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General Discussion => Choose Your Own Topic => Topic started by: Harvey on August 03, 2020, 12:23:58 pm

Title: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 03, 2020, 12:23:58 pm
In this thread (https://www.reasonablefaith.org/forums/index.php?topic=6057081.msg1275752365#msg1275752365) there was an objection to my statement:

Quote
Yes, there could be some ultimate naturalistic reason [for fine-tuning of the cosmological constant that] it is exactly such a small value and couldn't have been a few orders higher, but that seems very unlikely.

This comment is understood to be a reasonable scientific conclusion from such comments such as this famous paper (https://arxiv.org/abs/astro-ph/9701099) which Steven Weinberg (a nobel laureate in particle physics for developing the standard model) was an author:

Quote
Though the evidence is still equivocal, there are persistent hints that the vacuum energy
density Pv is positive, and up to 3 times greater than the present cosmic mass density Po. From the point of view of fundamental physics, such a value seems absurd. Crude estimates indicate a value of Pv some 120 orders of magnitude greater than Po, and while it is hard enough to imagine any sort of symmetry or adjustment mechanism that could make Pv vanish (for a litany of failed attempts, see Weinberg [1989]), it would be even more peculiar for fundamental physical theory to dictate a non-zero value for Pv that happens to be
comparable to the cosmic mass density Po at this particular moment in the history of the
universe. As far as we know, the only way to understand a value of Pv to Po is based on a weak form of the anthropic principle.

Of course the reason why an anthropic principle [utilizing a multiverse] is seen as necessary "to understand a value of Pv comparable to Po" is because a non-multiverse/naturalist view appears very unlikely -- hence my statement above. This opinion is widely shared in both the scientific and philosophical community that it is seldom questioned. For example:

Quote
..can science explain the extraordinary fact that the universe appears to be uncannily, nay, spectacularly well-designed for our own existence? ….. to make the first 119 decimal places of the vacuum energy zero is almost certainly no accident.” [Lenny Susskind]

Quote
There is for me powerful evidence that there is something going on behind it all….It seems as though somebody has fine-tuned nature’s numbers to make the Universe….The impression of design is overwhelming [Paul Davies]

Quote
For those readers who are interested, the arithmetic is in the notes. The answer, in round numbers, comes to about one chance in 10^229. To illustrate how truly ridiculous this number is, we might note that the part of the universe we can see from earth contains about 10^22 stars which together contain about 10^80 protons and neutrons. These numbers are gigantic, but they are infinitesimal compared to 10^229. In my opinion, a probability this tiny is not something we can let go unexplained. Luck will certainly not do here; we need some rational explanation of how something this unlikely turned out to be the case. [Lee Smolin]

Quote
In order to explain the fine-tuning, one has to postulate the existence of a multiverse, consisting of remote domains where the constants of nature are different. [Alexander Vilenkin]

Quote
Nothing has shaken my atheism as much as this discovery.[Fred Hoyle]

Quote
The laws of science, as we know them at present, contain many fundamental numbers… the values of these numbers seem to have been very finely adjusted to make possible the development of life. [Stephen Hawking]

Quote
The Universe we live in seems to be a very unlikely place… Are we just lucky? Or is there some deep significance to the fact that we live in a Universe just right for us?[New Scientist]

Quote
The universe is unlikely. Very unlikely. Deeply, shockingly, unlikely. [Discover Magazine]

So, this issue to justify a belief in this unlikeliness assuming naturalism and no multiverse is not just an apologist argument. It's just false to think that. However, regardless how compelling and how many come to this conclusion, it is still reasonable to explicate what is meant by unlikeliness for the same reason it is necessary to understand what makes for better scientific explanations. So, this thread tries to address this issue.

Let's define Q and R as follows:

Q: To account for fine-tuning of the cosmological constant requiring to cancel out 119 (or so) orders of magnitude without a multiverse (assuming a naturalistic metaphysics) then C1) some sort of symmetry or adjustment mechanism would need to exist to make Pv vanish. In addition, C2) such a fundamental physical theory would need to dictate a non-zero value for Pv that happens to be comparable to the cosmic mass density Po at this particular moment in the history of the universe.

