On Sun, Sep 15, 2019 at 12:05 PM Alan Grayson <[email protected]> wrote:
> > > On Sunday, September 15, 2019 at 9:58:53 AM UTC-6, Jason wrote: >> >> >> >> On Sun, Sep 15, 2019 at 7:36 AM Alan Grayson <[email protected]> wrote: >> >>> >>> >>> 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]> >>>> 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 >>> >> >> Okay. >> >> >>> >>>> >>>>> >>>>>> >>>>>>> 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 >>> >> >> Alright. Then you also need to clarify which perspective you are using. >> Since the bubble may be finite from the outside, but can appear infinite >> from the inside. >> > > Since there's no way to observe the bubble from the outside, I don't see > this as productive way to analyse the situation. 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.) >>> >> >> Smaller is not implied by the big bang model, only things being >> "previously closer". >> > > True, but if *inflation* is to solve the large scale homogeneity property > of our present universe, which it does, inflation had to occur when the > universe was exceedingly small. See my previous post on this issue. AG > I would make this correction: > True, but if inflation is to solve the large scale homogeneity property of our present universe, which it does, inflation had to occur when the *OBSERVABLE* universe was exceedingly small. See my previous post on this issue. AG > > >> I know many popular accounts of the BB say the universe was once smaller, >> but this is sloppy writing. They are referring to some fixed part of the >> universe being smaller, such as the observable part. But to say the >> universe in total was smaller is to assume one knows if it is infinite or >> finite, open/flat or closed. This is not known, so no accurate account of >> the BB would implicitly assume it to be known. >> >> >>> 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. >>> >> >> But to explain that rather than assuming it, then you need inflation, but >> below you call this "totally speculative". Which is it? >> >> >>> And I don't believe that at 380,000 years it was less dense than our >>> atmosphere (as you earlier alleged). AG >>> >> >> The present density of the universe is about 5 hydrogen atoms per cubic >> meter. At the time of 380,000 years, things were ~1100x closer together >> (the scale factor is ~1/1100) compared to today. This is a simple >> calculation of the temperature difference. If it's 2.73K now, and it was >> 3000K then, then the scale factor growth from then to now is 3000/2.73 = >> 1098. >> >> If each dimension changed by a factor of 1,000, this means the density >> back then would have been 1,000 x 1,000 x 1,000 or a billion times what it >> is now. So instead of 5 hydrogen atoms per cubic meter, you get 5 billion >> hydrogen atoms per cubic meter. This is many many orders of magnitude less >> dense than atmospheric pressure. A cubic meter of air at sea level weighs >> 1.3 kilograms ( https://hypertextbook.com/facts/2000/RachelChu.shtml ). >> Compare this weight to the weight of 5 billion hydrogen atoms. A Hydogen >> atom weighs 1.67 × 10^-24 g, 5 billion of them would get you to 8.37 × >> 10^-18 kilograms. >> >> So I was wrong, it wasn't a billion times less dense, it was closer to a >> billion billion times less dense than the atmosphere. >> >> >>> >>>> >>>>> 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. >>> >> >> The shape (closed, flat, open), depends on how much gravitating stuff is >> in the universe compared to how much anti-gravitating stuff is in the >> universe, and the current expansion rate and density. A closed universe >> implies gravitational attraction wins out in the end and things eventually >> collapse. In a universe where there is more gravitating stuff then anti >> gravitating stuff, the speed of expansion ought to be slowing down. If it >> is slowing down in a way that only after infinite time the expansion rate = >> 0 (loosely analogous to throwing something upwards at exactly the escape >> velocity) then the geometry is flat. But the only way for the universe >> expansion to be accelerating now is if the anti-gravity stuff exceeds the >> gravitating stuff. In this case, (should the condition persist), then the >> universe will not recollapse (can't be closed), nor will it come to a rest >> after infinite time (can't be flat), so the alternative is that it must be >> open. >> > > That's what the books say. But suppose the universe was a spherical > expanding hyperspace at some point in its history, closed, and then the > expansion rate started to increase. Would that closed universe somehow > "tear" and become open? AG > I'm not sure, it is a good question if the shape can evolve over time. Perhaps someone on this list more familiar with GR can answer. > >> >>> Why can't a spherical hyperspace retain its closure if its expansion is >>> accelerating? AG >>> >> >> Mathematically you can of course imagine an ever expanding hypersphere, >> but the reason it is not possible physically is comes down to general >> relativity, which informs of us of a relationship between the spatial >> curvature and the ultimate fate of the universe. So if anti-gravity stuff >> wins out such that the universe expands forever in an accelerating or >> constant rate, then GR requires that the spatial curvature be negative. It >> would not allow for a positive curvature. >> > > I find this rather dubious. Can you show me how GR requires this? AG > It is made clear in the Friedmann equations, which are derived from the field equations of GR: https://en.wikipedia.org/wiki/Friedmann_equations Where they contain a parameter k which is either -1, 0, or 1, corresponding to the curvature of space. The value of k determines how the expansion rate changes over time. Jason > >> >>> >>>> >>>>> 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, >>> >> >> They're more or less a direct consequence of inflation. Inflation is a >> little bit more than totally speculative. I would go so far to saying it >> is at least weakly confirmed. >> >> >>> 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 >>> >> >> The cosmological principle is not a firm rule or law, it is a rule of >> thumb which works under the assumption that the same laws operate >> everywhere and same conditions hold everywhere, and therefore things should >> be roughly the same everywhere. Inflation tells us that at certain scales >> the conditions are not the same everywhere, so we should not expect >> everything to seem homogeneous at those scales. >> > > The same laws must operate everywhere; otherwise we can't do physics. But > obviously, within those laws, whatever they are, different events can occur > in different locations. AG > >> >> 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/c7b2d6c8-41f4-4588-a668-a1ae824a2c06%40googlegroups.com > <https://groups.google.com/d/msgid/everything-list/c7b2d6c8-41f4-4588-a668-a1ae824a2c06%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/CA%2BBCJUjF-JZ6qAJy0MoE1D%2BQegR_dhvACfVuM8%2B-P8VhRi-ASg%40mail.gmail.com.
