L. Susskind -- The "Megaverse"

[Perpetual Student]

Are you wilfully being disingenuous? That was with regard to whether FRAMING a question that way was appropriate.
...

How amusing! You accuse me of being disingenuous right after accusing a significant part of the cosmology community of the same thing:

I wonder if framing the theories (which, as far as I can tell, are good theories) as solving a "fine-tuning" problem is simply a way to get media and people interested. I think framing something for publicity it's certainly an acceptable way to promote science.

By your reckoning, I guess I'm in good company.

 

[Acleron]

And the problem remains - what does your assertion that "we don't understand how they're interconnected, if at all" have to do with the question of why gravity is tuned for life?

To put it another way- can you tell us why a theory unifying General Relativity and electromagnetism (actually QM) is needed to explain the strength of gravity in this universe?

So far it looks like a "god of the gaps" type argument. We cannot explain X. There is a gap between theories A and B. Thus the explanation of X is in the unification of theories A and B without any idea what the unification means .

That's not quite fair. If there is a connection between them it may exclude certain combinations of constants. At the moment we have no idea. Any unification theory may not tell us that relationship.

 

[Fudbucker]

I wonder if framing the theories (which, as far as I can tell, are good theories) as solving a "fine-tuning" problem is simply a way to get media and people interested. I think framing something for publicity it's certainly an acceptable way to promote science.

It's too esoteric a topic for that. Max Tegmark, and others like him, seem pretty committed to the idea.

 

[Toontown]

The problem with this framing is that it is misleading and provides apparent support for those who present design arguments for the existence of the universe. A popular argument for creationists is that the universe as it exists is miraculous, that the universe is in such an unlikely state as to require a creator.

The multiverse hypothesis effectively nullifies the creationist design hypothesis, by offering a reasonable alternative.

There is no need to disprove creationism. It's only a hypothesis, and not a very good one. Simply offer a counter hypothesis that is more explanatory than goddunnit.

This argument requires that there is some robust sense in which the universe is unlikely to be the case. Often, this is presented in terms of anthropic arguments. This doesn't work for a number of reasons. The presence of the fine-tuning argument in physics gives creationists a chance to present an appeal to authority in place of the anthropic arguments they might otherwise present.

What 'authority'? You mean the 'authority' that supports the multiverse hypothesis?

If the multiverse hypothisis achieves mainstream acceptance, then the multiverse hypothesis will hold sway over the creationist fine tuning argument, because the multiverse hypothesis offers a better explanation for the apparent fine tuning than a fundamentally unexplainable creator god.

 

[Kwalish Kid]

Ah, so the root of all this hostility is a fear that someone will conjure up deities and fairies to explain the universe.
I hope evolutionary biologists don't lie about the fossil record for the same reason.
Misuse of scientific speculations is an old and tired game for the paranormal crowd, but
I suggest you both open up to an honest analysis of the question and not be so intimidated.

You misunderstand the point of my statement. If the idea was to frame research into the fundamentals of particle physics in a public friendly way, then fine-tuning is the wrong way to do it because it feeds into the talk of creationists.

Fine-tuning arguments are bad science when fine-tuning is assumed and inferences are drawn from this assumption. Fine-tuning arguments are bad when they are arguing from a weak anthropic argument to a grander claim of oddity; given that life has to fit into whatever environment we find it in, we cannot find it odd that life fits into whatever environment we find it in. That the universe might be just right for one type of life does not mean that there might be other kinds of life that might be fine in other kinds of universes. Fine-tuning arguments are, in principle, fine when physical evidence establishes that there is some reason to suppose that the current physical phenomena that we observe in our region of the universe are not those that we should see.

As of now, there is not good evidence that the physical phenomena that we see in our region of the universe are something that one should not expect or that one should treat as rare. That we can merely imagine theories with different values of various physical constants is not reason enough to assign some probability distribution to this range of possibility. This is what Susskind calls "strong theoretical" reasons, but so far these theories do not seem to enjoy strong empirical support.

