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 -- 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/e8669a4b-d388-41c7-b6b3-434eb77c4c23%40googlegroups.com.
