Why is String Theory Considered to be a Scientific Theory?

[MTd2]

Again, for the n-th time: the very nature of strings are stringy resonances. If they couldn't be observed, would prove string theory to be wrong. (Obviously this is a matter of principle, as we humans cannot build such accelerators, at least as far as we can imagine).

String theory is presented here often as a random theory with arbitrary predictions. In reality it is extremely constrained and rather the opposite of an arbitrary theory. This seems hard to grasp, tho.

No, that is easy to grasp. The point is, if a theory whose unique predictions are completely outside human feasibility for the foreseeable future are untainable, is it scientific? Sure it is in principle, but science is of experimental nature. So, it sounds like the answer is yes/no at the same time. This is really uncomfortable.

 

[suprised]

So, it sounds like the answer is yes/no at the same time. This is really uncomfortable.

Indeed. But what are the options? We are not engineers who can redesign a machine if the customer doesn't like it. The natural constants, or scales, are what they are and any theory of quantum gravity has to cope with this. Those armchair critics who cry after "alternative theories" just should go on and try to do better.

 

[tom.stoer]

The point is, if a theory whose unique predictions are completely outside human feasibility for the foreseeable future are untainable, is it scientific? Sure it is in principle, but science is of experimental nature. So, it sounds like the answer is yes/no at the same time. This is really uncomfortable.

Again: string theory and other theories of quantum gravity are constructed in order to explain quantum gravity - for which we have zero experimental support! So it's the first time that one has to construct a theory (mostly based on mathematical considerations) for a domain which is (at least today) not testable in practice.

Everybody working in QG knows about this problem. The alternative is not to construct a different theory as it makes QG not better testable. The alternative is not to ask for experiments as they are in principle not feasible (at least not directly; maybe some better hints com from cosmological data). And the alternative is not to construct no new theory at all b/c we know that quantum physics and gravity as of today are inconsistent when combined.

I agree that this situation is uncomfortable, but there is no easy way out.

 

[inflector]

Again: string theory and other theories of quantum gravity are constructed in order to explain quantum gravity - for which we have zero experimental support! So it's the first time that one has to construct a theory (mostly based on mathematical considerations) for a domain which is (at least today) not testable in practice.

Everybody working in QG knows about this problem. The alternative is not to construct a different theory as it makes QG not better testable. The alternative is not to ask for experiments as they are in principle not feasible (at least not directly; maybe some better hints com from cosmological data). And the alternative is not to construct no new theory at all b/c we know that quantum physics and gravity as of today are inconsistent when combined.

I agree that this situation is uncomfortable, but there is no easy way out.

The same exact situation existed for quantum mechanics with respect to realism before EPR. The existence of EPR prompted John Bell to come up with his inequalities and eventually these were found testable in practice. String theorists should come up with a test or set of tests. Even if it takes 200 years to get the technology to run the test it will still be a good exercise.

Just throwing up your hands and saying we can't do it now seems like a copout. You can't run the tests now but why can't you come up with the idea for the experiment?

 

[marcus]

...So it's the first time that one has to construct a theory (mostly based on mathematical considerations) for a domain which is (at least today) not testable in practice...

Maybe one should mention the CMB at this point. An empirical test can be either experimental or observational. The CMB is, after all, the enormously magnified map of a small region of space, which bears traces from a time when the same region was even much smaller.

...Just throwing up your hands and saying we can't do it now seems like a copout. You can't run the tests now but why can't you come up with the idea for the experiment?

I think the traditional discipline of empiricism is to accept the idea that one should not propose untestable theories. There is a kind of traditional "faith" that with enough ingenuity it is not *necessary* to propose untestable theories.

Have we seen convincing evidence that we have now to break with that 400-year old Baconian tradition?

I'm not convinced. I think that QC is the "business end" of QG---cosmology is where the truth comes out.

Have a look:
http://arxiv.org/find/grp_physics/1/au:+barrau_A/0/1/0/all/0/1

 

[negru]

Just throwing up your hands and saying we can't do it now seems like a copout. You can't run the tests now but why can't you come up with the idea for the experiment?

What do you mean can't come up with an idea? We just need to build a big accelerator.

