There’s an article in this week’s Nature by Geoff Brumfiel entitled Outrageous Fortune about the anthropic Landscape debate. The particle physicists quoted are ones whose views are well-known: Susskind, Weinberg, Polchinski, Arkani-Hamed and Maldacena all line up in favor of the anthropic Landscape (with a caveat from Maldacena: “I really hope we have a better idea in the future”). Lisa Randall thinks accepting it is premature, that a better understanding of string theory will get rid of the Landscape, saying “You really need to explore alternatives before taking such radical leaps of faith.” All in all, Brumfiel finds “… in the overlapping circles of cosmology and string theory, the concept of a landscape of universes is becoming the dominant view.”
The only physicist quoted who recognizes that the Landscape is pseudo-science is David Gross. “It’s impossible to disprove” he says, and notes that because we can’t falsify the idea it’s not science. He sees the origin of this nonsense in string theorist’s inability to predict anything despite huge efforts over more than 20 years: “‘People in string theory are very frustrated, as am I, by our inability to be more predictive after all these years,’ he says. But that’s no excuse for using such ‘bizarre science’, he warns. ‘It is a dangerous business.'”
I continue to find it shocking that the many journalists who have been writing stories like this don’t seem to be able to locate any leading particle theorist other than Gross willing to publicly say that this is just not science.
For more about this controversy, take a look at the talks by Nima Arkani-Hamed given today at the Jerusalem Winter School on the topic of “The Landscape and the LHC”. The first of these was nearly an hour and a half of general anthropic landscape philosophy without any real content. It was repeatedly interrupted by challenges from a couple people in the audience, I think David Gross and Nati Seiberg. Unfortunately one couldn’t really hear the questions they were asking, just Arkani-Hamed’s responses. I only had time today to look at the beginning part of the second talk, which was about the idea of split supersymmetry.
Update: One of the more unusual aspects of this story is that, while much of the particle theory establishment is giving in to irrationality, Lubos Motl is here the voice of reason. I completely agree with his recent comments on this article. For some discussion of the relation of this to the Intelligent Design debate, see remarks by David Heddle and by Jonathan Witt of the Discovery Institute.
I don’t understand how string theorists don’t realize that the idea of the landscape go against of the former philosophy of his theory: “standard model contains multitude of adjustable parameters, etc…”. With the landscape we don’t need string theory: we live in a multiverse and in each pocket universe the parameters of the standard model take different values, so we don’t need to explain that particular values of our universe.
It’s a shame for people that, like me, had some hopes in string theory, to see how it is transformed in a ridiculous sci-fi story by Susskind and company.
I think David Gross is a hero.
“I continue to find it shocking that the many journalists who have been writing stories like this don’t seem to be able to locate any leading particle theorist other than Gross willing to publicly say that this is just not science.”
This is called the “tactiturn problem”:
“An old Cambridge story, concerning a person who found himself sitting next to the taciturn Prof. X (X being variously named as Dirac, Stokes ..) at dinner.
“Person sitting next to X: “someone has bet me I won’t get more than 2 words out of you tonight”
“Prof. X: “You lose!”
– Josephson, see http://electrogravity.blogspot.com/
I just don’t get it.
During the course of a conversation at Cosmic Variance, I’ve learned of something like four or five testable hypotheses for extending the SM, some even involving extra dimensions with or without strings/branes, most very difficult to distinguish from one another, and it seems like in a decade or so there will be plenty of new stuff about our own universe to argue about. Stuff we’ve actually seen, because we can. Once we’ve seen what we will see, we’ll build a bigger machine to pin down some of the observed “BSM” physics. It’ll take time, but it looks like particle theorists have their hands very full already just preparing to interpret the LHC’s discoveries.
I just don’t understand why, in a universe so full of unsolved, yet conceivably tractable problems, a scientist would not recoil from a path that leads inevitably to the unobservable. I don’t understand the arguments for exploring the landscape because “it might be right” when one cannot ever assay causally isolated regions of the putative multiverse. What’s even more bizarre is the apparent notion that String Theory can incorporate all the plausible hypothetical models of TeV physics that have been constructed in anticipation of actually doing that TeV physics. Little Higgs? Well that’s just this version of String Theory with d branes on orbifolds. Low energy SUSY? String Theory predicts it. High energy SUSY? Same thing! (why not? there’s a landscape, after all…) UED? My guess is since it’s got a KK tower and extra dimensions, naturally it’s just a facet of string theory…
It’s everything, it’s everywhere, it’s bigger than we can ever know. Whatever you think it is, it’s strings. It can’t be killed!
Must be fun doing calculating God…
Very strange (maybe not) that we reach virtually the same conclusion coming from seemingly orthogonal directions.
