Is there anything in astronomical terms which isn't rotating? Is the universe rotating? (round what?)?

Question

Would it be possible to detect whether local galaxy clusters are rotating on the short timescale we've been looking? Why is rotation so common (the norm?)

Answer 1

"Rotation" implies "around something". It would be difficult to say if the Universe is rotating if we have no outside reference (and, right now, we don't).

It is possible to detect the motion of individual galaxies within clusters and, from that, establish if there is a trend of movement around some axis. This is done with doppler shift (giving us instantaneous radial velocity). Using statistical analysis -- and other hints such as the distribution of visible matter -- we can "guess" at an overall movement of the set of stars within the cluster.

Why common? An easy (albeit unfair) answer is: everything moves, yet clusters do survive for some time. Therefore the motion must be such that the individual objects tend to stay within the neighbourhood of the other objects (whatever that means in clusters of galaxies). Overall rotation seems the best explanation.

Actual movement of galaxies within a cluster cannot be seen over such small time intervals (centuries).

Answer 2

Yes, one can determine if local galaxy clusters are rotating by comparing the relative velocities (as measured by the red shift of the stars) between the individual galaxies in the cluster. In general, all bodies in space, when acted on by gravity from other objects, moved in a curved fashion which implies rotation. Planets move around stars; stars move around the center of their galaxies; galaxies move around the center of their local cluster; clusters move around the center of their supercluster.

However, I doubt it would be possible to find one common point of rotation for all objects in the universe (the center of mass of the universe?).

Answer 3

Everything moves, somesthing is always rotating around something. the end