 

[suprised]

Just throwing up your hands and saying we can't do it now seems like a copout. You can't run the tests now but why can't you come up with the idea for the experiment?

You think this is a necessary advice? Guess what string physicists work on! Do they need to be told? They sit down working hard to further developing their theories and understand them better.

It's the armchair critics who made this up, fabricate a "controversy" where there was none, invent "string wars", appear in the media crying "failure" and demand "you must stop now". Even here this has created veritable obsessions. In reality there are no such string wars and most of this discussion is pointless; and actually quite unimportant to the general public. At any rate, while those keep on shouting and writing books and blogs, the physicists continue with their hard and difficult work.

 

[inflector]

What do you mean can't come up with an idea? We just need to build a big accelerator.

And what will you find whenever we can build one? What predictions does string theory make?

That we'll find stringy stuff isn't a very well defined experiment.

 

[inflector]

You think this is a necessary advice? Guess what string physicists work on! Do they need to be told? They sit down working hard to further developing their theories and understand them better.

I won't dispute that string theorists work hard. I've just been trying to get to the bottom of the actual state of the theory without having to spend the 10 years it might require to understand it at the level of an expert.

I'm asking questions to figure out where things currently stand. It appears to me that string theorists are very defensive about the actual state of things. Why is this? Einstein couldn't come up with a theory of quantum gravity, neither could Wheeler, lots of smart people are working on this. So one can't fault string theorists for not solving a problem that no one else can solve yet either. I get that.

I proposed a simple discrimination above: the two different ways in which a theory can be falsifiable in principle, and showed that there were two different criteria:

1) Can we run the test now?

2) Do we even know what tests we could run and what they would show?

I never got an answer to this question. So I'll ask you straight: I know that string theory fails to be falsifiable on the first account, but does it fail on the second?

From what I've seen the answer must be yes, because I've never seen a proposed experiment or prediction of new behavior that would categorically disprove string theory if not found. Not even one that would require galactic-scale accelerators to test.

So does such a prediction and proposed experiment exist? That's all I want to know.

If the answer is no, I'm not proposing that string theory is a dead end or a failure.

I'm in favor of radical freedom in research. I think that any scientist should be able to fund any research they want and we should split the money evenly. If you want to do big research then you'd have to get a bunch of people together to pool funding. I don't think politicians or bureaucrats should divide up funding dollars. I think the individual scientists should do it.

So I have no problem with string theory or the people continuing to work on it. I also have no particular reason to believe that another approach like LQG or CDT is better.

I just want to know what the actual state of the research is.

 

[dx]

I just want to know what the actual state of the research is.

To know what the state of string theory research is requires already quite an advanced level of knowledge about theoretical physics. If I may ask, what is your current level of preparation in physics?

 

[marcus]

... It appears to me that string theorists are very defensive about the actual state of things. Why is this?...

I proposed a simple discrimination above: the two different ways in which a theory can be falsifiable in principle, and showed that there were two different criteria:

1) Can we run the test now?

2) Do we even know what tests we could run and what they would show?

I never got an answer to this question. So I'll ask you straight: I know that string theory fails to be falsifiable on the first account, but does it fail on the second?

From what I've seen the answer must be yes, because I've never seen a proposed experiment or prediction of new behavior that would categorically disprove string failure if not found. ...

... I also have no particular reason to believe that another approach like LQG or CDT is better...

You are posing a challenge. It's clear and makes sense, at least to me. It wouldn't be satisfactory for people to copout by saying "Well nobody else can either!"

For comparison's sake I will give some clue as to LQG falsifiability---it has no extra spatial dimensions and people talk about LHC seeing evidence of extra spatial dimensions. That would falsify LQG.

