Talk:Apsidal precession

Nahhas theory

I am removing the large block of text added on 23 April 2009 by the anonymous editor 65.50.23.77 for many reasons. First, it is a copyright violation because most of the text comes from Einstein's Nemesis#1: DI Herculis apsidal motion puzzle solution by Professor Joe Nahhas and the remainder comes from a dead link also by Nahhas. Second, it is a fringe theory because it states that Einstein's general relativity is wrong. Third, it is much too technical for an article in an encyclopedia. Fourth, it overpowers the rest of the article, which is concerned with Newtonian apsidal precession, that is, that due to the perturbations of other planets. — Joe Kress (talk) 02:12, 31 May 2009 (UTC)

Joe Kress is an idiot who did not look for peer reviewed articles and removed the only worthy physics in all of wikipedia. He comes from a military schools tame think elimination when science is a power game that generals exterminated by intelligence. — Preceding unsigned comment added by 2603:3015:964:0:F8B4:F7F5:EE7:2726 (talk) 00:25, 17 September 2018 (UTC)

Apsidal precession versus Axial precession

That chart at the bottom of this page about the "effect" of apsidal precession on the seasons can't possibly be right--at least, the reality is too much more complicated to make that chart useful. The chart implies--or requires--that the earth's axis maintains the same orientation as apsidal precession proceeds. Except this isn't true. Both axial and apsidal precession would have the exact same, and indistinguishable, "effect" on the seasons, but it is really incorrect to talk about either without mentioning the other. — Preceding unsigned comment added by 72.8.56.170 (talk) 17:30, 17 July 2012 (UTC)

I assume you are referring to the directions of the red arrows relative to the equinoctial and solsticial points, which are the four orientations that remain the same through all four figures (they rotate relative to the frame, but not relative to each other). This is what they should do. For example, the vernal equinox is defined such that the red arrow must be tangential to Earth's orbit and its north pole must point (tilt) toward the direction opposite to Earth's direction of revolution around its orbit.

While Earth's axis precesses −50.3"/Julian year, its elliptical orbit also precesses in the opposite direction +11.6"/Julian year, both relative to the fixed stars or inertial space. Their sum, 61.9"/Julian year, shows that the vernal equinox precesses relative to the perihelion in 1,296,000"/61.9" = 20,900 Julian years. Only one change could be made to the figure, which would be to regard its retangular frame as inertial space. As time progresses clockwise around the frame, the ellipse would then tilt slightly counter-clockwise through the four figures. However, this might be detrimental to understanding the phenomenon because the left figure would no longer be 5,000 years ago, only 15,000 years in the future. As Earth's axis precesses 58% of its 26,000-year axial precession cycle as time progresses through the figure's four ellipses (15,000/26,000=58%), so the red arrow/vermal equinox point (for example) should rotate 58% of 360° or 210° CW from the top figure to the time of the left figure, while the ellipse rotates about 50° CCW (15,000/113,000×360).

Axial precession and apsidal precession do not have the same affect on the seasons. The graphic shows that their combination has a cycle of 21,000 years, which only indicates a cycle in solar forcing. Another such cycle is the 41,000-year cycle due to Earth's obliquity, the tilt of Earth's axis relative to its orbit. Unfortunately, the ice ages have a 100,000-year period. Read Milankovitch cycles. — Joe Kress (talk) 03:48, 18 July 2012 (UTC)

I don't see a problem with combining the axial and apsidal precessions, but the figure is still wrong. That is, as of this date; I haven't checked whether it changed in the past 2.5 years. It shows the current equinoxes as coincident with the apsides, whereas they should differ by 12 degrees. The figure attempts to show this 12 degree difference, but fails because both the axis and apsides have been rotated. Correcting the figure would require returning the orbital ellipse to a vertical orientation, to match the future/past orbits, but keeping the axis tilt and also the tilted positions of the equinoxes and solstices.

