<p>The frequencies of orbital parameters are available directly from tables in the reference given on your wiki link</p>
<p>See:</p>
<p><a href="https://journals.ametsoc.org/view/journals/atsc/35/12/1520-0469_1978_035_2362_ltvodi_2_0_co_2.xml" rel="nofollow noreferrer">https://journals.ametsoc.org/view/journals/atsc/35/12/1520-0469_1978_035_2362_ltvodi_2_0_co_2.xml</a></p>
<p>These values are sufficient for looking back 1-5M years</p>
<p>It's generally a combination of dominant fixed frequencies and then split frequencies, (ie. cos(a+delta) + cos(a-delta)). And then there is a long tail of smaller amplitude frequencies</p>
<p>Trying to go from the time domain to frequencies with things like Fourier Transform will give you artifacts (as your sampling window can't really be a multiple of all the frequencies of interest) - so avoid doing that  :)</p>
<p>More info is available here:
<a href="https://paleodyn.uni-bremen.de/gl/tmp/Orbital.html" rel="nofollow noreferrer">https://paleodyn.uni-bremen.de/gl/tmp/Orbital.html</a></p>
<p>If you want to look further back in time, then you need to use other more advanced systems b/c it needs to account for things like the mass of icesheets (mass moving poleward) and other details. Small errors over millions of years (and thousands of cycles) will lead to large errors</p>
<p><a href="http://vo.imcce.fr/insola/earth/online/earth/online/index.php" rel="nofollow noreferrer">http://vo.imcce.fr/insola/earth/online/earth/online/index.php</a></p>
<p>But at those time scales you in effect have some frequency modulation going on, and looking at the spectrum won't make much sense</p>

CC BY-SA 4.0
2023-03-01T08:00:28.150Z
2023-03-01T08:33:20.440Z
2023-03-01T08:33:20.440Z
kxygk
<p>The Earth axis changes tilt with a period of 41 000 years, and with an amplitude of 1.2 degrees. What does the spectrum look like? Is it a steady periodic motion, or rather some quasi-periodic phenomenon?</p>
<p>To clarify, I want information about frequency content of plots like this one:</p>
<p><a href="https://i.sstatic.net/eeHys.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/eeHys.png" alt="enter image description here" /></a></p>
<p>Source: <a href="https://en.wikipedia.org/wiki/User:Tfr000#/media/File:Obliquity_berger_0_to_1000000.png" rel="nofollow noreferrer">Wikipedia</a></p>

CC BY-SA 4.0
2023-02-27T15:18:19.577Z
this question fits better over at https://astronomy.stackexchange.com/
trond hansen
<earth-history>
Spectrum of tilt motion of earth axis
user877329
# Spectrum of tilt motion of earth axis

(Asked by: username_0 on 2023-02-26)

The Earth axis changes tilt with a period of 41 000 years, and with an amplitude of 1.2 degrees. What does the spectrum look like? Is it a steady periodic motion, or rather some quasi-periodic phenomenon?

To clarify, I want information about frequency content of plots like this one:

[![enter image description here](https://i.sstatic.net/eeHys.png)](https://i.sstatic.net/eeHys.png)

Source: [Wikipedia](https://en.wikipedia.org/wiki/User:Tfr000#/media/File:Obliquity_berger_0_to_1000000.png)

**Tags:** earth-history

> **Comments:**
> **username_1**: this question fits better over at https://astronomy.stackexchange.com/  

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## 1 answers

### Answer by username_2 on 2023-03-01. Score: 1

The frequencies of orbital parameters are available directly from tables in the reference given on your wiki link

See:

<https://journals.ametsoc.org/view/journals/atsc/35/12/1520-0469_1978_035_2362_ltvodi_2_0_co_2.xml>

These values are sufficient for looking back 1-5M years

It's generally a combination of dominant fixed frequencies and then split frequencies, (ie. cos(a+delta) + cos(a-delta)). And then there is a long tail of smaller amplitude frequencies

Trying to go from the time domain to frequencies with things like Fourier Transform will give you artifacts (as your sampling window can't really be a multiple of all the frequencies of interest) - so avoid doing that :)

More info is available here:
<https://paleodyn.uni-bremen.de/gl/tmp/Orbital.html>

If you want to look further back in time, then you need to use other more advanced systems b/c it needs to account for things like the mass of icesheets (mass moving poleward) and other details. Small errors over millions of years (and thousands of cycles) will lead to large errors

<http://vo.imcce.fr/insola/earth/online/earth/online/index.php>

But at those time scales you in effect have some frequency modulation going on, and looking at the spectrum won't make much sense


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