Here's another indicator of how near to testability LQG is, or how far from testability it is. You have to judge how near or far:
http://arxiv.org/find/grp_physics/1/au:+Barrau_A/0/1/0/all/0/1

==quote arxiv list of most recent papers by a prominent phenom'ist at U.Grenoble==
Showing results 1 through 25 (of 59 total) for au:Barrau_A

1. arXiv:1009.5532 [pdf, other]
Baryonic acoustic oscillations simulations for the Large Synoptic Survey Telescope (LSST)
A.Gorecki (1), A.Abate (2), R.Ansari (2), A.Barrau (1), S.Baumont (1), M.Moniez (2), ((1) LPSC, Grenoble, (2) LAL, Orsay)
Comments: 4 pages, 2 figures, 10th Rencontres de Blois proceeding
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

2. arXiv:1009.4769 [pdf, ps, other]
Investigating The Uncertainty On The BAO Scale Measured From Future Photometric And Spectroscopic Surveys
Alexandra Abate (1), Alexia Gorecki (2), Reza Ansari (1), Aurelien Barrau (2), Sylvain Baumont (2), Laurent Derome (2), Marc Moniez (1) ((1) LAL, Orsay, (2) LPSC, Grenoble)
Comments: 5 pages, 3 figures, Proceedings of the conference "45th Rencontres de Moriond" - Cosmology Session, La Thuile, Val d'Aosta, Italy, March 13 - 20, 2010
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

3. arXiv:1003.4660 [pdf, ps, other]
Inflation in loop quantum cosmology: Dynamics and spectrum of gravitational waves
Jakub Mielczarek, Thomas Cailleteau, Julien Grain, Aurelien Barrau
Comments: 11 pages, 14 figures. Matches version published in Phys. Rev. D
Journal-ref: Phys.Rev.D81:104049,2010
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

4. arXiv:1001.2973 [pdf, ps, other]
Very high energy gamma-rays and the Hubble parameter
A. Gorecki, A. Barrau, J. Grain, E. Memola
Comments: Proc. of the 12th Marcel Grossmann meeting on general relativity. 3 pages, 1 figure
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

5. arXiv:0911.3745 [pdf, ps, other]
Loop quantum gravity and the CMB: toward pre-Big Bounce cosmology
Aurelien Barrau
Comments: Proceedings of the 12th Marcel Grossman Meeting on General Relativity. 3 pages, no figure
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

6. arXiv:0910.2892 [pdf, ps, other]
Fully Loop-Quantum-Cosmology-corrected propagation of gravitational waves during slow-roll inflation
J. Grain, T. Cailleteau, A. Barrau, A. Gorecki
Comments: 9 pages, no figure, minor corrections
Journal-ref: Phys.Rev.D81:024040,2010
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

7. arXiv:0902.4810 [pdf, ps, other]
Internal structure of a Maxwell-Gauss-Bonnet black hole
S. Alexeyev, A. Barrau, K.A. Rannu
Comments: 5 pages, 5 figures, published version with minor changes
Journal-ref: Phys.Rev.D79:067503,2009
Subjects: General Relativity and Quantum Cosmology (gr-qc)

8. arXiv:0902.3605 [pdf, ps, other]
Inverse volume corrections from loop quantum gravity and the primordial tensor power spectrum in slow-roll inflation
J. Grain, A. Barrau, A. Gorecki
Comments: 15 pages, 5 figures, published version with minor modifications, results unchanged
Journal-ref: Phys.Rev.D79:084015,2009
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

9. arXiv:0902.0145 [pdf, ps, other]
Cosmological footprints of loop quantum gravity
J. Grain, A. Barrau
Comments: Accepted by Phys. Rev. Lett., 7 pages, 2 figures
Journal-ref: Phys.Rev.Lett.102:081301,2009
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)

10. arXiv:0805.0356 [pdf, ps, other]
Holonomy corrections to the cosmological primordial tensor power spectrum
A. Barrau, J. Grain
Comments: 5 pages, Proc. of the 43rd Rencontres de Moriond "Cosmology 2008"
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

==endquote==

Barrau gave a talk in July at the Paris ICHEP (international HEP conference). Abstract and slides here:
https://www.physicsforums.com/showthread.php?p=2812649#post2812649
Loop quantum gravity and the early universe
Content: Loop quantum gravity is, together with string theory, one on the major candidate approach to quantize gravity. It provides a framework which allows for a non-perturbative and background-independant canonical quantization of general relativity. In this talk, I will briefly go through the basic conceptual groundings of the theory and switch to the latests developments associated with its implementation in the cosmological context. I will show that the Big Bang is replaced by a Big Bounce (therefore solving the initial singularity problem) and that inflation unavoidably occurs. Furthermore, the primordial tensor power spectrum should exhibit some characteristic features that could lead to experimental tests of this "Planck-scale" physics.

