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 says something I found confusing.

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

  • $\begingroup$ You can check EarthScience.SE $\endgroup$ Jul 23, 2022 at 4:27
  • $\begingroup$ Thanks for the suggestion! Should I close this question? $\endgroup$
    – hb12ah
    Jul 23, 2022 at 5:02
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    $\begingroup$ 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. $\endgroup$ Jul 23, 2022 at 5:47
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    $\begingroup$ @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. $\endgroup$ Jul 23, 2022 at 6:53
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    $\begingroup$ I have some info about the stability of the ecliptic and the invariable plane here: 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)". $\endgroup$
    – PM 2Ring
    Jul 23, 2022 at 7:07


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