Speaking of the “g” word… lol
yeah, He lives… somewhere – He has created a dacha in Landscape for Himself. (Santa probably sometimes goes and visits Him there, too.)
”I continue to find it shocking that the many journalists who have been writing stories like this don’t seem to be able to locate any leading particle theorist other than Gross willing to publicly say that this is just not science.”
Journalists the world over are boosterists for the current big thing—whatever it is. They swim in the same pond as publishers who are looking for the next big pop science book. At present it looks like Susskind has been the one canny enough to create the very wind that he is volplaning in. Tomorrow it will be someone else—with an outsized ego and zero intellectual responsibility.
”The modern world is rubbish”—Blur
JoseIRS wrote:
“With the landscape we don’t need string theory: we live in a multiverse and in each pocket universe the parameters of the standard model take different values, so we don’t need to explain that particular values of our universe.”
I understand that some find this disappointing or irritating, but what is the objection to the possibility that this happens to be exactly the way things are?
EF says ”what is the objection to the possibility that this happens to be exactly the way things are?”
What is it that ”makes” the values of the parameters take on different values?
Elmer,
The objection to this possibility is not that it is inherently impossible or inconceivable, but that there is no scientific evidence for this at all. No one has a consistent theory that makes some predictions that can be checked and also predicts this kind of multiverse. What is going on here is that string theory has failed as an idea about unification, and instead of acknowledging this, its proponents are giving up on the standard idea of how to do physics. They are turning theoretical physics into a pseudo-science whose only purpose is to come up with untestable explanations for why string theory should be believed, despite the lack of any evidence for it, and the impossibility of ever getting any evidence for it.
I suggest you check out Nima’s talk “Possible and Impossible In Effective Field Theory (2).” He gives field-theoretic arguments (to appear in a paper soon, I gather) that certain effective field theories used in phenomenological models are sick. They have a secret inconsistency with Lorentz invariance + causality + unitarity, which is only visible when you turn on a nontrivial background (so in that sense, it is a nonperturbative problem). This together with the recent paper by Nima, Lubos, Alberto Nicolis and Cumrun Vafa seem to be very interesting directions. They’re ruling out huge classes of effective field theories all at once, based on very solid general arguments. We can hope that continued study along these lines might reveal hidden inconsistencies in string vacua as well, but even if it’s limited to effective field theory this is powerful stuff. I have a feeling that a fairly large class of extra-dimensional models are ruled out on similar grounds.
Haven’t we had enough of this particular line of bullshit? The reason that so many people have come to accept the strangeness of quantum mechanics, notwithstanding its challenges to our intuitions and pre-existing philosophical prejudices, is that it is supported by a vast array of empirical evidence, and it has been extremely difficult to find empirically viable alternatives that are any more palatable. Do you remember what “empirical evidence” means? It means confirmation by actual observations that could easily have contradicted the theory, but once made, were found to be consistent with it.
If you want the Multiverse to deserve to be taken seriously as a scientific hypothesis then you have to do a hell of a lot better than saying, “well, after all, that could be the way things are”. You might object by pointing out that we were led in the first place to inflation, and then eternal inflation and the multiverse, by attempting to apply quantum field theory and general relativity to the whole universe. (I’m acknowledging the argument that a form of the multiverse predates the string theory ‘landscape’, although the landscape can be [and should be??] interpreted as an even bigger and messier multiverse.)
Well, to the extent that this has led fundamental physics into its current quandary, we ought to be questioning the theoretical (and philosophical!) assumptions that got us here, rather than just saying, “that could just be the way things are” in the total absence of genuine empirical evidence that they are that way. We could have settled for such a pseudo-solution to any number of problems in the last 350+ years. It’s as much of a copout now as it ever was. It’s like saying, “well, the ether could exist, and the properties of matter and electromagnetism could just happen to conspire to make its presence undetectable by any means we have been able to imagine. In fact, thanks to H. A. Lorentz and others, we have models for this. So let’s keep right on creating mechanical models of the ether itself and try to understand it better.”
—————————
— Peter: The above is little more than a polemical elaboration on your comment, but I felt the need to post it anyway. I too have felt for quite a while that the “things could actually be that way” argument is about as worthless as assertions that astrological influences could be real.
”What is it that ‘’makes’’ the values of the parameters take on different values?”
Maybe that was putiing my point too rhetorically. So to be clearer: I doubt that there is *any possible explanation* of how, or why, the free parameters assume the values that they are meant to assume. They can’t be taken as eigenvalues of some operator—which would be the QM path—for there would be no explanation of how the operator came to act; and it would not constitute an explanation to say that they can’t be taken as the solutions to some equation—the classical way: this would not tell you how any particular universe has the properties that it does. So the landscape idea is an explanation-free idea posing as an explanation.
