Why is there skepticism surrounding string theory?

[||spoon||]

Hey Guys,

I am currently reading Brian Greene's The Elegant Universe which introduces many of the basic ideas behind string theory.

While reading it i am constantly reminded of the skepticism with which many people regard string theory and it makes me wonder whether the book is biased or not.

Basically, why do (many) people have a skeptical view of string theory? Is it mainly the fact that it is, by today's practical means, unable to be directly confirmed by experiemnt? (Dont get me wrong i realize this is a pretty big issue! :) ) Or is there some inconsistency in the theory, mathematical or otherwise, which string theorists neglect to mention?

I should probably say that i haven't finished the book yet so such a consistency may come up. I only ask now because as i am reading it, although i am very open to new ideas, i am, as i mentioned, reminded of people's skepticism regarding the theory.

Thanks Guys,

- Spoon

 

[CompuChip]

As far as I know, the main objections to string theory are:
1) As you say, string theory is and will be for a long time (if ever) be unable to make any testable or falsifiable predictions. By some peoples definition, it is therefore not a "real" physical theory, just a mathematical one.
2) String theory needs at least 10 spatial dimensions to work. Currently a lot of people are working on the idea that only 3 are extended and the other ones are curled up on scales so small we just haven't observed this (yet). However, IMO some skepticism is warranted if you have a theory which supposedly (also) describes our everyday world, but only works in 10 dimensions.
3) String theory is by all standards a very complicated mathematical theory. Some people prefer to have theories as simple as possible (cf. Occam's razor) and the complexity of string theory may be a good reason for them to seriously wonder if there isn't anything more intuitive and mathematically clean to replace it.

Another problem was, that there seemed to be many different string theories, although I think theoreticians have recently succeeded in showing they are actually all one and the same theory (correct me if I'm wrong).

 

[Oberst Villa]

Another problem was, that there seemed to be many different string theories, although I think theoreticians have recently succeeded in showing they are actually all one and the same theory (correct me if I'm wrong).

I heard this too, it's called M-Theory.

http://www.damtp.cam.ac.uk/user/gr/public/qg_ss.html (I have no idea whether this stuff is correct, but it's from Cambridge, so let's hope for the best )

I have to confess that I'm an absolute layman on this topic, but for all I heard your point 1) (no testable / falsifiable predictions) is indeed the Achilles-heel of this theory. Perhaps your point 3) (very complicated mathematical theory) is not such a big problem - it surely is complicated, but I have often heard proponents of String theory talk about its deep "mathematical beauty", I guess that means it is complicated but not messy. I cannot really comment on this point of view because I wouldn't recognize mathematical beauty if it bit me in my behind...

 

[Demystifier]

2) String theory needs at least 10 spatial dimensions to work. Currently a lot of people are working on the idea that only 3 are extended and the other ones are curled up on scales so small we just haven't observed this (yet). However, IMO some skepticism is warranted if you have a theory which supposedly (also) describes our everyday world, but only works in 10 dimensions.

On the other hand, if string theory could work in any number of dimensions, they would object that the theory is not sufficiently predictive. But the most interesting thing, not understood by criticizers of string theory, is the following: If it turned out that string theory works only in 4 dimensions, then it would be clear that the theory is wrong, because it would be too simple to accommodate the Standard Model. Thus, extra dimensions are actually the virtue, not the drawback.

3) String theory is by all standards a very complicated mathematical theory. Some people prefer to have theories as simple as possible (cf. Occam's razor) and the complexity of string theory may be a good reason for them to seriously wonder if there isn't anything more intuitive and mathematically clean to replace it.

String theory does not look complicated at all if you start with the Zwiebach's "A First Course in String Theory".

 

[Phrak]

The arguments on both sides are emmotional.

 

[Fra]

it makes me wonder whether the book is biased or not.

I wonder what a book and what an opinion that is totally free from any bias even means. I don´t think I´ve ever read a book or paper free of bias.

I think bias is all over the place and unavoidable, in as much as the reader may also have some bias.

I personally think that string theory doesn´t address all the important questions I have. But then different people choose to ask different questions for whatever questions. I personally ask different questions than the one string theory apparently aims to (regardless of wether it succeeds or not) answer.

/Fredrik

 

[CompuChip]

On the other hand, if string theory could work in any number of dimensions, they would object that the theory is not sufficiently predictive. But the most interesting thing, not understood by criticizers of string theory, is the following: If it turned out that string theory works only in 4 dimensions, then it would be clear that the theory is wrong, because it would be too simple to accommodate the Standard Model. Thus, extra dimensions are actually the virtue, not the drawback.


String theory does not look complicated at all if you start with the Zwiebach's "A First Course in String Theory".

Yes, different people may oppose or agree with the objections I stated and in the end it may turn out that they are valid or not. Of course, there are also many good things about string theory which are not mentioned here. The question was explicitly what the main objections against string theory are, I just states the ones I think are most heard. (I explicitly tried to not give my personal opinion on them).

 

[Hyperreality]

Sure experimental verification of string theory is a big issue. But for us theorist, we cannot attack string theory as wrong or inconsistent just because we are unable to probe the Planck scale, there must be a scientific argument behind the claim.

As far as I can see, many skeptics dismisses string theory based on the predictions such as 11 dimensions or the landscape, but n o t on the actual mathematics. This is quite distrubing to me. In recent time, the debate of string theory among the physics community seems to have deviated from the actual physics and mathematics of the theory; it has becoming a war of words and public reations.

Anyhow, in my opinion, the best and most constructive critique on string theory I have seen are the works of axiomatic quantum field theorist Bert Schroer. His essay is available on the arXiv (bear in mind I have not finish reading these papers)

1. String Theory and the crisis of particle physics (a Samisdat on particle physics)

http://arxiv.org/abs/0712.0371

2. String Theory and the crisis of particle physics II or the ascent of metaphoric argument

http://arxiv.org/abs/0805.1911

3. String Theory deconstructed (a detailed critique of the content of ST from an advanced QFT point of view) dedicated to Philip Anderson on the occasion of his 83rd birthday

http://arxiv.org/abs/hep-th/0611132