R: Such a physical theory that is not apart of any multiverse theories [call such theories M] but assumes naturalist metaphysics and meets conditions in C1 and C2 has no counterpart in terms of finding a theory like this in the history of science, and given the extremity of those conditions that such a hypothetical physical theory would have to meet, the inductive probability of such a theory existing is very low. Hence, such an alternate naturalist-compliant theory [call it ~M] to a multiverse is very unlikely.

Since cosmologists are confident in Q, they have high confidence that R is true.  This inductive probability is epistemic since the cosmologists are acting with complete physical competence in their field while employing correct inductive principles that have consistently produced great results for the entirety of modern science. Hence, ~M is highly unlikely.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Mammal on August 03, 2020, 01:17:56 pm
Nobody is denying the need for an explanation of the scientific conundrum. Phycisists are working on it (https://en.m.wikipedia.org/wiki/Cosmological_constant_problem#Proposed_solutions).

But I'll leave it for lapetus as he asked for your motivation of this argument.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 03, 2020, 01:48:57 pm
Nobody is denying the need for an explanation of the scientific conundrum. Phycisists are working on it (https://en.m.wikipedia.org/wiki/Cosmological_constant_problem#Proposed_solutions).

But I'll leave it for lapetus as he asked for your motivation of this argument.

This is addressing Hatsoff's request. As far as your link I guess new physics (which sets the cosmological constant at zero) is certainly one approach but such approaches do nothing against other fine-tuning problems. Also, those who propose such a solution do not appear to be taken too seriously based on the people who seem to say that a multiverse is the only option as they see it. You are an avid atheist who doesn't want to admit any daylight to the Teleological Argument but that's not an epistemic approach to the issue. 
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Fred on August 03, 2020, 01:58:30 pm
In this thread (https://www.reasonablefaith.org/forums/index.php?topic=6057081.msg1275752365#msg1275752365) there was an objection to my statement:

Quote
Yes, there could be some ultimate naturalistic reason [for fine-tuning of the cosmological constant that] it is exactly such a small value and couldn't have been a few orders higher, but that seems very unlikely.

This comment is understood to be a reasonable scientific conclusion from such comments such as this famous paper (https://arxiv.org/abs/astro-ph/9701099) which Steven Weinberg (a nobel laureate in particle physics for developing the standard model) was an author:

Quote
Though the evidence is still equivocal, there are persistent hints that the vacuum energy
density Pv is positive, and up to 3 times greater than the present cosmic mass density Po. From the point of view of fundamental physics, such a value seems absurd. Crude estimates indicate a value of Pv some 120 orders of magnitude greater than Po, and while it is hard enough to imagine any sort of symmetry or adjustment mechanism that could make Pv vanish (for a litany of failed attempts, see Weinberg [1989]), it would be even more peculiar for fundamental physical theory to dictate a non-zero value for Pv that happens to be
comparable to the cosmic mass density Po at this particular moment in the history of the
universe. As far as we know, the only way to understand a value of Pv to Po is based on a weak form of the anthropic principle.

Of course the reason why an anthropic principle [utilizing a multiverse] is seen as necessary "to understand a value of Pv comparable to Po" is because a non-multiverse/naturalist view appears very unlikely -- hence my statement above. This opinion is widely shared in both the scientific and philosophical community that it is seldom questioned. For example:

Quote
..can science explain the extraordinary fact that the universe appears to be uncannily, nay, spectacularly well-designed for our own existence? ….. to make the first 119 decimal places of the vacuum energy zero is almost certainly no accident.” [Lenny Susskind]

Quote
There is for me powerful evidence that there is something going on behind it all….It seems as though somebody has fine-tuned nature’s numbers to make the Universe….The impression of design is overwhelming [Paul Davies]

Quote
For those readers who are interested, the arithmetic is in the notes. The answer, in round numbers, comes to about one chance in 10^229. To illustrate how truly ridiculous this number is, we might note that the part of the universe we can see from earth contains about 10^22 stars which together contain about 10^80 protons and neutrons. These numbers are gigantic, but they are infinitesimal compared to 10^229. In my opinion, a probability this tiny is not something we can let go unexplained. Luck will certainly not do here; we need some rational explanation of how something this unlikely turned out to be the case. [Lee Smolin]

Quote
In order to explain the fine-tuning, one has to postulate the existence of a multiverse, consisting of remote domains where the constants of nature are different. [Alexander Vilenkin]

Quote
Nothing has shaken my atheism as much as this discovery.[Fred Hoyle]