Peter: The above is little more than a polemical elaboration on your comment, but I felt the need to post it anyway. I too have felt for quite a while that the “things could actually be that way” argument is about as worthless as assertions that astrological influences could be real.
I really am ashamed to say that neo-darwinists do the same thing on a regular basis. They think that speculative theories are fair game in origins science just because they’re popularized.
‘maybe conditions are different somewhere else’
Prove it, or shut up.
Heroes save people (scientists) from difficulties/Monsters (string/M-theory) without thinking twice.
Heroes do not belong to the dark side…
Juan R.
Center for CANONICAL |SCIENCE)
If we forget for a moment string theory, the landscape speculation, our disdain for string theory or the disdain for the way some of it is being performed, then what remains is the following trivial fact.
Fact: We have no clue if the final theory, whatever it is, will fix the parameters of the standardmodel uniquely.
Claiming that we do know that the parameters should be unique solutions of some equation is just as much astrology as claiming the opposite.
The problem with the landscape discussion is not that it is a priori pointless to think about a theory in which the parameters of the standard model are not uniquely specified.
I think I agree with Urs here:
**The problem with the landscape discussion is not that it is a priori pointless to think about a theory in which the parameters of the standard model are not uniquely specified.**
The validity of Urs position was demonstrated by Smolin in “Scientific Alternatives to the Anthropic Principle” which exhibits an EXAMPLE of a falsifiable theory in which SOME of the parameters are locally optimal for black hole formation.
Urs seems to be saying “it is not a priori pointless to think about” theories in which some of the parameters are variable.
In fact one can be more definite than Urs was, and say it can be entirely POINTFUL to think about such theories—because the set of such theories that are predictive and falsifiable is non-empty.
Smolin CNS is a kind of “existence proof” example showing that one can have a theory in which perhaps some of the parameters are uniquely determined but where others are variable and assume values near local maxima for black hole formation. Then if some astronomer or experimentalist ever happened to observe that one of the variable parameters of this theory is NOT near-optimal for black hole abundance, this would be evidence against the theory.
To elaborate on what Urs said: I think maybe what IS the problem with landscape discussion (Urs says what it is not) is that when one does science one has a MORAL OBLIGATION TO USE TESTABLE THEORIES because the scientific community depends for its unity on the possibility of resolving differences of opinion by empirical methods.
(rather than by rhetoric or showbiz or war or burning-at-the-stake, or all the other ways people have of arriving at consensus)
Anonymous says that Nima gives “… field-theoretic arguments (to appear in a paper soon …) that certain effective field theories used in phenomenological models are sick. They have a secret inconsistency with Lorentz invariance + causality + unitarity, which is only visible when you turn on a nontrivial background … I have a feeling that a fairly large class of extra-dimensional models are ruled out on similar grounds. …”.
How “sick” do the “ruled out” effective field theory models appear to be?
Can they me “cured” by modifying them in some reasonable way, just as some unifications of gravity plus standard model were “cured” of “inconsistency” with Coleman-Mandula by using Lie superalgebras instead of ordinary Lie algebras ?
Even if “a fairly large class” of models were to be conclusively “ruled out”, wouldn’t that still leave the landscape subject to the same type of objections that are being made now, because the landscape after removal of such a “ruled out” part might still be a very large landscape,
unless
the “ruling out” process were able to “rule out” all but one unique physically realistic model ?
Is that the goal of Nima et al in that line of work?
What about, instead of starting with a landscape full of models that may or may not, as Urs says, “fix the parameters of the standard model uniquely”,
approach the situation by spending some time and effort studying models that do “”fix the parameters of the standard model uniquely”, no matter how unconventional they might appear at first glance. At least one such model (mine) can be formulated in terms of (non-supersymmetric) string theory.
Since it is not supersymmetric, would it not be included in the landscape in which Nima et al are searching?
Tony Smith
http://www.valdostamuseum.org/hamsmith/
Urs,
I’m not claiming at all that one has to believe that a final theory will fix the standard model parameters. Maybe it will, maybe it won’t, maybe it will fix some and not others. The problem with the anthropic landscape is that it not only predicts absolutely nothing whatsoever, it does not even come with a remotely plausible idea about how it will ever be able to predict anything. The best people like Susskind can do is say that if we devote thousands of physicist-years to investigating the landscape, maybe we’ll find some way to make a prediction, even though there is zero evidence so far of any such thing. As far as I can tell, the justification for doing this is pure wishful thinking and desire to avoid admitting failure. This isn’t science.
The issue of whether or not certain parameters are environmental is a red herring. Right now, we don’t know and our job as scientists is to figure out what determines them. If we’re successful at that, then we’ll know whether they are uniquely calculable or not. The real issue here is one of scientific ethics: we’re faced with the shocking phenomenon of leading figures in the field abandoning honest science. What do you do about this? Just say that maybe they’re right, and this has to be done? People like my commenter David Heddle and the Templeton foundation, who would love to mix religion and science together, think what is going on is great. I think it’s appalling.
