Earth's day lengthens by two milliseconds a century
https://www.theguardian.com/science/2016/dec/07/earths-day-lengthens-by-two-... Also an interesting explanation on why Earth's deceleration rate has decreased recently.
Thanks for the heads-up; I installed the attached patch into the development repository. When this news was published in today's Los Angeles Times, commenters jumped on the story and said that the math was all wrong, and that a 7-hour error after 2500 years cannot possibly be caused by an increase of the length-of-day by an average of 1.8 ms/century (i.e., 18 μ/s//year). The amusing thing wasn't merely that the commenters were scientifically illiterate: it was that they were sure they were right, that the "liberal" media were wrong, and that this had something to do with global warming being a hoax. For what it's worth, the only paper I found on the subject of human-caused global warming's effect on the length-of-day estimated an increase on the order of 1 μ/s//year, mostly due to an increase in the estimated mean zonal wind between 10–60 degrees of latitude. See: de Viron O, Dehant V, Goosse H, Crucifix M. Effect of global warming on the length-of-day. Geophys Res Lett 2002 Apr 12;29(7):50-1–4. http://dx.doi.org/10.1029/2001GL013672
I think it would be better to refer to the original paper, which can be found free online. http://rspa.royalsocietypublishing.org/content/472/2196/20160404 Measurement of the Earth's rotation: 720 BC to AD 2015 F. R. Stephenson, L. V. Morrison, C. Y. Hohenkerk Published 7 December 2016.DOI: 10.1098/rspa.2016.0404 Cheers, Oscar van Vlijmen
----Origineel Bericht---- Van : eggert@cs.ucla.edu Datum : 08/12/2016 21:43 Aan : elseifthen@gmx.com Cc : tz@iana.org Onderwerp : Re: [tz] Earth's day lengthens by two milliseconds a century
Thanks for the heads-up; I installed the attached patch into the development repository.
When this news was published in today's Los Angeles Times, commenters jumped on the story and said that the math was all wrong, and that a 7-hour error after 2500 years cannot possibly be caused by an increase of the length-of-day by an average of 1.8 ms/century (i.e., 18 μ/s//year). The amusing thing wasn't merely that the commenters were scientifically illiterate: it was that they were sure they were right, that the "liberal" media were wrong, and that this had something to do with global warming being a hoax.
For what it's worth, the only paper I found on the subject of human-caused global warming's effect on the length-of-day estimated an increase on the order of 1 μ/s//year, mostly due to an increase in the estimated mean zonal wind between 10–60 degrees of latitude. See:
de Viron O, Dehant V, Goosse H, Crucifix M. Effect of global warming on the length-of-day. Geophys Res Lett 2002 Apr 12;29(7):50-1–4. http://dx.doi.org/10.1029/2001GL013672
On 12/08/2016 01:34 PM, vanadovv@hetnet.nl wrote:
it would be better to refer to the original paper, which can be found free online. The proposed patch does that: the new Theory file uses the URL http://dx.doi.org/10.1098/rspa.2016.0404 as DOIs are supposed to be longer-lived. It's the same paper and it's freely readable.
Perhaps you may also want to cite this page from NASA, which presents a summary of the results of the same research, in a readily implementable format: http://eclipse.gsfc.nasa.gov/SEhelp/deltatpoly2004.html On Thu, Dec 8, 2016 at 10:54 PM, Paul Eggert <eggert@cs.ucla.edu> wrote:
On 12/08/2016 01:34 PM, vanadovv@hetnet.nl wrote:
it would be better to refer to the original paper, which can be found free online.
The proposed patch does that: the new Theory file uses the URL http://dx.doi.org/10.1098/rspa.2016.0404 as DOIs are supposed to be longer-lived. It's the same paper and it's freely readable.
On 2016-12-08 15:22, Pierpaolo Bernardi wrote:
On Thu, Dec 8, 2016 at 10:54 PM, Paul Eggert <eggert@cs.ucla.edu> wrote:
On 12/08/2016 01:34 PM, vanadovv@hetnet.nl wrote:
it would be better to refer to the original paper, which can be found free online. The proposed patch does that: the new Theory file uses the URL http://dx.doi.org/10.1098/rspa.2016.0404 as DOIs are supposed to be longer-lived. It's the same paper and it's freely readable. Perhaps you may also want to cite this page from NASA, which presents a summary of the results of the same research, in a readily implementable format: http://eclipse.gsfc.nasa.gov/SEhelp/deltatpoly2004.html
That paper is *not* a summary of the results of the same research: it is adapted from the 10 year old Canon partly based on some of the same authors' results from 2 years earlier, as the year in the URI indicates! -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
On Thu, Dec 8, 2016 at 11:54 PM, Brian Inglis <Brian.Inglis@systematicsw.ab.ca> wrote:
That paper is *not* a summary of the results of the same research: it is adapted from the 10 year old Canon partly based on some of the same authors' results from 2 years earlier, as the year in the URI indicates!
You are right! I stand corrected. I saw the same authors on whose research this reference that I knew is based, and assumed it was the same work without checking the new paper. Cheers
On 2016-12-08 16:17, Pierpaolo Bernardi wrote:
On Thu, Dec 8, 2016 at 11:54 PM, Brian Inglis <Brian.Inglis@systematicsw.ab.ca> wrote:
That paper is *not* a summary of the results of the same research: it is adapted from the 10 year old Canon partly based on some of the same authors' results from 2 years earlier, as the year in the URI indicates! You are right! I stand corrected. I saw the same authors on whose research this reference that I knew is based, and assumed it was the same work without checking the new paper.
No worries - thought that might be case - didn't want possibly spurious ref cited as a summary in distributed files - URI year made me suspicious - those guys have published a fair amount on the same topics over the decades - seem like pretty rigorous treatments - Canon/NASA summary polynomials appeared less uniform than the authors' current tables. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
On Thu 2016-12-08T16:35:15 -0700, Brian Inglis hath writ:
No worries - thought that might be case - didn't want possibly spurious ref cited as a summary in distributed files - URI year made me suspicious - those guys have published a fair amount on the same topics over the decades - seem like pretty rigorous treatments - Canon/NASA summary polynomials appeared less uniform than the authors' current tables.
Except that Morrison and Stephenson and Hohenkerk only show the past. NASA polynomials attempt to predict the future, but (as seen in the data of this new publication) to their peril. -- Steve Allen <sla@ucolick.org> 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 http://www.ucolick.org/~sla/ Hgt +250 m
On 12/08/2016 03:45 PM, Steve Allen wrote:
Except that Morrison and Stephenson and Hohenkerk only show the past. NASA polynomials attempt to predict the future, but (as seen in the data of this new publication) to their peril.
Yes, the Stephenson et al. paper is newer and presumably more authoritative and 'Theory' cites it first. I assume Espenak will update the other page eventually, and in the meantime it's an entertaining set of estimates. The 'Theory' file cites these two sources only to support the statement that we don't know historical solar time to more than about one-hour accuracy, a statement that I hope is vague enough to pass muster. If we wanted to get picky, we'd have to determine what's "historical": back to 3200 BC? or back to the earliest reliable astronomical records? if the former, we don't have even one-hour accuracy; if the latter, it depends on one's definition of "reliable". Still, the statement is in the right ballpark, which is all that's needed there.
participants (6)
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Steve Allen -
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