String a failure: Nobel-laureate in today's NY Times

[Martin]

today Tuesday 4 January NYT

--quote--

 

Philip W. Anderson

Physicist and Nobel laureate, Princeton

 

Is string theory a futile exercise as physics, as I believe it to be? It is an interesting mathematical specialty and has produced and will produce mathematics useful in other contexts, but it seems no more vital as mathematics than other areas of very abstract or specialized math, and doesn't on that basis justify the incredible amount of effort expended on it.

 

My belief is based on the fact that string theory is the first science in hundreds of years to be pursued in pre-Baconian fashion, without any adequate experimental guidance. It proposes that Nature is the way we would like it to be rather than the way we see it to be; and it is improbable that Nature thinks the same way we do.

 

The sad thing is that, as several young would-be theorists have explained to me, it is so highly developed that it is a full-time job just to keep up with it. That means that other avenues are not being explored by the bright, imaginative young people, and that alternative career paths are blocked.

--end quote--

 

http://www.nytimes.com/2005/01/04/science/04edgehed.html?pagewanted=3&oref=login

 

the NY Times article, in today's Science Section, is based on the responses to the Edge.org Question for 2005----"what do you believe but can't prove".

 

Here is the Anderson quote in original context:

http://www.edge.org/q2005/q05_10.html#andersonp'>http://www.edge.org/q2005/q05_10.html#andersonp

 

You may wish to check out the original Edge article---which has statements from a wider variety of thinkers

http://www.edge.org/

 

 

In this kind of article you get each person's high priority message. Instead of being asked about a specific topic they each got to speak out with whatever message they urgently wanted to get across---usually it was something having to do with their own field: in the case of Anderson the direction theoretical physics has been going but in other cases it could be anything including future of the human species, morality, whatever, even stuff like "intelligent design".

 

 

read today's NYT now for free----soon the article goes into NYT archives and becomes payfor

[Martin]

http://www.edge.org/q2005/q05_print.html#steinhardt

 

appealing to the anthropic principle is a "act of desperation"

 

good essay by Paul Steinhardt, who has made a reputation in string and brane research himself and done some highly regarded and original stuff, so he knows whereof he speaks

 

Anderson and Steinhardt both at Princeton

growing awareness in the scientific establishment that the string research effort looks like a flop and

increased willingness to say it publicly,

 

could revitalize physics to cut back on string and get more juice flowing into other research sectors

 

this outspokenness in the Edge essays seems like a hopeful sign

[atinymonkey]

Tubthumping.

[Martin]

Tubthumping.

 

you can call it that if you want but i think it takes courage

(with so much of the public, the body politic and the establisment convinced) so I respect them.

 

and i also respect Brian Greene for his recent statements quoted in the NYTimes----basically contemplating the possibility that String is wrong,

a failure as theoretical physics, and pointing out that if so it would be

good to discover this and recognize it so that physics can move on.

 

Since Brian Greene has devoted his career to string theorizing (and writing books about it) when he says things like that I think it takes moral courage.

 

there are only a few of these guys and I respect them a whole lot.

 

if one of them thumps the tub, well I'm willing to put up with a little rhetoric

[ecoli]

Interesting stuff, thank you.

[Asimov Pupil]

Too Pessimistic maybe?

[mattd]

Are we not in the process of testing this theory (to the best of our abilities) with particle accelerators?

[JaKiri]

Are we not in the process of testing this theory (to the best of our abilities) with particle accelerators?

 

'String Theory' isn't a theory, it isn't even a conjecture. It hasn't really predicted anything yet, because it doesn't really exist yet.

[mattd]

This is all very confusing.

[Martin]

Are we not in the process of testing this theory (to the best of our abilities) with particle accelerators?

 

Jakiri is right.

No, unfortunately mattd, we are not testing it.

String theorists have declined to go on record with definite predictions about what will be seen at the LHC (the next big one, scheduled to operate starting around 2007)

 

about observing supersymmetry or not, about electroweak symmetry breaking, they hedge, waffle, say expect this but maybe not maybe this instead.

