# Does the universe have a celestial north?

You are away from the Earth in one part of the universe and looking at a galaxy in another part of the universe, then which way is up? Does the universe (or near universe) have a celestial north? If you took a picture of that galaxy, then is there a correct orientation for displaying that photograph?

• Closing this well-received and well-answered question now seems counterproductive; voting to leave open!
– uhoh
Mar 23 at 7:21

No. There is no prefered direction of the universe. The universe is homogenous and isotropic, on the large scale, to the best of our knowledge. This means that there is no "special" location in the universe, and no "special" direction.

There is, therefore, no "correct" orientation for the photograph.

Short answer, no, not like we do for the Earth and solar system.

Longer answer: kinda. The IAU has defined the International Celestial Reference Frame (ICRF). It is the coordinate system used to locate an object in the universe in as near a fixed coordinate system as we can define, based on very distant radio sources. A simplified defintion is the Z axis is aligned with where the Earth's North pole was pointing Jan 1 2000 00:00 UT1. The X axis point to the J2000 ra/dec coordinate 0,0. And the Y axis is perpendicular to both of those.

So this Z axis is the best definition for North or "up" we have.

• The complex geometry of space-time means that the ICRF cannot be transported / patched to remote galaxies. And the ICRF, as this answer suggests, is very geocentric. Mar 20 at 12:41
• Picky detail: The J2000 frame is defined based on the Earth's orientation at noon Terrestrial Time on 1 Jan 2000 rather than Jan 1 2000 00:00 UT1. 12:00:00 TT on 1 Jan 2000 is equivalent to 11:58:55.816 UTC on 1 Jan 2000. Noon Terrestrial Time on 1 Jan 2000 is the J2000 epoch. TT is ahead of TAI by 32.184 seconds, which in turn was ahead of UTC by 32 seconds on 1 Jan 2000. Mar 21 at 11:59

The universe looks close to homogeneous and isotropic, but there are deviations and puzzles. The current puzzle is known as the axis of evil. Some features in the cosmic microwave background, along with a claimed pattern in the rotation axes of distant galaxies, appear to line up with the ecliptic (the plane of Earth's orbit around the Sun). Of course, all the data are taken from Earth or its vicinity, looking through the dust in the ecliptic. The ecliptic geometry also influences space-based observations: you need to look away from both the Earth and the Sun. So, perhaps, this is some sort of observational bias even though the folks who do this put a lot of effort into correcting for such biases.

• It seems clear that any sort of "puzzle" is related to finding where the error in the measurement or interpretation lies. en.wikipedia.org/wiki/Axis_of_evil_(cosmology) readily gives several categories of errors leading to it, and neatly points out that coincidence is also a factor. Occams Razor is abundantly clear here. The universe is not orienting itself along the plane of the Earth orbit.
– AnoE
Mar 21 at 15:31
• @AnoE You are likely correct, but good science requires an open mind. Part of the puzzle is that the galaxy rotation result aligns with the CMB result. Those are subject to different systematics. Mar 21 at 16:50

Maybe.

A study of 200,000 galaxies shows a significant bias in their rotation direction, increasing with redshift, suggesting that the entire early universe was rotating.

Caveat: This was reported in popular media almost two years ago, and I haven't heard any updates.