Quote
The laws of science, as we know them at present, contain many fundamental numbers… the values of these numbers seem to have been very finely adjusted to make possible the development of life. [Stephen Hawking]

Quote
The Universe we live in seems to be a very unlikely place… Are we just lucky? Or is there some deep significance to the fact that we live in a Universe just right for us?[New Scientist]

Quote
The universe is unlikely. Very unlikely. Deeply, shockingly, unlikely. [Discover Magazine]

So, this issue to justify a belief in this unlikeliness assuming naturalism and no multiverse is not just an apologist argument. It's just false to think that. However, regardless how compelling and how many come to this conclusion, it is still reasonable to explicate what is meant by unlikeliness for the same reason it is necessary to understand what makes for better scientific explanations. So, this thread tries to address this issue.

Let's define Q and R as follows:

Q: To account for fine-tuning of the cosmological constant requiring to cancel out 119 (or so) orders of magnitude without a multiverse (assuming a naturalistic metaphysics) then C1) some sort of symmetry or adjustment mechanism would need to exist to make Pv vanish. In addition, C2) such a fundamental physical theory would need to dictate a non-zero value for Pv that happens to be comparable to the cosmic mass density Po at this particular moment in the history of the universe.

R: Such a physical theory that is not apart of any multiverse theories [call such theories M] but assumes naturalist metaphysics and meets conditions in C1 and C2 has no counterpart in terms of finding a theory like this in the history of science, and given the extremity of those conditions that such a hypothetical physical theory would have to meet, the inductive probability of such a theory existing is very low. Hence, such an alternate naturalist-compliant theory [call it ~M] to a multiverse is very unlikely.

Since cosmologists are confident in Q, they have high confidence that R is true.  This inductive probability is epistemic since the cosmologists are acting with complete physical competence in their field while employing correct inductive principles that have consistently produced great results for the entirety of modern science. Hence, ~M is highly unlikely.
Oh my. It seems that the probability that life would exist is very low.  (yawn)
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 03, 2020, 02:21:16 pm
Oh my. It seems that the probability that life would exist is very low.  (yawn)

Lol. I thought your doctor said no fine-tuning discussions.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Mammal on August 03, 2020, 02:46:48 pm
As far as your link I guess new physics (which sets the cosmological constant at zero) is certainly one approach but such approaches do nothing against other fine-tuning problems. Also, those who propose such a solution do not appear to be taken too seriously based on the people who seem to say that a multiverse is the only option as they see it. You are an avid atheist who doesn't want to admit any daylight to the Teleological Argument but that's not an epistemic approach to the issue.
Well, afaik (at least some of) those suggested solutions (and others that I have also mentioned) are in fact taken seriously. No Harvey, it is not because I am an avid atheist. We agree (https://www.reasonablefaith.org/forums/index.php?topic=6057081.msg1275752329#msg1275752329) on why fine tuning is a bit of a misnomer, remember.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 03, 2020, 02:54:46 pm
Well, afaik those suggested solutions (and others that I have also mentioned) are in fact taken seriously.

You're mistaken. Here is what MSW said that I quoted in the OP:

Quote
Crude estimates indicate a value of Pv some 120 orders of magnitude greater than Po, and while it is hard enough to imagine any sort of symmetry or adjustment mechanism that could make Pv vanish (for a litany of failed attempts, see Weinberg [1989])

Here is what Weinberg says in the referenced paper:

Quote
Intriguing as these results are, they have not been taken seriously (even by the original authors) as a solution of the cosmological constant problem.

And, as I already pointed out, these attempts to deal with the cosmological constant problem do not begin to address other areas outside the CC where fine tuning exists.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Jabberwock on August 03, 2020, 03:37:31 pm
This is just a misunderstanding of probability. It makes no difference whether the multiverse exists or not.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 03, 2020, 04:03:43 pm
This is just a misunderstanding of probability. It makes no difference whether the multiverse exists or not.

Sorry, it takes more than an off handed comment to swipe away the opinion of multiple distinguished cosmologists.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: kurros on August 03, 2020, 05:44:53 pm
It depends what you are asking, exactly. The inference from fine-tuning to multiverse is not justified; however, *if* we had independent evidence of a multiverse *then* it would be a good explanation of fine tuning.

