Conceptual problem

Relativity theory asserts that there is no preferred frame of reference.

But...

What else is the Cosmic Microwave Background (CMB) radiation?

Doesn't this radiation give an universal frame of reference of a
frame that will be always at rest by definition?

If I accelerate in some direction, the CMB will be bluer in that
direction and redder in the opposite direction isn't it?

So I can detect movement respective to that absolute frame
of reference...

Where do I go wrong?

Thanks in advance for your help.

[Mod. note: that's not what 'preferred' means; local physics is not
different in a frame at rest wrt the CMB. This is a FAQ, see
http://www.astro.ubc.ca/people/scott/faq_basic.html -- mjh]

--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique
http://www.cs.virginia.edu/~lcc-win32