Le dim. 22 sept. 2024, 16:32, Alan Grayson <agrayson2...@gmail.com> a écrit :
> > > On Sunday, September 22, 2024 at 6:32:19 AM UTC-6 John Clark wrote: > > Alan Grayson <agrays...@gmail.com> wrote: > > *>> If you're assuming that at T=0 the ENTIRE universe could be contained > in a sphere of finite size then you're assuming that space is finite, the > very thing you're trying to prove. * > > > *> No. Not assuming that. Since there's universal agreement that our > bubble is expanding, you can always go back in time, to any time, say T = > 10 BY, and put a finite sphere around it.* > > > *But that wouldn't be the entire universe, that wouldn't even be the > entire observable universe, so what would be the point? * > > > You're confused about what I am assuming and concluding. I am saying an > infinite universe is eternal and never had a beginning, whereas a finite > one can be contained within a sufficiently large sphere at any time in its > history. AG > > > *> The question is whether that's the whole universe or just the > observable part,* > > > *We know the observable universe is flat, or at least very nearly flat, > and we know there is no evidence the observable universe is a 3-torus, so > if the observable part of the universe is the only part there is then the > Earth really is the center of the universe. Do you really wanna die on that > hill? * > > *> Apparently, you love spooky action at a distance. * > > > *I love any idea that fits the observational facts, and I don't care if > it's spooky or not. * > > > What observational facts are you referring to? There are none. I posit > that instantaneous expansion to infinity is a type of singularity. So, if > the universe is infinite, it never started and the BB never happened. > Another way of saying this is that an infinite universe is uncreated or > eternal. It never began! This is where the learned physicist from Case > Western got it wrong. He posits that the universe might be infinite, he > doesn't realize that such a possibility contradicts the BB (which he > presumably affirms). AG > > > > *> Dark Energy, like Inflation, hasn't been "discovered".* > > > *Inflation is a theory that may or may not be true, Dark Energy is an > observational fact. Astronomers discovered in 1997 that the universe is > accelerating, and energy is required for something to accelerate, we had to > find a name for whatever is causing that acceleration; "unknown energy" > would've probably been a better name but for some reason "dark energy" is > the name that was picked and we're stuck with that. * > > * > I would conjecture that GR might be able to establish that gravity can > be repulsive and attractive, and their respective influence over time might > change.* > > > *Every physicist who read the astronomer's paper showing that the universe > is accelerating started thinking about changing General Relativity to > explain it, but nobody can make it work. * > > > It's claimed that GR implies the universe could be expanding or > contracting, meaning there are solutions to both situations, that gravity > can be attractive and repulsive. If so, that's probably what we're dealing > with, at the same time. AG > > > > *It would be a great doctoral thesis. AG* > > > *It sure would! It would be the greatest breakthrough in physics since > Einstein, but it's easier said than done. * > > * > Because the universe is huge, our measurements can't distinguish flat > from slightly curved.* > > > *Nobody will ever prove that the universe is absolutely flat because there > is always some measurement error, but the Planck satellite discovered that > the cosmological scale curvature of space is 0.0007 ± 0.0019, and that is > consistent with zero, AKA perfect flatness. If the universe is curved but > it's too small for the Planck satellite to observe then it would have to be > at least 9.3 TRILLION light years in diameter. Please understand that is > just the lower bound, the upper bound is an infinite number of light > years. * > > > It could be that large. Did you pull that number out of a hat? Even though > the universe might be only slightly curved, it has immense implications > concerning finiteness and closure. AG > > > > *>>> I then realized that the unobservable part was very likely caused by > Inflation, and therefore the entire universe would remain finite provided > we ran the clock backward, prior to Inflation. * > > > *>> And as I said before, IF the universe was finite before inflation then > it was finite after it, and IF the universe was infinite before inflation > it was infinite after inflation.* > > > > *You've made this statement before, and I told you I agree. What's the > point in repeating it?* > > > *I repeated that point because you have apparently forgotten that the > question we were discussing is whether the universe is finite or infinite, > and in that context inflation is irrelevant. * > > > I haven't forgotten. Inflation probably issa irrelevant. AG > > > *>> inflation is irrelevant in a finite versus infinite discussion, * > > > *> If the unobservable part came into existence via Inflation we agree > it's finite,* > > > *No we do not agree! If both the transition between non-existence and > existence AND the finite process called "inflation" started at T=0 and > stopped at some unknown time later then: * > > *1) The entire universe is finite if and only if it was finite at T=0 * > *2) The entire universe is infinite if and only if it was infinite at T=0 * > > > I don't quite follow your logic. I disagree that T=0 is a beginning time > for an infinite universe, which IMO has no beginning. That's been my main > point all along, plus the fact that a