Peter,
This is the second time (once on a previous post) you mischaracterize my view. You claim I think it is “great.” I do not. In terms of the landscape similarities to ID, I think it is amusing, not great. I don’t spell that out in my posts, but I don’t think you have Fellini to figure it out.
If I promoted ID as science, then I might find it great. But I take no pleasure, as a physicist, that some of the brightest in HEP are telling us, in effect, that physics as we know and love it is, ultimately, a fool’s errand.
Anonymous,
I did look at Arkani-Hamed’s talk you mention, as well as his recent paper. It’s the same idea as Vafa’s “Let’s investigate the Swampland”, and I have the same objections. If one manages to show that some sorts of exotic brane-world scenarios can’t be embedded in our current understanding of string theory, so what? There’s zero evidence for either them or string theory, and our understanding of string theory is so primitive one can argue that when we understand it better it will accomodate even these exotic scenarios.
Amidst the swampland hype, you’re missing the main point. This has nothing to do with the problem of the landscape. The infinite number of known vacuum states of the landscape are still there and those mucking about in the swampland have nothing to say about them. You are attributing to this work some interesting possiblities that even its promoters don’t claim.
David,
Sorry for mischaracterizing your views. Sounds like we’re more in agreement than I thought, although “amusing” is not quite my reaction to Susskind.
David Heddle said:
If I promoted ID as science, then I might find it great…
Ah, but you do, (make an unfounded leap of fath to) promote the anthropic principle as scientific evidence for the existence of god, so you must, (like me, but for different reasons), be happy to see that Lenny has admitted that these special implications do exist if there is no multiverse?
island,
This is a great blog and I don’t want to be a troll so I’ll clarify my position just once. In the sense that Susskind is motivated by the problem of fine-tuning I am pleased because he has provided a service. I have spent so much time arguing that there is fine-tuning that I admit Susskind has been helpful in demonstrating that it is real and requires an explanation. You have no idea how many of the Panda’s Thumb folks have argued with me that only religious wingnuts claim there is fine tuning, and that the cosmological constant is off by 120 OoM only because the calculations are naïve (or because of the units one uses). I am now sensing, thanks in part to Susskind, fewer objections along those lines. For that you can’t fault Susskind—after all there really is a fine tuning problem.
But two points are obvious:
1) If Susskind is correct, then fine-tuning is an illusion
2) If Susskind is correct, it’s a dark day for physics
Still, if there were a way to test the landscape, I’d be all for it.
Similarly, if black-hole natural selection is correct, then once again fine tuning is an illusion–but hey, let’s do the science and see how it plays out.
I am always for doing the science. If it ever explains the fine-tuning, then I’ll stop talking about cosmological ID. Strangely, the best way to preserve the fine-tuning and to preserve cosmological ID would be a fundamental theory that explains the constants. That is where I hope progress in HEP is forthcoming. If no progress is ever made, I fear we’ll reach a point where undetectable multiverses are accepted as self-evident. That would be very bad.
This period we are in now–where cosmology is so metaphysical and really smart folks are ready to redefine science–well that’s not good news for anyone.
I just want to say that I do not think that David is a troll, and I actually have a fair amount of respect for the man as a mostly honest with themselves), scientist, regardless of our departure.
You have no idea how many of the Panda’s Thumb folks have argued with me that only religious wingnuts claim there is fine tuning,
Yes, I do, because I’ve done the same, myself, and I’ve made your point to this group on numerous occassions, without pulling any punches as to how I feel about their willfully ignorant, Devil’s-advocate approach.
I make this point so emphatically because it is so relevant to this whole mess that it isn’t even funny!
This attitude goes well beyond neodarwinians… and it is killing science!
It seems to me that (finally) scientists, string theorists in this case, are reaching the limits imposed by Godel’s theorem (the Godel Wall). One can get arbitrarily close to the wall, but it takes an infinite amount of time to actually touch it. The closer you get, the larger the number of Lanscapes you see. I find this debate extremely interesting indeed.
Main entry: faith
Pronunciation: ‘fAth
Function: noun
(1) : firm belief in something for which there is no proof
With respect to a “final theory” (perhaps maybe it should be called “next model” because there might be further and even better ones), Peter said:
“… Maybe it will, maybe it won’t … fix the standard model parameters …
… our job as scientists is to figure out what determines them …”.
How should scientists figure that out?
As to any parameters that might be unfixed by a “next model”, maybe the anthropic/landscape approach is the only way to go.
