On Friday, August 23, 2019 at 8:12:55 PM UTC-6, Lawrence Crowell wrote: > > On Friday, August 23, 2019 at 9:01:42 PM UTC-5, Alan Grayson wrote: >> >> >> >> On Friday, August 23, 2019 at 7:48:19 PM UTC-6, Lawrence Crowell wrote: >>> >>> 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 >>> >> >> If, using E=mc^2, one computes the rest energy of the material Earth, it >> seems implausible that this equals the negative potential energy of the >> Earth's gravitational field, to yield a net energy sum of zero. AG >> > > Consider the gravitation with expansion and cosmological constant. This > was first pointed out by Tolman many decades ago. > > LC >
If you're referring to the conjecture or alleged "fact" that the net energy of the Cosmos is zero, that concept, whatever its status, arose long before cosmologists became convinced in the existence of dark energy, which is thought to account for 73% of all energy in the Cosmos. Assuming dark energy exists, how does this fit in with the conjecture or alleged "fact" that the net energy of the Cosmic is exactly zero? AG -- 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/c04ed84b-3b65-4c61-95e1-4fdf0c2a70a7%40googlegroups.com.