I agree with the original poster. This page is on apsidal precession, and the title of the picture is "Effects of apsidal precession on the seasons". Therefore the fact that 15000 in the future = 5000 years ago means the picture is definitely taking into account axial precession, by definition. In fact, most of the change between frames is caused by axial precession. I agree with the proposed way to change it. The reader should be told that the rectangular frame is inertial space / stars, and the red arrows should rotate less around the frame while the orbit slightly. Then the reader could see that the orbit shifting is apsidal, the arrows rotating is axial, and it takes 20K years to complete the cycle between the two.

How do the two precession types not have the same effect on the seasons? They both change the length of a given season, and they both change the length of time between the equinox and periapsis. — Preceding unsigned comment added by 207.198.105.24 (talk) 01:29, 16 July 2015 (UTC)

JamesGibbsMcLean (talk) 03:44, 20 March 2015 (UTC)

References

correct syntax

could someone please use math-environments and type in the formulas correctly? it's not usable the way it is right now. thanks! --Kondephy (talk) 18:27, 12 November 2013 (UTC)

Done. SkoreKeep (talk) 17:23, 7 August 2014 (UTC)

dependence on gravity field / oblateness

The formulas (and explanations of course) should be added. See for example this paper: precession of orbits about an oblate planet (Greenberg, Astronomical Journal, vol. 86, June 1981, p. 912-914) --Kondephy (talk) 13:11, 19 November 2013 (UTC)

Perturbation theory section still vague, uncited, and now it's dubious.

I added Skorekeep's actual words from his (her?) edit summary (which he could/should have done himself). It's still confusing and seems to be making a point which is off-topic and dubious: that Newton's gravity model is pitted against something that appears to be a mathematical method. That's a nonsequitur because it's an apples and oranges comparison. Both Newton's model and perturbation theory are off topic. If they're actually on topic, that's not clear by the wording chosen.

Also, that Newton's model can't handle more than three bodies is just wrong. It can't make a neat little equation for more than 2 bodies, but the model doesn't break down as the new wording suggests. I'm also pretty sure perturbation theory (a mathematical method, not a model) can't do that either. The problem with Newton's model is that it doesn't produce the observed apside rotations, but the passage is unclear as to how that's related to perturbation theory or even what perturbation theory is.

In it's original state, the section was vague, it's meaning was inscrutable. Passages with inscrutable meanings have no meaning and must be removed unless someone can clarify the meaning. In it's new state, the passage is now dubious as well as uncited making its removal imperative.

So, PLEASE, if anyone wants to mention how perturbation theory actually applies, and why it's better, and what it's better than, then please please please adjust the wording to solve those problems, don't just make a reactionary reversion.

I'll leave the current (vague, dubious, uncited, etc.) wording up for a few days to allow someone to fix it (even though "dubious+uncited" is grounds for immediate removal). I'm not an expert and I cant do the fixing. I can only note the logical errors, on/off topic, lack of citation, etc. I'm also knowledgeable enough to detect some dubiosity (as above). If someone can't try to address the problems within a few days, I can only remove the material again and it will be the burden (see WP:burden) of someone who want's to replace it to include a reliable ref at that time (as well as restate it more clearly).

98.216.243.204 (talk) 03:13, 9 May 2016 (UTC)

I think the suggestion is that using perturbation methods gives better results than using Newton's theorem of revolving orbits as described in the preceding section. Since the second section is only one sentence long, it would be better to combine the two. Martijn Meijering (talk) 08:12, 9 May 2016 (UTC)

Good point. I implemented it. It still has the "method vs. model" apples v. oranges comparison though (retaining its inscrutability) which needs to be addressed. Also, if I got it wrong (misinterpreted the matter) please correct it. 98.216.243.204 (talk) 09:38, 9 May 2016 (UTC)

A little googling suggests that perturbation theory can be (and is) used to make a more accurate analysis of the phenomenon of apsidal precession than with the theorem of revolving orbits while staying within the inverse-square model. http://astro.cornell.edu/academics/courses/astro6570/Perturbation.pdf The wording should be improved, but it does look as if perturbation theory is an analytical technique that is used to study this phenomenon. Martijn Meijering (talk) 21:04, 9 May 2016 (UTC)

Hi there Martijn Meijering,
I reverted (mostly) the 12 May edits for "Vague" and "Dubious"... I should have said "inscrutable" instead of "vague".
The text:
"...the rate of apsidal precession calculated via Newton's theorem of revolving orbits is not as accurate as it is in a three-body model using the unmodified inverse-square law. Such calculations can be done either numerically or using methods such as perturbation theory."

