On Friday, August 23, 2019 at 5:48:13 PM UTC-5, Alan Grayson wrote: > > > > On Friday, August 23, 2019 at 3:31:36 PM UTC-6, Lawrence Crowell wrote: >> >> On Thursday, August 22, 2019 at 12:37:40 AM UTC-5, Alan Grayson wrote: >>> >>> >>> >>> On Wednesday, August 21, 2019 at 7:12:14 PM UTC-6, Alan Grayson wrote: >>>> >>>> >>>> >>>> On Wednesday, August 21, 2019 at 3:13:11 PM UTC-6, Lawrence Crowell >>>> wrote: >>>>> >>>>> On Tuesday, August 20, 2019 at 4:56:23 PM UTC-5, Alan Grayson wrote: >>>>>> >>>>>> https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology >>>>>> >>>>>> Is this a viable theory for avoiding a BB interpreted as a >>>>>> singularity? AG >>>>>> >>>>> >>>>> Penrose proposed a conformal identification of spatial infinity in the >>>>> past and future i^±∞ of FLRW spacetimes. A cosmology expands and in the >>>>> limit time → ∞ it transitions into a new cosmology. The de Sitter vacuum >>>>> is >>>>> not eternally stable, so the idea may have some germ of relevancy. I am >>>>> not >>>>> sure about how this would work with vacuum to vacuum transitions. The >>>>> exponential expansion of the universe is a sort of time dependent >>>>> conformal >>>>> transformation with a small vacuum expectation for the scale field. To >>>>> transition to a new cosmology, say with inflationary expansion, this >>>>> means >>>>> the vacuum expectation is increased. >>>>> >>>>> The overall physics community response to this has been tepid at best. >>>>> There are some possible conflicts with observed data. >>>>> >>>>> LC >>>>> >>>> >>>> FWIW, ISTM that what GR might be indicating about the BB, is that, >>>> insofar as it's a singularity, it couldn't have occurred, and didn't >>>> occur. This is to say the universe didn't become infinitely small in >>>> spatial extent, like a mathematical point, but rather that there was a >>>> maximal finite value of its energy density, hugely high but not infinite. >>>> For this reason I find the cyclic models promising, although, as you >>>> rightly indicate, they're far from complete or bug-free. AG >>>> >>> >>> Which brings up a possibly relevant question: If the total energy of the >>> universe occupied zero spatial volume (the presumed condition of the >>> universe at t=o according to the BB theory), wouldn't that contradict the >>> Uncertainty Principle? AG >>> >> >> The total mass-energy content of the universe is zero. >> >> LC >> > > Is that a provable fact, or something that can be measured? TIA, AG >
It is provable, because in general spacetimes there does not exist a Gaussian surface to define mass. This sets the energy to zero. Think of it as meaning gravitational potential energy as negative is equal in magnitude to positive mass-energy. LC -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/0eada2a9-b5f4-476f-b2a3-cef5a20edbb3%40googlegroups.com.
