars? Applying a whole day every so many years may keep the > civil authorities happy, > but when we all celebrate a new year we are not counting down the > completion of a planetary cycle > but the civil approximation to a new year. > Now, having thought about it a bit more, the year is the completing > of an orbit of our elliptical orbit around the sun. > The start and finish of an orbit is defined by the inclined axis of > rotation of the Earth crossing the plane of its orbit which is what > causes the seasons. > The elliptical orbit is moving, hence the precession of the > equinoxes. As we can not measure a year > by looking at a particular star crossing our meridian, > we measure the year by watching a fictitious star crossing our > meridian. This star (which used to be at the first point of Aries > on the vernal equinox) is slowly orbiting around our solar system as > our tilted ecliptic precesses. > cheers, Neville Michie > Neville There are many definitions of a year all of which differ slightly from each other. You appear to have confused the precession of the equinoxes (better described as the precession of the Earth's rotational axis i.e. the Earth precesses like a top) with the precession of the apsides of its orbit. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
I have been thinking about my problem, the major part of the problem is finding the right question. If leap seconds are applied to keep the meanderings of the planet in phase with our mean time clocks, then what about our leap year days which are applied to keep the seasons in phase with our calendars? Applying a whole day every so many years may keep the civil authorities happy, but when we all celebrate a new year we are not counting down the completion of a planetary cycle but the civil approximation to a new year. Now, having thought about it a bit more, the year is the completing of an orbit of our elliptical orbit around the sun. The start and finish of an orbit is defined by the inclined axis of rotation of the Earth crossing the plane of its orbit which is what causes the seasons. The elliptical orbit is moving, hence the precession of the equinoxes. As we can not measure a year by looking at a particular star crossing our meridian, we measure the year by watching a fictitious star crossing our meridian. This star (which used to be at the first point of Aries on the vernal equinox) is slowly orbiting around our solar system as our tilted ecliptic precesses. Which now gets me back to my question. If I want to make a clock that chimes once per solar year when we have completed a cycle it will count down a number of seconds then chime. So I want to know the number of seconds in a Mean Year, accurate enough so that in 200 years time it will still be right. It should be fun to see the time the new year really starts as we head around the orbit again. The time will not be midnight but will jump around in the day with different years. There are so many interference's in time keeping by accountants and politicians I was thinking of making a clock that showed real time as determined by sun and stars. Although that brings up the equation of time, and mean time is so convenient if you have an atomic clock. I might just try to make a clock that shows the mediaeval "Italian Hours", where every day has 24 hours with sunrise at 6 AM with sunset at 6PM. The old clocks had dials marked so that you read off the elastic Italian hours. cheers, Neville Michie > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
In message: <[EMAIL PROTECTED]> David Forbes <[EMAIL PROTECTED]> writes: : So there is no way to build a clock today that is guaranteed to count : seconds correctly in future years, short of having it receive leap : second announcements twice a year and adjust its timekeeping : accordingly. Unless it has a built-in sundial :-) Warner P.S. And even then only if DUT1 is held < 1s ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
At 9:38 AM +1100 10/15/08, Neville Michie wrote: >Hi, >the GPS system obviously counts seconds, and weeks. When the solar >year develops a phase >difference of more than half a second the UTC crowd consider a leap >second, so what is the current >rotational velocity of the Earth, either WRT the Sun or the stars? In >seconds. >I could find many answers on Google but none that seemed good enough >to set your clock by. >By clock I just mean a rubidium clock that is harmonised to the GPS >system. >cheers, Neville Michie Neville, Unfortunately, the Earth's rotation and revolution around are not as stable as the oscillations of your rubidium clock. There is no formula for leap seconds; the folks who insert or subtract the leap seconds do so using observations of the stars as a guide. You could say that leap seconds represent the noisy least-significant digit in the Earth's somewhat jerky movement. (Jerky relative to the smoothness of a rubidium clock, that is.) It would be convenient for clockmakers if they calculated the best fit to a long-term trend of the Earth's behavior and allocated leap seconds based on that fit, but alas they do not. So there is no way to build a clock today that is guaranteed to count seconds correctly in future years, short of having it receive leap second announcements twice a year and adjust its timekeeping accordingly. -- --David Forbes, Tucson, AZ http://www.cathodecorner.com/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
> Hi, > the GPS system obviously counts seconds, and weeks. When the solar > year develops a phase > difference of more than half a second the UTC crowd consider a leap > second, so what is the current > rotational velocity of the Earth, either WRT the Sun or the stars? In > seconds. > I could find many answers on Google but none that seemed good enough > to set your clock by. > By clock I just mean a rubidium clock that is harmonised to the GPS > system. > cheers, Neville Michie One leap second every few years is equivalent to about 1e-8. So the answer to your question only starts to matter when measurements are more precise than 8 digits. See also: http://www.leapsecond.com/museum/earth/ /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How many seconds in a year?
Neville Michie wrote: > Hi, > the GPS system obviously counts seconds, and weeks. When the solar > year develops a phase > difference of more than half a second the UTC crowd consider a leap > second, so what is the current > rotational velocity of the Earth, either WRT the Sun or the stars? > In seconds. > I could find many answers on Google but none that seemed good enough > to set your clock by. > By clock I just mean a rubidium clock that is harmonised to the GPS system. > cheers, Neville Michie > Neville Leapseconds are due to the fact that the Earths rotation period about its axis wrt the mean sun is not exactly 86400 seconds. The rate isnt spot on and the rotation period evolves with time due to earthquakes and other causes. The length of the year is another matter entirely. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] How many seconds in a year?
Hi, the GPS system obviously counts seconds, and weeks. When the solar year develops a phase difference of more than half a second the UTC crowd consider a leap second, so what is the current rotational velocity of the Earth, either WRT the Sun or the stars? In seconds. I could find many answers on Google but none that seemed good enough to set your clock by. By clock I just mean a rubidium clock that is harmonised to the GPS system. cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