 

String is beginning to look, as some have said, like a "machine for producing theories"

In other words, mush.

something that makes no definite predictions about outcomes of future measurement but, instead, is compatible with whatever is observed

 

there has been a fair amount about this at Peter Woit's blog

"Not Even Wrong"

he keeps track of the latest non-predictions and the latest string hype (for public consumption)

 

there was also a great interview last year with Leonard Susskind at Edge.org. He is a string-guru much embroiled in the controversy over the Landscape, the huge number of different possible string theories---the 10¹⁰⁰ vacua, the Anthropic principle. Paul Steinhardt took part in that Susskind interview. Maybe I or someone will get a link to it.

 

I like to be upbeat and optimistic about progress in science and especially in astronomy and physics, and so I look for hopeful signs. the most hopeful signs i see now is that string research output is declining and toplevel people in the scientific establishment are considering the need to cut back on string funding. It is basically a case of amputate the dying branches and get new growth in other areas. We need to get this episode behind us so physics can move on.

 

Brian Greene sounded this note clearly at a recent string conference, during the closing speech when Joe Polchinski was summing up.

 

Joe said words to the effect: "and let's hope that, before too long, we finally get some experimental confirmation!"

Brian said essentially "wouldn't it be great either way? If we got some experimental dis-proof, we'd know for sure it was wrong and physics could move on."

 

that was a pretty gutsy thing to say---the conference was celebrating the 20th anniversary of string theory and all the bigwigs were on hand and it was during the closing remarks.

Made me like and respect Brian Greene, he came across as someone with principles and not just a charismatic popularizer

 

Anyway theoretical physics has been in the doldrums since mid 1980s (up to then it had a run of successes with theorists rapidly predicting stuff that was then seen at the accelerators, but since about 1983 comparatively little of this sort)

and now some change seems to be underway. I think it can only be for the good.

[Martin]

This is all very confusing.

 

Maybe it is confusing because you have been influenced by string happy talk in the media. Books like "elegant" by Brian have raised the expectations of the public. this is too bad. I am afraid it will backfire on the scientific establishment, they really should not raise a lot of enthusiastic hopes about something until they have more hard experimental fact. Ultimately it risks undermining the credibility of the scientific enterprise and the institutions that fund and support research. they didnt used to do so much premature hype.

[mattd]

I see your point about not getting worked up by all this, but I still see it as a theory. But it's a theory that needs to be tested in some form for it to have any validity, as with any theory.

[Martin]

I see your point about not getting worked up by all this, but I still see it as a theory. But it's a theory that needs to be tested in some form for it to have any validity, as with any theory.

 

what you say sounds simpatico and reasonable to me

and I think we can resolve the language dispute too

 

there is a technical sense in which a theory, to be scientifically meaningful, to be a theory at all, in other words, must bet its life on the outcome of at least one future measurement

 

Sometimes this question gets asked of string theorists: "what is something we could see at LHC that would make you abandon string?" i.e. what observation would be so contrary that it would refute it? If this cannot be answered definitely then there is no meaningful theory. If a model has meaning there must be something it cannot accept: some possible future experiment's outcome that it says cant happen and that it could not accomodate.

 

 

if there is not at least one thing, one future experiment, about which it says "It is going to be this way and not that way, and if it turns out that way then I am wrong" then it is empty. It has no predictive value, and in a technical sense it is scientifically meaningless.

 

Fans of string theory sometimes will say "well, I realize it is not a theory in that sense but it is a theory under construction"

Maybe that is right, or it is a whole bunch of theories under construction, no one of which has yet matured to a sufficient point.

the trouble is that during the past year prominent string theorists have been waffling about what they predict. As regards LHC they say things like "well it would be very nice if this happened but on the other hand it would be all right too if it didnt."