So if someone is claiming that there is a fine-tuning problem in the sense that we must explain why we have the odd values of different physical constants that we do, they are mistaken. If someone is speaking of the fine-tuning problem in the sense that we have no explanation as to why we have one value rather than another, then this seems acceptable. Though it is not clear in what sense this is a "problem". That some physicists might wish to have a law-like explanation for everything does not mean that there is a law-like explanation for everything.

That is an honest approach to the science.

 

[Kwalish Kid]

If the multiverse hypothisis achieves mainstream acceptance, then the multiverse hypothesis will hold sway over the creationist fine tuning argument, because the multiverse hypothesis offers a better explanation for the apparent fine tuning than a fundamentally unexplainable creator god.

If the multiverse concept gains mainstream acceptance because we have a robust understanding of how our particular laws of physics came to be out of a number of possibilities, then fine. If, as is the case now, we have a number of physicists proclaiming that it really is a problem that requires an explanation, then the multiverse hypothesis fairs no better, and perhaps worse, than the creation hypothesis, at least in the public arena.

Given that all the work in mutliverse theory is incredibly hypothetical, it certainly suffers rhetorically when it seems that all sides in this debate grant that there is some oddity about the nature of our universe. I certainly accept that merely the existence of the multiverse hypothesis provides enough doubt to sink the creationist hypothesis, but I prefer to fight at a step removed, i.e., that we have no real sense that the universe as we know it is odd.

 

[Fudbucker]

If the multiverse concept gains mainstream acceptance because we have a robust understanding of how our particular laws of physics came to be out of a number of possibilities, then fine. If, as is the case now, we have a number of physicists proclaiming that it really is a problem that requires an explanation, then the multiverse hypothesis fairs no better, and perhaps worse, than the creation hypothesis, at least in the public arena.

Given that all the work in mutliverse theory is incredibly hypothetical, it certainly suffers rhetorically when it seems that all sides in this debate grant that there is some oddity about the nature of our universe. I certainly accept that merely the existence of the multiverse hypothesis provides enough doubt to sink the creationist hypothesis, but I prefer to fight at a step removed, i.e., that we have no real sense that the universe as we know it is odd.

Except that's wrong. The fact that the universe is odd is why there's a fine-tuning problem in the first place.

 

[TheRedWorm]

Except that's wrong. The fact that the universe is odd is why there's a fine-tuning problem in the first place.

Odd compared to which other universe?

 

[Fudbucker]

Odd compared to which other universe?

The ones we generate counterfactually if the values were different.

 

[Toontown]

Odd compared to which other universe?

Odd compared to everything that could have happened during the odd burst of activity, but didn't.

Odd compared to the entropic eternity that follows the odd burst of activity.

1 ringy-dingy.. . . . . . . . . . . . .

Let's see...a universe arbitrarily appears, expands to heat death, then spends eternity doing nothing, ever again.

Nope. Nothing odd there.. . . . . . . . . . . .

It is oddly comforting to know a one-off entropy-seeker isn't 'odd'.

 

[TheRedWorm]

The ones we generate counterfactually if the values were different.

Odd compared to everything that could have happened during the odd burst of activity, but didn't.

Odd compared to the entropic eternity that follows the odd burst of activity.

1 ringy-dingy.. . . . . . . . . . . . .

Let's see...a universe arbitrarily appears, expands to heat death, then spends a timeless eternity doing nothing, ever again.

Nope. Nothing odd there.. . . . . . . . . . . .

It is oddly comforting to know a one-off isn't 'odd'.

Still not seeing any odd behavior as compared to other universe(s). Have any examples?

 

[Toontown]

Still not seeing any odd behavior as compared to other universe(s). Have any examples?

Your oddly arbitrary requirement of oddness as compared to other odd universes is arbitrarily odd.

They're all odd. And if there is only one of them, it is odd. Oddness is a red herring. The requirement to compare relative oddness against other arbitrarily odd examples is a red herring.