I came across this argument yesterday in a recent paper, it seemed to make quite a lot of sense: https://link.springer.com/article/10.1007/s10838-018-9422-3 (https://link.springer.com/article/10.1007/s10838-018-9422-3)

I think this paper, like many others on the subject, neglects important issues in the interpretation of probability, but it nevertheless makes some good points.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: hatsoff on August 03, 2020, 07:13:59 pm
In this thread (https://www.reasonablefaith.org/forums/index.php?topic=6057081.msg1275752365#msg1275752365) there was an objection to my statement:

Quote
Yes, there could be some ultimate naturalistic reason [for fine-tuning of the cosmological constant that] it is exactly such a small value and couldn't have been a few orders higher, but that seems very unlikely.

I guess this is a response to my question.  But remember, I was only asking you what you meant by your claim, not for a justification.  After all, I can't evaluate any attempted justification until I first understand what exactly it is that you're claiming in the first place.  So, quotes from cosmologists aren't going to help with that.

But you did say this, which gives me a clue:

Quote
the inductive probability of such a theory existing is very low.

By "such a theory", I take you to mean a scientific theory that provides a naturalistic explanation for why the constants fall within the life-permitting range.  Is that correct?  And then, you think it's unlikely that such a theory could ever be true.  Correct?
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 03, 2020, 07:57:14 pm
It depends what you are asking, exactly. The inference from fine-tuning to multiverse is not justified; however, *if* we had independent evidence of a multiverse *then* it would be a good explanation of fine tuning.

I agree. However, the OP is specific to a ~M theory and its unlikeliness.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 03, 2020, 08:21:40 pm
By "such a theory", I take you to mean a scientific theory that provides a naturalistic explanation for why the constants fall within the life-permitting range.  Is that correct?

Yes, but it's a non-multiverse theory (which I call a ~M theory in the OP).

Quote from: hatsoff
And then, you think it's unlikely that such a theory could ever be true.  Correct?

Yes, that's correct. Just one clarification. It's always theoretically possible to adjust the current background theories such as GRT that the cosmological constant becomes zero (or is eliminated altogether), but that revision to the background theories (such as GRT) will result in an overly complicated and unconvincing background theories (not to mention it wouldn't work for fine-tuning of other constants other than the cosmological constant). But, in absence of modification to a current background theories it is very unlikely to find such a ~M theory that would cancel out 119 (or so) orders of magnitude that meets conditions C1 and C2.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: kurros on August 03, 2020, 08:50:45 pm
By "such a theory", I take you to mean a scientific theory that provides a naturalistic explanation for why the constants fall within the life-permitting range.  Is that correct?

Yes, but it's a non-multiverse theory (which I call a ~M theory in the OP).

Quote from: hatsoff
And then, you think it's unlikely that such a theory could ever be true.  Correct?

Yes, that's correct. Just one clarification. It's always theoretically possible to adjust the current background theories such as GRT that the cosmological constant becomes zero (or is eliminated altogether), but that revision to the background theories (such as GRT) will result in an overly complicated and unconvincing background theories (not to mention it wouldn't work for fine-tuning of other constants other than the cosmological constant). But, in absence of modification to a current background theories it is very unlikely to find such a ~M theory that would cancel out 119 (or so) orders of magnitude that meets conditions C1 and C2.

This just seems like pure speculation on your part. I don't see any reason to believe that a theory that removes all fine tuning completely is impossible or even unlikely. And indeed I think it would be a very severe mistake to believe that we will never make any modifications to the "background theories" like general relativity or quantum field theory. In fact all progress in quantum gravity points to the exact opposite conclusion.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 03, 2020, 09:02:03 pm
This just seems like pure speculation on your part. I don't see any reason to believe that a theory that removes all fine tuning completely is impossible or even unlikely. And indeed I think it would be a very severe mistake to believe that we will never make any modifications to the "background theories" like general relativity or quantum field theory. In fact all progress in quantum gravity points to the exact opposite conclusion.

Don't shoot the messenger of what the top notch cosmologists are saying.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Fred on August 03, 2020, 10:48:13 pm
Oh my. It seems that the probability that life would exist is very low.  (yawn)

Lol. I thought your doctor said no fine-tuning discussions.
Intelligent discussions are fine, it's the crazy talk that raises my blood pressure.