 

======================

 

then too, there is a broader more usual sense of "theory" that can be

a variety of things, mental imagery of how th world works, conjecture, speculation, a theory (in the technical sense) but unfinished, still untestable, still underconstruction, or perhaps some hunches and mathematical techniques for building theories----a "machine for making theories" which some people have faith will eventually succeed in producing a testable, predictive theory.

 

=============

Verbal disagreements are not too serious. It doesnt matter in the long run if one person says theory in a broad nontechnical sense and someone else is more careful about what he calls a theory.

History matters more than words.

But i think the history of science, at least of physics, is on the side of the narrower interpretation.

 

Einstein came out with Gen Rel in 1915. Gen Rel bet its life on light from a star being bent by a certain angle. In 1919 Eddington went and observed a solar eclipse and measured and it was bent by that angle.

Again and again in 20th century Gen Rel was tested. Coming out wrong on any of those tests would have refuted it. It was a theory in the narrower sense.

 

It was possible to refute or falsify because of predictions made about future experiments with as yet unknown results.

 

Also Quantum Field Theory and the Standard Model. up till mid 1980s

theoretical particle physics had an incredible run of predicting future results of experiments, time and time again the same drama as with Einstein and Eddington in 1915 and 1919, except this time with particle theory and accelerators.

 

It puts the bar fairly high. So there is no one right meaning of the word "theory" and it is fine to use it in a very broad sense. but based on the history of theoretical physics that would not be so typical and how it has been is more like Jakiri's narrower idea of a theory. Or anyway that is what I think.

 

from what you said I think you may in fact agree, and might say that string was a theory "still under construction" which hadnt reached the testable stage yet. maybe it is a grey area

[mattd]

okay, i see your point

[Martin]

okay, i see your point

 

thanks for hearing me out, matt!

I probably put some of this too strongly in an effort to get it across.

maybe there IS a chance of some significant test of some consequence of string-----like extra dimensions----say at LHC or anyway in the next few years. It has been speculated that a powerful collider might detect energy leaking into other dimensions, if they exist.

 

Unfortunately though, as I understand it, string theorists are NOT NOW PREDICTING on theoretical grounds that LHC will see this. It is just a speculative possibility. The theory is not solid enough to predict at what point one might see evidence. So if LHC does NOT see this they will just say "oh the extra dimensions are there all right but LHC just isnt powerful enough to make energy leak into them so we can detect them".

 

But maybe some indication of extra dimensions WILL be found! It's possible! so it is a half-way kind of test. If evidence is not seen, they will not consider string dead (because string did not place a bet) but if evidence is seen they will throw a party and celebrate.

 

Essentially the same with supersymmetry. Nobody will sign off on a prediction that Susy will be observed at LHC energies. But after the fact, if it is observed, they will celebrate. And if it isnt, they will say "oh probably LHC just isnt powerful enough to reveal those supersymmetric partner particles, but probably they are still there."

 

I think the pressure is growing for string theorists to sign off on some real predictions----that have the potential to refute or falsify the theory if they dont turn out. e.g. "At such and such energy if you try this you will see that, and if you dont then our model is wrong." (a sign the model has some real empirical content)

 

e.g. not "We think it would be nice if you see this, but if you don't it's all right too." (a sign of emptiness or protracted infancy)

 

I think this pressure could actually be helpful to string theorists, as a challenge to move in more testable directions. to act like physicists and take risks in encountering reality, not to act just like mathematicians fabricating beautiful and suggestive constructs.

 

so I think what we are seeing is a kind of cultural struggle about the rules by which empirical science is conducted

 

a key word is what Philip Anderson said-----"pre-Baconian".

Baconian means theory develops in close collaboration with experiment advancing like on two legs step by step, one leg doesnt wander off too far from the other.