 

[MTd2]

To know what the state of string theory research is requires already quite an advanced level of knowledge about theoretical physics. If I may ask, what is your current level of preparation in physics?

Do you even know the level? This is not a trivial issue. Suprised said low energy SUSY models are not string theory. That means things are not accessible for the average professor level physicist, for example, working with fundamental experimental high energy physics on CERN. Even if said person developed detectors and statistical analysis tools like Tommaso Dorigo.

To tell you the truth, it is possible to have a glimpse of the current level by a fast reading of string theory papers, specially those involving top down constructions from heterotic and f-theory compactification GUT models. But, most details that are understandable to a wider audiance are in the beginning and end of the paper. The critical advances requires very specialized details that are lost in the middle of several papers and whose comprehension would require a lot of reading.

So, for most non genius, one:

1. Either work on the theory,
2. Do some other research.

If one criticise, the specialist can always run into intricacies and call the accusing party "arm chair physicist". Which is quite correct, but, it ends up looking like trying to criticize biblical scholars on the matter of scatological issues.

 

[inflector]

To know what the state of string theory research is requires already quite an advanced level of knowledge about theoretical physics. If I may ask, what is your current level of preparation in physics?

I am currently an advanced amateur, I'd say.

I have a very high aptitude for math and science. I attended one of the top two public high-schools in Massachusetts and when I was on our math team as a freshman we won the state math competition. I was the best in my class at math and science. I got a perfect score on the math SATs and 99.7th percentile on the English before they dumbed down the test in the 90s.

Unfortunately, I stopped taking math in college after differential equations a long time ago because I dropped out of college to trade commodities in the mid-80s. This was after my second year at Worcester Polytechnic Institute (a decent school but no MIT or Caltech or Harvard). I left high-school a year early because I was bored. I dropped out of college because it started to be more like high-school and wasn't challenging enough. I was learning more on my job by myself than at school.

I took first-year physics in college but not chemistry or quantum mechanics.

I taught myself programming computers and got a job before I ever owned a computer and ended up programming algorithmic commodity trading systems on the Apple IIe in 1981 through 1983 while I was in high-school and commuting from college.

I learned enough to get a job trading for one of the best traders in the world in Chicago when I was 19 years old. I worked with some very smart people in a small group that became famous for our trading success. I personally turned $2 million of this trader's money into more than $33 million in just over four years. I quit trading after just over four years because I was bored and had enough money I could do anything I wanted. Several of the guys I traded with run hundreds of millions or billions in hedge funds now.

I taught myself business, started an Inc. 500 computer board repair company and several software companies, one of which I took public and ran for a while. I consulted to startups in Silicon Valley in the late 90s at the height of the internet craze helping with marketing and software architecture.

I am also an author, my first book which discussed my trading experience, sold over 70,000 copies and is printed in 10 languages.

I have never held a conventional job. I have always done something new because I hate boredom and I love to learn. I especially love challenges and anything that others consider to be impossible. I have made more mistakes than anyone I know because I have never been satisfied doing what I already know. I am always trying something new and difficult, and once I master any given subject, I move on to something more challenging.

I have been looking for a big challenge and a way to make a big difference in the world and I came to physics a few years back after I started looking at transportation systems. It was clear to me that we needed electric vehicles of various sorts and that let me to investigate fusion power and the reasons why we had not yet figured out how to do practical fusion. From those investigations, it became clear to me that science still did not have a clear picture of the nucleus and factors which affected nuclear binding energy. This surprised me.

I subsequently found that there are many open questions in physics which I had always assumed we had an answer for. What is mass? How does mass bend spacetime? What is time? What is responsible for the phenomena we attribute to dark matter and dark energy? and many more as I'm sure you all know.

So I feel like these are challenges that I can really dig into and ones that are supremely difficult. I like this.

So I've been working on some ideas and trying to learn enough physics so I can contribute something useful to science.

I am trying to figure out what directions to take with my personal research and have settled on the quantum gravity problem in particular as the most interesting challenge.