It's hard to see there how a "three-body model" is relevant, or even if it's a thing at all. A three-body isn't a model, it's a situation to which models are applied. I can't figure out what the text meant to say there. It's inscrutable, which is worse than "vague" because if something is "vague" then one at least has an idea of what it's about. I'm not trying to keep you from saying something (whatever it is you're trying to get across), I just want to make sure that whatever we say (as editors) is understandable at least (after that it should be not-dubious and possibly cited too of course).

98.216.243.204 (talk) 23:30, 20 May 2016 (UTC)

I don't like these changes, I think you've made things worse. You've deleted my clarifications so we're back to the original problem you complained about, and on top of that you've added more incorrect information. Newton's theorem has not been superseded, it is a mathematical theorem that remains as valid as ever, it's just that the inverse-cube term doesn't predict the phenomena very well, so the theorem isn't very helpful. It merely correctly analyses a model that doesn't describe reality very well.

As for the term three-body model, I'm not hung up on the terminology, but it is correct. Modelling the sun and planets as point masses and neglecting all outside influences is a simplification of reality, a model. Whenever you apply Newton's laws, you do so in terms of a model. You've simplified the mathematical description of the state of the system, even if you are still using the same physical laws. The simplest models take only the earth and moon into account, but adding a third body gives more accurate results. Sometimes you go even further than that. For earth-orbiting satellites for example the sun, earth, moon and spacecraft are all considered. All these models are different even though they use the same inverse-square law.

I think what we're both trying to say here is that Newton's attempt to model the phenomena more accurately by tinkering with the law of gravity is less accurate than models which use the unchanged inverse-square law but use more detailed three-body dynamics instead. I'm not sure if Newton really thought gravity had an inverse-cube term, it looks as if he merely proposed it as a more analytically tractable 'engineering model' for the earth-moon system than a full three-body model, not being familiar with the as yet uninvented methods of perturbation theory.Martijn Meijering (talk) 09:01, 21 May 2016 (UTC)

If a model doesn't make reliable predictions, it's not valid. If another model comes after it and it makes more reliable predictions and people come to know that and come to use the new model more than the first, then the first model is "superseded". If Newton's model tries to put forward an inverse-cubed force, and that force is found to not be present, then the model is quite invalid. Actually, "invalid" is more apt than "superseded" because "superseded" implies the first model was actually used at one point, which doesn't seem to be the case here.

All scientists mess around with many ideas that turn out to not work. They think one up. They test it in their minds to see if it makes any kind of sense (i.e. they try to think up something that would falsify it right off the bat). Then they test it for real, or write it down so others can test it. Surely Newton tried many models (in his mind at least) before he came upon F=GMm/r2 (his big success). It's no big deal for a model to be later seen as invalid or to be superseded. It's just part of the process.

In any case, whatever we say must first be understandable. Then, it must be not-dubious. Then if it's at all unexpected, it must cited. I removed the text because it was inscrutable. No one could even tell if it was dubious or not because its meaning couldn't be clearly discerned.

98.216.243.204 (talk) 23:26, 21 May 2016 (UTC)

Nahhas theory is correct The editor who removed it is clueless It is a peer reviewed article. Here is a first Proof "Newton's time dependent equation" synthesis of relativity and quantum mechanics By Roger Anderton "Nahhas' Newtonian derivation of Mercury's perihelion by Roger Anderton

Newton's equation is solved wrong for 350 years The Correct solution produces Einstein's relativity theory numbers

The editor need be not editing — Preceding unsigned comment added by 24.96.60.139 (talk) 03:53, 2 July 2018 (UTC)

How much?

