« on: 14/06/2021 21:12:23 »
OK, I know what you mean by geodesically complete now. I think that mathematically one can see CMB radiation in the direction of a black hole. The thing formed at some point, and a steady stream of CMB light was suddenly severed, but the trailing end of it is still coming at us, just like you never stop seeing a light dropped into a black hole. From a distance, yes, it is insanely redshifted, but it's there. Just food for thought. Not suggesting that means there's isotropy in any frame. If I look at the CMB in the direction of a distant black hole, I will very much notice the distortion there regardless of my motion. The CMB will not be isotropic.
However A FRW universe is NOT one with lumps in it, it is one where there is a homogeneous cosmological fluid.So the standard model is wrong because it disallows rocks? I would say it simply doesn't attempt to describe local details.
Halc was unduly concerned that a CMB frame allows for some universal ordering of all events throughout the universe.That wasn't my concern at all. My observation was that no known coordinate system orders all events, covering both large scale (events outside our event horizon) and local variations (lumps as you put it). This seems to be a problem in need of solving by any metaphysical assertion of there being a preferred ordering of events. It is of no actual concern to me because I propose no such metaphysical premise.
Any co-ordinate system specifies events with co-ordinates and (as Halc implied) you can choose to look at the time co-ordinate as a number and order the events according to that number, if you wish.Not any coordinate system. One one that defines a coordinate to both events being compared.
There's no reason why you should do thisTotally agree, but not everybody does. I'm currently conversing with someone who very much cannot even conceive of a universe where there isn't a co-ordinate system that is truthful to the exclusion of all others.
the existence of the CMB frame is interesting but it doesn't break special relativity.SR is a local theory, so the CMB is irrelevant to it. If SR is to be applied to the universe as a whole (as occurs if one approaches the zero-energy-density limit of the FLRW model), then one prediction that follows is a lack of CMB. Hence the demise of the Milne solution which proposed just that: SR for large scales and GR only for local variances.
I have no doubt that students of special relativity were taught that SR prevents us from identifying one inertial reference as being preferred over anotherOnly in Minkowskian spacetime, and the universe at large scales is apparently not Minkowskian. So all one needs to do is a non-local test.
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