On Sunday, September 15, 2019 at 1:01:23 AM UTC-6, Jason wrote: > > > > On Sun, Sep 15, 2019 at 12:02 AM Alan Grayson <[email protected] > <javascript:>> wrote: > >> >> >> On Saturday, September 14, 2019 at 4:34:28 PM UTC-6, Jason wrote: >>> >>> >>> >>> On Sat, Sep 14, 2019 at 3:06 PM Alan Grayson <[email protected]> >>> wrote: >>> >>>> >>>> >>>> On Saturday, September 14, 2019 at 7:46:27 AM UTC-6, Jason wrote: >>>>> >>>>> >>>>> >>>>> On Sat, Sep 14, 2019, 4:36 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. >>>>>>> >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> 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. >>>>>>> >>>>>> >>>>>> I've never read a description of inflation where the universe is >>>>>> described as very large spatially when it initiates. Never. It's always >>>>>> claimed it begins a few Planck durations (10^-43 seconds) after the BB, >>>>>> at >>>>>> which time the spatial diameter is many orders of magnitudes smaller >>>>>> than >>>>>> the diameter of a proton. It then expands to the diameter of the Earth >>>>>> or >>>>>> the Solar System before terminating, all this occuring within the first >>>>>> second after the BB. AG >>>>>> >>>>> >>>>> I think we need to clearly distinguish between three periods, which >>>>> are frequently confused: >>>>> >>>>> 1. "quantum vacuum phase" Size: ??? Time: ??? >>>>> If inflation began as a fluctuation in the vacuum, the vacuum was a >>>>> pre-existing initial condition. We can say nothing of it's size or how >>>>> long >>>>> it has existed. Alternatively, this vacuum may have already been in a >>>>> state of exponential expansion and required no fluctuation to get started. >>>>> >>>>> >>>>> 2. "Inflation start" Size: (min = Planck size, max = ???) Time: (min = >>>>> fraction of second before hot stage of BB, max = finite but otherwise >>>>> unlimited time ago). >>>>> If inflation started as a fluctuation it could have started very >>>>> small, but it would then grow exponentially forever. How big it was when >>>>> it stopped for us we can't say, but we can guess it had to have gone on >>>>> for >>>>> at least 10^-32 seconds to fit with observations. This is only the >>>>> minimum >>>>> time, there's no known upper bound. There's not necessarily any cooling >>>>> during this time as the heat doesn't enter the picture until inflation >>>>> begins to stop somewhere. >>>>> >>>>> 3. "Local inflation end", Size of inflating space: (undefined but ever >>>>> growing), Size of pocket from outside: (finite but growing), Apparent >>>>> size >>>>> of pocket from inside: (finite or infinite depending on shape of the >>>>> universe), Time: 13.8 BY ago. >>>>> >>>>> The "T = 0 of the BB" no longer makes sense in the inflation picture, >>>>> the only place we can begin to speak of absolutes with time is when we >>>>> speak of the local end to inflation in our pocket. >>>>> >>>>> Jason >>>>> >>>> >>>> I'll say it again. One the main reasons to posit inflation is to >>>> explain the observable large scale homogeneity of a universe that is now >>>> NOT causally connected. If the universe was very very tiny when inflation >>>> started, it WAS then causally connected, >>>> >>> >>> The *observable* part of the universe is posited to have once been >>> causally connected to come to thermal equilibrium but not necessarily the >>> entire universe. >>> >> >> OK, but based on our best measurements, we live in a closed, accelerating >> and expanding hypersphere, since the curvature is NOT zero and NOT negative. >> > > Do you have a citation for this? All the estimates I am familiar with > assume a flat or slightly open shape. > > >> I prefer to go with what we think we know, rather than with a model which >> is completely speculative. AG >> > > Which is what? >
I am looking for a citation, but I recall that someone on this thread stated the measured curvature is close to zero, but POSITIVE. AG > > >> >>> >>>> and inflation preserved the homogeneity. This is what Guth was trying >>>> to solve with inflation, among other problems, such as no detectable >>>> monopoles. This entire logic breaks down if one assumes an infinite >>>> universe at the time of inflation. >>>> >>> >>> Correct, using inflation and previous causal connectedness does not >>> produce for homogeneity of temperature to all parts of the universe if the >>> universe is infinite. >>> >> >> So far, as I just stated, our best evidence >> > > There's no evidence either way, as far as I am aware, which is why i is > still considered an open question. If you can point me to some evidence I > would be interested. > > >> does NOT suggest an infinite universe. AG >> > > What are you calling as the universe here? How are you defining it? > I am referring to our bubble, which arose with the BB, and refers to the observable and UNobservable regions (not to the possibly infinite substrate from which it arose). AG > > >> >> >>> At best it can only extend to some finite region of that universe. >>> But once you are working in an inflationary model, you already have >>> accepted there is a large scale where the universe is not homogenous >>> (pocket regions vs. the rapidly inflating regions of vacuum). >>> >> >> I don't see why assuming inflation implies acceptance of large parts of >> the UNobservable universe which is NOT homogeneous. AG >> > > Because decay events of the vacuum do not happen everywhere at once, this > leads to isolated "pocket universes" separated by exponentially expanding > space. The inhomogenity I am referring to are the different parts of the > vacuum in different energy states. > > >> >>> >>>> In this case, the infinite universe was always homogeneous even though >>>> it was never causally connected. >>>> >>> >>> That is another possibility that avoids inflation as an explanation of >>> homogeneity: To simply assume everything at all places began at the same >>> temperature and density. >>> >> >> If so, why did Guth think homogeneity needed an explanation? On its