<p>The axial tilt of the Earth changes its direction due to the influence of other planets, the moon, and the sun.</p>
<p>Nutation is due to the effects of the moon and the sun's gravity, but it is mainly due to the regression of the moon's nodal line during an 18.5-year cycle.</p>
<p>The precession is due to the torque exerted on the earth due to its oblateness from the moon, the sun, and other planets. Its period is about 26000 years.</p>

CC BY-SA 4.0
2024-07-26T02:40:35.380Z
2024-07-26T02:42:58.493Z
2024-07-26T02:42:58.493Z
ChuckM
<p>I have recently learned that the polar axis of Earth moves in a complex fashion. There are both precession and nutation. I have learned that Earth's obliquity varies between 22.1 and 24.5 degrees on a 41,000-year cycle. My questions are:</p>
<ul>
<li><p>What accounts for the change of obliquity in the range of 22.1 to 24.5 degrees besides nutation, which I assume is a relatively high-frequency process consisted of many terms (like a Fourier expansion series)?</p>
</li>
<li><p>Do the ecliptic or the invariant plane of the solar system rotate with respect to the distant stars, and if so, are they responsible for the variation of Earth's obliquity?</p>
</li>
<li><p>Lastly, how should we understand the period of 41,000 years. The <a href="https://en.wikipedia.org/wiki/Axial_tilt" rel="noreferrer">wiki</a> says something I found confusing.</p>
</li>
</ul>
<blockquote>
<p>This cycle is a combination of precession and the largest term in the
motion of the ecliptic</p>
</blockquote>

CC BY-SA 4.0
2022-07-23T04:27:27.840Z
You can check EarthScience.SE
Nilay Ghosh
CC BY-SA 4.0
2022-07-23T05:02:30.270Z
Thanks for the suggestion! Should I close this question?
hb12ah
CC BY-SA 4.0
2022-07-23T05:47:10.793Z
This question is perfectly on-topic here. @NilayGhosh I don't think it's appropriate to make new members double-post - a thing which is definitely not wanted.
planetmaker
CC BY-SA 4.0
2022-07-23T06:53:10.933Z
@planetmaker I am not saying OP to double post. I am suggesting OP that we have a sister site for Earth related topics. OP may check if there is any post on this topic.
Nilay Ghosh
CC BY-SA 4.0
2022-07-23T07:01:02.547Z
@NilayGhosh This question is mainly about the astronomical motions of the Earth, so it's probably mostly suited to this site. Of course, EarthScience.SE should have good info regarding the irregularities of Earth's rotation, but that's on-topic here too, because it impacts every astronomical observation made from Earth's surface.
PM 2Ring
CC BY-SA 4.0
2022-07-23T07:05:15.830Z
However, there are multiple questions here, and although they're related, it might be a good idea to split them up and ask about the wobbles in Earth's axial rotation and in the ecliptic plane  in separate questions.
PM 2Ring
CC BY-SA 4.0
2022-07-23T07:07:08.133Z
I have some info about the stability of the ecliptic and the invariable plane here: https://astronomy.stackexchange.com/a/44412/16685 "the inclination of the ecliptic plane to the invariable plane of the Solar System varies by ~3°, over a very long time scale. The invariable plane itself is very stable relative to the International Celestial Reference Frame (ICRF)".
PM 2Ring
CC BY-SA 4.0
2022-07-23T10:39:59.447Z
@PM2Ring for the link. That was useful. I have removed the duplicated post in EarthScience SE.
hb12ah
CC BY-SA 4.0
2024-07-26T03:32:12.567Z
There is a long history there, this paper covers some of it.  But if you really want a full story, you can dig into the references.  https://www.aanda.org/articles/aa/pdf/2017/01/aa28717-16.pdf
Greg Miller
<solar-system><orbital-mechanics><earths-orbit>
Why does the axis tilt (obliquity) of Earth change over time?
hb12ah
# Why does the axis tilt (obliquity) of Earth change over time?

(Asked by: username_0 on 2022-07-22)

I have recently learned that the polar axis of Earth moves in a complex fashion. There are both precession and nutation. I have learned that Earth's obliquity varies between 22.1 and 24.5 degrees on a 41,000-year cycle. My questions are:

* What accounts for the change of obliquity in the range of 22.1 to 24.5 degrees besides nutation, which I assume is a relatively high-frequency process consisted of many terms (like a Fourier expansion series)?
* Do the ecliptic or the invariant plane of the solar system rotate with respect to the distant stars, and if so, are they responsible for the variation of Earth's obliquity?
* Lastly, how should we understand the period of 41,000 years. The [wiki](https://en.wikipedia.org/wiki/Axial_tilt) says something I found confusing.

> This cycle is a combination of precession and the largest term in the
> motion of the ecliptic

**Tags:** solar-system, orbital-mechanics, earths-orbit

> **Comments:**
> **username_1**: You can check EarthScience.SE  
> **username_0**: Thanks for the suggestion! Should I close this question?  
> **username_2**: This question is perfectly on-topic here. @username_1 I don't think it's appropriate to make new members double-post - a thing which is definitely not wanted.  
> **username_1**: @username_2 I am not saying OP to double post. I am suggesting OP that we have a sister site for Earth related topics. OP may check if there is any post on this topic.  
> **username_3**: @username_1 This question is mainly about the astronomical motions of the Earth, so it's probably mostly suited to this site. Of course, EarthScience.SE should have good info regarding the irregularities of Earth's rotation, but that's on-topic here too, because it impacts every astronomical observation made from Earth's surface.  
> **username_3**: However, there are multiple questions here, and although they're related, it might be a good idea to split them up and ask about the wobbles in Earth's axial rotation and in the ecliptic plane  in separate questions.  
> **username_3**: I have some info about the stability of the ecliptic and the invariable plane here: https://astronomy.stackexchange.com/a/44412/16685 "the inclination of the ecliptic plane to the invariable plane of the Solar System varies by ~3°, over a very long time scale. The invariable plane itself is very stable relative to the International Celestial Reference Frame (ICRF)".  
> **username_0**: @username_3 for the link. That was useful. I have removed the duplicated post in EarthScience SE.  
> **username_4**: There is a long history there, this paper covers some of it.  But if you really want a full story, you can dig into the references.  https://www.aanda.org/articles/aa/pdf/2017/01/aa28717-16.pdf  

---

## 1 answers

### Answer by username_5 on 2024-07-26. Score: 1

The axial tilt of the Earth changes its direction due to the influence of other planets, the moon, and the sun.

Nutation is due to the effects of the moon and the sun's gravity, but it is mainly due to the regression of the moon's nodal line during an 18.5-year cycle.

The precession is due to the torque exerted on the earth due to its oblateness from the moon, the sun, and other planets. Its period is about 26000 years.


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