As to parameters that might possibly be fixed, what methods might be used to fix their values? Here are some possibilities that come to my mind (not necessarily in order of how useful they might or might not be):
1 – Renormalization techniques – For example, Alvarez-Gaume, Polchinski, and Wise (Nuclear Physics B221 (1983) 495-523) said “… Weak interaction breakdown occurs for top-quark masses between 100 and 195 GeV … The renormalization group equation … tends to attract the top quark towards a fixed point of about 125 GeV …”.
2 – Volumes and measures related to symmetry groups – For example, Wyler’s calculation ( see his IAS papers at http://www.valdostamuseum.org/hamsmith/WylerIAS.pdf ) of the fine structure constant.
3 – Combinatorial methods – For example, in their book Combinatorial Physics (World Scientific 1995), Bastin and Kilmister offer an extension of Eddington-type calculations.
4 – Chaotic structures of quantum fields – For example, the work of Christian Beck in hep-th/0207081and other publications.
5 – P-adic structures – For example, the work of Matti Pitkanen.
6 – Algebraic structure of quantum field theory – For example, the work of Connes and Krein in hep-th/0201157.
7 – Phenomenological structures in string theory – For example, the work of Lust in hep-th/0401156 (since this is a part of string theory and is well-funded, there are many other examples of this).
8 – Clifford algebra structures – For example, the works of Traying and Baylis in hep-th/0103137 and of Chisolm and Farwell in J. Phys. A: Math. Gen. 20 (1987) 6561-6580.
I am not saying that the above list is exhaustive, nor that all the examples are the best that might have been chosen, and I am not saying that any or all of the listed methods may or may not be useful (in fact, I use more than one of the listed methods in my model, which does fix the parameters of the standard model).
I am saying that it would be a good idea if some funding and support were available for work on all such methods (not just the “popular” or “superstringy” ones) and that none of them should be banned, or people who work on them blacklisted, just because some influential people don’t like them.
If any of them produce calculations, then comparison with experiment can determine how useful they are.
Tony Smith
http://www.valdostamuseum.org/hamsmith/
Kind of off-topic, and kind of not: Sharon Begley of the WSJ has this to say about recent experiments in nano- and mesoscale quantum mechanics:
(* of NIST)
I feel like listing more trivial facts.
Fact: If you don’t fully understand your theory yet, it is speculative to talk about its space of solutions.
Fact: Interesting speculations tend to play an important role in the development of physics (like conjectures do in mathematics).
Fact: Debate over speculations tends to be fruitless unless concrete substantial questions can be addressed with non-philosophic means.
Once we agree on these fact we can move on with the really interesting questions. (That was my optimistic statement for today.)
David Heddle 6 January 1:18P
**Similarly, if black-hole natural selection is correct,…–but hey, let’s do the science and see how it plays out.**
the science IS being done whenever the mass of a neutron star is measured.
the theory is empirically testable and it is being tested—-although more could be done by way of working out detail and deriving other predictions (other means of testing the theory).
Urs 7 January 8:57A
**Fact: If you don’t fully understand your theory yet, it is speculative to talk about its space of solutions.**
I don’t think this is right. A famous counterexample is Darwin’s theory of evolution by natural selection. In the mid-1800s, genes were not known—the mechanism of heredity which allowed for small variations in offspring was not understood—but one could still test the theory.
If a theory makes a prediction, then one can test the theory, and “address substantial questions” by empirical (non-philosophic) means even though the theory is not completely understood.
**…
Fact: Debate over speculations tends to be fruitless unless concrete substantial questions can be addressed with non-philosophic means.**
I believe what you say here is true and it implies that discussion of black hole natural selection is NOT speculative, since the theory can already be addressed by empirical (nonphilosophic) means.
As reminder, a core prediction of black hole natural selection is that you cannot point to any parameter of the standard model which, if it were changed slightly, would lead to a greater abundance of black holes.
I wonder why there is debate about nonsense (i.e. Landscape).
It remember me ancient discussions about the sex of angels…
Perhaps people would take again a course on scientific methodology:
The ‘Landscape’ is not pseudo-science as Gross admits. It is pure philosophy or best religion (since God appears in the debate of some ‘stringers’).
The problem of particle physics and string theorists is that do not understand the world we can see. But is is their problem…
I am a bit tired of all this nonsense; that Landscape here, that Landscape there; that the cosmological constant only can be undertood via antropic reasoning [arXiv:hep-th/0511037], etc.
Stop nonsense, I am a scientist!
—
Juan R.
Center for CANONICAL |SCIENCE)
there’s a danger that I’m being misunderstood and need to clarify. If you disagree with these please correct me:
BH natural selection has nothing to do with the “Landscape” of string vacua.
BH natural selection has nothing to do with “God” or “cosmological ID”
BH natural selection is not a “Multiverse” theory in the usual sense.
