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

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    $\begingroup$ 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. $\endgroup$ – peterh - Reinstate Monica Jan 24 '18 at 12:39
  • $\begingroup$ 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. $\endgroup$ – David Hammen Jan 24 '18 at 14:33
  • $\begingroup$ 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. $\endgroup$ – David Hammen Jan 24 '18 at 15:39
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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?

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

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    $\begingroup$ upvoted for welcome, but if upvoted answer already exists, question should be flagged as duplicate. $\endgroup$ – J. Chomel Jan 24 '18 at 7:03
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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. The latter is what is currently used to define the International Celestial Reference Frame.

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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