Another physicist in mental decline (Sean Carroll)

[Alan Grayson]

https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/

[spudb...@aol.com]

Thanks, I will buy Carroll's book later today. I always liked Hugh Everett's MWI because it's excellent, in an emotionally-appealing way for us sci-fi fans. Beyond this. (kudos, to Bryce DeWiit &John A. Wheeler as well!), I also see commercial possibilities with this $$. Like, what if it takes less energy to cross world lines, then it is to travel between stars? Carroll would recoil in horror at my premise, but, I still like the concept, if he and many other physicists roll their collective eyes, and walk away. For them, this is probably a wise idea!  I am not sure if Everett is correct on what triggers splits in the observer moment? Random choices, or black holes, or energy releases, or dips?? You buying a different coffee than you normally purchase? I like the trade aspects like buying spices from the Neanderthal Earth, EV129?? 

-----Original Message-----
From: Alan Grayson <agrays...@gmail.com>
To: Everything List <everyth...@googlegroups.com>
Sent: Thu, Sep 12, 2019 12:45 am
Subject: Another physicist in mental decline (Sean Carroll)

https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/

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[Philip Thrift]

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

[Alan Grayson]

I like that! You know, before QM, people could watch a horserace and infer that the probabilties of which horse would win, place, or show, would change dynamically in real time. When the race ended, no one wondered what happened to that dynamic probability distribution.  It was obvious it no longer applied, since the race was done! Today, the situation has become obscure and unintelligible, and like a religion, there's no apparent way to cure the true believers. AG

[Lawrence Crowell]

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

[Philip Thrift]

QBism is not the dialectical opposite of MWI. This is:

https://twitter.com/DowkerFay/status/1110683583570759680

@philipthrift 

[Alan Grayson]

If you read the link, it's pretty obvious that Carroll believes the many worlds of the MWI, literally exist. AG 

[spudb...@aol.com]

I prob'ly' smack yo face fo say'in dat! Dat's probability fo ya! Word! 

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To: Everything List <everyth...@googlegroups.com>

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[Evgenii Rudnyi]

When the physicist says "The best answer we can give is that reality is a vector in Hilbert space", it shows that he cannot be cured.

Evgenii

Am Donnerstag, 12. September 2019 06:45:41 UTC+2 schrieb Alan Grayson:

https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/

[spudb...@aol.com]

And yet...when somebody has a problem in physics needing resolving, they likely go to Professor Carroll and not many here. Possibly Standish from Aus, or Bruno from The Heart of Europe, than anyone on this auguste mailing list. Hilbert Space, De Sitter Space, it's probably the same (hypothesis!). It is all phase space, sez the Swami. 

-----Original Message-----
From: Evgenii Rudnyi <use...@rudnyi.ru>
To: Everything List <everyth...@googlegroups.com>
Sent: Thu, Sep 12, 2019 2:02 pm
Subject: Re: Another physicist in mental decline (Sean Carroll)

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[Evgenii Rudnyi]

I am not sure that Carroll could solve a practical problem. To solve
something I would go to engineers. Evgenii

[Lawrence Crowell]

The MWI and this path integral interpretation are both  ψ-ontic and are thus not opposite.

LC

[spudb...@aol.com]

On that Evgenii, we do concur. Yet, big companies or big governments probably head to this guy's door, if they need something to ask?

Now, that may not be a big deal unless he is contributing to the DoD? 

Those comprising this group have interesting mathematical & quantum and cosmological philosophy, but we are not so prominent. 

The thinkers here participate because they love these topics, but their immediate impacts are something far off, potentially. 

Now, for me, MWI is fun, in the sense of science fiction is fun--unless we can somehow do trade somehow between Earths?

I will buy Carroll's book if only for this reason. "A hominid's reach must exceed his grasp, or what's a multiverse for?" 

If he is absolutely wrong and we can prove it, then, very well, onward, to the World Series (Think FIFA World Cup).

-----Original Message-----
From: Evgenii Rudnyi <use...@rudnyi.ru>
To: everything-list <everyth...@googlegroups.com>
Sent: Thu, Sep 12, 2019 2:15 pm
Subject: Re: Another physicist in mental decline (Sean Carroll)

I am not sure that Carroll could solve a practical problem. To solve
something I would go to engineers. Evgenii

Am 12.09.2019 um 20:09 schrieb spudboy100 via Everything List:
> And yet...when somebody has a problem in physics needing resolving, they likely go to Professor Carroll and not many here. Possibly Standish from Aus, or Bruno from The Heart of Europe, than anyone on this auguste mailing list. Hilbert Space, De Sitter Space, it's probably the same (hypothesis!). It is all phase space, sez the Swami.
>
>
> -----Original Message-----
> From: Evgenii Rudnyi <use...@rudnyi.ru>
> To: Everything List <everyth...@googlegroups.com>
> Sent: Thu, Sep 12, 2019 2:02 pm
> Subject: Re: Another physicist in mental decline (Sean Carroll)
>
> When the physicist says "The best answer we can give is that reality is a vector in Hilbert space", it shows that he cannot be cured.
> Evgenii
>
> Am Donnerstag, 12. September 2019 06:45:41 UTC+2 schrieb Alan Grayson:
> https://www.wired.com/story/ sean-carroll-thinks-we-all- exist-on-multiple-worlds/
>

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[Alan Grayson]

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.  What's the argument for such a claim? Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite. Here I'm referring to our bubble, not some infinite substratum from which it might have arose. AG 

[Alan Grayson]

On Thursday, September 12, 2019 at 12:02:20 PM UTC-6, Evgenii Rudnyi wrote:

When the physicist says "The best answer we can give is that reality is a vector in Hilbert space", it shows that he cannot be cured.

Evgenii

Not only that, but the vector physicists refer to can have many distinct representions -- that is, it's NOT unique -- so it CAN'T be claimed that it represents different possible states simultaneously. AG

[Stathis Papaioannou]

Given a sufficient number of trials, the probability that an event that can occur will occur approaches one. 

 

--

Stathis Papaioannou

Virus-free. www.avast.com

[Alan Grayson]

For countable trials, it might arbitrarily approach, but never reach unity. But what if the possible number of trials are uncountable? AG 

Virus-free. www.avast.com

[Brent Meeker]

That assumes identical trials.  A countably infinite set of universes could all be different. 

Brent

[Philip Thrift]

many worlds : deterministic 

path integrals : stochastic 

The role of path integrals in stochastic processes was anticipated by Wiener:

The subject began with the work of Wiener during the 1920's, corresponding to a sum over random trajectories, anticipating by two decades Feynman's famous work on the path integral representation of quantum mechanics. However, the true trigger for the application of these techniques within nonequilibrium statistical mechanics and stochastic processes was the work of Onsager and Machlup in the early 1950's. 

https://www.worldcat.org/title/path-integrals-for-stochastic-processes-an-introduction/oclc/830162352

but of course with a quantum-probability rule, e.g.:

(a1)

is replaced in the quantum case by the theorem of composite amplitudes

https://www.encyclopediaofmath.org/index.php/Quantum_stochastic_processes

@philipthrift

[Stathis Papaioannou]

Yes, but consider an infinite universe where the cosmological principle applies, which does not seem an unreasonable assumption.

--

Stathis Papaioannou

[Alan Grayson]

It is unreasonable if the universe has been expanding for finite time, which is generally accepted. AG 

--

Stathis Papaioannou

[Lawrence Crowell]

This is of course Bayes' theorem and the second is what might be called the "square root" of Bayes' theorem. The modulus square the the second gives probabilities that obey Bayes' theorem.  

LC

[Bruno Marchal]

On 12 Sep 2019, at 06:45, Alan Grayson <agrays...@gmail.com> wrote:

https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/

Sean Carroll assumes that reality is a vector in Hilbert space. But he used Mechanism (implicitly) but forget computer science. That reality is a vector in Hilbert space has to be derived from the relative statistic on all computations realised in arithmetic.

To say that someone who thinks differently than you is in mental decline teaches us something about you, no about Carroll.

Bruno

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[Alan Grayson]

On Friday, September 13, 2019 at 5:08:41 AM UTC-6, Bruno Marchal wrote:

On 12 Sep 2019, at 06:45, Alan Grayson <agrays...@gmail.com> wrote:

https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/

Sean Carroll assumes that reality is a vector in Hilbert space. But he used Mechanism (implicitly) but forget computer science. That reality is a vector in Hilbert space has to be derived from the relative statistic on all computations realised in arithmetic.

