OK, maybe they haven’t offered it to him yet, but over at the Edge web-site, in a comment about John Horgan’s recent piece about the Templeton Foundation, Susskind writes:
I don’t understand the idea that a convergence between science and religion is taking place. I don’t believe in any such convergence. Throwing huge amounts of money at scientists who claim to see such a convergence can only lead to a dangerous blurring of boundaries.
I hereby pledge to refuse any prize for advancing the so called convergence between science and religion.
I missed Susskind’s recent public talk here in New York, about his book which the New York Academy of Sciences describes as “revolutionizing the field of physics”. There is a podcast recorded just before his talk. He makes his usual points including claiming that the situation of the string theory anthropic landscape is similar to that of Darwin and the theory of evolution. He also claims that anyone who thinks it doesn’t have experimental implications is wrong, pointing to Weinberg’s “prediction” of the cosmological constant.
Christine, I often find your comments helpful but in this case I can not make sense of your quote from
http://arxiv.org/abs/gr-qc/0501053
the paper by Giovanni Amelino-Camelia et al.
The quote is not self-consistent. If a theory “can easily be tuned” to avoid making a prediction then it simply does NOT make the prediction.
The point of restricting scientific theories to ones which make testable predictions is that the theory must bet its life on a future observation or measurement so that it can be falsified and discarded.
the question one asks of a theorist is what future observation, what specific result of a specific measurement, would make you give up your theory and change fields?. If a string theorist can not answer that question then string theory does not make any predictions in the empirical science sense.
It is not like the “predictions” that people make at New Years which are more vague and informal, really just guesses. A scientific prediction STAKES THE THEORY.
As an astrophysicist, I am sure that you know this! So how do you interpret the passage you quoted from Amelino-Camelia? To me it is self-contradictory. What am I missing?
I suppose the quote could be taken as confirming what Peter said. Did you mean it as corroboration? I really am confused about what you are driving at, please be a little more explicit!
=================================
Zelah said “And frankly nobody has any idea of how to unify QM and Gravity such that low energy physics could test the results.”
That is not correct Zelah. Many papers. Here is a recent one you can check out by Shahn Majid (noncommutative geometry, Cambridge)
http://arxiv.org/abs/hep-th/0604130
Algebraic approach to quantum gravity II: noncommutative spacetime
S. Majid
26 pages, 2 figures; book chapter to appear in D. Oriti, ed., Cambridge Univ. Press
“We provide a self-contained introduction to the quantum group approach to noncommutative geometry as the next-to-classical effective geometry that might be expected from any successful quantum gravity theory…”
Majid has something to say which is FALSIFIABLE, and it would seem rather interesting, about putting QM and spacetime geometry together.
People should stop applying the sloppy model of string theory indiscriminately to other QG fields, which ARE turning out to be predictive.
—quote Majid second paragraph page 2—
This is also the first noncommutative spacetime model with a genuine physical prediction[1],… The NASA GLAST satellite to be launched in 2007 may among other things be able to test this prediction through a statistical analysis of gamma-ray bursts even in the worst case that we might expect for the parameter …
—endquote—
Majid’s idea is quite conceivably wrong, in which case measurements by the NASA satellite will refute the idea. Either way, win or lose, it’s progress. (keep your fingers crossed that GLAST goes up as planned)
Please not to suggest that non-string QG theories fail to be testable at accessible energy (in this case it is Gammaray Burst energy)
I love string theory. It has enough branes behind it to cover all possibilities, so it’s a safe bet. It’s can’t be disproved!
LOL! That convinced me, I’m joining the string theory pack! I can’t loose!
Peter Woit,
Graviton:
String/M-theory with gravitons incorporates the full structure of Einstein’s theory. At the atomic level, it departs from Einstein’s, which doesn’t work quantum mechanically. The nature of the departure is unique to the string/M-theory. So, the prediction isn’t just the existence of the gravitons but their unique properties.
Supersymmetry:
String/M-theory’s prediction is that there should be supersymmetry. Supersymmetry predicts that for every elementary particle there is a superpartner particle. It makes detailed predictions about how superpartners will behave.
