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Tim88

Oscillation calculations of Earth axis?

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Recently I was made aware of papers by a Russian institute which claims to have performed more precise calculations of the oscillations of the Earth's axis. The result (emphasis mine):

"[..] this problem is solved here
without simplification. The calculations demonstrate significant oscillation of the Earth’s axis. These
results were confirmed with other three independent solutions of the Earth’s rotation problem. [..]"

The paper suggests great confidence:

"Thus, miscellaneous tests and verifications of the initial method of solving the Earth rotation problem,
as well as independent solutions of this problem using three other methods, confirmed that the Earth’s
axis of rotation fluctuates with an amplitude 7 times greater than that previously computed by our
predecessors."
Smulsky J.J. Fundamental Principles and Results of a New Astronomic Theory of Climate Change. 

Roughly the same was next published here: http://www.sciencedirect.com/science/article/pii/S1068797116300918
"The oscillation amplitude of obliquity ε is seven–eight times larger [..] than the value determined in the previous theories."

If correct, this may have a huge impact on science programs that deal with climate, exoplanets etc.

But that was one year ago, and as you can see, there are 0 citations; still no paper has been published that either confirms it or shows it wrong. Such calculations are totally not my piece of cake, and so I have no idea how to form an opinion about the reliability of these new accurate calculations of the Earth's motion, nor about the reliability of the earlier approximate calculations. Nevertheless, I suppose that this involves nothing more than Newton's laws. Is there anyone here who knows more about such calculations?

Edited by Tim88
precision

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1 hour ago, Tim88 said:

 But that was one year ago, and as you can see, there are 0 citations; still no paper has been published that either confirms it or shows it wrong. Such calculations are totally not my piece of cake, and so I have no idea how to form an opinion about the reliability of these new accurate calculations of the Earth's motion, nor about the reliability of the earlier approximate calculations. Nevertheless, I suppose that this involves nothing more than Newton's laws. Is there anyone here who knows more about such calculations?

How did these calculations match up with predictions (or did they do such a comparison)? I have colleagues who measure the orientation of the earth's axis. There are also models, which as I understand it are fairly complex. There are a number of different oscillation cycles present, as well as effects of redistributing mass on the earth.

You can see here that the pole wanders by a few tenths of an arc-second over the course of a year, and is cyclical
http://www.usno.navy.mil/USNO/earth-orientation/eo-info/faq/what-is-pm

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On 8/3/2017 at 10:41 AM, swansont said:

 There are a number of different oscillation cycles present, as well as effects of redistributing mass on the earth.

 

What has enough mass and is moving to affect the orientation of the earth?  Surely the ocean's have reached a sort of synchrony after all this time and are one of the cycles.  I know I struggle to cope with how accurate your and your colleague's data are - but, even with this caveat, I cannot envisage anything other than the sloshing of the oceans which would be big enough to make a difference

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53 minutes ago, imatfaal said:

What has enough mass and is moving to affect the orientation of the earth?  Surely the ocean's have reached a sort of synchrony after all this time and are one of the cycles.  I know I struggle to cope with how accurate your and your colleague's data are - but, even with this caveat, I cannot envisage anything other than the sloshing of the oceans which would be big enough to make a difference

Earthquakes. Melting snow from mountains, droughts. We're talking very small angles here. There are often stories after we've had a large earthquake discussing the effect on the movement of the rotational axis.

---
edit:
http://content.usatoday.com/communities/sciencefair/post/2011/03/japan-earthquake-shifted-earth-axis-shorter-day-nasa/1#.WYRa3caZMc0
---

I'm more familiar with rotational speed effects; moment of inertia varies as mr^2, so mass movement near the surface has the largest effect., but it would also have the largest effect on the orientation. Even weather patterns have an effect — a hurricane/typhoon has angular momentum, whose axis does not coincide with the earth's rotation, but angular momentum must be conserved. 

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A meter shift in the pole is ~0.15 microradians, and a microradian is ~0.2 seconds of arc. 

