On Sat, 14 Sep 2019 at 22:57, Jason Resch <[email protected]> wrote:
> > > On Sat, Sep 14, 2019, 2:44 AM Alan Grayson <[email protected]> wrote: > >> >> >> On Saturday, September 14, 2019 at 12:34:18 AM UTC-6, Jason wrote: >>> >>> >>> >>> On Friday, September 13, 2019, Alan Grayson <[email protected]> wrote: >>> >>>> >>>> >>>> On Friday, September 13, 2019 at 4:42:00 PM UTC-6, Jason wrote: >>>>> >>>>> >>>>> >>>>> On Fri, Sep 13, 2019 at 8:25 AM Alan Grayson <[email protected]> >>>>> wrote: >>>>> >>>>>> >>>>>> >>>>>> On Friday, September 13, 2019 at 5:24:11 AM UTC-6, Bruno Marchal >>>>>> wrote: >>>>>>> >>>>>>> >>>>>>> On 13 Sep 2019, at 04:26, Alan Grayson <[email protected]> wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Thursday, September 12, 2019 at 11:01:54 AM UTC-6, Alan Grayson >>>>>>> wrote: >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Thursday, September 12, 2019 at 7:45:22 AM UTC-6, Lawrence >>>>>>>> Crowell wrote: >>>>>>>>> >>>>>>>>> On Thursday, September 12, 2019 at 4:20:46 AM UTC-5, Philip Thrift >>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On Wednesday, September 11, 2019 at 11:45:41 PM UTC-5, Alan >>>>>>>>>> Grayson wrote: >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/ >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Many Worlds is where people go to escape from one world of >>>>>>>>>> quantum-stochastic processes. They are like vampires, but instead of >>>>>>>>>> running away from sunbeams, are running away from probabilities. >>>>>>>>>> >>>>>>>>>> @philipthrift >>>>>>>>>> >>>>>>>>> >>>>>>>>> This assessment is not entirely fair. Carroll and Sebens have a >>>>>>>>> paper on how supposedly the Born rule can be derived from MWI I have >>>>>>>>> yet >>>>>>>>> to read their paper, but given the newsiness of this I might get to >>>>>>>>> it. One >>>>>>>>> advantage that MWI does have is that it splits the world as a sort of >>>>>>>>> quantum frame dragging that is nonlocal. This nonlocal property might >>>>>>>>> be >>>>>>>>> useful for working with quantum gravity, >>>>>>>>> >>>>>>>>> I worked a proof of a theorem, which may not be complete >>>>>>>>> unfortunately, where the two sets of quantum interpretations that >>>>>>>>> are ψ-epistemic and those that are ψ-ontological are not decidable. >>>>>>>>> There >>>>>>>>> is no decision procedure which can prove QM holds either way. The >>>>>>>>> proof is >>>>>>>>> set with nonlocal hidden variables over the projective rays of the >>>>>>>>> state >>>>>>>>> space. In effect there is an uncertainty in whether the hidden >>>>>>>>> variables >>>>>>>>> localize extant quantities, say with ψ-ontology, or whether this >>>>>>>>> localization is the generation of information in a local context from >>>>>>>>> quantum nonlocality that is not extant, such as with >>>>>>>>> ψ-epistemology. Quantum interprertations are then auxiliary >>>>>>>>> physical axioms or postulates. MWI and within the framework of what >>>>>>>>> Carrol >>>>>>>>> and Sebens has done this is a ψ-ontology, and this defines the >>>>>>>>> Born rule. If I am right the degree of ψ-epistemontic nature is >>>>>>>>> mixed. So the intriguing question we can address is the nature of the >>>>>>>>> Born >>>>>>>>> rule and its tie into the auxiliary postulates of quantum >>>>>>>>> interpretations. >>>>>>>>> Can a similar demonstration be made for the Born rule within QuBism, >>>>>>>>> which >>>>>>>>> is what might be called the dialectic opposite of MWI? >>>>>>>>> >>>>>>>>> To take MWI as something literal, as opposed to maybe a working >>>>>>>>> system to understand QM foundations, is maybe taking things too far. >>>>>>>>> However, it is a part of some open questions concerning the >>>>>>>>> fundamentals of >>>>>>>>> QM. If MWI, and more generally postulates of quantum >>>>>>>>> interpretations, are connected to the Born rule it makes for some >>>>>>>>> interesting things to think about. >>>>>>>>> >>>>>>>>> LC >>>>>>>>> >>>>>>>> >>>>>>>> If you read the link, it's pretty obvious that Carroll believes the >>>>>>>> many worlds of the MWI, literally exist. AG >>>>>>>> >>>>>>> >>>>>>> Carroll also believes that IF the universe is infinite, then there >>>>>>> must exist exact copies of universes and ourselves. This is frequently >>>>>>> claimed by the MWI true