Now I represent an oddity here, perhaps. You won't find many people who have been as successful (and failed spectacularly at times) and who have done so many other things in life, or who are as old as I am digging into a field as difficult as physics, and especially quantum gravity. You also won't find very many people with the aptitude for science and math that I have who took as little actual math in college as I have yet who are still going to jump into physics for the first time in their mid 40s. I think my perspective from other fields and disciplines and skills will be useful. I also think it is possible I might perhaps be able to see something new. Of course, I know that a lot of scientists think this at some level.

I am trying to take advantage of my fresh perspective so I have spent a lot of the last two years coming up to speed on the historical development of physics and the reasons why we have our current beliefs. I believe that there are clues in the history that may hint at possible assumptions that science is making that won't hold in the end, and that perhaps some of the answers are difficult to find because everyone holds the same assumptions. So I am very skeptical of anything that I read unless I personally understand the logic behind it. I take nothing at face value and consider no one to be an unimpeachable expert on every subject.

I believe I can learn from almost anyone, yes, even the cranks and quacks at times, but I take no one's opinions as my own without having investigated the reasons for their beliefs myself. I am trying to build a giant tree in my head of all the assumptions of physics and how they interrelate so that I can understand what we actually know and what we just mostly think must be true but haven't really proven. I distinguish very carefully between the specific results of experiments and their specific interpretations.

I am currently reading Feinstein's Lectures on Physics, Mary Boaz's Mathematical Methods in the Physical Sciences, and Penrose's The Road to Reality to bone up on the basics. I'm trying to figure out what next steps to take which is why I am interested in finding out the state of String Theory. I want to know if I should explore it further or work on something else.

That's probably way more information that you wanted or required but some of that may be relevant to your answer.

 

[marcus]

...
If one criticise, the specialist can always run into intricacies and call the accusing party "arm chair physicist". Which is quite correct, but, it ends up looking like trying to criticize biblical scholars on the matter of scatological issues.

MTd2, your command of English would be excellent even were you a native speaker. But be careful to distinguish between eschatological and scatological. Two separate meanings, one Bible-related and the other slightly off-color.

I am currently an advanced amateur, I'd say.

I have a very high aptitude for math and science...

...I am also an author, my first book which discussed my trading experience, sold over 70,000 copies and is printed in 10 languages.

...So I've been working on some ideas and trying to learn enough physics so I can contribute something useful to science.

...I am trying to figure out what directions to take with my personal research and have settled on the quantum gravity problem in particular as the most interesting challenge...

... I am trying to build a giant tree in my head of all the assumptions of physics and how they interrelate so that I can understand what we actually know and what we just mostly think must be true but haven't really proven. I distinguish very carefully between the specific results of experiments and their specific interpretations...

I am currently reading Feinstein's Lectures on Physics, Mary Boaz's Mathematical Methods in the Physical Sciences, and Penrose's The Road to Reality to bone up on the basics. I'm trying to figure out what next steps to take which is why I am interested in finding out the state of String Theory. I want to know if I should explore it further or work on something else.
...

I see how you might be able to "contribute something useful to science". Write a book about the revolutions going on in physics, from a layman's perspective.

Your assets are that you think clearly and write well, and have high aptitude, and have had an interesting life (presumably born around 1965), which means that your own story as an adventurous character going around in search of understanding, talking to various physicists, visiting various observatories, accelerators, institutes, etc would likely make a good narrative.

The public tends to like these books telling the story of an individual's science odyssey. It makes it easier for the reader to put himself into it and get engaged with the subject matter. Both Smolin and Susskind have used this device. You get to include photographs.

Go visit IceCube the neutrino telescope in Antarctica, and interview somebody. Go visit the MAGIC air cherenkov imaging telescope on San Juan island in the Canaries. Visit that "Auger" large area cosmic ray detector spread in Argentina. Visit the ESA (euro space agency) and talk to the people handling the Planck spacecraft mission---mapping the cosmic microwave background. Talk to people at LISA gravity wave detector.
You'd learn a lot and have a successful book and teach other people a lot by seeing frontier science through an intelligent layman eyes.
Just a thought. No time to edit. Sorry if too pretentious sounding.

 

[dx]

Thats very interesting inflector.

Well, I'm no expert in string theory, but here's a brief outline of its starting point.