To say that someone who thinks differently than you is in mental decline teaches us something about you, no about Carroll.

Bruno

Carroll is in irreversible mental decline. He's lost contact with reality. Sad case. I stand by my assessment. He doesn't even understand basic linear algebra, and that his "state vector" has no unique representation, and thus the mythical interpretation of the superposition of the wf is totally illusional. AG 

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[Bruno Marchal]

I agree. I would even add that with Feynman path formalism, the reduction of the wave packet does no more make sense. Feynman said it in his little book on light: he consider the Wave reduction as a confusion and appeal to magic (footnote at the end of the second chapter).

Bruno

LC

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[Bruno Marchal]

The idea comes from Tegmark, and I agree with you, it necessitate more than an infinite universe. It requires also some assumption of homogeneity.

Of course, (for those who are aware of Gödel 1931 and Turing 1936), arithmetic contains all computations, which entails, when assuming mechanism, an infinity of each os us. That explains both where the appearance of universe come from, and the quantum mechanical type of formalism. In “many-world”, the “many” makes sense, but the term “world” is not well defined and should not been taken literally. It is more histories than worlds per se.

Bruno

What's the argument for such a claim? Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite. Here I'm referring to our bubble, not some infinite substratum from which it might have arose. AG 

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[Alan Grayson]

On Friday, September 13, 2019 at 5:24:11 AM UTC-6, Bruno Marchal wrote:

On 13 Sep 2019, at 04:26, Alan Grayson <agrays...@gmail.com> 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 

Of course, (for those who are aware of Gödel 1931 and Turing 1936), arithmetic contains all computations, which entails, when assuming mechanism, an infinity of each os us.

I really don't see how you make that jump. And what exactly does "assuming mechanism" mean? AG

 

That explains both where the appearance of universe come from, and the quantum mechanical type of formalism. In “many-world”, the “many” makes sense, but the term “world” is not well defined and should not been taken literally. It is more histories than worlds per se.

Bruno

What's the argument for such a claim? Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite. Here I'm referring to our bubble, not some infinite substratum from which it might have arose. AG 

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[Alan Grayson]

On Friday, September 13, 2019 at 5:18:50 AM UTC-6, Bruno Marchal wrote:

On 13 Sep 2019, at 00:44, Lawrence Crowell <goldenfield...@gmail.com> wrote:

On Thursday, September 12, 2019 at 11:44:51 AM UTC-5, Philip Thrift wrote:

On Thursday, September 12, 2019 at 8:45:22 AM UTC-5, 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

QBism is not the dialectical opposite of MWI. This is:

https://twitter.com/DowkerFay/status/1110683583570759680

@philipthrift 

The MWI and this path integral interpretation are both  ψ-ontic and are thus not opposite.

I agree. I would even add that with Feynman path formalism, the reduction of the wave packet does no more make sense. Feynman said it in his little book on light: he consider the Wave reduction as a confusion and appeal to magic (footnote at the end of the second chapter).

Bruno

Not for those of us who watch horseraces! Applied to QM, the wf becomes irrelevant when the measurement occurs. Wave packet reduction, by which I assume you mean "collapse", is nothing more than a bookkeeping device. AG 

LC

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[Philip Thrift]

On Friday, September 13, 2019 at 6:17:12 AM UTC-5, Alan Grayson wrote:

Carroll is in irreversible mental decline. He's lost contact with reality. Sad case. I stand by my assessment. He doesn't even understand basic linear algebra, and that his "state vector" has no unique representation, and thus the mythical interpretation of the superposition of the wf is totally illusional. AG 

He can play with math, like anyone else, but his fictions are a little too real for him.

In the landscape of fictions modeling quantum phenomena, his not only denies probability, but denies the 'self' (in the sense of consciousness bring a real thing).

@philipthrift

[Philip Thrift]

On Friday, September 13, 2019 at 8:28:10 AM UTC-5, Alan Grayson wrote:

Not for those of us who watch horseraces! Applied to QM, the wf becomes irrelevant when the measurement occurs. Wave packet reduction, by which I assume you mean "collapse", is nothing more than a bookkeeping device. AG 

It's a matter of what is the right sort of probability space one wants to have to make this be the case.

Quantum Dynamics without the Wave Function

https://arxiv.org/abs/quant-ph/0610204

@philipthrift

 

[Stathis Papaioannou]

Is it certain that it had to be of finite volume initially, or that the expansion must always have been at a finite rate?

--

Stathis Papaioannou

[Alan Grayson]

The rate of expansion can vary, can be huge, much faster than the SoL, but it can't be infinitely fast, based on the view that singularities are not physically possible.  Initially, I suppose it could have been infinitely large, but the data seems to indicate otherwise, such as the CMBR at 380,000 years after the BB. If it was infintely large at that time, it should have already cooled to near absolute zero. AG

[Brent Meeker]

The cosmological principle is only a heuristic referring to classical uniformity at a level of (very) coarse graining.

Brent

[Lawrence Crowell]

On Friday, September 13, 2019 at 6:24:11 AM UTC-5, Bruno Marchal wrote:

On 13 Sep 2019, at 04:26, Alan Grayson <agrays...@gmail.com> 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.

Of course, (for those who are aware of Gödel 1931 and Turing 1936), arithmetic contains all computations, which entails, when assuming mechanism, an infinity of each os us. That explains both where the appearance of universe come from, and the quantum mechanical type of formalism. In “many-world”, the “many” makes sense, but the term “world” is not well defined and should not been taken literally. It is more histories than worlds per se.

Bruno

It would be best to separate MWI from the multiverse for at least the moment. There are several levels of the multiverse. MWI does define a high level multiverse, but MWI is not all multiverses.

The first level has to do with what exists beyond the cosmological horizon and in particular if the spatial surface of spacetime is flat. This would be an infinite R^3 manifold. Since the level of complexity or the number of possible states is bounded by the size of the cosmology horizon, out about 13 billion light years, this means there are other regions that are copies of this world. This is just plain combinatorics. 

 

The type II multiverse, or maybe type IIA, is where a deSitter or FLRW spacetime with an inflationary vacuum at high energy is unstable and there are vacuum transitions in regions within it. These regions have a vacuum at a much lower energy and define what are sometimes called pocket worlds. Since this inflationary cosmology is in a hugely accelerated expansion then these pockets of vacuum instability are only local. There are some interesting questions. In particular is the boundary of any such pocket world pinched off, so to speak, to define a new detached and topologically complete spacetime? The boundary has quantum field information, and if this transitions to a spatial surface that is a sphere S^3 or R^3, then this quantum field information may play some role.

The next is a type IIB multiverse, which is a multiplicity of these eternally inflating spacetimes. These may be emergent from entanglement wedges with AdS spacetimes.

There is then the type III multiverse, which is the identification of the MWI as a multiverse. This is where things may get a bit odd. The problem is that quantum interpretations are physically questionable, or maybe metaphysics, and this would mean the type III multiverse is really a sort of metaphysics. The other multiverse scenarios may hold without MWI.

Then there is type IV multiverse that is Max Tegmark's mathematical universe hypothesis. This is so completely metaphysical that it is hard to take this as a serious scientific proposition.

LC

What's the argument for such a claim? Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite. Here I'm referring to our bubble, not some infinite substratum from which it might have arose. AG 

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[John Clark]

On Thu, Sep 12, 2019 at 10:26 PM Alan Grayson <agrays...@gmail.com> wrote:

 

> 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.  What's the argument for such a claim?

Of course it's been proven! It's simple math, there are only a finite number of ways the atoms in your body, or even the entire OBSERVABLE universe, can be arranged so obviously if the entire universe is infinite then there is going to have to be copies, an infinite number of them in fact. Max Tegmark has even calculated how far you'd have to go to see such a thing. 

Your closest identical copy is 10^12 light years away. About 10^76 light years away there is a sphere of radius 100 light-years identical to the one centered here, so everything we see here during the next century will be identical to those of our counterparts over there. And 10^102 light years away the is a exact copy of our entire observable universe. And all this is true regardless of if the Many Worlds Interpretation of Quantum Mechanics is correct or not, it only depends on the universe being spatially infinite.