Essentially this is meant to respond to what Peter said:
woit 6 January 12:12P
**The issue of whether or not certain parameters are environmental is a red herring. Right now, we don’t know and our job as scientists is to figure out what determines them. If we’re successful at that, then we’ll know whether they are uniquely calculable or not.**
BH natural selection does not assume the cosmology/standard model parameters are apriori environomental. If I understand correctly, it is an appeal to the usual principle of MEDIOCRITY.
We live in a part of the universe that is not atypical
There is a single connected universe—-all part of the same uniform process. Some parameters are allowed to vary slightly during a BH bounce. These will evolve to favor BH formation. A TYPICAL region of the universe will have values of those constants which are at or near local maxima. The prediction is, since we live in a typical region, we will not be able to find any parameter which could be varied slightly so as to make BHs more abundant.
Because this theory is simple, explanatory, and testable, I am arguing that it should be examined FIRST before imagining multiple (causally disjoint) universes, or anthropic selection effects, or the Landscape of 10^500 string vacua, or intentional manipulation by a conscious “Fine Tuner”.
Given that this theory may explain simply some of the parameters in question, for Occam Razor reasons, the research priortiy should be to determine WHICH of the parameters affect BH abundance and then TEST whether their values local optima. This offers a chance to invalidate the theory, whereupon more complex and far-fetched theories could be considered. Basically I am saying that the “Landscape” discussion is out of order until this simple matter has been cleared up.
Who,
I would not say “nothing to do”. Thecnically both are different, but both are related in a conceptual way. In some sense both deal with a multiverse.
It may depend of author. I do not remember Smolin specific arguments but i believe that you are right.
What do you mean by ‘usual sense’? Multiverse means “more than one universe” and if i remember correctly, Smolin dealed with multiple universes, each child being more optimized than previous one for the generation of BH. If i remember correctly, Smolin even explicitely used the term multiverse in his writtings…
What is the definition of “atypical”? If by atypical i mean far from mean values then i (personally) live in a very atypical region of universe:
– typical temp, 3 K. Vigo temp today, 288 K.
– typical dens, 10^(-25) kg m^(-3). Earth dens. 5,52 kg m^(-3)
Nobody know anything of that. That is pure speculation (as string landscape)
Idem
That is not a prediction, no scientifc one at least!
I do not call simple a theory with a landscape number of unobserved universes in a great cosmological evolutionary family. ‘That’ has explained nothing of this world. I think that it would be ignored like the rest of nonsense you cite next.
—
Juan R.
Center for CANONICAL |SCIENCE)
Juan thanks for your response. Smolin’s hypothesis saves the idea of the universe as a single connected deterministic process evolving everywhere by the same laws.
This is not the usual idea of Multiverse. The usual idea involves many DISCONNECTED causally disjoint items.
The usual Multiverse is not encompassed in a a single uniform evolution.
So there is a clear difference, even if you or Smolin wishes to call his picture a “multiverse”.
I think it was simply a bad choice of word on Smolin’s part, to call his picture a “multiverse”, because it is distinct from the usual in so many basic ways.
I do not know whether BH natural selection is correct or not—-I do not even know if the “Bigbang” event was actually a bounce, with a prior contraction (as some approaches to QG suggest). But the prior contraction should be regarded as JUST AS OBSERVABLE as the first instants of expansion because it is connected to us by a lawful progression.
In the same sense that we can infer things about the first three minutes (of expansion) using independently testable theory, we could also in principle infer things about the final stages of contraction prior to the bounce again using independently testable QG theory.
All observation (at least in cosmology) requires assuming some theoretical model, which must be independently tested, in order to interpret and only in this sense can one say that one can observe the early stages of our expansion—it is an extrapolation of causality.
Granted that we do not yet have an independently testable model of a BH bounce! and so I can only say that the prior stage is IN PRINCIPLE observable.
At the present time we cannot infer back because we have no model of what occurs during the bounce.
I disagree with you here:
W: The prediction is, since we live in a typical region, we will not be able to find any parameter which could be varied slightly so as to make BHs more abundant.
JR: That is not a prediction, no scientifc one at least!
It is clearly a prediction which is able to falsify the hypothesis of BH natural selection. If one can find a parameter of the standard model which could be varied in such a way as to make BHs more abundant it would shoot down BH natural selection. The hypothesis is highly exposed to falsification and it amazes me that it has survived for over 10 years without serious challenge.