 

Bacon was a guy who at the end of the middleages got tired of purely verbal Scholastic debate (about what Aristotle really meant) and proposed empirical science where you integrate experiment and theory. I think it was at the beginning of the renaissance and he was discovering the rules for what has been called "the scientific method" and it seems to have been very productive over several centuries and paid off

 

Anderson and people like that say there is no need, now, to depart from those rules because there are still good opportunities and we dont have to give up and wander around in speculative mathematical fairyland. they say get back to playing standard empirical hardball. construct a theory that puts itself immediately on trial and says "I make this definite prediction and if it doesnt turn out that way then I'm wrong"

 

they say if you go for 20 years and dont seem to be getting any closer to constructing such a theory then this is not empirical science and it is time to try some other theories, some other approaches. because continued elaboration of string, not getting any closer to testability, is beginning to look "pre-Baconian" (not really empirical science as we know it from the past 3 or 4 centuries.)

 

it is actually the historical angle that interests me personally about this

Personally i dont find string/M interesting as such. I dont think physics is anywhere near ready for a unification of forces or a "theory of everything". I think the clear nearterm goal is finally to quantize General Relativity. (which string does not do---it exhibits a graviton in some restricted situations, not the same thing). A limited goal: just quantize Gen Rel, the classical theory of gravity which works. After that, a general relativistic quantum physics----physics on a dynamic geometrical background instead of a fixed background.

since string doesnt address this I am not interested in it.

But what does get my attention is the historical/cultural issue of whether

the scientific establishment is going to allow theoretical physics to go mushy and non-empirical (and in which countries: if the US continues to fund string research and ignore quantum gravity alternatives, will the German establishment take the lead in funding alternative theoretical lines, or europe in general). At this level it is a fascinating story.

String seems stubbornly entrenched in the US but elsewhere (and at Penn State here) you see advances being made in non-string QG. so there is a possible shift in leadership underway in theoretical physics.

[ExplorerLeia]

I have read the above and wonder...

 

How would quantum gravity alternatives answer the same questions that String is trying to?

 

On a quantum leval of looking at things, if we ask what makes up electrons, protons and neutrons and causes atoms to be different one from another on a smaller scale...where can we find the answers?

 

Please advise,

Leia

[chadn]

String is beginning to look, as some have said, like a "machine for producing theories"

 

= job security

[Martin]

I have read the above and wonder...

 

How would quantum gravity alternatives answer the same questions that String is trying to?

 

On a quantum leval of looking at things' date=' if we ask what makes up electrons, protons and neutrons and causes atoms to be different one from another on a smaller scale...where can we find the answers?

 

Please advise,

Leia[/quote']

 

Hello Leia, I see you just became a member a couple of days ago---14 jan.

(the day Huygens landed on Titan)

Welcome.

 

If you read Anderson's view carefully what you will see is that he (as a Princeton physics prof, Nobel, member of the US scientific establishment) is calling for a more diverse stategy.

String has been not pannning out---has been looking worse and worse in the past couple of years----so don't put all your research eggs in one basket.

 

In other words, cut string funding and research positions and shift the resources to explore other newer approaches.

 

Warren Siegel (who has done a fair amount of string research in the past)

has some funny remarks----he now does string satires---making the same point. Notice the photo of the two baskets of eggs, prominently displayed:

 

http://insti.physics.sunysb.edu/~siegel/parodies/next.html

 

Siegel teaches quantum field theory and has a graduate level textbook on QFT.

QFT is the basis of the socalled Standard Model an enormously successful model explaining most of basic particle-level physics. But QFT is only relativistic in the sense of special relativity. That is the limited 1905 spacetime theory that prepared the way for the general relativity theory of 1915.

 

So QFT, although it works impressively well, is defficient in a certain sense. Instead of renovating QFT, however, theorists have gotten hung up in string for the past 20 years. Among the many things they have neglected to do is formulate a fully relativistic version of QFT,

(by fully I mean in accordance with the general theory). It is possible that doing that could be a first step, if they weren't so hung up with string.

 

The last 20 years in particle physics bear a close resemblance to some "get rich quick" scheme----like the Ostrich Farming craze---or the Tulip Mania in Holland. Theorists have taken a long vacation from reality.