Is there a copy of you

> Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite.

I see no reason in principle why something can't be finite along one dimension and infinite along another dimension.

John K Clark

[Stathis Papaioannou]

On Sat, 14 Sep 2019 at 08:08, John Clark <johnk...@gmail.com> wrote:

On Thu, Sep 12, 2019 at 10:26 PM Alan Grayson <agrays...@gmail.com> wrote:

 

> 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.  What's the argument for such a claim?

Of course it's been proven! It's simple math, there are only a finite number of ways the atoms in your body, or even the entire OBSERVABLE universe, can be arranged so obviously if the entire universe is infinite then there is going to have to be copies, an infinite number of them in fact. Max Tegmark has even calculated how far you'd have to go to see such a thing. 

Your closest identical copy is 10^12 light years away. About 10^76 light years away there is a sphere of radius 100 light-years identical to the one centered here, so everything we see here during the next century will be identical to those of our counterparts over there. And 10^102 light years away the is a exact copy of our entire observable universe. And all this is true regardless of if the Many Worlds Interpretation of Quantum Mechanics is correct or not, it only depends on the universe being spatially infinite.

Assuming that the structure of the universe is uniform.

--

Stathis Papaioannou

[Jason Resch]

On Fri, Sep 13, 2019 at 8:25 AM Alan Grayson <agrays...@gmail.com> 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 <agrays...@gmail.com> 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.

Some references:

• https://www.cfa.harvard.edu/seuforum/faq.htm
• https://www.youtube.com/watch?v=K8gV05nS7mc

Jason

[Bruce Kellett]

The trouble with all such arguments is that they miss the fact that our initial conditions might have been very special, of measure zero. In an infinite universe there are certainly many copies of individual universes, but they might well all be copies of completely boring lifeless universes.

Bruce 

[Lawrence Crowell]

As I indicate a few posts above early today, there are some questions about this. Let us consider this within the level II multiverse, and even if people do not "believe," a term I dislike using here, that just go along with the argument. The inflationary manifold has a huge vacuum energy that is unstable. This results in these "Swiss cheese" bubbles of lower energy that roll off the inflationary domain and form a pocket that has a boundary. To my mind that boundary poses a lot of questions. This will contain quantum field information. Does this quantum information go into popping this pocket off so it is a topologically complete spacetime? In other words this boundary information is transferred into topological information, maybe as entanglements etc. Then if so is this topologically complete space a sphere S^3 or is it R^3, where in a projective geometric setting that topological information is sent to "infinity" or on RP^3. If this is sphere then things are finite and this level I multiverse can't be complete. If this sphere is small enough it essentially does not exist. It it is R^3, or what I really think is interesting is Poincare's dodechedron space, then we can have copies and level I multiverse. 

LC

[Alan Grayson]

On Friday, September 13, 2019 at 4:08:23 PM UTC-6, John Clark wrote:

On Thu, Sep 12, 2019 at 10:26 PM Alan Grayson <agrays...@gmail.com> wrote:

 

> 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.  What's the argument for such a claim?

Of course it's been proven! It's simple math, there are only a finite number of ways the atoms in your body, or even the entire OBSERVABLE universe, can be arranged so obviously if the entire universe is infinite then there is going to have to be copies, an infinite number of them in fact. Max Tegmark has even calculated how far you'd have to go to see such a thing. 

What I think you're missing (and Tegmark) is the possibility of UNcountable universes. In such case, one could imagine new universes coming into existence forever and ever, without any repeats.  Think of the number of points between 0 and 1 on the real line, each point associated with a different universe. AG

Your closest identical copy is 10^12 light years away. About 10^76 light years away there is a sphere of radius 100 light-years identical to the one centered here, so everything we see here during the next century will be identical to those of our counterparts over there. And 10^102 light years away the is a exact copy of our entire observable universe. And all this is true regardless of if the Many Worlds Interpretation of Quantum Mechanics is correct or not, it only depends on the universe being spatially infinite.

But our universe is NOT spatially infinite if its been expanding for finite time, starting very small, as can be inferred from the temperature of the CMBR. AG 

Is there a copy of you

> Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite.

I see no reason in principle why something can't be finite along one dimension and infinite along another dimension.

In general, one can of course have some dimensions finite and others infinite. But if our universe is finite in time since the BB, 13.8 BY, its spatial extent must be finite, since that's how long its been expanding. AG 

John K Clark

[Alan Grayson]

Whether they're boring or not is irrelevant. As I previously posted, an uncountable infinity of universes is possible without any repeats. AG 

[Alan Grayson]

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. 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. If it were infinite at that time, its temperature would have been near absolute zero. AG

[Evgenii Rudnyi]

Am 13.09.2019 um 03:11 schrieb spudboy100 via Everything List:
> On that Evgenii, we do concur. Yet, big companies or big governments probably head to this guy's door, if they need something to ask?Now, that may not be a big deal unless he is contributing to the DoD?

By organizing a military strike from the parallel universe?

Evgenii

>Those comprising this group have interesting mathematical & quantum and cosmological philosophy, but we are not so prominent. The thinkers here participate because they love these topics, but their immediate impacts are something far off, potentially. Now, for me, MWI is fun, in the sense of science fiction is fun--unless we can somehow do trade somehow between Earths?I will buy Carroll's book if only for this reason. "A hominid's reach must exceed his grasp, or what's a multiverse for?" If he is absolutely wrong and we can prove it, then, very well, onward, to the World Series (Think FIFA World Cup).
>

[Jason Resch]

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.

 

 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.

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.  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

Jason

[Alan Grayson]

On Saturday, September 14, 2019 at 12:34:18 AM UTC-6, Jason wrote:

On Friday, September 13, 2019, Alan Grayson <agrays...@gmail.com> 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 <agrays...@gmail.com> 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 <agrays...@gmail.com> 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. If it has been expanding for finite time, its spatial extent must be finite, like a huge hypersphere. All the models I see pictorially illustrated, have it much much smaller than it presently is. AG 

 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 

 

 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. Yes, all space was hot and dense, but much smaller in spatial extent than today. Just play the movie backward. AG 

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?

 

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 

Jason

[Alan Grayson]

Yes, time extends infinitely into the future, and so does space unless the universe is closed. But then he claims time and space flip with viewed externally to the bubble. But how does one get outside the bubble to observe it? Not possible AFAICT. AG

[Alan Grayson]

We don't know why inflation started and what stopped it, if it stopped. AG 

Each pocket universe may be finite in volume, but extends infinitely in the time direction. 

Yes, time extends infinitely into the future, and so does space, unless the universe is closed. But then he claims time and space flip when viewed externally to the bubble. But how does one get outside the bubble to observe it? Not possible AFAICT. AG

[Alan Grayson]

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

[Lawrence Crowell]

On Friday, September 13, 2019 at 10:22:38 PM UTC-5, Alan Grayson wrote:

On Friday, September 13, 2019 at 4:08:23 PM UTC-6, John Clark wrote:

On Thu, Sep 12, 2019 at 10:26 PM Alan Grayson <agrays...@gmail.com> wrote:

 

> 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.  What's the argument for such a claim?

Of course it's been proven! It's simple math, there are only a finite number of ways the atoms in your body, or even the entire OBSERVABLE universe, can be arranged so obviously if the entire universe is infinite then there is going to have to be copies, an infinite number of them in fact. Max Tegmark has even calculated how far you'd have to go to see such a thing. 

What I think you're missing (and Tegmark) is the possibility of UNcountable universes. In such case, one could imagine new universes coming into existence forever and ever, without any repeats.  Think of the number of points between 0 and 1 on the real line, each point associated with a different universe. AG

Your closest identical copy is 10^12 light years away. About 10^76 light years away there is a sphere of radius 100 light-years identical to the one centered here, so everything we see here during the next century will be identical to those of our counterparts over there. And 10^102 light years away the is a exact copy of our entire observable universe. And all this is true regardless of if the Many Worlds Interpretation of Quantum Mechanics is correct or not, it only depends on the universe being spatially infinite.

But our universe is NOT spatially infinite if its been expanding for finite time, starting very small, as can be inferred from the temperature of the CMBR. AG 

This is wrong. The CMB is at a distance of 46 billion light years while it was also generated 13.8 billion years ago. The more distant things are the more it is frame dragged by the accelerated expansion, in a sense a "soft inflationary" expansion. If this were not the case the CMB would have markedly different characteristics. 

