Fred

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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. 
Fred

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Harvey

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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.

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lucious

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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.

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kurros

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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.

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hatsoff

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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.

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Jabberwock

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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?
First learn to spell "ironic discussion"...

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Harvey

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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?

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Harvey

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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.

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Harvey

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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.

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hatsoff

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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?

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Harvey

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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.
« Last Edit: August 04, 2020, 07:34:04 am by Harvey »

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hatsoff

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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.

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Harvey

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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.

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Fred

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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?
Fred

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Harvey

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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.