 

Anyway Anderson is evidently saying "make it possible for graduate students to pursue other approaches, spread the funding, diversify the research in theoretical physics and get it back in touch with experiments and data"

[Martin]

Here's an exerpt from one of Warren Siegel's latest

in case anyone is curious:

----quote from http://insti.physics.sunysb.edu/~siegel/parodies/next.html ---

 

"String theory is often called the "Theory of Everything" (TOE). However, since so far it makes no predictions observable by experiment, a better name might be the "Theory of Everything Not Appearing in Laboratories" (TOENAIL).

 

This is not string theory's fault; high energy physics now takes a lot more energy than most people have. The real problem with string theory is that there is no alternative. However, the reason there is no alternative is that no one ever bothers to look for one; in fact, there is a strong resistance to even considering looking for one. Consequently, practically all theoretical high energy physics (and even most of phenomenology) is now string theory. Thus, string theory is not so much the Theory of Everything (since it explains nothing), but rather the "Everything of Theory", since it now encompasses all of theory. This era in string research is strongly reminiscent of the Dutch tulip trade just before the Tulip Crash of 1637.

 

The main reason string theory is incapable of explaining anything is that it has no predictive power. But even if it could predict anything, it would be only at the Planck scale, which is way beyond experiment of the foreseeable future. As a result, string theory has become boring. One solution might be to work on something that has more to do with observable energies..."

[Dave]

I've always been of the mind that string theory really isn't going to go anywhere. It seems to be very esoteric in nature and really (from reading some of the links) just looks like its stagnating.

[chadn]

The real problem with string theory is that there is no alternative.

 

What about Loop Quantum Gravity? Of course as I understand, it has few supporters and is no where as advanced as String Theory. I've been meaning to look into it some more, but just havent had the time.

[Martin]

hi Chadn,

LQG is not the only non-string Quantum Gravity being developed.

If you would like NON-STRING QG that is also not LQG either, and has considerable potential, then read Ambjorn. he has done string reserarch and also developed a very interesting alternative called

Dynamical Triangulation, they run computer simulations of quantum spacetime. Look at these two papers

Ambjorn Jurkiewicz Loll

"Emergence of a 4D World from Causal Quantum Gravity"

http://www.arXiv.org/abs/hep-th/0404156

 

"Semiclassical Universe from First Principles"

http://arxiv.org/abs/hep-th/0411152

 

Also Rodolfo Gambini has an alternative to LQG. In this paper he is bringing into a possible merger with LQG. the two approaches may benefit from the proposed alliance

http://arxiv.org/abs/gr-qc/0409057

Consistent discretization and loop quantum geometry

=============

 

So LQG is not the whole menu of possibilities

but if you particularly want an introduction to LQG then try these:

 

Smolin An Invitation to Loop Quantum Gravity

http://arxiv.org/hep-th/0408048

 

RovelliLoop Quantum Gravity

http://cgpg.gravity.psu.edu/people/Ashtekar/articles/rovelli03.pdf

 

The Rovelli article is the one most aimed at general audience.

 

Maybe you would find this debate interesting:

the Debate between Lee Smolin and string-theorist Lenny Susskind

http://www.edge.org/3rd_culture/smolin_susskind04/smolin_susskind.html

that took place this summer (2004) under auspices of the online magazine Edge

 

 

Here is Abhay Ashtekar's list of links to online popular Loop Gravity articles

http://cgpg.gravity.psu.edu/people/Ashtekar/articles.html

====================

 

What about Loop Quantum Gravity? ...it has few supporters ....

 

I wouldnt worry about the fewness of the supporters. Loop is a growing field, researchers are entering it and the number of papers published each year is rising.

 

I think what should matter is for young researchers in the U.S. to have access to SEVERAL alternative approaches to quantizing gravity. And practically speaking they dont have the choice.