In ordinary physics, we have a background spacetime M, and particles/fields propagating on that space in a relativistic way. This picture of particles/fields propagating in space, interpreted quantum mechanically, is the basis of quantum field theory. For example, we can have a field \varphi : M \rightarrow R, called a scalar field, where R is the set of real numbers. From the field, we construct a 'Lagrangian', such as g(d\varphi,d\varphi), where g is the 'metric tensor' which encodes the metric properties of spacetime. This object determines the equations of motion of the field. Quantum field theory is the basis for the comprehension of a large amount of experimental data, but on the logical level, there are many contradictions and difficulties when one tries to extrapolate this to extreme situations.

In string theory, instead of a background spacetime, the basic space is an auxiliary space called the worldsheet (the string analog of the world-line of a particle). There is no classical spacetime in the ordinary sense. The coordinates of spacetime become fields on the worldsheet. Spacetime is supposed to arise out of quantum fields propagating on the worldsheet. Research in string theory has mainly been a mathematical exploration of this idea, and its consequences for physics. Gauge theory, general relativity etc. (the other main ingredients of ordinary physics) are not put into string theory, but seem to arise out of it. The only input that string theory takes are special relativity and quantum mechanics. Many of the leaders of string theory research, like Witten, think that the precise fomulation of string theory will involve a radical generalization of the notion of geometry, and finding this is one of the themes of current efforts.

 

[atyy]

Let me suggest that when David Gross says we don't know what string theory is, it's not much different from physicists who said we didn't know what renormalization of QED means even after the *successful* work of Schwinger, Feynman, Tomonaga. The understanding of renormalization had to wait till Wilson, following a bunch of clues that went back to Gell-Mann and Low. (And if you read the Clay Institute prize, apparently we still don't even know what QCD is!) But we don't say that Feynman's work did not provide in principle testable hypotheses. In the same way, string theory already does provide in principle testable hypotheses - although unlike Feynman's predictions, those of string theory are not in current practice testable.

An example of string theory prediction near the Planck scale is
http://arxiv.org/abs/hep-th/0601001

There are also only a *finite* number of possibilities for experimentalists to test in string theory.
http://arxiv.org/abs/hep-th/0606212

 

[inflector]

You are posing a challenge. It's clear and makes sense, at least to me. It wouldn't be satisfactory for people to copout by saying "Well nobody else can either!"

For comparison's sake I will give some clue as to LQG falsifiability---it has no extra spatial dimensions and people talk about LHC seeing evidence of extra spatial dimensions. That would falsify LQG.

Here's another indicator of how near to testability LQG is, or how far from testability it is. You have to judge how near or far:
http://arxiv.org/find/grp_physics/1/au:+Barrau_A/0/1/0/all/0/1

marcus, thanks for the specific examples.

This is exactly the kind of thing that I trying to find for string theory. I haven't really dug too deeply but I have been looking and haven't found anything in my hunt so far.

I see how you might be able to "contribute something useful to science". Write a book about the revolutions going on in physics, from a layman's perspective.

...[snip]...

Go visit IceCube the neutrino telescope in Antarctica, and interview somebody. Go visit the MAGIC air cherenkov imaging telescope on San Juan island in the Canaries. Visit that cosmic ray detector spread in Argentina. Visit the ESA (euro space agency) and talk to the people handling the Planck spacecraft mission---mapping the cosmic microwave background. Talk to people at LISA gravity wave detector.

You'd learn a lot and have a successful book and teach other people a lot by seeing frontier science through an intelligent layman eyes.

I certainly hope to write a book about science, or a series of books on science in the future. I really enjoyed the Asimov books (especially the chemistry books) growing up so I have high standards and I feel I have a lot to learn first.

But more important than that, I want to do some actual science myself first. That will make any books all that much better.

 

[atyy]

marcus, thanks for the specific examples.

This is exactly the kind of thing that I trying to find for string theory. I haven't really dug too deeply but I have been looking and haven't found anything in my hunt so far.