Extra dimensions:
String/M-theory predicts that there are extra dimensions with unique features. It doesn’t tell you everything about extra dimensions’ sizes, shapes, etc. as Einstein’s theory doesn’t about spacetime’s. E.g. the topology of empty spacetime in Einstein’s theory can be R^4, RxTor^3, R^2xTor^2, etc..?
Changes in the topology of spacetime:
Once again Einstein’s theory doesn’t tell what the topology of spacetime is either, but it tells you that whatever topology is it won’t change. String/M-theory predicts that it will change in distinctive ways.
I’m going to ignore your last comment. It’s offensive.
String theory does not depart from GR “at the atomic level”.
It does not predict unique, distinctive properties for gravitons.
It does not make detailed predictions about how superpartners will behave: it can’t even predict their mass.
It does not predict “unique features” of extra dimensions, it is consistent with an infinite variety of different sorts of extra dimensions.
It does not tell you how topology will change.
Please stop repeating hype you have heard elsewhere. If you know of specific, scientific predictions from string theory that can in principle be checked, tell us what they are, don’t just claim that they exist. Let me be specific: If you were given an accelerator capable of accelerating particles to Planck-scale energies, what would be the experimental signature that would show that string theory was true, such that if you didn’t see it, you would know string theory was wrong?
Dear Who,
Amelino-Camelia et al. are indeed not being scientifically rigorous
in their use of the verb ‘predict’ (at least in that passage), since
they use it interchangeably with the term ‘allow for’.
Thus, having acknowledged the fact that they are using the word
“prediction” in the more ordinary, vague sense, the interpretation
of that quote is as straightforward as it could be.
They are just mentioning that string theory can accommodate a plethora of new phenomena, and at the same time, that accommodation is not a scientific prediction (and I hope it will never be). Accommodation often presuposes that things can be adjusted, or brought to an adaptable state. One thing is to claim or conclude by whatever means that new phenomena could be expected. Another thing is to supply the quantitatively precise conditions at which these phenomena are supposed to be measured or observed.
In conclusion, what I really interpret from that passage on
Amelino-Camelia et al.’s paper is a simple background message that
string theory cannot be a theory after all (at least, not yet).
Perhaps they could have said it differently, so as to avoid
the understandable feeling that what they are saying is not self-consistent.
My present attitude towards string theory is that it is just an
approach to quantum gravity (or to unification), but not a theory (yet). There are several worrisome things like the landscape (and all the anthropic issue) and the lack of predictability in string theory that makes me uncomfortable. So I often agree with what Peter Woit continuously write here. An of course I completely acknowledge that other approaches have their own serious problems as well. But that is another story.
Best regards,
Christine
In the accelerator I will be colliding very high-energy particles. Occasionally a high-energy graviton will be produced that will move off into extra dimensions and disappears. It will look like a jet of high-energy particles and there would be nothing balancing the energy and momentum of that very high-energy jet.
Accelerators produce all sorts of things that show up as missing energy, this has nothing to do with string theory. I think you’re repeating the standard example of what would be evidence for a brane-world scenario. But string theory doesn’t predict a brane-world scenario. In the most popular “string theory phenomenology” models, we don’t live on a brane in higher dimensions, observable by energy escaping the brane. Instead the extra dimensions are planck scale. The signatures for this are different than the brane-world signatures and depend completely on the size and shape of the extra dimensions.
Baan, phenomenologists tried to compute collider signals of gravitons escaping in extra dimensions using the (non-renormalizable) Einstein gravity, because strings (and other quantum gravity models) failed to give concrete results.
Observing extra dimensions would be evidence for extra dimensions, not for strings.
Hech Baan wrote,
“What would be your reaction if string/M-theory predicts only universes without live forms?”
A more interesting questions is
“What would be string theorists reaction if string/M-theory predicts only universes without live forms?”
It is clear that many string theorists would claim that live forms are stupid 😉
You claim that string M-theory does many predictions but after you lack to cite even a single!
You said
“String/M-theory predicts that we all consist of strings, including people who don’t appreciate the theory.”
This reflect a complete misunderstanding of the concept of prediction. The string is not a prediction of string theory, it is one of axioms of the “theory”. Moreover, even if i forget this point, your claim is wrong, because it is now know that string is not fundamental. That is reason of joke “string theory is now a theory without strings”.
