Is String Theory the Limit of Our Understanding?

[tozhan]

if string theory is so brillient how come i can't find any info on how string theory says beta decay MUST happen. I keep asking and getting the answer "string theory does not yet deal with that level of detail". I mean, how can this be?? how can a theory be so widly accepted and not explain the smallest interactions? Maybe it does fit with the grand scale universe and quantum world but one of the greatest achievments of mankind in the 20th century was spliting the atom, as far as I am aware (which is extremely limited) string theory can't explain simple events like weak interaction. If each particle is a single string that is ocillating at some given frequency then how can beta decay produce an electron and electron antineutrino from a 'd' quark?? surly this would mean that the quark is an ocillating string and the electron and electron antineutrino two other 'new' strings. Where did these come from? can we just create string? maybe from energy, like in quantum chromodynamics where it is more energy efficient to create a new quark-antiquark pair.

Is there a basic underlying flaw in my idea of string theory because it seems hard to accept as a leading theory when ANY event of this type seems not to fit in?

PLEASE HELP

thx

Tom

 

[marcus]

... be so widly accepted and not explain...

widely accepted?
probably among physicists it is not yet seen as time either to accept or reject

string theorizing has not yet produced a mature theory that has been able to make even a single prediction about the future outcome of an experiment that would allow the theory to be tested against reality

there has been a great deal of mathematically sophisticated theorizing but it has led to a great number of physically different cases (the famous 10¹⁰⁰ different vacua of Kachru et al, sometimes called the "String Theory Landscape") and thus to no one clear prediction that can be tested.

In popular writing and among the public there may be much enthusiasm but I get the sense that among working scientists the time is not yet ripe to accept or to reject. At present it is more time for hopes and wishful imaginings.

So I would say please do not expect too much but why not admire all the progress so far (which however is not certain ever to lead anywhere besides to mathematician's heaven)

 

[Gold Barz]

Its popular but I don't think its widely accepted...atleast not yet

 

[marcus]

tozhan, for balance to the idea of "widely accepted" here is a recent statement by a Nobel laureate physicist on the faculty at Princeton
http://www.edge.org/q2005/q05_10.html#andersonp

---quote from Philip Anderson---
"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---

what he means by "pre-Baconian fashion, without any adequate experimental guidance" is that it is not conducted as science has since Francis Bacon described the method of empirical science some 400 years ago. His criticism is that it is not really science as we know it, because not guided by experimental testing. And so, in his view, may be a waste of resources (time, intelligence, money) that were intended for theoretical physics.

Another interesting view is from a string theorist Paul Steinhardt, also on the Princeton faculty. This concerns the String Theory "Landscape" of so many different versions of physics and what he sees as giving up trying to explain
http://www.edge.org/q2005/q05_print.html#steinhardt

---quote from Paul Steinhardt---
"I believe that our universe is not accidental, but I cannot prove it.

Historically, most physicists have shared this point-of-view. For centuries, most of us have believed that the universe is governed by a simple set of physical laws that are the same everywhere and that these laws derive from a simple unified theory.

However, in the last few years, an increasing number of my most respected colleagues have become enamored with the anthropic principle—the idea that there is an enormous multiplicity of universes with widely different physical properties and the properties of our particular observable universe arise from pure accident. The only special feature of our universe is that its properties are compatible with the evolution of intelligent life. The change in attitude is motivated, in part, by the failure to date to find a unified theory that predicts our universe as the unique possibility. According to some recent calculations, the current best hope for a unified theory—superstring theory—allows an exponentially large number of different universes, most of which look nothing like our own. String theorists have turned to the anthropic principle for salvation.

Frankly, I view this as an act of desperation. I don't have much patience for the anthropic principle. I think the concept is, at heart, non-scientific. A proper scientific theory is based on testable assumptions and is judged by its predictive power. The anthropic principle makes an enormous number of assumptions—regarding the existence of multiple universes, a random creation process, probability distributions that determine the likelihood of different features, etc.—none of which are testable because they entail hypothetical regions of spacetime that are forever beyond the reach of observation. As for predictions, there are very few, if any. In the case of string theory, the principle is invoked only to explain known observations, not to predict new ones. (In other versions of the anthropic principle where predictions are made, the predictions have proven to be wrong. Some physicists cite the recent evidence for a cosmological constant as having anticipated by anthropic argument; however, the observed value does not agree with the anthropically predicted value.)

I find the desperation especially unwarranted since I see no evidence that our universe arose by a random process. Quite the contrary, recent observations and experiments suggest that our universe is extremely simple. The distribution of matter and energy is remarkably uniform. The hierarchy of complex structures ranging from galaxy clusters to subnuclear particles can all be described in terms of a few dozen elementary constituents and less than a handful of forces, all related by simple symmetries. A simple universe demands a simple explanation. Why do we need to postulate an infinite number of universes with all sorts of different properties just to explain our one?

Of course, my colleagues and I are anxious for further reductionism. But I view the current failure of string theory to find a unique universe simply as a sign that our understanding of string theory is still immature (or perhaps that string theory is wrong). Decades from now, I hope that physicists will be pursuing once again their dreams of a truly scientific "final theory" and will look back at the current anthropic craze as millennial madness."
---end quote---

So he sees other string theorists giving up trying to explain, and he is critical of this. He is one of those who wants to keep on trying.

 

[Chronos]

In my mind, the easiest way to discredit multiverse theories is to explain why the universal constants are so finely tuned as to permit the existence of complex structures - observers, like us.

 

[tozhan]

I share your thoughts Chronos! but i don't think that it discredits it just makes it seem even more unlikly. Thanks marcus for all the quotes, they are very interesting. I read back though my original post and i think i miswrote that part about acceptance. I am aware that it isn't accepted as a scientific fact i was merly wondering how it can be called a great leading theory when it seems so fundementally ...umm...wierd. I am not sure what to call it, I am sure it is a great piece of math and i like the idea but i guess I am just a traditional 'prove it' kinda scientist. Thanks for writing though i can see I am not the only string theory sceptic now. I think i preferred it when there was 5 flavors and many more dimensions instead of this 'eponetial universes' thing.

Thanks guys, so no weak interaction then... :)

Tom

 

[lordinfamous]

String theory is like giving a 17th century farmer a combustable engine and then asking him how it works! This is the problem behind string theory and why it is unable to answer the smallest questions we may have for the theory. We do not yet have the 21st century math/physics to yeild the information that string theory may one day previde for us in the future.
Its accepted and not by all by no means but not understood to the foolest of its potential. On another note, I accept it and like the theory. THEORY...