LC

[Alan Grayson]

Doesn't the high temperature and density at BB +380,000 years imply the universe was small at that time? AG 

[Lawrence Crowell]

It implies that matter and radiation had a higher density. Whether the space of this cosmology was smaller is problematic. If the space is R^3 without bounds it makes no sense to say it was smaller. The same if the space is the Poincare dodecahedron space.

LC 

[John Clark]

On Fri, Sep 13, 2019 at 7:27 PM Bruce Kellett <bhkel...@gmail.com> wrote:

>> Your closest identical copy is 10^12 light years away. About 10^76 light years away there is a sphere of radius 100 light-years identical to the one centered here, so everything we see here during the next century will be identical to those of our counterparts over there. And 10^102 light years away the is a exact copy of our entire observable universe. And all this is true regardless of if the Many Worlds Interpretation of Quantum Mechanics is correct or not, it only depends on the universe being spatially infinite.

> The trouble with all such arguments is that they miss the fact that our initial conditions might have been very special, of measure zero.

I assume you mean the overall spacetime curvature of the universe should be zero, but if Inflation Theory is correct it would explain why it is if not zero at least very very small, small enough that even if it's not infinite the entire universe would be large enough to be able to travel 10^102 light years and find a exact copy of our observable universe.

John K Clark

[Jason Resch]

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.

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

[Alan Grayson]

To reiterate:  I've never read a description of inflation where the universe is described as very large spatially when it initiates. It's always claimed inflation 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. Inflation then expands the universe to the diameter of the Earth or the Solar System before terminating, all this occuring within the first second after the BB. The idea behind inflation is to preserve the original homogeneity of a universe presumed be very small, and therefore causally connected.This entire model breaks down if one insists on a large universe immediately after the BB. As I understand it, present models have the expansion continuing until present, and even at 380,000 it's still relatively small but homogeneous. AG

[Jason Resch]

Right there's probably no vantage point with observers in it to see the other bubbles.

But the global picture is used to explain how space and time work through eternal inflation to create new pockets, which are perceived as open (infinite) universes even though they share space with other pockets in the global view.

Jason

 

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

Jason

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[Jason Resch]

We don't know where the initial vacuum state came from, but with certain assumptions we can say why it stops in some places and continues in others.tge reasons are inherently quantum in nature, like the decay of a radioactive element.

Inflation may bring it's own questions, but it solves at least four problems:

Why space is so flat

Why the universe is still expanding

Where the heat and energy came from

Why we see no magnetic monopoles

It might also explain some fine tuning mysteries, if other vacuum states are possible, as they are under string theory.

Finally, there's observational support for inflation based on the latest measurements of the CMB by the Planck satellite.

Jason

[John Clark]

On Fri, Sep 13, 2019 at 11:22 PM Alan Grayson <agrays...@gmail.com> wrote:

> What I think you're missing (and Tegmark) is the possibility of UNcountable universes. In such case, one could imagine new universes coming into existence forever and ever, without any repeats.  Think of the number of points between 0 and 1 on the real line, each point associated with a different universe. AG

There is no reason to think physics needs all the real numbers and considerable evidence to think it does not. To my mind the strongest evidence is that a physical Turing Machine is incapable of even approximating most real numbers, I happened to have posted a proof of this yesterday on the "Observation versus assumption" thread.

Actually, physics might not even need all the rational numbers as there is probably a grainy structure to both space and time. Distances can't get smaller than the Planck Length and time shorter than the Planck Time. Maybe.

 

>> true regardless of if the Many Worlds Interpretation of Quantum Mechanics is correct or not, it only depends on the universe being spatially infinite.

> But our universe is NOT spatially infinite if its been expanding for finite time,

Sure it can, space could have started out infinitely large 13.8 billion years ago and still be expanding today, it could even be accelerating. The radius of the observable universe is 45.5 billion light years ( the light from the most distant galaxies took 13.8 billion years to reach us but during that time the galaxies have been accelerating away from us) but that doesn't mean there aren't galaxies much more distant than 45.5 billion light years.

 John K Clark

[Alan Grayson]

If the universe was infinite in spatial extent at the time of, or immediately after the BB, the various parts wouldn't have been causally connected and we wouldn't need inflation to preserve (a non existent) homogeneity. It's because it was small at the time of, or just after the BB, that inflation was imagined to preserve the original homogeneity. FWIW, I'm convinced our bubble is a finite hypersphere, almost but not flat, due to its huge size. AG

[Alan Grayson]

On Saturday, September 14, 2019 at 7:29:33 AM UTC-6, Alan Grayson wrote:

On Saturday, September 14, 2019 at 7:18:40 AM UTC-6, John Clark wrote:

On Fri, Sep 13, 2019 at 11:22 PM Alan Grayson <agrays...@gmail.com> wrote:

> What I think you're missing (and Tegmark) is the possibility of UNcountable universes. In such case, one could imagine new universes coming into existence forever and ever, without any repeats.  Think of the number of points between 0 and 1 on the real line, each point associated with a different universe. AG

There is no reason to think physics needs all the real numbers and considerable evidence to think it does not. To my mind the strongest evidence is that a physical Turing Machine is incapable of even approximating most real numbers, I happened to have posted a proof of this yesterday on the "Observation versus assumption" thread.

Physics doesn't need all the real numbers, just some of them, say any continuous range of any variable; like the mass of the electron. FWIW, I am convinced there are no exact copies of any universes or ourselves. AG 

[Jason Resch]

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

[Stathis Papaioannou]

Unless it was finite in size and infinitely dense and at some point it expanded infinitely fast.

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Stathis Papaioannou

[Alan Grayson]

You're positing a singularity. AG 

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Stathis Papaioannou

[Alan Grayson]

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, 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. In this case, the infinite universe was always homogeneous even though it was never causally connected. Further, how could it have been so hot 380,000 years after the BB if it wasn't dense at that time? An infinite universe right after the BB would be COOL, 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 

[Alan Grayson]

On Saturday, September 14, 2019 at 7:18:40 AM UTC-6, John Clark wrote:

On Fri, Sep 13, 2019 at 11:22 PM Alan Grayson <agrays...@gmail.com> wrote:

> What I think you're missing (and Tegmark) is the possibility of UNcountable universes. In such case, one could imagine new universes coming into existence forever and ever, without any repeats.  Think of the number of points between 0 and 1 on the real line, each point associated with a different universe. AG

There is no reason to think physics needs all the real numbers and considerable evidence to think it does not.

Einstein's field equations use PI, and so do Maxwell's equations. And I think some of the laws of physics use the natural logarithm. As I previously postulated, all one needs is some continuous range of some variable to determine new universes in which no copies emerge. I find the hypothesis of infinite copies of anything highly repugant, like the MWI, which I don't claim is a proof of anything. But a univere with zero copies seem more elegant than the opposite. AG

[John Clark]

On Sat, Sep 14, 2019 at 9:33 AM Alan Grayson <agrays...@gmail.com> wrote:

>> There is no reason to think physics needs all the real numbers and considerable evidence to think it does not. To my mind the strongest evidence is that a physical Turing Machine is incapable of even approximating most real numbers, I happened to have posted a proof of this yesterday on the "Observation versus assumption" thread.

> Physics doesn't need all the real numbers, just some of them, say any continuous range of any variable; like the mass of the electron.

The electron doesn't have a continuous range of mass. And mass is the force on a object divided by its acceleration, but acceleration is the change in speed per unit of time and speed is the change in positional distance per unit of time, so if neither time or space is continuous then mass can't be either. 

> Einstein's field equations use PI, and so do Maxwell's equations. 

Physics theories may need PI but physics itself probably doesn't. PI has been calculated to 31 trillion digits and even that is only an approximation, but only 8 or 9 digits are needed to explain every physical observation ever made, and the same thing is true for e.

John K Clark

[Jason Resch]

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.

 

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.  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).

 

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.

 

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 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.

