On Friday, August 23, 2019 at 11:32:47 PM UTC-6, Alan Grayson wrote: > > > > On Friday, August 23, 2019 at 11:16:36 PM UTC-6, Alan Grayson wrote: >> >> >> >> 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 >>> >> > Do you have links on this specific topic? TIA, AG > >> >> I will. But maybe in the meantime you could explain how, using E=mc^2 and >> the negative potential energy of Earth's gravity field , you can get them >> to cancel out for an isolated Earth. Something very puzzling here. >> Additionally, ISTM that one would have an impossible task making a nuclear >> weapon from negative potential energy. What am I doing wrong, if anything? >> AG >> > A test particle falling in a gravitational field gains in kinetic energy exactly what it loses in potential energy. However, what matters in this calculation is NOT the value of the potential energy at say two radial points in the falling path, say R2 and R1, but the DIFFERENCE in potential energy between these points. IOW, the potential energy is not well DEFINED as having some specific value. That is, one could add a constant to the potential energy at all points along the falling path and the calculation is unchanged. This is a long winded way of saying that it's a fallacy to add rest energy, calculated by mc^2, and gravitational potential energy, in an attempt to claim the total energy of the universe is exactly zero. Rest energy is well defined, but gravitational potential energy is not. AG
What exactly did Tolman prove many decades ago? Do you have a link to read on this? 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/05c9c448-8c18-4000-8b8e-871e7dc6e43b%40googlegroups.com.
