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L. Susskind -- The "Megaverse"

Kwalish Kid said:
In the literature on the subject, one finds some irresponsible speculation but one also finds attempts to produce probability distributions for the values of certain physical constants.
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Speculation is science is an important activity -- especially in cosmology. Define "irresponsible speculation" or provide an example -- assuming you are referring to cosmologists and not to crackpots.

These are generally, if I recall correctly, based upon hypotheses about the nature of physical phenomena at high energies and how this physics changes into the behaviour of phenomena at the energies we are most familiar with. Ideally, if these hypotheses become well-supported theories, they could be used to predict (or, rather, infer) the existence of other spacetime regions or other spacetimes in which there are different values for what we now consider to be physical constants.
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That seems to be a worthy endeavor; however, there is no reason not to speculate about the question of fine-tuning in the absence of establishing such probability distributions, which may or may not be achievable.
 
TubbaBlubba said:
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I agree that it can be a springboard for ideas. "What if our universe is unlikely? What could it all look like then?", but I simply cannot (no matter however Perpetual Student feels) consider it a problem the same way the unification of GR and QM is a problem, or the question of what will happen to the universe in the future is soimething to be solved.
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The unification of GR and QM looms large as a problem for physics and it very well may have important cosmological implications, but fine-tuning is a major issue within the field of cosmology, which is the subject of this thread.
Here in my advanced years (age 73), I am very interested in cosmological (ontological, epistemological) questions like the one being discussed here. So, the unification of GR and QM does not reach the same level of importance for the kind of answers I seek: What is this existence all about? How did it come about? Was it random chance? Was it inevitable? Why is the universe so exquisitely mathematical? What was there before the universe? Is this the only universe? How do we account for consciousness?
As a non-believer in paranormal stuff like deities and the like, I seek natural answers. These questions loom much larger as mysteries for me than the unification of GR and QM, which are only models of reality, and may someday be replaced by models that do not require unification -- or not. Actually, the only reason I spend a good deal of my time studying physics is to have a better basis to understand these bigger questions.
I have no illusions that anyone will stumble on answers to these questions in my remaining lifetime, but at least understanding the questions provides some information and, to some degree, narrows down the possible answers.
 
The difference I was trying to point out is that with QM and GR, there's somthing that ought to be there and we're trying to find it.

With fine-tuning, you have to make a long list of assumptions before you even arrive at it; again, the issue is of a higher order: what is the origin of various physical constants?
 
Perpetual Student said:
That seems to be a worthy endeavor; however, there is no reason not to speculate about the question of fine-tuning in the absence of establishing such probability distributions, which may or may not be achievable.
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What you are advocating seems to be irresponsible speculation. Without a probability distribution, there is nothing to address; there would be nothing finely tuned to explain. If one wants to investigate this matter, then one has to investigate whether or not one can come up with some underlying physical laws that could produce different values of the various physical constants. If one could establish these theories, then one could establish that the constants are finely tuned in some way.

It is not likely to make for good evidence to merely assume some probability distribution for the values of these constants and try to derive statements about the nature of the universe from this assumption. The exception to this could be if we could expect to see something in distant reaches of the universe that would match the features of the derivation.

It seems like a better project to attempt to get evidence from things that we can investigate and use this to justify our claims. I would be willing to accept claims about distant and unobserved regions of spacetime is they were a consequence of well-established theory based on what we can observe.
 
Kwalish Kid said:
What you are advocating seems to be irresponsible speculation. Without a probability distribution, there is nothing to address; there would be nothing finely tuned to explain. If one wants to investigate this matter, then one has to investigate whether or not one can come up with some underlying physical laws that could produce different values of the various physical constants. If one could establish these theories, then one could establish that the constants are finely tuned in some way.

It is not likely to make for good evidence to merely assume some probability distribution for the values of these constants and try to derive statements about the nature of the universe from this assumption. The exception to this could be if we could expect to see something in distant reaches of the universe that would match the features of the derivation.

It seems like a better project to attempt to get evidence from things that we can investigate and use this to justify our claims. I would be willing to accept claims about distant and unobserved regions of spacetime is they were a consequence of well-established theory based on what we can observe.
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I find it peculiar that you would label "irresponsible" anyone's speculating about why the fundamental constants have the values that produce the universe we know. As a layman, I'm not sure what responsibilities I have in this respect so I'm perplexed how I might be "irresponsible."
Getting more evidence is certainly a worthy enterprise; but I don't think logic supports telling a professional like Susskind that, if he does not immediately cease his speculations, he is somehow "irresponsible."
In fact, I fine your comments more than peculiar; they are quite absurd!
 
Perpetual Student said:
I find it peculiar that you would label "irresponsible" anyone's speculating about why the fundamental constants have the values that produce the universe we know.
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I find it peculiar that you insist on never reading what I post and instead merely imagine what I write. My position is the opposite of what you just described it as. Layman or not, it looks like your understanding of this issue is lacking in part because of your esteem of Susskind and fear that he might not be correct.
 
Kwalish Kid said:
I find it peculiar that you insist on never reading what I post and instead merely imagine what I write. My position is the opposite of what you just described it as.
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Hmm... It must have been your evil twin who said, "What you are advocating seems to be irresponsible speculation..."