 

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

event	temperature (K)	scale factornow / scale factorthen	time
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 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

 

event	temperature (K)	scale factornow / scale factorthen	time
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

[Alan Grayson]

On Saturday, September 14, 2019 at 3:03:38 PM UTC-6, John Clark wrote:

On Sat, Sep 14, 2019 at 9:33 AM Alan Grayson <agrays...@gmail.com> wrote:

>> There is no reason to think physics needs all the real numbers and considerable evidence to think it does not. To my mind the strongest evidence is that a physical Turing Machine is incapable of even approximating most real numbers, I happened to have posted a proof of this yesterday on the "Observation versus assumption" thread.

> Physics doesn't need all the real numbers, just some of them, say any continuous range of any variable; like the mass of the electron.

The electron doesn't have a continuous range of mass.

Sure, in OUR universe, but it might be a continuous variable when other universes are created. That was my conjecture, and it need not be mass, but other properties of other variables. AG

 

And mass is the force on a object divided by its acceleration, but acceleration is the change in speed per unit of time and speed is the change in positional distance per unit of time, so if neither time or space is continuous then mass can't be either. 

Space and time could be continuous. Just because there's a lower limit on what we can measure, doesn't guarantee any inherent graininess. AG 

[Alan Grayson]

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. I prefer to go with what we think we know, rather than with a model which is completely speculative. 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 does NOT suggest an infinite universe. 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  

 

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

 

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 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. 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 am just saying that it does seem to be cooling as it expands, and the curvature data seems to imply smallness just after the BB. 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

[Jason Resch]

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?

 

 

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?  

 

  

  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 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.

 

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?

 

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/

Jason

 

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[Alan Grayson]

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 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

 

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[Alan Grayson]

Oh, because the temperature is decreasing from just after the BB to 380,000 years, we need a very small universe to inflate to explain the current homogeneity. Otherwise the present large scale homogeneity is only explicable by appealing to highly improbable chance in a causally disconnected universe, our present universe. AG 

[Jason Resch]

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.

 

 

  

  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 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".  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.

 

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.

 

 

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.

 

Jason

[Jason Resch]

On Sun, Sep 15, 2019 at 7:45 AM Alan Grayson <agrays...@gmail.com> wrote:

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.

Oh, because the temperature is decreasing from just after the BB to 380,000 years, we need a very small universe to inflate to explain the current homogeneity. Otherwise the present large scale homogeneity is only explicable by appealing to highly improbable chance in a causally disconnected universe, our present universe. AG 

Inflation requires a minimum starting size size (which can be microscopic), and minimum duration of inflation (which can be as little as ~100 doublings) taking as little as 10^-35 seconds, but as far as I know these are only the minimums to be congruent with observations.  Inflation, by no means requires the preinflation universe to be tiny, nor the time period of inflation to be short.  Either the preinflation size could be unoundedly large, or the inflation duration could be unboundedly long.

Jason

Jason

[Alan Grayson]

On Sunday, September 15, 2019 at 10:08:00 AM UTC-6, Jason wrote:

On Sun, Sep 15, 2019 at 7:45 AM Alan Grayson <agrays...@gmail.com> wrote:

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.

Oh, because the temperature is decreasing from just after the BB to 380,000 years, we need a very small universe to inflate to explain the current homogeneity. Otherwise the present large scale homogeneity is only explicable by appealing to highly improbable chance in a causally disconnected universe, our present universe. AG 

Inflation requires a minimum starting size (which can be microscopic), and minimum duration of inflation (which can be as little as ~100 doublings) taking as little as 10^-35 seconds, but as far as I know these are only the minimums to be congruent with observations.  Inflation, by no means requires the preinflation universe to be tiny, nor the time period of inflation to be short.  Either the preinflation size could be unboundedly large, or the inflation duration could be unboundedly long.

Jason

If inflation is to solve large scale homogeneity in a causally non-connected universe, which is the case of our present observable universe, it must start with a very small universe that IS causally connected. I think this is pretty obvious, unless you want to insist that the large scale homogeneity is purely accidental -- which I do not. AG

Incidentally, I didn't claim that inflation per se is totally speculative. It solves a number of problems so it is more than pure speculation. I was then referring to speculation that some parts of the total universe, either within our observable or unobservable regions, or in the presumed substratum from which bubbles arise, or in other bubbles, are experiencing any types of inflations. The only inflation that I am discussing is within our bubble, and perhaps extended to our unobservable regions by applying the Cosmological Principle. AG

[Alan Grayson]

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 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 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

 

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 

 

 

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

[Jason Resch]

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

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[spudb...@aol.com]

That's genius, Evgenii, sheer, unadulterated, genius!  

-----Original Message-----
From: Evgenii Rudnyi <use...@rudnyi.ru>
To: everything-list <everyth...@googlegroups.com>
Sent: Sat, Sep 14, 2019 2:09 am
Subject: Re: Another physicist in mental decline (Sean Carroll)

Am 13.09.2019 um 03:11 schrieb spudboy100 via Everything List:
> On that Evgenii, we do concur. Yet, big companies or big governments probably head to this guy's door, if they need something to ask?Now, that may not be a big deal unless he is contributing to the DoD?

By organizing a military strike from the parallel universe?

Evgenii

>Those comprising this group have interesting mathematical & quantum and cosmological philosophy, but we are not so prominent. The thinkers here participate because they love these topics, but their immediate impacts are something far off, potentially. Now, for me, MWI is fun, in the sense of science fiction is fun--unless we can somehow do trade somehow between Earths?I will buy Carroll's book if only for this reason. "A hominid's reach must exceed his grasp, or what's a multiverse for?" If he is absolutely wrong and we can prove it, then, very well, onward, to the World Series (Think FIFA World Cup).

>

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[Philip Thrift]

 

Sean Carroll's many-selves

https://www.youtube.com/watch?v=zsXCwUsuvKo

@philipthrift

[Alan Grayson]

On Sunday, September 15, 2019 at 3:34:10 PM UTC-6, Philip Thrift wrote:

 

Sean Carroll's many-selves

And the good news is ... the one in this world is going bald. AG 

[Philip Thrift]

On Sunday, September 15, 2019 at 5:46:13 PM UTC-5, Alan Grayson wrote:

On Sunday, September 15, 2019 at 3:34:10 PM UTC-6, Philip Thrift wrote:

 

Sean Carroll's many-selves

And the good news is ... the one in this world is going bald. AG 

And (many would say) going crazy.

There is obviously (in his view) a world where a Sean Carroll is a "one world" quantum theorist. 

@philipthrift

[spudb...@aol.com]

My guess is among the physics community, most, would be mildly, skeptical of MWI, because it's a bridge too far to get evidence of, as yet and thus, unconcerned. Having said this, many cosmologists are still having a cat fight about the Hubble Constant (The rate of cosmological expansion). my suspicion is, that once we get to the point of hanging truly gigantic telescopes on the periphery of the solar system, new discoveries will be made, and revisions to old laws of physics will be done. We'll gain a few definitive answers through observation, and we shall see that quantum in action at a vastly large scale. Relatedly, hey!, where's my dark matter? in fact, hey!, where's my fusion reactors. Ah! So much for the 'mentally fit' physicists and astronomers....

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To: Everything List <everyth...@googlegroups.com>
Sent: Sun, Sep 15, 2019 7:03 pm
Subject: Re: Another physicist in mental decline (Sean Carroll)

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.

[Alan Grayson]

OK, but I would include the UNOBSERVABLE part of our bubble, because as far as we know it became unobservable because of the expansion. 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.

The problem may lie in the fact that the Friedmann equations are idealizations and not physically realizable.  As I see it, one can get transitions between flat and open universes in both directions, but a closed universe cannot became flat or open; nor can the reverse occur. AG

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

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[Alan Grayson]

On Wednesday, September 11, 2019 at 10:45:41 PM UTC-6, Alan Grayson wrote:

https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/

Jason; it turns out you were right about the consensus among cosmologists; that the universe is thought to be flat. But I am studying some videos which seem to suggest that a flat universe can be finite in spatial extent, maybe like a cyclinder without an edge. Try try this, and the two which follow:

https://www.youtube.com/watch?v=_k3_B9Eq7eM&feature=youtu.be

AG

[Bruno Marchal]

On 13 Sep 2019, at 15:24, Alan Grayson <agrays...@gmail.com> 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 <agrays...@gmail.com> 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.

Assuming that there is a physical universe, and that the big bang is its origin. OK.

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 might be with you on this, at least from a physicalist perspective (in which I do not believe, but which could be a consistent theory). From my understanding, space itself is born with the Big Bang, *if* the Big Bang is the origin (which I doubt), and that implies it is still finite after a finite time.

