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The physicist Lee Smolin has written a new book, 'The Trouble With Physics'. According ot the review of this book in Amazon (I have not yet bought the book), he has lost faith in String Theory and now considers it a blind alley. Smolin claims that since String Theory has become the fashion, new developments in physics have slowed becuase of the failures of String Theory. What are the thoughts of the people here on String Theory?
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To me, String Theory is a classic case of reaching for something that is out of reach. It could be that it is 'right', but we just have too large a gap to get from our experimental abilities to the point where we can demonstrate something concrete about String Theory.
I am unaware of the specifics of budget and how much money actually goes into funding String Theory efforts as opposed to other lines of research that are a little closer, and reachable, so I cannot speak to the idea that studying it has done us any harm.
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My thought is on Thread Theory: is this the proper forum -- Universe Today Story Comments, Discuss stories posted on Universe Today -- for this thread? Was there a Universe Today story on String Theory that inspired this?Originally Posted by samsara15
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Good point. I have moved it to Q&A.
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As a layman (well, high school science teacher), I have been reading books about cosmology and arm-waving physics for about 15 years or so. Personally, I have always been bothered about the inability of string theory to be testable or make predictions. Maybe the LHC will be capable of testing some of the precepts of ST (like extra dimensions) and can shed some light on things.
However, as a fan of Smolin, it seems that he has a valid point, that string theory has sucked up the brightest and the best (and a disproportionate amount of funding) in what might eventually turn out to be a wrong idea.
From a couple of the reviews of the book (and I actually got my local public library to order it so I am first on the list), I glean that he is as concerned about the overemphasis on string theory in the past couple of decades as he is the actual science of it.
I am really looking forward to reading it (he is an excellent writer).
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hum,
it is worth reading this thread...
http://www.bautforum.com/showthread....rouble+Physics
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Good Idea
This is not at all correct, but has been repeated so many times that it is just commonly believed to be true. String theory does make predictions and it is testable. In particular, string theory is the only theory I am aware of which explicitly predicts supersymmetry. Each particle in the standard model table will have a supersymmetric partner, the mass of which is predicted from the theory, and measureable in a high energy particle accelerator. The predictions are for masses that are too high to detect with the current generation of accelerators, but not so high as to be beyond reach. In principle, a decade or two of technological improvement should make the predictions experimentally viable.
Smolin is not alone, a lot of smart people think string theory is a dead end. But it is worth pointing out that a lot of equally smart people do not agree. That's why we do "research". How do those of us who are not experts in the field decide, arbitrarily, which group of "really smart people" is right?
String theory is "seductive" because it is a quantum theory of gravity, and there aren't too many of those around (but note that it is only "a" theory, not necessarily "the" theory). String theory also just happens to include general relativity as a subset of the theory, which is also a highly desireable property of any plausible quantum theory of gravity. String theory also makes possible a quantum description of the "bang", and opens the door to pre big bang cosmology. These should be obvious reasons for being interested in pursuing an understanding of string theory.
The real weakness of string theory is that there really isn't any string theory. The stuff we/they call "string theory" is a set of perturbative approximations, but the real theory remains unknown. So, the two major efforts at work are (1) to find the real equations of string theory, and (2) to derive the consequences of the theory, as best we can, so as to predict observational effects.
Considering the potential for an enormous leap forward in understanding the universe, at the fundamental level, it seems to me that continued research in string theory is a good idea.
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I heard suggestions a while back that these supersymmetric partners could be the cold dark matter. What's the current thinking on that?
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We haven't observed any supersymmetric particles yet, though we hope to in a few years. There are several ideas as to what the cold dark matter WIMPs are, but the one I like best, is that they are neutralinos, which are the supersymmetric partner to neutrinos. They are the uncharged relics which are the only stable supersymmetric particle, and the ones carrying the non-zero supersymmetric quantum number.
We don't know that much about the properties of the yet unobserved unstable supersymmetric particles, but it is possible that they dominated the universe for the first femtosecond (wild guess as far as time frame goes), but by the end of the first picosecond, all that remained were the neutralinos.
As far as I know, there is no reason not to extend this and guess that there is also a family of super-duper-symmetric particles that were gone before the first yoctosecond ended. Likewise these could have left neutral WIMPs behind.
We really won't know until we manage to start getting statistical measurements of the CDM particles.
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Just to clear the cobwebs from my own head, Antoniseb, what are WIMPs? Looking at that acronymn makes me want to say "weakly interactive massive particles." I'm pretty sure that is it, but what would those be? Particles not affected by strong and weak nuclear forces, or gravity? Particles that cannot combine or react with each other?
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That's pretty much it, though it is a little strong to say "cannot combine or react with each other". They might rarely react with each other. Neutralinos, for example, are thought to annihilate each other, but have a very small cross-section for interaction.
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Didn't they do a test for neutrinos once? The foggy areas of my memory have dredged up a picture of an underground tank of very pure water with a diver in it. Something about neutrinos hitting atoms in the molecules of water, creating a cone of light that cameras were to pick up.
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Neutrinos are different from Neutralinos... but yes there are several on-going experiments detecting neutrinos, more or less as you describe. There are some new ones giant being built in Antarctica and near the bottom of the Mediterranean Sea.