face, >> thermal equilibrium for a non causally connected universe seems improbable. >> AG >> > > It came for free, with the other explanations. On its own, I am not sure > it would be justified to trade one assumption for another, but inflation > replaced 4 or 5 assumptions with a single one, which is its main strength. > > >> >>> >>>> Further, how could it have been so hot 380,000 years after the BB if it >>>> wasn't dense at that time? >>>> >>> >>> Actually the universe was not very dense at the time of 380,000 years. >>> It was billions of times more sparse than Earth's atmosphere. Each time >>> the scale factor >>> <https://en.wikipedia.org/wiki/Scale_factor_(cosmology)> halves going >>> backwards in time, the temperature doubles, and the density increases by a >>> factor of 8 (2 cubed). You can follows this backwards at least until the >>> temperature is about 10^27 K, far far hotter and denser than 380,000 years, >>> back to a time just a fraction of a second after inflation ended. >>> >> >> Yes, it was far hotter and denser just after the BB, than at 380,000 >> years. >> > > Okay. > > >> But contrary to what you allege above and below, it must have far hotter >> and denser at 380,000 years, than it is today, 2.7 deg K, so hot and dense >> that it was opaque to light. >> > > I'm not sure how this is contrary to what I say above and below... I > agree it was hotter and denser the farther back you go. > And smaller as well? (BTW, "smaller" can't be a property of a spatially infinite universe.) It had to have gotten smaller to explain its present homogeneity. I want to avoid the assumption that homogeneity can arise spontaneously in a causally DIS-connected universe, the one we observe. And I don't believe that at 380,000 years it was less dense than our atmosphere (as you earlier alleged). AG > > >> I am just saying that it does seem to be cooling as it expands, >> > > Yes. > > >> and the curvature data seems to imply smallness just after the BB. >> > > What curvature data are you referring to? The latest Planck data say the > curvature is flat to within the limits of our measurement accuracy. Is > there a new result that indicates positive curvature? > "Flat" means curvature is exactly zero; that is, flat like a Euclidean plane. But if we measure slightly positive, which I think is the case, it must be a closed hyperspace, but HUGE. Physicists tend to equate "almost flat", which if true would mean a huge spherical hyperspace, with Euclidean flat. This is a persistent error. AG What I don't understand is why, a universe with accelerating expansion, must be open, like a saddle. Why can't a spherical hyperspace retain its closure if its expansion is accelerating? AG > > >> Moreover, applying the Cosmological principle, it couldn't have been >> homogeneous on large scale in the finite observable region, and at the same >> time infinite and non-homogeneous in regions we can't observe. AG >> > > It all comes down to scale. At the scale of stars or galaxies, the > universe is non homogeneous, on the scale of super clusters and above it > is, but at larger scales of inflating vacuums and pocket universes, again > it is non homogeneous, but perhaps if you zoom out far enough the picture > becomes homogeneous again. The non-homogeneous part I am referring to can > be seen as the spiky image, a rendering of eternal inflation: > https://www.preposterousuniverse.com/blog/2011/10/21/the-eternally-existing-self-reproducing-frequently-puzzling-inflationary-universe/ > I would forget about inflating vacuums and pocket universes, which are totally speculative, and focus on what we can observe -- which, on a large scale, is homogeneous. Why trash the Cosmological Principle by appealig to unobservable phenomena? AG > > Jason > > >> >>> >>>> An infinite universe right after the BB would be COOL, >>>> >>> >>> Right after inflation predicts it could have been as high as 10^27 >>> degrees. >>> Our observations agree with our theory which predicts at about 1 second >>> it was 10s of billions of degrees, falling to 10s of millions of degrees >>> after 20 minutes. >>> At 380,000 years the temperature was about 3000 degrees. >>> At 13.8 billion years it is about 2.7 degrees. >>> >>> From: http://kias.dyndns.org/astrophys/cosmology.html >>> eventtemperature (K)scale factornow / scale factorthentime >>> strong forces freeze out 1027 3.7 * 1026 10-35 s >>> weak forces freeze out 1015 3.7 * 1014 10-10 s >>> protons, neutrons freeze out 1013 3.7 * 1012 0.0001 s >>> neutrinos <http://kias.dyndns.org/astrophys/particles.html> decouple 3 >>> * 1010 1.1 * 1010 1 s >>> electrons freeze out 6 * 109 2.2 * 109 100 s >>> primordial 2H, 4He form 9 * 108 3.3 * 108 2-15 minutes >>> >>> eventtemperature (K)scale factornow / scale factorthentime >>> photons decouple, atoms form 3000 1091 377000 years >>> first stars 60 10.4 109 years >>> today 2.73 1 1.378 * 1010 years >>> >>> and COOLER after 380,000 years had elapsed. All of the foregoing makes a >>>> decent case for a universe which was very very tiny right after the BB. AG >>>> >>> >>> I still see no connection between the temperature at time 380,000 years, >>> and the size of the universe. Can you do more to explain more why you >>> think there is a relation? I can see how you might relate the initial >>> temperature and density at an earlier time to the temperature and density >>> after 380,000 years, but I am not seeing how you relate the size of the >>> universe to either the temperature or density at time 380,000 years. >>> >>> 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] <javascript:>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/everything-list/666ba0a0-918d-422f-b2ed-f0ded39b82b1%40googlegroups.com >> >> <https://groups.google.com/d/msgid/everything-list/666ba0a0-918d-422f-b2ed-f0ded39b82b1%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- 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/95606ef1-f586-4a26-86da-4e9c3ff7b8ef%40googlegroups.com.