believers, but never, AFAICT, proven, or even >>>>>>> plausibly argued. >>>>>>> >>>>>>> >>>>>>> The idea comes from Tegmark, and I agree with you, it necessitate >>>>>>> more than an infinite universe. It requires also some assumption of >>>>>>> homogeneity. >>>>>>> >>>>>> >>>>>> Our universe is, on a large scale, homogeneous. But it can't be >>>>>> infinite since it has only been expanding for finite time, 13.8 BY. I >>>>>> had a >>>>>> discussion with Brent about this some time ago, and he claimed finite in >>>>>> time doesn't preclude infinite in space. I strongly disagree. Perhaps I >>>>>> am >>>>>> missing something. Wouldn't be the first time. AG >>>>>> >>>>> >>>>> I think what you may be missing is that in popular (but misleading) >>>>> accounts of the BB they often say everything originated from a point, >>>>> rather than everywhere at once. To say "everything came from a point" is >>>>> at best only valid for describing the observable universe (or any finite >>>>> portion of the universe) but is invalid to extrapolate it to the whole >>>>> universe, which may be spatially infinite. >>>>> >>>> >>>> I am not assuming our universe began from a mathematical point, but I >>>> do assume that 13.8 BYA it was very very small, the observable and >>>> unobservable parts. >>>> >>> >>> Why do you assume this? Most cosmologists make no such assumption. >>> Under the concordance (standard assumed) model of cosmology, space is >>> infinite. >>> >> >> If the universe is expanding, it had to be smaller in the past. >> > > Things were closer together in the past. It's more accurate to think of > the situation as distances stretching rather than the universe expanding. > Because if the universe is infinite then technically speaking it isn't > expanding in size. Yet whether finite it infinite, things in it are growing > apart. It is as if the space inside was self-reproducing. > > If it has been expanding for finite time, its spatial extent must be >> finite, >> > > If the universe is finite now it's always been finite. If it's infinite > now it's always been infinite. It is true it cannot jump from finite to > infinite. The question is what was it's size at the start. This is an open > question. > Unless it was finite in size and infinitely dense and at some point it expanded infinitely fast. > like a huge hypersphere. All the models I see pictorially illustrated, >> have it much much smaller than it presently is. AG >> > > The hypersphere model is a good demonstration of the mechanics of > expansion, but whether the universe is a finite hypersphere, an infinite > flat space, or an outwardly curved infinite space is unknown. Our > measurements suggest space is flat to within 0.4%. This implies it would > have had to be much flatter in the past. That suggests that the universe > is much larger than the observable part, and the extreme flatness is one of > the problems inflation solves. The question of "the shape of the universe" > is the very question if the spatial geometry, is it a hypersphere, flat, or > saddle shaped? This is another unknown, but the working assumption if the > standard cosmological model is that it is flat. > > > >>>> I don't think there is an implied disconnect between our measurements >>>> of the CMBR and what an observer would measure in parts we have no access >>>> to. It was everywhere hot and dense, and very very small. >>>> >>> >>> There's no observational motivation for the universe being very very >>> small at the beginning. It could have been small, large or infinite, for >>> all we know. >>> >> >> It was opaque just before 380,000 years, when the CMBR emerged, precisely >> because it was hugely hot and dense, so much so that light could get out. >> Is this not observational evidence? AG >> > > The universe becoming transparent at 380,000 years is strongly confirmed, > we can see it. We can confirm through observation our ideas concerning a > much hotter earlier phase up to about one second, which confirms among > other things the fraction of the primordial elements. > > Going back further things get less certain since we can't tie our > predictions to observations, and eventually our theories break down as the > temperatures would approach "absolute hot" and the blackbody photons