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On 03/08/2017 at 11:41 AM, swansont said:

How did these calculations match up with predictions (or did they do such a comparison)? I have colleagues who measure the orientation of the earth's axis. There are also models, which as I understand it are fairly complex. There are a number of different oscillation cycles present, as well as effects of redistributing mass on the earth.

You can see here that the pole wanders by a few tenths of an arc-second over the course of a year, and is cyclical
http://www.usno.navy.mil/USNO/earth-orientation/eo-info/faq/what-is-pm

As I understand it, they only compared different accurate calculations with each other and with the old ones, which most others still use. Apart of that, they obtained a better match with the historical ice ages - but that is of course very indirect. Thus I like your reference to direct measurements -thanks! I may write to the author and ask if they considered comparing with such direct measurements.
However it may be that the time frame is much too short. And I do not quite understand that picture: "a reference frame which is defined by the adopted locations of terrestrial observatories. The coordinate x is measured along the 0o (Greenwich) meridian [..]". I thought that the North Pole defines that reference frame - in which case it cannot move relative to it, right??

 

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4 minutes ago, Tim88 said:

As I understand it, they only compared different accurate calculations with each other and with the old ones, which most others still use. Apart of that, they obtained a better match with the historical ice ages - but that is of course very indirect. Thus I like your reference to direct measurements -thanks! I may write to the author and ask if they considered comparing with such direct measurements.
However it may be that the time frame is much too short. And I do not quite understand that picture: "a reference frame which is defined by the adopted locations of terrestrial observatories. The coordinate x is measured along the 0o (Greenwich) meridian [..]". I thought that the North Pole defines that reference frame - in which case it cannot move relative to it, right??

 

 

AFAIK pole wander is measured with respect to a celestial reference frame, defined by distant stars which are too far away for parallax or their own motion to affect the results. This is from VLBI (very long baseline interferometry) that the people literally down the hall from me analyze.

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On 04/08/2017 at 0:19 PM, swansont said:

Earthquakes. Melting snow from mountains, droughts. We're talking very small angles here. There are often stories after we've had a large earthquake discussing the effect on the movement of the rotational axis.

---
edit:
http://content.usatoday.com/communities/sciencefair/post/2011/03/japan-earthquake-shifted-earth-axis-shorter-day-nasa/1#.WYRa3caZMc0
---

I'm more familiar with rotational speed effects; moment of inertia varies as mr^2, so mass movement near the surface has the largest effect., but it would also have the largest effect on the orientation. Even weather patterns have an effect — a hurricane/typhoon has angular momentum, whose axis does not coincide with the earth's rotation, but angular momentum must be conserved. 

So again it was my inability to properly conceptualise how accurate our readings can be. 

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As I now understand it, the approximate and the accurate calculations are all accurate (agreeing with each other and with measurements) for the time of human history.
Consequently, it is necessary to compare the calculated variations with the geological record. In the paper a comparison is made with the ice ages, as established with dating techniques.

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I now got a reply from Smulsky.

He points out that in fact there is an additional, astronomical verification: the constant of nutation. That's an oscillation of 9.2'' with a period of 18.6 years - https://en.wikipedia.org/wiki/Astronomical_nutation#Nutation_of_the_Earth.27s_axis

As described in Smulsky's fig.10, this observed phenomenon is exactly reproduced by his calculation model  -  Smulsky J.J. Fundamental Principles and Results of a New Astronomic Theory of Climate Change. 

He further comments in his email (with a slight correction of his Google Translate Russian->English), with added emphasis:

Quote

In addition, the previous solutions of the problem of the Earth’s rotation are incorrect in the interval 0-2000 thousand years, since they do not give short-period oscillations of the Earth's axis. New solutions give them (see Fig. 10).

It looks to me that there is no reason to doubt the new calculation results. Thus, the one year silence after his peer reviewed publication suggests to me that people are putting their heads in the sand, in an attempt to just ignore it.

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49 minutes ago, Tim88 said:

I now got a reply from Smulsky.

He points out that in fact there is an additional, astronomical verification: the constant of nutation. That's an oscillation of 9.2'' with a period of 18.6 years - https://en.wikipedia.org/wiki/Astronomical_nutation#Nutation_of_the_Earth.27s_axis

As described in Smulsky's fig.10, this observed phenomenon is exactly reproduced by his calculation model  -  Smulsky J.J. Fundamental Principles and Results of a New Astronomic Theory of Climate Change. 