 

[TheRedWorm]

But you're not comparing our universe to anything else. How can you say it is odd when you only have a sample size of one?

 

[Kwalish Kid]

Except that's wrong. The fact that the universe is odd is why there's a fine-tuning problem in the first place.

And now were back to this idea. Sigh.

If you have a probability distribution of the possible universe, I would love to see it. If you don't then why are you saying that the universe is odd?

It is possible to come up with theories that have variable physical constants at high energy that get fixed at a random value at lower energy. Are these theories true? Who knows? They do not yet seem to offer us a means to determine whether or not what we see is odd or not.

The fine-tuning problem encourages people to think in poor ways, to jump to conclusions about probability without thinking things all the way through.

 

[sol invictus]

Because we don't understand how they're interconnected, if at all. It could be analogous to, say, "why is the magnetic field active only when moving?" pre-SR.

Indeed. And asking that question turned out to be rather useful, didn't it?

The problem with this framing is that it is misleading and provides apparent support for those who present design arguments for the existence of the universe. A popular argument for creationists is that the universe as it exists is miraculous, that the universe is in such an unlikely state as to require a creator.

When it was first proposed, people objected to the big bang on similar grounds.

Science proceeds by asking questions about phenomena that look intriguing to scientists. If some of those investigations or their (possibly tentative) conclusions disturb your personal worldview, tough luck. Science and scientists couldn't care less (or at least they shouldn't, unless we are discussing things that might actually pose a real risk).


The fundamental physical constants indeed look fine-tuned. Why? Here are several possibilities:

(1) There is only one possible set of values for physical constants, and they are what they are. In this case, we should focus on understanding why only that set is possible. I find this highly implausible (for reasons I'd be happy to elaborate on).

(2) There are many possible values, and we are very finely adapted to the values they happen to take (the anthropic or "puddle" argument). This is more plausible, but not the whole story.

I think - and yes, this is speculative, but based on mathematics and what we have learned about fundamental physics - that there are probably many, many possible values that vary as you move around in the universe, but not every conceivable set of values can occur, and some sets occur far more frequently than others. Some of the apparent fine tuning is anthropic (if the values weren't in certain ranges, no one would be here to ask about them), and some of it is due to interesting and as-yet poorly understood constraints on what is possible or common.

There is an active subfield in which people are exploring these possibilities. Speculative? You bet. Dead end? Maybe - time will tell. What's certain is that people are not going to stop discussing these questions. They're too interesting for that to happen.

 

[Toontown]

But you're not comparing our universe to anything else. How can you say it is odd when you only have a sample size of one?

You have substituted the adjective "odd" for the adjective "unlikely", as if the two adjectives have the same meaning. The two adjectives do not convey the same meaning. They are only remotely related, if at all.

Get rid of the red herring, and maybe we can talk.

Actually, you may have slammed two red herrings on the table. You seem to have used the word substitution as a springboard to infer that the multiverse hypothesis is false because there is no data base of observed universes to compare with one another to determine which ones are "odd". Therefore multiverse proponents cannot say this one is "odd". Therefore they have no argument.

But that never was the argument in the first place. If anything is being compared, it is possibilities, not observed universes.

Example: I have never tried to shoot a dime-sized target a mile away. Therefore I have no statistical data base upon which to base my hypothesis that it is highly unlikely that I could do it with one shot. I know it is possible to shoot a dime-sized target a mile away with one shot. Nevertheless, I consider it a near certainty that I would miss if I tried it.

Do you doubt my hypothesis that I would miss? By your reasoning, you should. I have no data base. I don't even have a sample size of 1. I've never tried it. I've never seen anyone try it. By your reasoning, I can't even say it would be "odd" if I were to hit the target. But of course, we both know I'm not saying it would be odd. I'm saying it would be unlikely.

 

[Hellbound]

Indeed. And asking that question turned out to be rather useful, didn't it?



When it was first proposed, people objected to the big bang on similar grounds.

