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A quasar, too heavy to be true
In article , Gary
Harnagel writes: Yes, he was a priest, but, unlike some other scientists who are Christian (i.e., Christian scientists, not necessarily Christian Scientists), such as Don Page, he managed to keep the two areas separate. I didn't realize that about Don Page, or much about him at all. From this little treatise: http://www.preposterousuniverse.com/...and-cosmology/ One Bob Zannelli responded, "Don Page is a first rate cosmologist, and a very nice guy to boot. He is scrupulously honest and while I reject his evangelical Christianity I have great respect for him." I don't understand your denigration of him. As my history teacher used to say, just an observation, not a judgement. The point is that his belief does affect his science. He believes "that the universe was created by a...personal God...who relates to it as His creation" who also may have created "new heavens and new earth for us after death". (Quotation is from The Philosophy of Cosmology, edited by K. Chamcham, J. Silk, J. D. Barrow, and S. Saunders (Cambridge University Press), 2017.) This is not something he said in a pub, but something he wrote in a cosmology book. Because the Schwarzschild radius, as I already mentioned, applies in an asymptotically flat spacetime. That does not describe the universe. Well, that flat claim of yours doesn't agree with observation: https://en.wikipedia.org/wiki/Flatness_problem The flatness problem (about which I have written an entire paper) refers to the spatial flatness of the universe on large scales, not to Minkowski space (which is what the black hole is embedded in). You are confusing two different uses of "flat" here. (Again, maybe the moderator can insert some standard explanation here.) [[Mod. note -- There are three distinct concepts involved he (a) *Spacetime* as a whole can be flat, i.e., it's the Minkowski spacetime of special relativity, where the 4-dimensional spacetime Riemann tensor is zero. (b) A spacetime can be *asymptotically flat*, which means that there's a region "far away" where the gravitational field is small. This provides a setting to mathematically formalize such concepts as gravitational radiation, black holes, and measurements of gravitational radiation far away from its sources. (c) A spacetime (which may be non-flat) may be *spatially flat*, i.e., its 3-dimensional t=constant "spatial slices" (roughly speaking, these represent "all of space at a moment in time") may be flat (3-dimensional *spatial* Riemann tensor is zero). Such a spacetime may still have 4-dimensional spacetime curvature. A Venn diagram would show (a) as a single point, and (b) and (c) as partially overlapping regions (whose overlap contains (a)), within the larger region of all spacetimes. In the context of cosmology the universe in which we live is (c) to within experimental error. It is not (a) or (b). However, for astrophysics purposes other than cosmology (e.g., studying black holes and/or gravitational waves emitted by sources other than the big bang itself), it's a very very *very* good approximation to treat the universe as (b). I'll say a bit more about this approximation in a separate posting. -- jt]] Of course, this ASSUMES that the FLRW metric describes our universe. All observations suggest that out universe is well described by the FLRW metric. Since, as Don Page pointed out in the link given above, "We simply do not know whether or not our universe had a beginning." What actually happened at the beginning, if there was one, is a different question. My belief system says that it didn't. And I reject the "bounce" model, too. IOW, "big bangs" happen repeatedly without bouncing. In such a universe (multiverse?) curvature is only a "local" phenomenon. Science is not about belief. |
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