Speaking of crazy talk, the title of this tread is crazy:

Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?[/i]
Actually, cosmologists may be justified in thinking life is very unlikely, not that "fine-tuning" is unlikely. 
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 03, 2020, 11:35:23 pm
Based on our background theories (e.g., GRT) the naturalist is forced to say that the cosmological constant is extremely fine-tuned which is so unlikely to have occurred without a multiverse, hence naturalism fails in that case.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: lucious on August 03, 2020, 11:47:50 pm
I actually thought this was common knowledge and entirely uncontroversial that the naturalist would need to multiply his explanatory resources with trillions of multiverses to explain away the fine tuning.


Even still, you are left with the issue of meta-fine tuning for the multiverse ensemble and the problem of Boltzmann brains.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: kurros on August 03, 2020, 11:52:55 pm
This just seems like pure speculation on your part. I don't see any reason to believe that a theory that removes all fine tuning completely is impossible or even unlikely. And indeed I think it would be a very severe mistake to believe that we will never make any modifications to the "background theories" like general relativity or quantum field theory. In fact all progress in quantum gravity points to the exact opposite conclusion.

Don't shoot the messenger of what the top notch cosmologists are saying.

I am not aware of this being any sort of consensus among cosmologists. In fact I know quite a few cosmologists and I don't think any of them think this.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: hatsoff on August 04, 2020, 01:29:40 am
This just seems like pure speculation on your part. I don't see any reason to believe that a theory that removes all fine tuning completely is impossible or even unlikely. And indeed I think it would be a very severe mistake to believe that we will never make any modifications to the "background theories" like general relativity or quantum field theory. In fact all progress in quantum gravity points to the exact opposite conclusion.

Don't shoot the messenger of what the top notch cosmologists are saying.

As kurros has already pointed out, there's no reason to think this is a consensus among cosmologists.  Indeed, I would be surprised if very many at all thought such a thing.  And the quotes you regularly provide from cosmologists like Weinberg don't say anything like that either, as far as I can tell.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Jabberwock on August 04, 2020, 03:54:29 am
Sorry, it takes more than an off handed comment to swipe away the opinion of multiple distinguished cosmologists.

The article that kurros linked basically says the same thing.

Suppose that you have two scenarios: both involve a lottery and in both Jones wins by buying the first ticket. The difference is in the first case all other tickets are bought and in the second the lottery is stopped after the sale of the first ticket. What are the odds of Jones' winning in both cases? Exactly the same. So what difference does it make whether the rest of the tickets is bought (the multiverse exists) or not?
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 04, 2020, 05:59:08 am
I am not aware of this being any sort of consensus among cosmologists. In fact I know quite a few cosmologists and I don't think any of them think this.

Think what?
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 04, 2020, 06:03:56 am
As kurros has already pointed out, there's no reason to think this is a consensus among cosmologists.  Indeed, I would be surprised if very many at all thought such a thing.  And the quotes you regularly provide from cosmologists like Weinberg don't say anything like that either, as far as I can tell.

This is why I put the quotes in the OP. As MSW said:

Quote
As far as we know, the only way to understand a value of Pv to Po is based on a weak form of the anthropic principle.

And by Weinberg (1989) referring to competing ~M theories:

Quote
Intriguing as these results are, they have not been taken seriously (even by the original authors) as a solution of the cosmological constant problem.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 04, 2020, 06:08:00 am
Suppose that you have two scenarios: both involve a lottery and in both Jones wins by buying the first ticket. The difference is in the first case all other tickets are bought and in the second the lottery is stopped after the sale of the first ticket. What are the odds of Jones' winning in both cases? Exactly the same. So what difference does it make whether the rest of the tickets is bought (the multiverse exists) or not?

See my reply to Kurros for that paper. I apologize for the quock answer but I'm trying to reply to multiple people.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: hatsoff on August 04, 2020, 06:25:05 am
As kurros has already pointed out, there's no reason to think this is a consensus among cosmologists.  Indeed, I would be surprised if very many at all thought such a thing.  And the quotes you regularly provide from cosmologists like Weinberg don't say anything like that either, as far as I can tell.

This is why I put the quotes in the OP. As MSW said:

Quote
As far as we know, the only way to understand a value of Pv to Po is based on a weak form of the anthropic principle.

And by Weinberg (1989) referring to competing ~M theories:

Quote
Intriguing as these results are, they have not been taken seriously (even by the original authors) as a solution of the cosmological constant problem.