Thanks again for your critique,
Who
Who wrote:
Why? Why could you not counter that our present universe is merely good at producing black holes? Maybe there haven’t been many generations. Why does it have to be optimal? No, I don’t think your falsification test is legitimate.
good objection Heddle,
what I said needs qualification with some vague words like “substantial” and there is a judgment-call involved
if a parameter were found to be within ONE PERCENT of local optimum then I personally would not discard the BH natural selection hypothesis.
but if it were discovered that a gradual change in some parameter by as much as TEN PERCENT
sorry, I struck the wrong key while typing the above, so it got entered prematurely. Here’s what I was trying to say: If it turned out that you could vary some parameter gradually and get a steady monotone improvement in BH abundance until the parameter was changed by some ten percent or more, then I would consider BH natural selection refuted and forget about it.
So less than ONE percent from a local maximum seems to me IMHO to be all right, and more than TEN percent from a local maximum would seem in my opinion to be fatal.
In between seems to me to be a grey area and I would listen to expert opinion arguing pro and con. It is a judgment call and I wouldn’t try to make up my own mind about it.
It has to do with the primitive (partly intuitive) idea of MEDIOCRITY. I picture a typical region as having gone through enough iterations to get to within one percent of local maximum—-if this process has been going on at all.
if parameters are not within one percent, then my feeling would be that there is something wrong and maybe this process has NOT been occurring. But I would still listen to experts if they disagreed about it—maybe they know something I haven’t thought of. And if it is a worse than ten percent fit, then forget it.
thanks for your critical response Heddle. I hope you see the falsification test as legitimate (as qualified) now, or can give me some more definite reasons why you think it isn’t.
Well I can see a couple objections.
One is that falsification of BHNS should ultimately be related to an experiment, not to consistency with the standard model.
Second, I don’t think one can tweak the parameters of the standard model and reliably calculate the resulting density of black holes.
**…falsification of BHNS should ultimately be related to an experiment, not to consistency with the standard model.**
to experiment, that is, OR astronomical observation.
For that, see
http://arxiv.org/abs/hep-th/0407213
and also references therein going back to 1994
**… I don’t think one can tweak the parameters of the standard model and reliably calculate the resulting density of black holes.**
Must take up that with Lee Smolin. See the discussion of neutron star mass in the same paper
http://arxiv.org/abs/hep-th/0407213
The paper gives several examples where a few percent change in some standard model parameter is argued to reduce BH abundance
Who,
Thanks for the references. Perhaps my assertion was incorrect. I’ll read the papers
… so the Theory of Everything will be a Web Page where anybody – the Inteligent Designers – will be able to build Toy Universes by guessing the 31 or so parameters (I bet the final number will be 42) that according to Tegmark and coworkers define the Laws of Physics. The rest of science will continue feeding technological innovation as usual to feed. Perhaps research in Extra Dimensions will even lead to spaceships capable of populating the Landscape of all the anthropically valid Universes constructed by the Inteligent Designers.
I am sorry to say this but Lee Smolin paper [http://arxiv.org/abs/hep-th/0407213], even ignoring several thecnical mistakes and acepting (as true) several unproved premises, is NOT a scientific paper.
In no way, the S premise our universe is optimized for production of BH is scientific one. In fact, i ask,can even Smolin rigorously prove the existence of BH?
Question: is S from Smolin?
—
Juan R.
Center for CANONICAL |SCIENCE)
Juan, S is not a premise, but a statement which Smolin challenges us to show is false—-by empirical means.
S is defined on page 29 of the paper
section 6.3 (page 33) is
“How a single heavy pulsar would refute S ”
section 6.4 (page 34) is
“How observations of the CMB could refute S ”
section 6.5 (page 35) is
“How early star formation could refute S ”
Smolin challenges us to make astronomical observations and find a neutron star above a certain mass, which will falsify the hypothesis he has offered us.
Some people believe that science is done this way, can you explain why you think this is not the case?
——————————
Peter, I want to emphasize the aspect of falsifiability to support and elaborate your quote from David Gross. You wrote:
I believe you and others have pointed out that it is unethical for anyone calling himself or herself a scientist to traffic in unfalsifiable suppositions (as do the Landscapers) because the community of scientists depends in an essential way on the ability to resolve differences by empirical test. Scientists a moral obligation to propose only testable theories. David Gross is saying that the Landscapers are not behaving as morally responsible members of the community.
This theory S may very well be wrong—that is a secondary issue. I think it is being offered, in some measure, to SHOW WHAT A SCIENTIFIC THEORY WOULD LOOK LIKE as an implicit criticism of Landscapery. This supports David Gross’ objection by illustration. It shows that one can have a theory with some explanatory power as regards the values of fundamental dimensionless constants, which nevertheless is not in any sense anthropic and which is highly (one might say almost indecently) exposed to refutation.
thanks,
Who
Who,
Thanks by your opportunity to explain better my point.
In my opinion Smolin Natural selection view is a camouflaged version of anthropic arguments.
About the nomenclature for S, simply to state that, in logic, a premise is “One of the propositions in a deductive argument.”