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As I recall, Smolin used to be an ST supporter, and has now soured on it. That carries weight.
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Excuse my imprecision. I should have added the constraint about tests and predictions of ST "at this time". That is why I mentioned potential discoveries by the LHC.
I certainly don't think ST needs to be abandoned, nor, do I think, does Smolin.
This is all such a wonderful example of what I am always telling my students about science: that it is always evolving, that there are always discoveries to be made. Just remember the buzz when ST was first being looked at seriously and imagine the excitement if something comes along to enhance or supplant it. That's one thing that makes science so appealing to people such as myself.
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Has anyone read Smolin's book? I assume it sheds light as to specifically why Smolin feels ST is not viable.
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As Tim indicated above, Lee Smolin has NOT given up on String/'M' Theory!
Once he determined for himself that the main issue String/"M" has is that it is 'background dependent', and couldn't find a way (along with everyone else) to solve that, he explains that he just felt that the 'best' chance for finding physical evidence for either theory was in the LQG.
Here is his sight.
http://www.edge.org/3rd_culture/smol...n03_index.html
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Oops, I posted this in the wrong thread a second ago.
Anyway, here is a New Yorker critique of String Theory.
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I've picked up Smolin's book. I haven't finished it yet, but will try to give a quick gloss with the understanding that I may mis-state some fine points. His complaint is two fold. One is that string theory, at least in its current state is not falsifiable. This is not because it cannot make predictions but rather that it makes too many. To quote the jacket blurb "..no part of it has been tested and no one knows how to test it. In fact, the theory appears to come in an infinite number of versions meaning that no experiment will ever be able to prove it false." Now Smolin probably puts it better in the book, but I haven't had time to find his statement. Basically his concern is that string theory can appear to be infinitely adjustable (as many ATM types incorrectly accuse all of modern physics to be) and that it requires a fall back to the anthropic principle. That is, if string theories predict an infinite number of possible universes why does ours have the properties it does? Answer, we're here.
The second issue Smolin brings up is a more sociological one. Namely string theory has the potential to squeeze out and marginalize other potential lines of inquiry. This is not a healthy situation.
As a final note, with all due respect, I would not accept the New Yorker as an authoritative physics resource. Although they also have problems, I'd direct people toward the popular science press (New Scientist, Scientific American, etc.)
Last edited by Eta C; 2006-Sep-29 at 01:04 PM. Reason: spelling (original mistake preserved in quotes. Damn.)
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Weren't WIMPS proposed as a type of dark matter? If so, then these WIMPS must be gravitationally interactive because otherwise their presence would not help solve the galactic rotation anomalies.
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I've been around long enough to remember when string theorists would have had reason to complain that their efforts were being squeezed out and marginalized. Success, whatever form it takes, tends to overcome that.
Smolin should have spent more time on the theory, and less on the whine chapters.
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The New Yorker article was actually a critique of a couple of these books. It basically expanded on the points in your post.
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I have a pet peeve about the name “String Theory” and this seems as good a place as any to get it off my chest (hopefully someone can soothe my troubled soul).
Should it even be called “String Theory”?
Most standard science textbooks define “Theory” using phrases like “well established” or “explanation with lots of experimental evidence to support it”. Does String Theory meet this criterion? Is there any direct experimental evidence for String Theory (it is my understanding that there is none, but I am hardly an expert in this area)?
A while back I was listening to a discussion of evolution versus creation between a couple of scientists and one of them was commenting on how some creationists say that evolution is only a theory. Implying that since evolution was “only a theory” it is not much more than a guess. The scientist went on to say that this is not what science means by a theory. A theory is well an established explanation with lots and lots of evidence to support it (sounding just like most of the science textbooks I have read).
If I was debating this scientist I would us String Theory as an example of an exception to the above description of a theory and as the saying goes, it only takes one exception to disprove some thing.
So my point is, if definitions of terms are important in scientific discussions, shouldn’t we (science) be consistent in our use of these terms?
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Wikipedia: Theory
It's unfortunate that the stretching occurs, but it does.The term theory is occasionally stretched to refer to theoretical speculation that is currently unverifiable. Examples are string theory and various theories of everything. In common speech, theory has a far wider and less defined meaning than its use in the sciences.
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Thanks for the Wikipedia reference.
Dr. Plait was the one discussing what scientists mean when they use the term “theory”.
Apparently, scientists do not always mean “well established, lots of evidence, etc.” when they use the term “theory”. This is unfortunate, because modifying Dr. Plait’s sentiments to “scientists usually mean …” sounds lame and weakens the position that theories hold in science. Because of this stretching, when one hears about a theory (science and non-science folks alike), even if it is from a mainstream science source, they will have to wonder, is there lots of experimental evidence to support it or is this just another example of stretching the definition of “theory”? (I don’t mean to hijack this thread, I just felt like ranting for a while so if any of the moderators want to delete it, I fully understand).
The discussion I was referring to was between Dr. Seth Shostak and Dr. Phil Plait on Are We Alone? The SETI Institute’s Weekly Science Radio Program.
http://www.seti.org/site/pp.asp?c=ktJ2J9MMIsE&b=178892
(Unfortunately, I cannot remember the exact show on which the discussion occurred and since I am currently on a dial-up modem, it would take way too long find the correct episode.)
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