He further comments in his email (with a slight correction of his Google Translate Russian->English), with added emphasis:

It looks to me that there is no reason to doubt the new calculation results. Thus, the one year silence after his peer reviewed publication suggests to me that people are putting their heads in the sand, in an attempt to just ignore it.

I don't understand your comment. The 18.6 year nutation period was already known and used in earth orientation models. It's not being ignored.

This web page is from 2009
http://maia.usno.navy.mil/whatiseop.html

"Periodic variations are associated with periodically repeatable physical processes affecting the Earth. Tides raised in the solid Earth by the Moon and the Sun produce variations in the length of the day with a total amplitude on the order of 0.001 seconds and with individual periods of 18.6 years, 1 year, 1/2 year, 27.55 days, 13.66 days and others."

I get the impression that the models lag the measurements. That there's a model that predicts the observed nutation changes nothing for the people who were already using the accurate measurements in their work. What exactly were you expecting?

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On 17/08/2017 at 0:04 PM, swansont said:

I don't understand your comment. The 18.6 year nutation period was already known and used in earth orientation models. It's not being ignored.

This web page is from 2009
http://maia.usno.navy.mil/whatiseop.html

"Periodic variations are associated with periodically repeatable physical processes affecting the Earth. Tides raised in the solid Earth by the Moon and the Sun produce variations in the length of the day with a total amplitude on the order of 0.001 seconds and with individual periods of 18.6 years, 1 year, 1/2 year, 27.55 days, 13.66 days and others."

I get the impression that the models lag the measurements. That there's a model that predicts the observed nutation changes nothing for the people who were already using the accurate measurements in their work. What exactly were you expecting?

Apparently the approximate calculations that everyone used until now do not even include the nutation; in other words, those do not "lag" the measurements but simply don't reproduce them - and apparently they were wrong for their intended use as well. The correct and accurately calculated nutation is one of the verifications of the correctness of the new, exact calculations that are discussed in the paper. Regretfully, we cannot directly verify the calculations over 100'000s of years with measurements.

Edited by Tim88

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32 minutes ago, Tim88 said:

Apparently the approximate calculations that everyone used until now do not even include the nutation 

Doubtful
https://en.wikipedia.org/wiki/Earth_orientation_parameters
http://hpiers.obspm.fr/eop-pc/earthor/EOP.html

Why would they mention a precession-nutation model if they didn't include nutation in it?

"a precession-nutation model (such a model is kept as a part of the IERS Conventions) cannot take into account the variable components due to atmospheric, oceanic, and earth internal processes. The actual departure of the motion with the model is observed by VLBI and LLR."

As I had discussed. Unless this new model predicts earthquakes and the weather, it won't account for everything, either.

 

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On 21/08/2017 at 1:26 PM, swansont said:

Doubtful
https://en.wikipedia.org/wiki/Earth_orientation_parameters
http://hpiers.obspm.fr/eop-pc/earthor/EOP.html

Why would they mention a precession-nutation model if they didn't include nutation in it?

[..]

No, not those; that's not what is meant with "the predecessors". The comparison is with the simplified calculations for time periods of 100'000 yrs and more, the so-called Milankovitch calculations and variants thereof - http://www.indiana.edu/~geol105/images/gaia_chapter_4/milankovitch.htm .

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12 minutes ago, Tim88 said:

No, not those; that's not what is meant with "the predecessors". The comparison is with the simplified calculations for time periods of 100'000 yrs and more, the so-called Milankovitch calculations and variants thereof - http://www.indiana.edu/~geol105/images/gaia_chapter_4/milankovitch.htm .

I don't understand the connection. Milankovitch cycles are much longer period than 18.6 years, so it's no surprise to me that nutation (which is not one of the components of the cycles) with an 18.6 year period would be ignored. And the title of the paper in question is about climate change, which is typically on much longer time scales than 18.6 years (recent history aside)

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