Now, with mechanism, I could show a model where space is infinite, but I think time can be deduced from it to be infinite too, so yes. Maybe Brent can add something (maybe he did already).

Of course, (for those who are aware of Gödel 1931 and Turing 1936), arithmetic contains all computations, which entails, when assuming mechanism, an infinity of each os us.

I really don't see how you make that jump.

The fact that all computations are executed in arithmetic is "well known” by the expert in the field since the 1930s.

("Executed”is used in the mathematical sense of the logiciens who discovered the computer). A (universal) Turing machine cannot distinguish, by introspection, between being emulated by a physical reality, a god-created reality, or an arithmetical reality, or any universal machinery. But the point is that they can count the experimental evidences, as mechanism imposed extreme strong constraints on what the physical laws can be.

And what exactly does "assuming mechanism" mean? AG

As I said I my other post, it is just Descartes’ idea that our body obeys laws which are locally computable, made precise by using Turing mathematical definition of computability. It is the hypothesis that there no magic happening in the brain, somehow. Or that the brain is Digitally emulable *at some description level* relevant for staying alive and well.

With mechanism there is a many “world” (computation) of arithmetic, toward which, in arithmetic, all sound machines converge.

Bruno

 

That explains both where the appearance of universe come from, and the quantum mechanical type of formalism. In “many-world”, the “many” makes sense, but the term “world” is not well defined and should not been taken literally. It is more histories than worlds per se.

Bruno

What's the argument for such a claim? Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite. Here I'm referring to our bubble, not some infinite substratum from which it might have arose. AG 

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[Bruno Marchal]

On 13 Sep 2019, at 15:28, Alan Grayson <agrays...@gmail.com> wrote:

On Friday, September 13, 2019 at 5:18:50 AM UTC-6, Bruno Marchal wrote:

On 13 Sep 2019, at 00:44, Lawrence Crowell <goldenfield...@gmail.com> wrote:

On Thursday, September 12, 2019 at 11:44:51 AM UTC-5, Philip Thrift wrote:

On Thursday, September 12, 2019 at 8:45:22 AM UTC-5, 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

QBism is not the dialectical opposite of MWI. This is:

https://twitter.com/DowkerFay/status/1110683583570759680

@philipthrift 

The MWI and this path integral interpretation are both  ψ-ontic and are thus not opposite.

I agree. I would even add that with Feynman path formalism, the reduction of the wave packet does no more make sense. Feynman said it in his little book on light: he consider the Wave reduction as a confusion and appeal to magic (footnote at the end of the second chapter).

Bruno

Not for those of us who watch horseraces! Applied to QM, the wf becomes irrelevant when the measurement occurs.

I agree. But relevant/irrelevant is not relevant when we search a conceptual understanding. That the wave is irrelevant after a measurement does not mean that there has been an actual physical collapse, which would entails FTL action at a distance, as Einstein explained in 1927 at the Solvay Congress (and made precise in the EPR paper, and then more with Bell, etc.). Then Everett QM (QM without collapse) the appearance of collapse is explained by the wave (adding or not the Born rule).

Wave packet reduction, by which I assume you mean "collapse", is nothing more than a bookkeeping device. AG 

I can’ agree more, but then, you get the many relative worlds/histories. Which is nice, given that the many computations is a theorem of arithmetic, and the “many worlds” appearance is provable from that, even without ever mentioning quantum mechanics.

Bruno

LC

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[Bruno Marchal]

On 13 Sep 2019, at 15:40, Philip Thrift <cloud...@gmail.com> wrote:

On Friday, September 13, 2019 at 6:17:12 AM UTC-5, Alan Grayson wrote:

Carroll is in irreversible mental decline. He's lost contact with reality. Sad case. I stand by my assessment. He doesn't even understand basic linear algebra, and that his "state vector" has no unique representation, and thus the mythical interpretation of the superposition of the wf is totally illusional. AG 

He can play with math, like anyone else, but his fictions are a little too real for him.

That is the problem with fictionalism. Like atheism it is not a doctrine, it is the statement that “my god is the real one”. 

I guess you know that the physical reality is not itself a fiction, but how can you know that?

The idea of doing research is searching the truth.

In the landscape of fictions modeling quantum phenomena, his not only denies probability, but denies the 'self' (in the sense of consciousness bring a real thing).

The complete contrary. I start from consciousness, I recover consciousness in the discourse of the machine, and I listen to what the machine already says, and the sound one see quick where the illusion/fiction of a physical primary reality comes in.

More precisely, I explain why machine cannot identify the third person self ([]p) with their first person self ([]p & p) that they cannot even define, unless invoking some notion of truth (that they cannot define either by Tarski theorem) and … mechanism.

Then I don’t deny probability, again, I justify them, without bring absurd notion like events without a cause. That is the whole point of Mechanism: it transforms physics into a study of the probability on our consistent (and arithmetically sound) extensions. With mechanism, we understand quickly why physics is before all a statistic calculus.

You might study my sane04 paper(*), perhaps.

Bruno

(*)B. Marchal. The Origin of Physical Laws and Sensations. In 4th International System Administration and Network Engineering Conference, SANE 2004, Amsterdam, 2004.

http://iridia.ulb.ac.be/~marchal/publications/SANE2004MARCHALAbstract.html (sane04)

@philipthrift

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[Bruno Marchal]

On 13 Sep 2019, at 23:44, Lawrence Crowell <goldenfield...@gmail.com> wrote:

On Friday, September 13, 2019 at 6:24:11 AM UTC-5, Bruno Marchal wrote:

On 13 Sep 2019, at 04:26, Alan Grayson <agrays...@gmail.com> 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.

Of course, (for those who are aware of Gödel 1931 and Turing 1936), arithmetic contains all computations, which entails, when assuming mechanism, an infinity of each os us. That explains both where the appearance of universe come from, and the quantum mechanical type of formalism. In “many-world”, the “many” makes sense, but the term “world” is not well defined and should not been taken literally. It is more histories than worlds per se.

Bruno

It would be best to separate MWI from the multiverse for at least the moment. There are several levels of the multiverse. MWI does define a high level multiverse, but MWI is not all multiverses.

The first level has to do with what exists beyond the cosmological horizon and in particular if the spatial surface of spacetime is flat. This would be an infinite R^3 manifold. Since the level of complexity or the number of possible states is bounded by the size of the cosmology horizon, out about 13 billion light years, this means there are other regions that are copies of this world. This is just plain combinatorics. 

 

The type II multiverse, or maybe type IIA, is where a deSitter or FLRW spacetime with an inflationary vacuum at high energy is unstable and there are vacuum transitions in regions within it. These regions have a vacuum at a much lower energy and define what are sometimes called pocket worlds. Since this inflationary cosmology is in a hugely accelerated expansion then these pockets of vacuum instability are only local. There are some interesting questions. In particular is the boundary of any such pocket world pinched off, so to speak, to define a new detached and topologically complete spacetime? The boundary has quantum field information, and if this transitions to a spatial surface that is a sphere S^3 or R^3, then this quantum field information may play some role.

The next is a type IIB multiverse, which is a multiplicity of these eternally inflating spacetimes. These may be emergent from entanglement wedges with AdS spacetimes.

There is then the type III multiverse, which is the identification of the MWI as a multiverse. This is where things may get a bit odd. The problem is that quantum interpretations are physically questionable, or maybe metaphysics, and this would mean the type III multiverse is really a sort of metaphysics. The other multiverse scenarios may hold without MWI.

To be franc, I have no interpretation of quantum mechanics (without collapse)which do not imply something akin to the type III multiverse, and when talking about QM, I talk only about this one.

It is this type of many-worlds, or better many histories, which confirms the many computations which exists in arithmetic, and whose statistics confirms (up to now) the physical appearance emerging from the many computations (which exists in the same sense that the prime numbers exist (no need to introduce metaphysics here).

Then there is type IV multiverse that is Max Tegmark's mathematical universe hypothesis. This is so completely metaphysical that it is hard to take this as a serious scientific proposition.

