<p>I had a nice long answer all mapped out, then I came across a similar (identical?) question...
refer answer here:
<a href="https://astronomy.stackexchange.com/questions/19592/how-does-the-earths-plane-of-orbit-ecliptic-vary-over-time">How does the earth&#39;s plane of orbit (ecliptic) vary over time?</a></p>

<p>Basically it is changing about 1.4 degrees per 10000 years about now, but that will change chaotically over longer periods.</p>

CC BY-SA 3.0
2018-01-24T07:03:42.643Z
upvoted for welcome, but if upvoted answer already exists, question should be flagged as duplicate.
J. Chomel
CC BY-SA 3.0
2018-01-24T03:05:23.763Z
2018-01-24T03:05:23.763Z
theonetruepath
<blockquote>
<p>How to fix a direction in the context of universe?</p>
</blockquote>
<p>Simple (or not so simple): Use the remote stars, or even better, use the extremely remote quasars. The former is what astronomers have done for centuries, culminating in the <a href="http://adsabs.harvard.edu/full/1986HiA.....7...85K" rel="nofollow noreferrer">Hipparcos Celestial Reference Frame</a>. The latter is what is currently used to define the <a href="https://www.iers.org/IERS/EN/DataProducts/ICRF/ICRF/icrf.html" rel="nofollow noreferrer">International Celestial Reference Frame</a>.</p>
<p>Note very well: The ICRF is not universal. There is no such thing as a universal reference frame thanks to the non-Euclidean nature of space and time. The ICRF does however quite work nicely across the expanse of the solar system.</p>
<br>
<blockquote>
<p>My question is regarding the direction/orientation of earth. Is it a constant with reference to universal parameters?</p>
</blockquote>
<p>No, it is not. The Earth's axis of rotation precesses thanks to gravitational torques by the Moon and the Sun on the Earth's equatorial bulge.</p>

CC BY-SA 3.0
2018-01-25T20:20:41.190Z
2018-01-25T20:20:41.190Z
2020-06-17T09:47:40.653Z
David Hammen
<p>My question is regarding the direction/orientation of earth. Is it a constant with reference to universal parameters?</p>

CC BY-SA 3.0
2018-01-24T12:39:13.313Z
*There is no directional Universal parameter.* Which is quite funny. You can measure the orientation of the Earth to the Mars, to the Sun, to the Galaxy, anything, but you can't measure it to the Universe itself.
peterh
CC BY-SA 3.0
2018-01-24T14:33:20.190Z
I'd argue that this a duplicate because the supposed duplicate asks about the plane of the Earth's orbit rather than the orientation of the Earth's rotation axis, which is what this question asks about. The two should not be conflated.
David Hammen
CC BY-SA 3.0
2018-01-24T15:39:16.160Z
In fact, I'd argue that this is two separate questions, the question raised in the title, and the question raised in the body. The latter question gets into the concept of the Earth's axial precession. The former question gets into the concept of a local pseudo-inertial coordinate system, with "local" meaning "valid across the solar system, including relativistic effects". There are multiple questions about axial precession at this site, but there are only a few about coordinate systems such as the ICRF here.
David Hammen
<universe>
How to fix a Direction in the context of universe?
Varkeyachan KC
# How to fix a Direction in the context of universe?

(Asked by: username_0 on 2018-01-24)

My question is regarding the direction/orientation of earth. Is it a constant with reference to universal parameters?

**Tags:** universe
> **Comments:**
> **username_1**: *There is no directional Universal parameter.* Which is quite funny. You can measure the orientation of the Earth to the Mars, to the Sun, to the Galaxy, anything, but you can't measure it to the Universe itself.  
> **username_2**: I'd argue that this a duplicate because the supposed duplicate asks about the plane of the Earth's orbit rather than the orientation of the Earth's rotation axis, which is what this question asks about. The two should not be conflated.  
> **username_2**: In fact, I'd argue that this is two separate questions, the question raised in the title, and the question raised in the body. The latter question gets into the concept of the Earth's axial precession. The former question gets into the concept of a local pseudo-inertial coordinate system, with "local" meaning "valid across the solar system, including relativistic effects". There are multiple questions about axial precession at this site, but there are only a few about coordinate systems such as the ICRF here.  

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## 2 answers

### Answer by username_3 on 2018-01-24. Score: 1

I had a nice long answer all mapped out, then I came across a similar (identical?) question...
refer answer here:
[How does the earth's plane of orbit (ecliptic) vary over time?](https://astronomy.stackexchange.com/questions/19592/how-does-the-earths-plane-of-orbit-ecliptic-vary-over-time)

Basically it is changing about 1.4 degrees per 10000 years about now, but that will change chaotically over longer periods.

> **Comments:**
> **username_4**: upvoted for welcome, but if upvoted answer already exists, question should be flagged as duplicate.  

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### Answer by username_2 on 2018-01-25. Score: 1

> How to fix a direction in the context of universe?

Simple (or not so simple): Use the remote stars, or even better, use the extremely remote quasars. The former is what astronomers have done for centuries, culminating in the [Hipparcos Celestial Reference Frame](http://adsabs.harvard.edu/full/1986HiA.....7...85K). The latter is what is currently used to define the [International Celestial Reference Frame](https://www.iers.org/IERS/EN/DataProducts/ICRF/ICRF/icrf.html).

Note very well: The ICRF is not universal. There is no such thing as a universal reference frame thanks to the non-Euclidean nature of space and time. The ICRF does however quite work nicely across the expanse of the solar system.

  
> My question is regarding the direction/orientation of earth. Is it a constant with reference to universal parameters?

No, it is not. The Earth's axis of rotation precesses thanks to gravitational torques by the Moon and the Sun on the Earth's equatorial bulge.


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