Another imprecision yours is that you lack to state that M-theory is not formulated (even Witten claims that nobody know M-theory is). It is difficult that an inexistent theory can do predictions. Another point is that the most *close* to M-theory has been formulated (M)atrix theory is not a theory of strings, it is a theory of pointlike objects: D0-branes.
The lesson is that initial string theory was so wrong that today nobody (including string theorists) believes on perturbative metric, nobody believes on 10D spacetimes, nobody believes on 2D extended objects as fundamental. The three were claimed to be correct a few years beyond…
Some comments on the rest.
String/M-theory with gravitons does not incorporates the full structure of Einstein’s theory. The causal structure of string is wrong when compared with GR, and this is reason for a non-perturbative generalization of string theory. That generalization breaks basic axioms of string theory and this is reason nobody has formulated M-theory still.
Supersymmetry is not a String/M-theory’s prediction. Supersimmetry is a need of the theory because internal difficulties. The problem you are ignoring is that String/M-theory needs supersymmetry at all levels as cure of internal inconsistencies and cannot offer a description of the world was non-supersimmetric. THat is we observe.
We may offer a non-supersimmetric model (the SM) and if in a future supersimmetry is found in laboratory then develop a more general theory with supersimmetry at high energies. String/M-theory introduces supersimmetry at all energies and none mechanism for which we can recover a non-supersimmetric description at low energies. That is reason that in 40 years none string theorist has been able to derive the SM.
In science, any new theory unable to explain known data is inefficient and if cannot derive previous theories at use then it is metaphysics.
Moreover, it is simply false that String/M-theory makes detailed predictions about how superpartners will behave.
String/M-theory does not predicts that there are extra dimensions with unique features. The history of number of dimensions in theoretical physics is a fascinating example:
4D, 5D, 26D, 10D, 11D, 12D? 4D?
In fact, there is people claimining a return to 4D string models.
It is interesting see you absolute claim on “prediction” of dimensions from string theory. What is a dimension in string theory?
Witten recognizes “On the other hand, we don’t understand the theory too completely, and because of this fuzziness of spacetime, the very concept of spacetime and spacetime dimensions isn’t precisely defined.”
Juan R.
Center for CANONICAL |SCIENCE)
Hech Bann: String/M-theory predicts that we all consist of strings, including people who don’t appreciate the theory.
This reminds me of something. In my late teens I read B. F. Skinner’s Beyond Freedom and Dignity. In contemplating the all-encompassing scope of Skinnerian behaviorism, it occurred to me that the theory could be used to explain (and dismiss) the behavior of its critics.
I was secretly infatuated with this idea for about a year and a half, and then began to recover my senses. A few years later I began to study Karl Popper’s writings and to consider his epistemological critique of Freudian psychology, and thereby began to truly understand the potentially pathological nature of “universal” explanations.
Of course, Hech Baan was just joking.
Christine,
I agree with you on those issues.
(At first I did not understand the thrust of your quote.)
Thanks for clarifying.
Who
Surely Susskind can redeem himself once and for all? If he can get a Hydrogen and Oxygen molecule to bond in any dimension other than 3? If for instance he can theoretically proove that it is possible to combine these two elements, and thus produce water in the, say 5th dimension, then he can bring to an end the “Many Worlds”, Parallel Universe’s, and Anthropic issues to a concluding close?
And as a side line, he could start a factory that sells this 5th dimensional water and retire with a “nice little earner” !
The first step to the proof of “life” in other Universe’s or Extra Dimensions, is to experimentally or Theoretically?.. Proove that “H2O” can be created in “other” dimensions.
Anthropically Susskind can argue that Water, and all our Elements of our periodic table have “leaked” from other dimensions into our, but somehow that does not seem to wash with me!
Lenny, fetch me a glass of water from any dimension other than 3-D, and I would gladly raise it as a toast to your good health and wealth!
Actually, I do not see Lenny opening a factory, it would be more to his stature that he opens a Baptising Water Spa?..I can see Peter Woit being first in line to this Anthropic Cleansing?
On the subject of combining the worship of religion and law-givers in physics, see http://zapatopi.net/lordkelvin.html
😉