Oh, if you want stuff at that level, there's tons of that in string theory.
http://arxiv.org/abs/0807.3333
http://arxiv.org/abs/0908.0409
http://arxiv.org/abs/0904.3547
http://arxiv.org/abs/1001.0577
http://arxiv.org/abs/1008.2379
http://arxiv.org/abs/0806.3905

Observations of these will favour string theory. The problem is that non-observation will not falsify string theory. Just like observing our solar system favours Newtonian gravity, but non-observation of it does not falsify Newtonian gravity, since there are many other configurations consistent with Newtonian gravity. For that, you have to rule out all the finite number of possibilities in the string landscape http://arxiv.org/abs/hep-th/0606212, which will in principle falsify string theory - but in practice the energies needed to eliminate some possibilities of the landscape are too high, and the number of possibilities, though finite, is impracticably large.

 

[inflector]

presumably born around 1965

Yes, I was born in January 1964, one day before Michelle Obama.

I view myself as a post-boomer but not quite gen-X even though by some definitions my year is the cutoff date for being a boomer. I guess I feel we've been slacking off and making excuses while there is still a lot of important work to be done. Too much for someone like me to just go out and make money for myself doing something that won't help out (or make things worse in many cases).

Perhaps that's one of the reasons that I feel the need to join the effort in science. I don't think we'll have a political solution to many of the world's problems in time to avoid very significant worldwide pain unless we get a breakthrough in physics soon. Fusion power would go a long way towards helping with global warming, for example.

Plus, I was a little kid when Apollo 11 landed on the moon. I remember the Apollo 13 mission and the drama of that. I guess I grew up assuming we'd have clean energy and would be traveling to the stars by now. I'm not ready to give up on that dream while I'm still alive.

 

[MTd2]

The only input that string theory takes are special relativity and quantum mechanics.

That is not quite true because branes are fundamental objects of the theory but they must be put in the theory for consistency. So, what you write is more of a starting point.

Also, there are a lot of non fundamental inputs to realize realistic compactifications, which requires most of the expertize needed to model possible experiments to test it. And that goes way beyond any textbook available. So, either one studies those or do something else or is called an armchair critic.

 

[inflector]

Thanks atyy, that helps a lot. I figured that the theorists must be trying to find evidence, so there should be some hints that things are going the string way before we get to the Planck scale. It is good to see the specific papers/reviews you listed.

The problem is that non-observation will not falsify string theory. Just like observing our solar system favours Newtonian gravity, but non-observation of it does not falsify Newtonian gravity, since there are many other configurations consistent with Newtonian gravity. For that, you have to rule out all the finite number of possibilities in the string landscape http://arxiv.org/abs/hep-th/0606212, which will in principle falsify string theory - but in practice the energies needed to eliminate some possibilities of the landscape are too high, and the number of possibilities, though finite, is impracticably large.

Yes, this is certainly a problem that won't be easily surmounted. It's a weakness but if reality is stringy it's one we'll have to live with.

 

[MTd2]

Yes, I was born in January 1964, one day before Michelle Obama.

I cannot help but thinking that you, and mainly marcus, are around 19-21 years old...

 

[inflector]

And that goes way beyond any textbook available. So, either one studies those or do something else or is called an armchair critic.

This goes along with my general impression that for me to make an impact in string theory would probably require 3 to 6 years of work (and perhaps as much as 10) first, just to get to the point where I can evaluate the papers and have an intelligent discussion at the professional level about the latest aspects of the theory.

That's probably reason enough for me to work in some other area.

 

[inflector]

I cannot help but thinking that you, and mainly marcus, are around 19-21 years old...

Why is that?

 

[Fra]

I just want to add what I think the immediate question is.

One can evaluate a research program from any perspective one wants. One does not need to be an experienced reputed "string theorist" in order to be allowed to have an opinon on string theory.

On the contrary, it's up to those that feed on public funding to explain to the public what they get back. The public want benefit for society and makind, not feed mental masturbation of minorities. To think that the public should fund any crazy ideas of everyone that wanted to do research is unreasonable. I think it would be wrong.

It's not a question of answering to wether it is ultimately "correct" or not, because not even string theorists know that. NOone is then "qualified". Maybe in another 100 years mankind can look back and answer this, to see wherther we were heroes or fools to invest 140 years in this.