Science proceeds by asking questions about phenomena that look intriguing to scientists. If some of those investigations or their (possibly tentative) conclusions disturb your personal worldview, tough luck. Science and scientists couldn't care less (or at least they shouldn't, unless we are discussing things that might actually pose a real risk).


The fundamental physical constants indeed look fine-tuned. Why? Here are several possibilities:

(1) There is only one possible set of values for physical constants, and they are what they are. In this case, we should focus on understanding why only that set is possible. I find this highly implausible (for reasons I'd be happy to elaborate on).

(2) There are many possible values, and we are very finely adapted to the values they happen to take (the anthropic or "puddle" argument). This is more plausible, but not the whole story.

I think - and yes, this is speculative, but based on mathematics and what we have learned about fundamental physics - that there are probably many, many possible values that vary as you move around in the universe, but not every conceivable set of values can occur, and some sets occur far more frequently than others. Some of the apparent fine tuning is anthropic (if the values weren't in certain ranges, no one would be here to ask about them), and some of it is due to interesting and as-yet poorly understood constraints on what is possible or common.

There is an active subfield in which people are exploring these possibilities. Speculative? You bet. Dead end? Maybe - time will tell. What's certain is that people are not going to stop discussing these questions. They're too interesting for that to happen.

This, most definately.

The fine tuning problem isn't a statement that "everything is fine-tuned, therefore whatever".

It's a statement that, as far as we can tell, the values needed for the various constants in order for life to exist is fairly narrow. It isn't so much the water marvelling at it's fit to the puddle shape, but rather to the fact that there's a depression for a puddle to form in at all. If we change any of the constants, it seems we don't get holes big enough for puddles: we get bumps, or flat surfaces that won't hold water, or thousands of microscopic pits scattered evenly instead of a depression that would hold water.

The "fine-tuning" question is simply "Why is this the case?" It's not making an assumption. And the answers are variable, as sol pointed out.

I see no need to find a probability distribution, because we can't do that without a theory. To fid the theory, we have to ask the questions. And the answers so far are addressing various possible probability features...to wit:

The "underlying theory" idea, sol's number 1. THere's some underlying theory, or some interdependence amongst the constants, that we haven't found yet. This limits their values to specified amounts.

Then there's "multiple values" hypothesis. There are several speculations here, hypothesis if you will, that are awaiting the ability to do some form of testing. The multiverse theory is one, in various incarnations: multiple universes with random constants, whther the probability values are uniform or not; universe "spawning", where certain processes like black holes spawn "daughter" universes that share some (but not all) of the parent characteristics, leading to an almost evolutionary progression of universes tailored for black holes (which has the side effect of allowing for life); or others I can't recall.

And then there are some who claim that life would take on a different form if the constants were different (call it the "pure puddlers"). This seems difficult to fathom, as many of these values combinations would prevent the formation of any complex structure (like, you know, molecules), which seems to make any possibility of life rather remote (and is just as much an assumption as is being argued against...faith that life will always find a way).

THe whole point is that for any progress to be made, the questions have to be asked and the answers thought about, so that testable hypothesis can be constructed and we can find out what the probability distributions are, and why the values are what they are.

THe fine-tuning problem isn't "why are we fine-tuned"...it doesn't make that assumption. It does make the claim that there is a narrow range of values consistant with life, which is true (outside that narrow range complex structures aren't possible...no stars, for example). It simply asks why are the values what they are.

Argument against it seems like arguing that we shouldn't be curious (thus my Borg comment earlier).

To quote Einstein, "If we knew what we were doing, it wouldn't be research."

 

[TheRedWorm]

You have substituted the adjective "odd" for the adjective "unlikely", as if the two adjectives have the same meaning. The two adjectives do not convey the same meaning. They are only remotely related, if at all.

Ok.

Get rid of the red herring, and maybe we can talk.

Actually, you may have slammed two red herrings on the table. You seem to have used the word substitution as a springboard to infer that the multiverse hypothesis is false because there is no data base of observed universes to compare with one another to determine which ones are "odd". Therefore multiverse proponents cannot say this one is "odd". Therefore they have no argument.