With mechanism, you can limit the ontology on the natural numbers, and the corresponding metaphysics can make sense of this, in some restricted way. What Tegmark missed is that, with mechanism (which he seems to have adopted) the physical reality becomes a theological reality, which is itself part of the arithmetical truth (with the understanding that the arithmetical truth, although as well definable that the set of real number, is not definable by the machine, nor really by us, and that it is well beyond the computable. Now both human and machine can point on it.

Note that eventually we really do not assume more than the natural numbers, and we never assume something like the set of all natural numbers, which we leave at the meta level. 

So we are back to Pythagorus ontology: only 0, 1, 2, 3, … with the laws of addition and multiplication. The physical reality is then explained by the phenomenological reality the machines are confronted too by internalising their own incompleteness, which Gödel already know the machine are capable of.

Physicalism for me is not just quite speculative, it contradicts Mechanism, which is used (explicitly or implicitly) in many domain, like Darwin in biology, or Everett in Quantum Physics.

0 universe, 1 universe, 2 universes, … aleph_0 universes, … aleph_1 universes, etc. are all speculative. But with mechanism, we can prove that there is 0 universe, but one precise set of physical laws emerging from the statistics on all computations seen from inside arithmetic (or Turing equivalent).

Bruno

LC

What's the argument for such a claim? Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite. Here I'm referring to our bubble, not some infinite substratum from which it might have arose. AG 

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[Bruno Marchal]

On 14 Sep 2019, at 05:22, Alan Grayson <agrays...@gmail.com> wrote:

On Friday, September 13, 2019 at 4:08:23 PM UTC-6, John Clark wrote:

On Thu, Sep 12, 2019 at 10:26 PM Alan Grayson <agrays...@gmail.com> wrote:

 

> 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.  What's the argument for such a claim?

Of course it's been proven! It's simple math, there are only a finite number of ways the atoms in your body, or even the entire OBSERVABLE universe, can be arranged so obviously if the entire universe is infinite then there is going to have to be copies, an infinite number of them in fact. Max Tegmark has even calculated how far you'd have to go to see such a thing. 

What I think you're missing (and Tegmark) is the possibility of UNcountable universes. In such case, one could imagine new universes coming into existence forever and ever, without any repeats.  Think of the number of points between 0 and 1 on the real line, each point associated with a different universe. AG

Tegmark missed this? 

Deutsch did not, and in his book “fabric of reality”, he gave rather good argument in favour of Everett-type of multiverse having non countable universe. That makes sense with mechanism which give raise to a continuum (2^aleph_0) of histories, but the “equivalence class” brought by the measure can have lower cardinality, or bigger. Open problem, to say the least.

Your closest identical copy is 10^12 light years away. About 10^76 light years away there is a sphere of radius 100 light-years identical to the one centered here, so everything we see here during the next century will be identical to those of our counterparts over there. And 10^102 light years away the is a exact copy of our entire observable universe. And all this is true regardless of if the Many Worlds Interpretation of Quantum Mechanics is correct or not, it only depends on the universe being spatially infinite.

But our universe is NOT spatially infinite if its been expanding for finite time, starting very small, as can be inferred from the temperature of the CMBR. AG 

Is there a copy of you

> Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite.

I see no reason in principle why something can't be finite along one dimension and infinite along another dimension.

In general, one can of course have some dimensions finite and others infinite. But if our universe is finite in time since the BB, 13.8 BY, its spatial extent must be finite, since that's how long its been expanding. AG 

I agree with Grayson here. (Accepting a lot of premises, like the BB is the beginning of the physical reality, which I doubt).

Bruno

John K Clark

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[Bruno Marchal]

> On 14 Sep 2019, at 08:09, Evgenii Rudnyi <use...@rudnyi.ru> wrote:
>
> Am 13.09.2019 um 03:11 schrieb spudboy100 via Everything List:
>> On that Evgenii, we do concur. Yet, big companies or big governments probably head to this guy's door, if they need something to ask?Now, that may not be a big deal unless he is contributing to the DoD?
>
> By organizing a military strike from the parallel universe?

Weinberg, and Plaga on this list, if I remember well, have argued that for this to be possible (an interaction in between parallel universe) you need to “delinearise” a little bit Quantum Mechanism. Then you can steal the oil in the parallel universe, and perhaps even meet your doppelgänger.

But there is a price. Not only Special relativity get wrong, but even the second principle of thermodynamic get wrong, which demands a lot.

So, no need to frighten us, there are few chance we get invade by super-alien from the parallel universe. They can only interfere statistically, like in arithmetic, without magic, but by our ignorance on which parts of the structure of all computations emulate us.

Bruno

>
> Evgenii
>
>> Those comprising this group have interesting mathematical & quantum and cosmological philosophy, but we are not so prominent. The thinkers here participate because they love these topics, but their immediate impacts are something far off, potentially. Now, for me, MWI is fun, in the sense of science fiction is fun--unless we can somehow do trade somehow between Earths?I will buy Carroll's book if only for this reason. "A hominid's reach must exceed his grasp, or what's a multiverse for?" If he is absolutely wrong and we can prove it, then, very well, onward, to the World Series (Think FIFA World Cup).
>

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[Alan Grayson]

On Monday, September 16, 2019 at 9:00:46 AM UTC-6, Bruno Marchal wrote:

On 14 Sep 2019, at 05:22, Alan Grayson <agrays...@gmail.com> wrote:

On Friday, September 13, 2019 at 4:08:23 PM UTC-6, John Clark wrote:

On Thu, Sep 12, 2019 at 10:26 PM Alan Grayson <agrays...@gmail.com> wrote:

 

> 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.  What's the argument for such a claim?

Of course it's been proven! It's simple math, there are only a finite number of ways the atoms in your body, or even the entire OBSERVABLE universe, can be arranged so obviously if the entire universe is infinite then there is going to have to be copies, an infinite number of them in fact. Max Tegmark has even calculated how far you'd have to go to see such a thing. 

What I think you're missing (and Tegmark) is the possibility of UNcountable universes. In such case, one could imagine new universes coming into existence forever and ever, without any repeats.  Think of the number of points between 0 and 1 on the real line, each point associated with a different universe. AG

Tegmark missed this? 

Deutsch did not, and in his book “fabric of reality”, he gave rather good argument in favour of Everett-type of multiverse having non countable universe. That makes sense with mechanism which give raise to a continuum (2^aleph_0) of histories, but the “equivalence class” brought by the measure can have lower cardinality, or bigger. Open problem, to say the least.

What you're not addressing is that with uncountable universes -- which I haven't categorically denied could arise -- it's not obvious that any repeats necessarily occur. I don't believe any repeats occur. AG 

As to your general theory, that with mechanism (replacing brains and presumably consciousness, with digital copies), computability, and the natural numbers, we can derive the physical universe we observe. This is your theory, isn't it? If so, I just don't see it as explanatory. AG

Your closest identical copy is 10^12 light years away. About 10^76 light years away there is a sphere of radius 100 light-years identical to the one centered here, so everything we see here during the next century will be identical to those of our counterparts over there. And 10^102 light years away the is a exact copy of our entire observable universe. And all this is true regardless of if the Many Worlds Interpretation of Quantum Mechanics is correct or not, it only depends on the universe being spatially infinite.

But our universe is NOT spatially infinite if its been expanding for finite time, starting very small, as can be inferred from the temperature of the CMBR. AG 

Is there a copy of you

> Morevover, I don't believe a universe of finite age, such as ours which everyone more or less agrees began some 13.8 BYA, can be spatially infinite.

I see no reason in principle why something can't be finite along one dimension and infinite along another dimension.

In general, one can of course have some dimensions finite and others infinite. But if our universe is finite in time since the BB, 13.8 BY, its spatial extent must be finite, since that's how long its been expanding. AG 

I agree with Grayson here. (Accepting a lot of premises, like the BB is the beginning of the physical reality, which I doubt).

Bruno

John K Clark

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[Bruno Marchal]

OK. But if the physical space was already there before the Big Bang, the Big Bang is no more the theory of the origin of the physical universe. OK?

My understanding was that the whole space-time was the bubble itself. At the same time, I am not sure we can really solves this without a quantum theory of space-time/gravity. My early critics on string theory was that it assumes some space-time at the start. I think that space-time will be explained as a quantum effect, perhaps entanglement topology, or something, and in that picture I expected that the BB would made the entire universe in the “starting” vacuum with all dimension being very small (for some mathematical outside view, and not much big from inside due to the Planck length). But I guess I was wrong, although I am not even sure of that. 