Shouldn't there be a table of observed and calculated precession rates of solar system bodies and contributions of different causes? Or a pointer to such table if one can be found elsewhere. — Preceding unsigned comment added by 213.216.243.75 (talk) 06:13, 11 June 2019 (UTC)

A complaint

Hi. It's frustrated me to come here and find relativistic precession, along with the statement (surely true) that tidal effects are orders of magnitude more significant, without any citation or reference to them. It is those tidal (J2) effects I'd like to know about and understand. Maybe after that the secondary and tertiary nuances but sheesh we're missing the forest for the leaves here. — Preceding unsigned comment added by 174.216.12.220 (talk) 10:56, 3 August 2019 (UTC)‎

[I moved this from above the title box down to where it belongs, added the title. SkoreKeep (talk) 17:18, 3 August 2019 (UTC)]

Mercury: the planet and its orbit gives an equation for Mercury's apsidal precession due to solar J₂ on page 543 (0.012"/cy), concluding its effect is marginal. Perihelion Precession of Mercury states that an accurate calculation of the apsidal precession of Mercury due to the gravitational affects of the other planets is 5.32"/year (532"/cy) but does not calculate it, giving instead a simpler derivation for the planets treated as concentric mass rings that results in 5.50"/year. The observed precession is 5.75"/year (575"cy) which includes 43"/cy due to General Relativity. Another similar solution is at Calculation of apsidal precession via perturbation theory deriving 5.48"/year for the concentric rings version. Another similar solution, Newtonian Precession of Mercury’s Perihelion includes Urbain Le Verrier's 1859 solution of 526.7"/cy. An observed precession rate for Mercury's perihelion of 5600"/cy mentioned by many sources is relative to Earth's precessing equinox, not inertial space. A summary of all effects, mostly planetary, was given by Clemence in 1947 at Relativity Effect in Planetary Motions. Including the effect of the oblateness of the Sun (0.010"/cy), and the precession of Earth (5026.645"/cy), the calculated total was 5557.18"/cy, compared to the observed total of 5599.74"/cy. The difference of 42.56"/cy is quite close to Einstein's calculated relativity effect of 43.03"/cy. Removing only Earth's precession from the calculated total yields 532.535"/cy. The largest planetary effects are due to Venus (277.856"/cy), Jupiter (153.584"/cy), and Earth (90.038"/cy). All other effects total 35.031"/cy. — Joe Kress (talk) 23:52, 3 August 2019 (UTC)

I fully agree here with 174.216.12.220… There is no mention of any formula for nonrelativistic effects, while it is known that they are about 11 times stronger (in Mercury’s case at least). I lack the time and patience, but most importantly, the knowledge to add the formula(s?) here, but I sure hope someone could do that sooner than later. CielProfond (talk) 04:36, 10 June 2023 (UTC)

Ptolemy and lunar apsidal precession

In the "History" section it says that Ptolemy didn't take into account lunar apsidal precession, this is probably a misquote from somewhere that claims that Ptolemy didn't take into acount the solar apsidal precession. In fact Ptolemy has the apogee of the sun's orbit fixed on the ecliptic relative to the equinoxes (which he uses as a basis for his ecliptic coordinates). However, in the first lunar model inherited from Hipparchus, he has the apogee of the moon have a period of 8.85 years, approximately. The second lunar model only adds adjustments that are significant when the moon is away from the apogee. So this claim at the minimum needs a source. EricPiphany (talk) 14:15, 17 September 2022 (UTC)

I'll add here that the number 8.88 doesn't seem to appear in the source given, only "about 9 years". EricPiphany (talk) 14:56, 17 September 2022 (UTC)

I do find 8.8826 on the wikipedia Antikythera mechanism page, as the computed interval based off the number of teeth on the different gears (some of the gears it seems were missing so their teeth counts were calculated to reasonable amounts). EricPiphany (talk) 15:30, 17 September 2022 (UTC)

Combined effect

How does 112000 apsidal and 26000 axial combine to an average of 23000?

Shouldn't it be 112000 / (112000 / 26000 + 1) = 21,101.449...? Bumy Goldson (talk) 18:52, 10 June 2023 (UTC)

If you read the article by van den Heuvel, it explains that there are variations, hence the average doesn’t (necessarily) fit with the raw data. CielProfond (talk) 01:30, 18 June 2023 (UTC)