<p>General relativity is only one cause of the precession of Mercury's orbit, and not the largest factor. Gravitational perturbation by the other planets and the non-spherical sun also cause precession. Newtonian gravity predicts precession of 532 arcseconds per century, but 575 arcseconds is observed. The discrepancy can be explained if one uses General Relativity as the model of gravity.</p>

<p>The extra precession of 43 arcseconds caused by GR would be the same, the perturbations due to the other planets would not be the same, unless they were also orbiting the sun in the opposite direction.</p>

CC BY-SA 4.0
2019-08-09T23:50:37.683Z
While the answer is correct, I think there must be a missing decimal point in the precession rates. The [Messenger results](https://iopscience.iop.org/article/10.3847/1538-3881/aa5be2) from 2017 show a measured total precession rate for Mercury of 575.31"/cy, with the largest contribuitons due to perturbations from Venus, Jupiter and Earth/Moon. The GR contribution is 43"/cy, as given in your answer. You should check your source for the precession data.
amateurAstro
CC BY-SA 4.0
2019-08-10T20:04:33.197Z
This [question](https://physics.stackexchange.com/questions/26408/what-did-general-relativity-clarify-about-mercury) and its answers likely explain the ~10X difference in values for perihelion precession of Mercury noted in my previous comment. Apparently some older sources added a contribution from precession of the Earth's axis, now called general precession in longitude. I don't know why change in Earth's axis was included in Mercury's orbital precession. These measurements were made from Earth, but corrections for general precession are well known, and unrelated to Mercury's orbit.
amateurAstro
CC BY-SA 4.0
2019-08-11T05:58:00.777Z
I don't know much about it, but wouldn't GR [frame dragging](https://en.wikipedia.org/wiki/Frame-dragging) result in a tiny difference between prograde and retrograde precession?
uhoh
CC BY-SA 4.0
2019-08-11T06:15:21.950Z
Probably, but frame dragging is not the cause of the discrepancy
James K
CC BY-SA 4.0
2019-08-11T12:23:47.030Z
Is space dragging the same as space curvature....it seems it is not?Dragging seems something like action-reaction Newton law.
Janko Bradvica
CC BY-SA 4.0
2019-08-11T22:06:15.980Z
Frame dragging is a feature of General relativity, I'm not going to try to explain further here.  Read the wikipedia article.
James K
CC BY-SA 4.0
2019-08-09T22:28:59.033Z
2019-08-10T22:41:38.617Z
2019-08-10T22:41:38.617Z
James K
<p>My question is the following,would the scalar of precession of Mercury orbit be the same if Mercury orbited Sun in the oposit direction?</p>

CC BY-SA 4.0
2019-08-10T05:34:52.540Z
There might be the smallest variation due to the rotation of the sun pulling space along with it.    https://www.sciencedaily.com/releases/1998/03/980330073701.htm  Too small to be observed perhaps, but there might be the tiniest of differences.
userLTK
<general-relativity>
Relativistic Mercury orbit around the Sun
Janko Bradvica
# Relativistic Mercury orbit around the Sun

(Asked by: username_0 on 2019-08-09)

My question is the following,would the scalar of precession of Mercury orbit be the same if Mercury orbited Sun in the oposit direction?

**Tags:** general-relativity

> **Comments:**
> **username_1**: There might be the smallest variation due to the rotation of the sun pulling space along with it.    https://www.sciencedaily.com/releases/1998/03/980330073701.htm  Too small to be observed perhaps, but there might be the tiniest of differences.  

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## 1 answers

### Answer by username_2 on 2019-08-09. Score: 8

General relativity is only one cause of the precession of Mercury's orbit, and not the largest factor. Gravitational perturbation by the other planets and the non-spherical sun also cause precession. Newtonian gravity predicts precession of 532 arcseconds per century, but 575 arcseconds is observed. The discrepancy can be explained if one uses General Relativity as the model of gravity.

The extra precession of 43 arcseconds caused by GR would be the same, the perturbations due to the other planets would not be the same, unless they were also orbiting the sun in the opposite direction.

> **Comments:**
> **username_3**: While the answer is correct, I think there must be a missing decimal point in the precession rates. The [Messenger results](https://iopscience.iop.org/article/10.3847/1538-3881/aa5be2) from 2017 show a measured total precession rate for Mercury of 575.31"/cy, with the largest contribuitons due to perturbations from Venus, Jupiter and Earth/Moon. The GR contribution is 43"/cy, as given in your answer. You should check your source for the precession data.  
> **username_3**: This [question](https://physics.stackexchange.com/questions/26408/what-did-general-relativity-clarify-about-mercury) and its answers likely explain the ~10X difference in values for perihelion precession of Mercury noted in my previous comment. Apparently some older sources added a contribution from precession of the Earth's axis, now called general precession in longitude. I don't know why change in Earth's axis was included in Mercury's orbital precession. These measurements were made from Earth, but corrections for general precession are well known, and unrelated to Mercury's orbit.  
> **username_4**: I don't know much about it, but wouldn't GR [frame dragging](https://en.wikipedia.org/wiki/Frame-dragging) result in a tiny difference between prograde and retrograde precession?  
> **username_2**: Probably, but frame dragging is not the cause of the discrepancy  
> **username_0**: Is space dragging the same as space curvature....it seems it is not?Dragging seems something like action-reaction Newton law.  
> **username_2**: Frame dragging is a feature of General relativity, I'm not going to try to explain further here.  Read the wikipedia article.  

---

