Not buying it. If the answer were that simple, then either Einstein or Mach would have had to have been an idiot for not seeing it.
No, that’s a double False Dilemma.
Firstly Einstein was a human being, not a god. He could be both not-an-idiot and not understand something, just like any other human being. Your choice between “It’s wrong or Einstein was an idiot” is thus clearly a False Dilemma.
Secondly, even if Einstein did see it, you assume it was pertinent to his argument, which is unwarranted. Einstein and Mach may have been arguing a purely philosophical point. They may have been arguing a scientific issue that you have misunderstood and misrepresented in this thread. Even* if *we accept the False Dilemma that Einstein had to be an idiot not to see my point, there are a great many other options than “If your argument is so good Einstein would have used it/refuted it”. So a double False Dilemma.
But if your sole point is that I must be wrong because someone else “smarter” than me disagrees, that’s not convincing. These aren’t complicated and esoteric points I’m raising. It’s basic logic. An argument from authority carries no weight.
Either you can rebut my points or all you are saying is “No it isn’t”. And that’s not an argument.
So, can you actually address my position above:
If the cosmos consists of a single mass and some method that allows rotation to be detected, then it must be possible to detect whether it rotates. And if it is possible to detect whether it rotates, then there can be no argument over whether it rotates. It either does or it does not. It can only be possible to argue this if there is no way to detect whether it rotates.
Do you agree or disagree with that statement? And if you disagree, which part do you disagree with?
The question of whether rotation is relative or absolute is an old one, dating back at least to the Leibniz/Newton debates on the question of absolute vs. relative space/motion. Basically, the issue is wheter rotation as a property is innate, or intrinsic, or relational, that is, only definable with respect to some auxiliary reference frame/system of coordinates/background space/matter distribution etc.
Pointing here to the material developments if something were put into spinning motion in the actual universe puts the cart before the horse: yes, in every concrete situation, a state of affairs might develop such that rotation can be detected, say through the splitting off some distribution of mass, etc. But this is compatible with both possibilities: if rotation is relational, then the splitting just introduced a reference with which to define the rotation; if it is intrinsic, then the splitting has just introduced the necessary means of ascertaining the presence of what was there all along.
The question itself is logically prior to the behaviour of matter. And yes, it’s a philosophical issue, albeit one that can, and has, guided the formulation of scientific theories, such as General Relativity or the more recent Shape Dynamics, which was expressly conceived to fully implement Mach’s principle regarding the relativity of motion. Both theories are, in fact, locally indistinguishable, though only the latter is ‘fully Machian’: thus, nothing you can do locally can settle the issue, and any global experiment of course again runs into the problem of necessarily involving more than one frame of reference.
There are as I understand it four conserved quantities, and as best we can measure it looks all four of them net to zero, the last of which is angular momentum. I would interpret that as implying the universe as a whole does not rotate.
How do they measure the rotation of a point-like object (electron) and the rotation of a hairless beast (black hole)?
I have acknowledged this possibility several times.
Nope; I’ll stand by it. If the answer were so very simple as you make it out, Einstein and Mach would easily have seen it. Also, if you can say, “That’s not convincing,” then I can say “That’s not convincing.”
I disagree with your statement; the final conclusion does not follow from the premises. The debate is also entirely possible if it is not known whether or not there is a way to detect rotation.
Is it known whether or not there is a method to detect rotation? Einstein and Mach seem to have been debating that. Specifically, they were debating the outcome of an experiment which it is, quite obviously, impossible to perform.
I only note that others, who know far more than I ever can about physics, have had a disagreement over rotation of objects in an otherwise empty universe, and that there was, for a time, a significant debate over it. I do not remember who took which side in the debate, and I do not know if the debate is still ongoing or if it has been settled.
Half Man Half Wit: Thank you! As always, you bring greater depth to a physics discussion, and much more detailed knowledge, at least, than I have.
Frank Merton: According to the Bad Astronomer, the entire universe could rotate. It’s possible to model the universe that way, and there aren’t any glaring impossibilities. The rotation could be of any magnitude, and about any point. The mathematical description of such a universe is insanely complicated, and there simply isn’t any point for it. But there’s no proof it isn’t true.