Hmm, but this doesn't address my concern.  And then I noticed you also asked kurros (who has the same concern) what he was referring to.  So, it seems you've forgotten what the current topic of conversation is right now.  I suppose that can happen when the conversation is strewn out over multiple days.  So, let me remind you.

You claimed that it's unlikely for there to ever be a true scientific theory, compatible with single-universe naturalism, that explains why the constants in physics take on life-permitting values.  This is the same claim that kurros called "pure speculation on your part".  I for one would like to know what's your basis for this claim.

If you don't have any good argument or evidence, then you could instead appeal to authority, which is what it seems like you want to do.  In this context, an appeal to authority might be appropriate, so long as we're careful.  But none of the authorities you've quoted say anything like what you've claimed.  Again, that could just be because you were giving the wrong quotes since you lost track of the topic over the course of several days.  Now that you've been reminded, what do you think?
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 04, 2020, 07:31:19 am
You claimed that it's unlikely for there to ever be a true scientific theory, compatible with single-universe naturalism, that explains why the constants in physics take on life-permitting values.  This is the same claim that kurros called "pure speculation on your part".  I for one would like to know what's your basis for this claim.

No, I said it is unlikely that based on the current background theories (e.g., GRT) and assuming natiralism that fine-tuning of the cosmological constant having conditions C1 and C2 can be explained without a multiverse. Theoretically it's possible to make changes to the background theories to remove the problems to the cosmological constant (e.g., by making equal to zero or eliminating the cosmological constant altogether), but Weinberg (1989) showed why this is not very likely. Of course, it's possible that Weinberg was basing his view on a lack of information, but there are many more constants that are fine-tuned which even if the CC is made to zero or eliminated, it would still not account for all of that fine-tuning. Kurros suggested quantum gravity eliminating fine-tuning, but the fine-tuning problem assumes the current background theories (such as GRT) and that whatever happens in the future with respect to new theories we will not see such a major revamp. Of course, no cosmologist could ever say that any major revamp is "unlikely" in a logically inductive sense since no physicist is God. Even biologists cannot say that evolution won't be rewritten by little green men if hidden cameras spot them modifying a genome of a frog deep in the Amazon. What I think is the general view among cosmologists is that fine-tuning of the cosmological constant needs an explanation and due to C1 and C2 it is unlikely that current background theories will be modified to remove those coincidences and therefore a multiverse is needed. Susskind says that this is probably the general view of cosmologists if someone was holding a gun to their heads.

Quote from: hatsoff
If you don't have any good argument or evidence, then you could instead appeal to authority, which is what it seems like you want to do.  In this context, an appeal to authority might be appropriate, so long as we're careful.  But none of the authorities you've quoted say anything like what you've claimed. 

How do you think my quotes in the OP fail to make that claim? Vilenkin says: "In order to explain the fine-tuning, one has to postulate the existence of a multiverse, consisting of remote domains where the constants of nature are different.."

Quote from: hatsoff
Now that you've been reminded, what do you think?

I'm wondering if we're talking past each other. I am only saying what Vilenkin and MSW are saying about a multiverse as the only explanation known, assuming naturalism, that can account for fine-tuning given the current background theories with modifications currently understood as possible. I think you and Kurros think I'm saying that cosmologists know for certain that physical theories of the future won't do away with fine-tuning. I'm not saying that. Maybe I said something to make you think that, but if so I apologize for the confusion.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: hatsoff on August 04, 2020, 08:14:03 am
No

Hmm.  Okay, but then we're back to square one.  Let me recap the conversation, if you don't mind.  It all started with this claim (emphasis mine):

A constant value that is not zero has no reason being that value (that we know of) compared to millions of other apparently possible values. Yes, there could be some ultimate naturalistic reason it is exactly such a small value and couldn't have been a few orders higher, but that seems very unlikely.

This seems to be a key claim---your argument seems to hinge on it in a crucial way.  And yet when I go to consider whether it's true, I find myself puzzled as to what your claim even means.  That's what I've been asking you to explain to me, and what I wish you would address. ...I want to know how to make sense of your claiming that it's 'very unlikely' that the constants are what they are, or that they are life-permitting, or whatever it is that you were trying to say.

Yes, there could be some ultimate naturalistic reason [for fine-tuning of the cosmological constant that] it is exactly such a small value and couldn't have been a few orders higher, but that seems very unlikely.  ...the inductive probability of such a theory existing is very low.