Normally we should belong to some branches of the quantum vacuum superposition, and already extract space and time from this, which could be a step in the extraction of the physical laws from the sum on all computations.

Bruno

 

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.

 

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.

 

 

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.

 

Jason

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[Bruno Marchal]

Can it depend on the “shape” of Dark Energy, or the great attractor? 

Here a short Patreon video pointing on that difficult subject:

https://www.youtube.com/watch?v=ZxSxuRWlHCs&list=WL&index=7&t=0s

(All this assuming some physical laws, which Mechanism shows that they have themselves evolved in some “consciousness/semantic” differentiation process, internal to arithmetic due to the reflexive incompleteness. 

This will not explain our personal historico-geographical relative position in all of this, though)

I would bet that the winning correction of GR, with respect to QM, is the one saving 3p determinacy and 3p locality, but also the 1p-plural locality (which is formally guarantee by the linearity of the tensor product).

I have reason that the numbers of histories might be as huge as the cardinal of Laver (the biggest know today) due to some possible (very intriguing) relations between braids and large cardinals. 

Descriptive set theory will play a role in the extraction of the unique physical measure in arithmetic. There are relation between the Pythagorean Heaven and Cantor Paradise!

Bruno

 

 

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

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[Bruno Marchal]

On 16 Sep 2019, at 02:46, spudboy100 via Everything List <everyth...@googlegroups.com> wrote:

My guess is among the physics community, most, would be mildly, skeptical of MWI, because it's a bridge too far to get evidence of, as yet and thus, unconcerned.

Hmm… I will criticise this on two levels.

1) there are evidence: Nature loves to multiply things, and each time we said that we know what our universe is, we get later that it was multiple. We have believe that Earth was the world, then that the solar system was the world, then that the galaxy was the world, then thanks to Hubble the guy, we eventually accept what Kant did suggest, that our galaxies are themselves multiple, and now we see them like little bacteria engulfed in filaments made of a mysterious matter, along with an observable matter no less mysterious as it implies a still bigger multiplication. 

2) Occam Razor. If you can explain everything with the axiom A and without the axiom B, get rid of axiom B, especially if it put some mess in your theory.

The theory 

Mechanism + SWE 

is simply much more conceptually simple than the theory 

SWE + an ontological physical collapse of on ontological physical wave (without mentioning the dualism in the implicit theory of mind).

Only one problem, for Mechanism to work, and notably to get the qualia extending the quanta (like G* extend G, or Z1* extends Z1), we need to re-prove constructively that Mechanism -> SWE, but there are promising result (I dare to say) in that direction.

Yes, the less axioms you have, the more possibilities/models you get, and with mechanism, there is a simple explanation why the possibilities have to interfere at some point. 

The most plausible theory is Mechanism. You need only to believe in 2+2=4 & Co. The appearance of the many worlds and they laws is explained from that, and in a precise way so that it can be tested, and thanks to QM, it works, and it explains the relation between qualia and quanta, consciousness and matter, etc. Maybe wrongly, but that has to be shown.

There are zero universe, also. So we get the conceptual Occam (smaller theory) and the ontological Occam, no physical universe at all, but a universal dreamer (the universal machine lost in an incredible web of dreams, some coherent up to make it able to say “hello” to itself, and develop infinite conversations, like bacteria ...

Having said this, many cosmologists are still having a cat fight about the Hubble Constant (The rate of cosmological expansion). my suspicion is, that once we get to the point of hanging truly gigantic telescopes on the periphery of the solar system, new discoveries will be made, and revisions to old laws of physics will be done. We'll gain a few definitive answers through observation, and we shall see that quantum in action at a vastly large scale. Relatedly, hey!, where's my dark matter? in fact, hey!, where's my fusion reactors. Ah! So much for the 'mentally fit' physicists and astronomers….

Nothing is simple. Not even Nothing.

Bruno

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[Jason Resch]

That is interesting and it is a good reminder how how flexible math is to representing various spaces and geometries.  Most cosmologists work under the assumption that space is "simply connected", rather than doughnut shaped or otherwise, in which case if space is simply connected, and flat, then it ought to be infinite.

There are also interesting things that can be done as far as compacting space, so that a finite cylinder can represent an infinite space evolving through time.  There are some good illustrations of this here:

https://www.podevin.com/single-post/2019/01/24/Einsteins-Dream-of-a-Grand-Unified-Theory

Also known as a "Poincare disk" https://en.wikipedia.org/wiki/Poincar%C3%A9_disk_model   http://mathworld.wolfram.com/PoincareHyperbolicDisk.html

Jason

[Alan Grayson]

Concerning a flat and spatially finite geometry, say shaped like a square, when you get to what appears an edge, how do you wind up emerging on the opposite appearing edge? AG 

[Brent Meeker]

On 9/16/2019 5:39 AM, Bruno Marchal wrote:
> As I said I my other post, it is just Descartes’ idea that our body
> obeys laws which are locally computable, made precise by using Turing
> mathematical definition of computability. It is the hypothesis that
> there no magic happening in the brain, somehow. Or that the brain is
> Digitally emulable *at some description level* relevant for staying
> alive and well.

But then you conclude that physical objects, like brains, are not Turing
computable...and thus arrive at contradiction to your starting hypothesis.

Brent

[spudb...@aol.com]

Yes, Bruno, it's all axiomatic. Having said this, we can do away with MWI by simply calling it all, an infinite (my term is near-infinite, a non sequitur), and we still hypothetically receive the same results as chaotic inflation, or the happy Hugh Everett, dance of worlds. From trans-cosmic invaders from alternate Earths, I'd hope it would be from 3 different cosms where other human species were successful. Dance with Denisovans, battle with Neanderthals, do mathematics with Boskones (they gota be good at math with those big heads?). We leave one discussion out of our thoughts. Which is how many of these oblate spheroids that we split off to, are just empty vacuums, or false vacuums? Thus, it's the internal content of any given cosmos that matters. No minds (to me) equals non-consciousness, and that Swiss guy, Schrodinger seems to agree with me. I'll just jot off and submit this to the committee and await my Fields Prize. 

https://groups.google.com/d/msgid/everything-list/DDAE2632-6951-443B-B64F-C15D92BD2C26%40ulb.ac.be

.

[Russell Standish]

On Fri, Sep 13, 2019 at 08:25:06PM -0700, Alan Grayson wrote:
>
> Whether they're boring or not is irrelevant. As I previously posted, an
> uncountable infinity of universes is possible without any repeats. AG 
>

Incorrect. Each world has a finite amount of information that defines
it, and consequently nonzero measure. If these worlds are drawn from
an uncountable infinite set, then there must be an uncountable number
of copies of each world.


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[Alan Grayson]

On Monday, September 16, 2019 at 7:20:57 PM UTC-6, Russell Standish wrote:

On Fri, Sep 13, 2019 at 08:25:06PM -0700, Alan Grayson wrote:
>
> Whether they're boring or not is irrelevant. As I previously posted, an
> uncountable infinity of universes is possible without any repeats. AG 
>

Incorrect. Each world has a finite amount of information that defines
it, and consequently nonzero measure. If these worlds are drawn from
an uncountable infinite set, then there must be an uncountable number
of copies of each world.

This argument breaks down if worlds are infinite. To prove any of this, 

we need to do some real mathematics. So far I see it as conjectural. AG 

[Russell Standish]

On Mon, Sep 16, 2019 at 07:42:18PM -0700, Alan Grayson wrote:
>
>
> On Monday, September 16, 2019 at 7:20:57 PM UTC-6, Russell Standish wrote:
>
> On Fri, Sep 13, 2019 at 08:25:06PM -0700, Alan Grayson wrote:
> >
> > Whether they're boring or not is irrelevant. As I previously posted, an
> > uncountable infinity of universes is possible without any repeats. AG 
> >
>
> Incorrect. Each world has a finite amount of information that defines
> it, and consequently nonzero measure. If these worlds are drawn from
> an uncountable infinite set, then there must be an uncountable number
> of copies of each world.
>
>
> This argument breaks down if worlds are infinite. To prove any of this, 
> we need to do some real mathematics. So far I see it as conjectural. AG 
>

I just don't see how it could be possible for a world to contain an
infinite amount of information. But as people have noted here, the
word "world" is ambiguous.