become > so energetic that their wavelength would be less than a Planck length and > anything they touch recieves so much energy it becomes a black hole. To go > beyond this time we would need a quantum theory of gravity. > > But practicality all cosmologists think it is an over extrapolation to > reach the singularity at time zero (they don't think that happened). > > That the universe eventually fell below 3000 degrees (at time 380,000 > years) and became transparent, while in evidence, implies nothing of the > universe's size. Only that it has been cooling as a result of space > expanding. A particle collision between two particles being separated by a > growing space will each bounce away with less energy, just like gas > particles hitting the wall if an expanding piston. > > >>> >>>> If it were infinite at that time, its temperature would have been near >>>> absolute zero. AG >>>> >>> >>> I think you're working under the assumption that some finite amount of >>> energy was injected into space at one particular point. This is not what >>> the big bang theory says, rather all space (everywhere there was space), >>> was equally hot and dense. >>> >> >> I am not assuming what you allege. >> > > Okay. > > Yes, all space was hot and dense, but much smaller in spatial extent than >> today. Just play the movie backward. AG >> > > It's more correct to say things were closer together in the past than to > say anything of the universe's size. Because to extrapolate from average > closeness to size only works in the case of a finite universe. > > I invite you to try playing the movie backwards for an infinite universe. > If things get closer rewinding the clock, it's still infinite. Cut the > "scale factor" in half as many times as you like and the size would remain > infinite. > > > >>> Inflation modifies the picture a bit where the vacuum of space expands >>> rapidly due to its high energy density (which suggests a negative >>> pressure). Under the equations of GR, such a state would expand itself >>> exponentially. Eventually parts of this vacuum decay to a lower energy >>> density, and this dump of energy into space gives us the early hot stage of >>> the big bang. >>> >>> We don't know how big this initial inflating space was, but if inflation >>> is right, most of the universe is still experiencing exponential growth. >>> >>> Each pocket universe may be finite in volume, but extends infinitely in >>> the time direction. >>> >> >> Then why is there general agreement that the age of our bubble is 13.8 BY? >> > > That time (13.8 BY) can now be viewed as the time since inflation ended > (in our pocket). But we don't know how long it's been since inflation > started. It is believed to have started a finite time ago, but we can't say > when. > > In the video with Guth, he draws a series of concentric parabola shapes, > each one is a successive "now" for observers in the pocket. The length of > those lines is infinite because they curve upwards borrowing their extent > into the future time dimension, but to observers within that distance is > perceived as spatial. > > >> >>> As Alan Guth explains, GR can warp things in the internal view of each >>> pocket universe such that the time and space dimensions flip, the infinite >>> time dimension within the pocket universe can give rise to the appearance >>> of infinite space, and the finite space appears as finite time: >>> >>> https://youtu.be/rfeJhzPq3jQ >>> >> >> Time might, and probably does extend into an infinite future, but not >> into an infinite past. Otherwise, cosmologists wouldn't agree that the age >> of our bubble is 13.8 BY. What do you think that *measurement* means? AG >> > > I agree with that. There's strong evidence for our pocket being 13.8 BY > old, and arguments exist for why the universe should not be past eternal. > > Jason > > -- > 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/CA%2BBCJUjvW5pQ7v4Ex490SfUFOcBeUF5EJkxQzsVYyFHXgHmbXQ%40mail.gmail.com > <https://groups.google.com/d/msgid/everything-list/CA%2BBCJUjvW5pQ7v4Ex490SfUFOcBeUF5EJkxQzsVYyFHXgHmbXQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- Stathis Papaioannou -- 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]. 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