By "such a theory", I take you to mean a scientific theory that provides a naturalistic explanation for why the constants fall within the life-permitting range.  Is that correct?  And then, you think it's unlikely that such a theory could ever be true.  Correct?

Yes, that's correct. Just one clarification. It's always theoretically possible to adjust the current background theories such as GRT that the cosmological constant becomes zero (or is eliminated altogether), but that revision to the background theories (such as GRT) will result in an overly complicated and unconvincing background theories (not to mention it wouldn't work for fine-tuning of other constants other than the cosmological constant). But, in absence of modification to a current background theories it is very unlikely to find such a ~M theory that would cancel out 119 (or so) orders of magnitude that meets conditions C1 and C2.

And here are C1 and C2, according to you:

C1) some sort of symmetry or adjustment mechanism would need to exist to make Pv vanish. In addition, C2) such a fundamental physical theory would need to dictate a non-zero value for Pv that happens to be comparable to the cosmic mass density Po at this particular moment in the history of the universe.

So, this is all very puzzling to me.  It could be that I'm just too dense to see what you mean.  But you might want to also consider the possibility that perhaps you aren't very clear yourself on what you're trying to say.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 04, 2020, 08:36:26 am
So, this is all very puzzling to me.  It could be that I'm just too dense to see what you mean.  But you might want to also consider the possibility that perhaps you aren't very clear yourself on what you're trying to say.

I'm definitely willing to look at where I'm being inconsistent (perhaps many times over). But, in my mind, I have an image of what I'm saying:

1) "Yes, there could be some ultimate naturalistic reason it is exactly such a small value and couldn't have been a few orders higher, but that seems very unlikely.": So MSW say that they "As far as we know, the only way to understand a value of Pv to Po is based on a weak form of the anthropic principle." And, Vilenkin says "In order to explain the fine-tuning, one has to postulate the existence of a multiverse," I take those two statements to be equivalent expressions that having the current background theories (such as GRT) it seems very unlikely to develop a ~M theory of fine-tuning (at least on an epistemic-inductive view of unlikeliness). I agree it's not so in a logically-inductive view because that would mean to say we know every logical fact about the universe and would therefore know the likelihood of the next theory of science. That's completely unknowable by science as my reference to little green men on hidden cameras was meant to illustrate. However, based on what we know now, there's no reason to think it at all likely that an ~M theory is forthcoming. I base that on the comments by Vilenkin, MSW, et al. in my OP.

2) "I want to know how to make sense of your claiming that it's 'very unlikely' that the constants are what they are, or that they are life-permitting, or whatever it is that you were trying to say." So, as said in (1) I am distinguishing epistemic and logical forms of inductive probability. One is fallible based on what many of the most esteemed cosmologists believe to be "very unlikely" which is why they feel a multiverse theory is "the only way to understand a value of Pv to Po" or, alternatively, "in order to explain the fine-tuning, one has to postulate the existence of a multiverse." That is an epistemic version of inductive probability which is my proposal to explicate my notion of "unlikely" in the OP.

Is this answer still not satisfactory for you? Thanks.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Fred on August 04, 2020, 09:13:38 am
Based on our background theories (e.g., GRT) the naturalist is forced to say that the cosmological constant is extremely fine-tuned which is so unlikely to have occurred without a multiverse, hence naturalism fails in that case.
LOL! You are truly incorrigible. Do you seriously believe that, or are you playing games?
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 04, 2020, 09:26:14 am
LOL! You are truly incorrigible. Do you seriously believe that, or are you playing games?

You should be happy I'm right. It means if tragedy strikes or someone you love reaches their end that there is still heaven. I should be your best friend giving you such good news.
Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Fred on August 04, 2020, 10:17:11 am
LOL! You are truly incorrigible. Do you seriously believe that, or are you playing games?

You should be happy I'm right. It means if tragedy strikes or someone you love reaches their end that there is still heaven. I should be your best friend giving you such good news.
I feel sad that you actually believe your statement:

Based on our background theories (e.g., GRT) the naturalist is forced to say that the cosmological constant is extremely fine-tuned which is so unlikely to have occurred without a multiverse, hence naturalism fails in that case.

Title: Re: Are cosmologists justified that fine-tuning is very unlikely w/o a multiverse?
Post by: Harvey on August 04, 2020, 10:23:37 am
Matbe your sadness comes from you not believing it.