finite universe cannot be flat since > that implies infinity in spatial extent (torus's excluded). AG > According to the theory of eternal inflation, proposed by cosmologist Alan Guth and others, before the beginning of the inflation of our observable universe, there was a state of eternal inflation. Here's an overview of what that means: 1. Eternal Inflation: This theory suggests that there is a "meta-universe" or multiverse composed of multiple "bubble universes." Inflation never ceased in certain regions of this meta-universe. However, bubbles, like our own observable universe, form when portions of this inflating space stop expanding exponentially and begin to evolve according to the laws of physics as we know them. 2. Before the inflation of our universe: If we follow this idea, before the specific inflation of our universe, there was a continuous inflationary expansion, with quantum fluctuations producing these bubble universes. Our universe would have emerged as one of these bubbles, when inflation in our particular region ended, giving rise to the Big Bang and the development of the universe we observe today. 3. A rapidly expanding vacuum: The state of space before the start of inflation in our bubble would have been a rapidly expanding quantum vacuum, characterized by a high energy density. This vacuum would be unstable, allowing the creation of multiple bubble universes, each with different initial conditions. 4. The role of quantum fluctuations: Quantum fluctuations within this inflationary vacuum would have caused local variations that, in certain regions, halted inflation and gave rise to universes like ours. This means each bubble could have distinct physical properties, potentially leading to universes with different laws of physics. Therefore, before the start of inflation in our observable universe, there would have been a state of continuous inflation within the framework of a global process, constantly creating new bubble universes in an ever-expanding multiverse. In the framework of classical inflation theory, which is a less speculative version than eternal inflation, the idea is simpler and mainly focuses on our observable universe, without invoking a multiverse or bubble universes. Here are the key points: 1. Classical Cosmic Inflation: This theory explains that the early universe went through a phase of extremely rapid expansion, known as "inflation," shortly after the Big Bang. This expansion occurred within a fraction of a second, during which the universe expanded exponentially, increasing its size by an enormous factor. 2. Before Inflation: In classical inflation theory, what happened before inflation is less well understood. It is generally assumed that before inflation, the universe was in a state of very high energy, often described as a "pre-inflationary" phase. This would have been a state where vacuum energy (associated with a hypothetical scalar field called the inflaton field) dominated the universe. 3. A Hot and Dense Universe: Before inflation, the universe was probably extremely hot, dense, and filled with particles, but still very small. Classical theory does not precisely specify what triggered inflation, but it proposes that this unstable vacuum state or inflaton field led to rapid expansion. 4. Phase Transition: Inflation could be related to a phase transition of this scalar field, similar to changes of state in matter (such as water turning into ice). This transition would have released energy, causing the universe to expand exponentially. Once inflation ended, the remaining energy reheated the universe (a process called "reheating"), leading to the Big Bang as we understand it, where the universe began cooling and forming the matter we observe. 5. The Problem of the Initial Singularity: Classical inflation theory doesn't necessarily resolve the question of what existed "before" inflation or before the Big Bang. It doesn't avoid the problem of the initial singularity—the moment when the universe would have been infinitely dense and small, as suggested by traditional Big Bang models. In the context of classical inflation theory, what existed before inflation was a high-energy state, likely related to a scalar field (the inflaton) and a very dense and hot universe. The theory does not describe in detail what preceded this state, and the ultimate origin of the universe remains an unresolved question within this framework. > *And inflation has absolutely positively nothing to do with it. * > > *> Do you believe Euclid's 5th postulate?* > > > *Of course not! It is not true in general, only in the very special case > of a perfectly flat space. If the fifth postulate was correct then General > Relativity would be nonsense. * > > > Stop wasting my time with your stupid sophistry. Euclid's 5th postulate is > something totally believable but unprovable -- many famous mathematicians > tried to prove it from the other four postulates and failed. And BTW, every > semi-educated asshole knows it applies solely to plane geometry, so stop > your BS. My obvious point was that there are many things we believe as > true, but can't prove. AG > > > John K Clark See what's on my new list at Extropolis > <https://groups.google.com/g/extropolis> > 76c > > -- > 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 everything-list+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/938d07da-0af0-45a3-b1eb-40068f5c2e27n%40googlegroups.com > <https://groups.google.com/d/msgid/everything-list/938d07da-0af0-45a3-b1eb-40068f5c2e27n%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 everything-list+unsubscr...@googlegroups.com. 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