For people who has not read cited Smolin preprint, S is defined as follow
where P is the ‘phase’ space of dimensionless parameters of the standard models of physics and cosmology, and the ‘phase’ point characterizing our universe is denoted by p. F(p) is a fitness function which is equal to the average number of descendents of a universe with parameters p.
Yes, it is true that Smolin propose certain observations for the refutation of S and this would be an advance over the untestable anthropic reasoning of stringers, but i continue to say that S is not a scientific premise. In fact, i think that Smolin misunderstand the measuring of certain observables with the scientific testing of his premise S.
Take, as illustration, the next hypotetical J premise
where Lambda(x) is the value of the cosmological constant for our universe.
Then, following with this hypotetical example of a ‘theory’ of “natural cosmological evolution” we could imagine that each universe generates baby universes via a process similar to Linde chaotic inflation.
Now well, could the J premise be refuted?
Reply is negative.
If we measure the actual value for Lambda in OUR universe (order of 10^(-52)) and it is not the value J ‘predicted’, we am not refuting J. Imagine now a hypotetical premise J2 claiming a value of 10^(-52). Any measuring of Lambda for OUR universe does not verifies or refutes J2.
To your question
I may say that i practice a very strict definition of science and, as many people, I consider that cosmology is not a pure scientific discipline since is based more in observation that in experiment.
I agree with George F.R. Ellis when says that the core of cosmological questions form more a metaphysical discipline that physical one.
Moreover, even if Smolin Cosmological Selection was a scientific theory, I would still wait that Smolin presents us an astrophysical BH.
Each x time all of us heard of a confirmation of a BH, but all previous candidates failed in more detailed test…
—
Juan R.
Center for CANONICAL |SCIENCE)
In view of the possibility of alien life somewhere out there, isn’t the use of the term anthropic a bit anthropomorphic? Why not generalize it to “panthropic”?
I read this month’s Discovery & followed this story here. Very interesting BLOG. I have been hearing about BLOG’s for a while but this is the first BLOG I have visited. Really interesting – more interesting than the last 10 years of Scientific American.
It has been 25 years since I left physics (my field was statistical mechanics – very far from this debate) so I am a bit rusty but I would like to comment.
First – Who:
You say, “S is not a premise, but a statement which Smolin challenges us to show is false—-by empirical means” and then you say “Some people believe that science is done this way, can you explain why you think this is not the case?”
Proving a negative is a high bar to jump – much more difficult than proving a positive. This has the appearance of being a reasonable request but in reality it puts the onus on the refuter to disprove any claim made by the author rather than having author show that the theory suits our reality. These so-called empirical tests seem very fuzzy to me. Most of the tests build on measurements, assumptions and theories that can be challenged – thus ultimately they are false tests.
Secondly in economics they distinguish between “empirical facts” and “stylized facts”. Empirical facts are facts that can be verified in repeatable and controlled experiments while stylized facts are observed consistencies that are observed in non-repeatable and non-controlled systems. Often stylized facts are observed in a limited number of data sets. I believe what you are calling empirical facts are actually stylized facts.
Thirdly as a general comment on the issue. I am avid reader of sci-fi & in the last few years I observed a phenomena that troubles me. More & more sci-fi writers are claiming their fictional ideas are supported by current physics theories. To support these scientifically outlandish ideas they usually point to articles or talks from well-known string or landscape theorists. When the line between sci-fi & science blurs I worry about where science is going.
Lastly, for over 30 years I have been an avid reader of Scientific American and my impression is that starting in the 80s, outside of genetics, fundamental breakthroughs and discoveries have really slowed down in many sciences, especially in physics. Where there use to be 1 or 2 really interesting and thought provoking articles each months, recently 1 or 2 a year is the average. I personally don’t think the decline is due to a decline in the quality of the writers – rather it is a reflection of a decline in the quality of the science being produced.
A layman’s thoughs.
Hi Jack,
Glad you like the blog. I certainly share your perception that fundamental breakthroughs in physics have slowed down (although there are some subfields like astrophysics and cosmology, which have been very active). In particle physics, the problem is that the field has been a victim of its own success. The standard model, developed by 1973-74, is just too good, and addressing some of its remaining problems requires energies that are technologically very hard to reach. As a result, things have gotten strange in particle theory…
Jack,
It has been 25 years since I left physics (my field was statistical mechanics – very far from this debate)
If you had stayed on for another five years, the gap would have been much smaller. In 1984, conformal field theory, which counts as stringy math, was applied to 2D phase transitions, certainly a subfield of statphys. Unlike the situation in string theory, this application of CFT has been experimentally confirmed beyond reasonable doubt. But that something is relevant to 2D statphys does not mean that it is relevant to 4D gravity, or even 3D statphys.