What? I think that the multiverse is most probable. My contention is that it would be in the very least inaccurate to say that there is anything special or unique about our universe based solely on the ignorance of any other universe(s). Yes; we don't know if our universe is the one and only, or if it is merely one of myriad universes extant.

But that never was the argument in the first place. If anything is being compared, it is possibilities, not observed universes.

But that's the thing; we don't know the possibilities. We can guess, and play around with certain constants, but we don't know if such universes are possible, or what laws are different elsewhere, if there is an elsewhere. As it stands, the things that are possible in this universe, have so far happened a few times in this universe.

Example: I have never tried to shoot a dime-sized target a mile away. Therefore I have no statistical data base upon which to base my hypothesis that it is highly unlikely that I could do it with one shot. I know it is possible to shoot a dime-sized target a mile away with one shot. Nevertheless, I consider it a near certainty that I would miss if I tried it.

I know that no analogy is perfect, but this one is not overly great. You aren't comparing a difficult shot you take to a difficult shot that someone else takes. You are comparing a completely unknown thing to itself, and calling it unlikely. Let's put it this way: I have a Xa'thotgrah. It is a good little Xa'thotgrah, all neon pink feathers and bright yellow chitinous plate stripes. It also hums "hunk of burning of love" to any stimulus. Is my Xa'thotgrah's behaviour unlikely? Who's to say, as there is only one Xa'thotgrah.

[/quote]Do you doubt my hypothesis that I would miss? By your reasoning, you should. I have no data base. I don't even have a sample size of 1. I've never tried it. I've never seen anyone try it. By your reasoning, I can't even say it would be "odd" if I were to hit the target. But of course, we both know I'm not saying it would be odd. I'm saying it would be unlikely.[/QUOTE]


As a shooter, no I don't doubt your hypothesis. Now, plop yourself on a different planet, into a different culture, one that had never even seen a gun, nor had any concept of one, and ask their opinion. I have no idea what they would think or how they'd react, do you?

 

[steenkh]

That's certainly not the case. *Obviously the numerical values of the constants depend on human convention (you could always define a new constant that is 2 times the old one). *But once you fix a convention, the values are what they are, and if they were different the physical world would be different.

My inability to express myself mathematically may have garbled Stenger's argument.

Re-reading the chapters, I see that he lists all of the constants that have been claimed to be fine-tuned. Only three of these are being dismissed as "trivial and arbitrary". They are the speed of light, c, Planck's constant, h, and Newton's gravitational constant, G. He only consider those constants as "legitimate" objects of fine-tuning that are "dimensionless".

Sorry about the confusion.

 

[Toontown]

As a shooter, no I don't doubt your hypothesis.

To be consistent with your own reasoning, you should doubt my hypothesis. You have never seen me attempt a shot at any range. You have no data on me. You have no way of knowing how "odd" I am.

All you have is some indirect data about shooting. But by your reasoning, that should be dismissed. Nothing will suffice except direct observation of my shooting ability, by your reasoning. That is the inescapable point of your repeated requirement of a database of universes to compare this one to, presumably in order to test for the herring-like 'oddity'.

Now, plop yourself on a different planet, into a different culture, one that had never even seen a gun, nor had any concept of one, and ask their opinion. I have no idea what they would think or how they'd react, do you?

I don't need to plop myself on a different planet to give you a strawman to beat up. It is not my job to give you a strawman to beat up. My job is to prevent you from (very predictably) substituting an altered analogy for my analogy and then beating up the altered analogy.

However, I do have an idea how the aliens would likely react, after being provided the information we both have. After I showed them the rifle, explained how it works, and explained what I proposed to attempt, they would agree I couldn't do it. They would not require a data base of repeated attempts by me to reach that conclusion. They would be able to reach the conclusion by other means.

Since you wanna play criticize-the-analogy-and-then-change-it-to-something-worse-to-show-how-dumb-it-is.