The question is IMHO: given what we think we konw now, and given the quest we face, to expand knowledge, to what extent is it RATIONAL to INVEST money and manhours into string theory reasearch?

This is a question everyone will answer on it's own. Individual researcher ask themselves this, do I feel the best use of my time is to research ST? Also the society that does funding should ask to what extent it's rational to fund this or that?

I judge research programs in it's starting points, methodology and logic of reasoning, and of course state of progress. I have an opinon of string, but I'm certainly no string expert, but that does not invalidate my opinon, because my opinion is important just for my own actions.

So what is the option to ST funding? Well there are OTHER ideas than string theory, also from the point of view of funders, there are OTHER scientific work to fund.

The point is that the decision we all have to ask ourselves is decision based on incomplete information, and it's a bet. We are all our own qualifiers of where to place the bets. If the experts dismiss critique as armchar criticts, that's a failure of the experts to communicate (still after 40 years) the benefits of what they do.

So I don't personally accept the armchair rejection of all critique. Although it's probably fair to say that SOME critique aren't that well thought out, it's silly to think that the only ones that are allowed to critque the program is the experts themselves. It should be the other way around.

Edit: ie. you need to convince your opponents that you are right, you need to present for them, objective and undeniable progress. Usually this is in the form of corroboration after falsification attempts. Now if that still hasn't been done after 40 years, we need to find new ways to describe our work. Perhaps like trying ot measure progress, and then hypothesis could be that "this research program or algorithm" will perform better than the compoeting programs, in terms of reducing the number of "options" etc, then this could be tested in terms of effiencty of algortihms if you see the research as such. But here the landscape problem of ST seems to have diverged rather than converged, this is a problem as I see it. So one may ask where the progress is, when the set of possibilities just seems to expand, rather than shrink? There seems to be an imbalance between generation of new possibilities and selection from them. To me this looks like a flawed algorithm.

/Fredrik

 

[Micha]

I am currently an advanced amateur, I'd say.

If you are serious to become a good physicist, I think you should read this:

http://www.phys.uu.nl/~thooft/theorist.html

 

[inflector]

Thats very interesting inflector.

Well, I'm no expert in string theory, but here's a brief outline of its starting point.

Thanks dx, that was a helpful outline.

 

[inflector]

If you are serious to become a good physicist, I think you should read this:

http://www.phys.uu.nl/~thooft/theorist.html

An excellent and valuable reference. I'm shocked that this was the first I've seen that reference since I've been reading and looking for a long time.

Thank you.

 

[arivero]

This thread is advancing to a topic of more general interests that plain "Beyond Standard Model". The question is now, it seems, how to be trained as physicist at a late age (beyond 30, say). I think that the internet is providing enough resources, from pirated books to open lecture notes from the main campuses. The great problems is how to provide the discipline (if needed) to keep going, the feedback (to correct errors) and the local human contact (to be encouraged generally, and to reinforce both discipline and feedback).
Of course, it is not even a question of theoretical physics, we could think about math or about other disciplines where some advance can be done without access to a laboratory.

 

[atyy]

This thread is advancing to a topic of more general interests that plain "Beyond Standard Model". The question is now, it seems, how to be trained as physicist at a late age (beyond 30, say). I think that the internet is providing enough resources, from pirated books to open lecture notes from the main campuses. The great problems is how to provide the discipline (if needed) to keep going, the feedback (to correct errors) and the local human contact (to be encouraged generally, and to reinforce both discipline and feedback).
Of course, it is not even a question of theoretical physics, we could think about math or about other disciplines where some advance can be done without access to a laboratory.

I'm an experimental biologist, so I have no idea how theorists work (if you can't think, just measure - unfortunately, that's sometimes expensive - I mean scotch tape was just the first step, wasn't it)? Anyway, I read an interesting story of what a good non-genius (ie. not Ramanujan) amateur can achieve in http://books.google.com/books?id=shuJFCWWql4C&dq=king+of+infinite+space&source=gbs_navlinks_s. Douglas Hofstadter had discovered for himself some beautiful geometry theorem. To find out whether his discovery was unknown to anyone else, he wrote to Donald Coxeter, who didn't know, but pointed him to some books. It turns out that after some searching, his discovery was already known. Nonetheless, he did have lots of fun in the process.