Dr. Barr:
I remember you stating in a previous post (last year) that rotation is absolute in general relativity. This is factually untrue. It is absolute in special relativity. Einstein invented general relativity to solve this issue (relativity of rotation).
We can all make errors.
Mark
Having now read some of your posting history, it seems to me that you are something of a one-trick pony.
Allow me to ask a pressing question unrelated to your favorite topic:
Should gumdrops be illegal in Switzerland or not?
you are absolutely wrong, Mark! All experts in General Relativity would agree that in GR acceleration is an absolute concept. The concept of an "inertial frame" is a crucial one in GR. An inertial frame is a non-accelerating frame. One can tell by local measurements whether one is in an inertial frame or not. This is non-controversial. Anyone who knows GR understands this. It is true that Einstein was led to GR by Machian ideas, and according to Mach's ideas acceleration is relative. But it is generally agreed by that the theory Einstein actually came up with is NOT Machian. Though he was inspired by Mach's ideas, Einstein's theory does not actually realize Mach's principle of the relativity of acceleration.