Is There Such A Thing As Absolute Rotation?

[John-Francis]

My understanding of General Relativity is that there are no absolute frames of reference and therefore all rotation is relative. Is this in conflict with the quantized rotation that occurs with superfluid helim4?

[jim360]

No.

The precise statement of Relativity is that inertial frames, those in which an observer is not accelerating, are all relative to each other by the Lorentz transformations. However rotation is not inertial -- in particular a frame rotating at any speed would at some point away from the origin be rotating faster than the speed of light -- so that rotation isn't magicked away by Relativity.

This isn't to say that you can't do rotation or acceleration in special relativity, it's more that you can't make them disappear. An object is either rotating, or it is not. An object is either accelerating, or it is not. Every inertial observer will agree on this statements, though they may (will) disagree on the actual numbers.

Therefore anyway, rotation (quantised or not) is not at all in conflict with Relativity. The way in which they interact can be interesting, though.

[Khandro]

Possibly.

[John-Francis]

I cannot accept Mark's answer because Einstein clearly regards rotation as relative according to what he calls "the general principle of relativity", see Albert Einstein (1879–1955). Relativity: The Special and General Theory. 1920. Chapter XXIII: Behaviour of Clocks and Measuring Rods on a Rotating Body of Reference. This can be found at, for example, http://www.bartleby.com/173/23.html.
Mark states that at some distant point the speed would be greater than that of light - but this is not what the rotating observer measures because of the contraction of his measuring rods, space being grossly distorted.

[John-Francis]

Sorry to get the nomenclature wrong - by 'Mark' I meant 'Jim360'

[jim360]

The actual measurement of a rotating body is dependent upon one's frame of reference -- yes, dilating of clocks and so on will affect your result. Whether or not a body is rotating is not. So the quantisation of rotation still holds.

A lot depends on what precisely you mean by "conflicts with".

[jomifl]

What Khandro probably means is that if you use Tao as your frame of reference anything is possible, however unlikely.

[jim360]

http://en.wikipedia.org/wiki/Thomas_rotation

Most relevant effect I can find. In most cases relativistic corrections are important but not drastic for atomic energy levels.

[jomifl]

Centripetal force is only apparent when an object is not a rest. As far as I understand it when an objet is at rest it must be at rest relative to something. It can't be that simple can it?