 

In the U.S there is only one university (Penn State) where you get adequately exposed to the different lines of theoretical development in Quantum Gravity, and where you have a good chance to launch a career in the non-string approaches.

 

fortunately choices are not so restricted outside the US.

if you can go to Cambridge, Potsdam, Marseille, Univ. Western Ontario, Waterloo (also Canada), Utrecht, Rome, Imperial College London,...etc... then you have access to more choice. Potsdam right outside Berlin, is one of the most active centers. these places do string AND non-string, and they have post-doc jobs for people working in LQG and/or related Loop Quantum Cosmology.

 

I wouldnt say to think of LQG as the only non-string approach! Besides Loop there is Ambjorn's dynamical triangulation approach and Gambini's discrete quantum gravity.

 

in the U.S. the string Fraternity has a rather exclusivist mind-set. they deprecate or dismiss other approaches to quantizing gravity, and thereby maintain the appearance that string is the only way to go. Theory-wise, they pretty much have the jobs and the post-doc research positions sewn up in the US, so at least if you want to do theoretical particle physics as a career you have to do string theory.

 

At present people are leaving string theory (in the U.S. anyway, so I hear) and even getting out of theoretical particle physics as a whole!----the numbers of papers in string theory posted on arxiv has been declining.

 

Unfortunately, if you are fed up with string and want to get out, there are few opportunities (at least in U.S.) to move into non-string Quantum Gravity. I think the problem is basically with the funding and the institutions that do it.

 

a real obstacle to rationalizing QG research funding in the U.S. is that the DOE supports particle physics and the NSF supports the rest. non-String quantum gravity is not considered particle physics. So the only kind of quantum gravity research that DOE will fund is string.

DOE is connected to military and to the energy industry and its science budget was NOT cut, it actually grew IIRC. But NSF is more science-only and its budget has been cut.

this split in how quantum gravity research is funded acts as an obstruction to redirecting support away from string and into alternative lines.

[chadn]

Thanks for the info Martin. I am interested in particle physics, however, as I am sure you are aware, the availability of information on theories other than string is limited. Until you last post I was completely unaware of Ambjorn and had only had time to really examine string theory. I will greatly enjoy the resources you have posted. Thanks.

[ExplorerLeia]

Thank you Martin,

I took a look at the places you listed. Very interesting...the picture of the eggs made me think. I was wondering how many theories out there refer to there being more than one dimension of existence where things exist other than 3 and or 4 dimensionally, besides String which I understand can have 10?

 

The fourth dimension is time. We operate in a three dimensional non-linear existence. String suggests things are operating and exist in different dimensions where we cannot see them. Is there the possibility that another theory that is considered trustful also suggests the same thing? If so…is it possible to form an idea that vastly in the future people or objects from this three dimensional non-linear existence could be changed by energy into operating in a fourth dimensional linear existence or a different dimension?

 

 

Thanks,

Leia

[Martin]

... unaware of Ambjorn ....

 

then you might like Ambjorn's website, where he has some computer graphics of lower-dimension (toy) spacetimes

that their computer model cranked out some 2 or 3 years back

 

in the meantime they have been busy getting it to work in 4D

that is in 3+1 dimensions

and that is what the two papers from 2004 that I pointed to earlier are about.

 

there is no harm in going back to Ambjorn and friends work of 2001 etc and seeing how it goes in dimensions 1+1 and 2+1

because that gives the flavor

 

basically they produce little "histories" of the geometry of the universe

and these are random

like a "Feynman path integral" which includes a contribution from all possible paths a particle could take from here to there.

 

so they explore all these possible little histories of a (so far toy) universe.

 

some of the computer graphics are animation

 

I will get the Ambjorn website link, since you might find it intriguing

this has the animations (click on the picture and wait for it to start)

http://www.nbi.dk/~ambjorn/lqg2/'>http://www.nbi.dk/~ambjorn/lqg2/

 

this is his main page at the university of Copenhagen

http://www.nbi.dk/~ambjorn/