Harvey

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In this thread 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 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.
« Last Edit: August 03, 2020, 12:28:25 pm by Harvey »

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Mammal

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Nobody is denying the need for an explanation of the scientific conundrum. Phycisists are working on it.

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

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Nobody is denying the need for an explanation of the scientific conundrum. Phycisists are working on it.

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. 

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Fred

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In this thread 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 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)
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Harvey

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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.

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Mammal

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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 on why fine tuning is a bit of a misnomer, remember.
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Harvey

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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.

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Jabberwock

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This is just a misunderstanding of probability. It makes no difference whether the multiverse exists or not.
First learn to spell "ironic discussion"...

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Harvey

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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.

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kurros

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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

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.
« Last Edit: August 03, 2020, 05:46:37 pm by kurros »

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hatsoff

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In this thread 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?

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Harvey

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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.

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Harvey

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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.

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kurros

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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.

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Harvey

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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.