On Sunday, August 25, 2019 at 12:21:37 AM UTC-6, Alan Grayson wrote: > > > > On Saturday, August 24, 2019 at 10:16:56 AM UTC-6, Alan Grayson wrote: >> >> >> >> 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 >> > > It's easy to calculate the (negative) potential energy (PE) of an OBJECT > in a gravitation field, but how does one calculate the PE of the field > itself? I've looked on Internet but can't find an answer to this question, > upon which, it seems, the postulate of a zero energy universe rests. AG >
Is the calculation done by simply integrating the energy density over all space containing the gravitational field? 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/0853d847-300b-41d5-b79b-f5cbbbe5c5e2%40googlegroups.com.