Layman or not, it looks like your understanding of this issue is lacking in part because of your esteem of Susskind and fear that he might not be correct.
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I do the best I can, but perhaps, as you say, my understanding of this issue is indeed lacking. Nevertheless, you are clearly letting your dogma get in the way of logic. One can be correct (or incorrect) about science that has empirical support. It's quite odd to say someone is incorrect about his speculations, as long as those speculations do not contradict evidence. They are, after all, merely speculations, something very consistent with the subject of this thread.

(Frankly, I find this tendency of yours to personalize and insult an unnecessary distraction. In retrospect I see that as a weak pre-emptive defense you accused me of insulting tb, which I most certainly did not do. If you can't discuss this matter in a civil way, just go away.)
 
Perpetual Student said:
Here in my advanced years (age 73), I am very interested in cosmological (ontological, epistemological) questions like the one being discussed here. So, the unification of GR and QM does not reach the same level of importance for the kind of answers I seek: What is this existence all about? How did it come about? Was it random chance? Was it inevitable? Why is the universe so exquisitely mathematical? What was there before the universe? Is this the only universe? How do we account for consciousness?
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Ask those anthropic questions, and you will invariably be told: "The probability that you exist is 1. You're a puddle-boy if you think it unlikely."

But not by me. Like Disney's Lone Ranger, I'm just lucky to be here. Real lucky. I've always been lucky when it comes to existing no matter what.

The atoms that made me were gathered together from the cores of dead stars across the universe, brought inexorably to this time and this place, formed into this organization by whatever laws of nature might prevail, variable, invariable, singular, multiple, whatever. It didn't matter. Goddamn, here I am. Suck on it, nothingness.

Incredible luck runs deep in my ancestral family. All my direct ancestors were invariably lucky beyond all reason. While other species dropped into the bottomless pit of extinction, my ancestors marched onward against all odds, carrying what would become my DNA forward from epoch to epoch. My great-great-great-great......grandmother, Eve Of The Olduvai, was the mother of an entire species which today dominates the planet from pole to pole, our nearest galactic competitors nowhere to be seen.

And if the Everett interpretation of QM is correct, my doppelgangers populate the universal wave function in indeterminate numbers.

I am the Undead Lone Ranger. No way you can stop the Spirit of Rock.:cool:

http://www.youtube.com/watch?v=TDgeoRBQQtc
 
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Kwalish Kid said:
I find it peculiar that you insist on never reading what I post and instead merely imagine what I write. My position is the opposite of what you just described it as. Layman or not, it looks like your understanding of this issue is lacking in part because of your esteem of Susskind and fear that he might not be correct.
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I read it the same way Perpetual Student reads it.

Kwalish, it's obvious to me you have a chip on your shoulder.
 
I try to view the "fine tuning problem" from the P.O.V. of the universe: "What the hell went wrong in the laws to prevent me from being one, nice, unchanging, uniform blob?" :D
 
I wrote that I think merely assuming that there is a problem without any basis in an actual probability distribution is a mistake, especially if one is attempting to derive claims about the universe from this supposed problem. I also wrote that I thought the responsible thing to do is actually investigate the fundamental physics.
 
Kwalish Kid said:
I wrote that I think merely assuming that there is a problem without any basis in an actual probability distribution is a mistake, especially if one is attempting to derive claims about the universe from this supposed problem. I also wrote that I thought the responsible thing to do is actually investigate the fundamental physics.
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So, what do you want from the whitecoats? They built a Large Hadron Collider. They found the Higgs Boson, looking like a die balanced precariously on one of it's corners atop a strangely balanced statue of dice. So a couple of them dared to mutter 'How the fk did those dice get that way??"

And now you're really offended. I see why. Unfortunately, all that work has only brought the despised fine tuning question into sharper focus.

As John Leslie explained, we must observe fine tuning, or we observe nothing at all. Which effectively eliminates the oft-cited "inverse gambler's fallacy" rebuttal. This is no post-hoc observation of some meaningless random number. This number means something.

http://en.wikipedia.org/wiki/Inverse_gambler's_fallacy
 
Kwalish Kid said:
I wrote that I think merely assuming that there is a problem without any basis in an actual probability distribution is a mistake, especially if one is attempting to derive claims about the universe from this supposed problem. I also wrote that I thought the responsible thing to do is actually investigate the fundamental physics.
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The professionals who have pondered the question of fine-tuning are accomplished physicists (at least, the ones I pay attention to) so we can assume they have spent a good portion of their lives investigating the fundamental physics -- responsibly. I believe it is reasonable to conclude that their speculations about fine-tuning come about because of their years of investigation.
As a layman. I an not in a position to do any investigation of my own -- but I am free to learn as much as I can about physics and speculate and learn about the speculations of others. Fine-tuning is a question pondered by many, with or without any theory or basis for a probability distribution, the lack of which (logic tells me) is part of the problem.
 
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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.
 
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.

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.
 
Kwalish Kid said:
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.

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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.
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Agreed, that's my main gripe with this specific case.
 
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.
 
Perpetual Student said:
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.
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Are you wilfully being disingenuous? That was with regard to whether FRAMING a question that way was appropriate.

"The question" has already been honestly analyzed. I find it odd that you did not notice this, as you took part in the discussion where it occurred.
 
TubbaBlubba said:
Because we don't understand how they're interconnected, if at all.
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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 :eek:.
 
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