String Theory, at 20, Explains It All (or Not)

[pmbryant]

From the New York Times, Dec 7 2004:

String Theory, at 20, Explains It All (or Not)

By DENNIS OVERBYE

ASPEN, Colo. - They all laughed 20 years ago.

(snip)

In the last 20 years, string theory has become a major branch of physics. Physicists and mathematicians conversant in strings are courted and recruited like star quarterbacks by universities eager to establish their research credentials. String theory has been celebrated and explained in best-selling books like "The Elegant Universe," by Dr. Brian Greene, a physicist at Columbia University, and even on popular television shows.

Last summer in Aspen, Dr. Schwarz and Dr. Green (of Cambridge) cut a cake decorated with "20th Anniversary of the First Revolution Started in Aspen," as they and other theorists celebrated the anniversary of their big breakthrough. But even as they ate cake and drank wine, the string theorists admitted that after 20 years, they still did not know how to test string theory, or even what it meant.

As a result, the goal of explaining all the features of the modern world is as far away as ever, they say. And some physicists outside the string theory camp are growing restive. At another meeting, at the Aspen Institute for Humanities, only a few days before the string commemoration, Dr. Lawrence Krauss, a cosmologist at Case Western Reserve University in Cleveland, called string theory "a colossal failure."

(snip)

Critics of string theory, meanwhile, have been keeping their own scorecard. The most glaring omission is the lack of any experimental evidence for strings or even a single experimental prediction that could prove string theory wrong - the acid test of the scientific process.

Strings are generally presumed to be so small that "stringy" effects should show up only when particles are smashed together at prohibitive energies, roughly 10^19 billion electron volts. That is orders of magnitude beyond the capability of any particle accelerator that will ever be built on earth. Dr. Harvey of Chicago said he sometimes woke up thinking, What am I doing spending my whole career on something that can't be tested experimentally?

This disparity between theoretical speculation and testable reality has led some critics to suggest that string theory is as much philosophy as science, and that it has diverted the attention and energy of a generation of physicists from other perhaps more worthy pursuits. Others say the theory itself is still too vague and that some promising ideas have not been proved rigorously enough yet.

Dr. Krauss said, "We bemoan the fact that Einstein spent the last 30 years of his life on a fruitless quest, but we think it's fine if a thousand theorists spend 30 years of their prime on the same quest."

(snip)

More: http://www.nytimes.com/2004/12/07/science/07stri.html?pagewanted=print&position=

Edit: Note that most of this article is actually about string theory and string theorists, and not about the critics. But I felt the parts excerpted above are worth highlighting.

[shoelace414]

1. After watching

the Nova show about string theroy, I come up with the same theroy.

the math adds up.. if you add more dimensions. They way the scientests talked.. it seemed... weird..

[On the Road]

2. I May Take Awhile

Since string theory has been described as a branch of mid-21st century mathematics that accidentally fell into the 20th century.

I understand why they're saying that the theory can't be experimentally tested. But I'll bet that at some point, someone will come up with a doable experiment in which string theory and traditional quantum mechanics give different predictions.

[pmbryant]

4. How long should we wait?

It's not like there haven't been a huge number of physicists working on this problem during those 20 years. Thinking of the huge amount of resources going into string theory, which may or may not be a dead end, and thinking of the relatively sparse amount of resources going into alternatives, makes me worry for the immediate future of physics.

String theory is certainly worth pursuing, but perhaps it is being overemphasized at the expense of other worthwhile pursuits?

The 21st century versus 20th century quote was made by a string theorist, I believe, and it has always struck me as being a bit defensive—an excuse for why string theory hasn't been able to break out of its philosophical/mathematical enclave, despite many years of time and energy from much of the physics community over the last two decades.

But I'm just an outside observer.

:shrug:

--Peter

[On the Road]

10. It Doesn't Necessarily Involve Waiting

If enough physicists think string theory is useful, they'll continue to publish articles on it. Anyone not buying into it can choose to ignore them.

Right now, there's no way to experimentally validate string theory because of the enormous energy involves to break particles into strings. But I don't believe that's a reason to abandon it. Observational and historical sciences like geology, astronomy, paleontology and field biology are usually difficult or impossible to perform experiments on. They're still regarded as sciences because they are still based on observation and reason. They still construct hypotheses and judge which explanations fit the observed world the best.

So far, string theory illustrates that there is a line in physics between experimental and non-experimental sciences. Up until now, the Higgs particle wasn't able to be verified and its reputation did not suffer as a result. Personally, I think someone will figure out an implication of string theory that will differ from conventional particle physics under normal testable energies. At that point, it will become testable.

[papau]

3. I am sure all the math will find some use - but I already have a religion.

:-)

:toast:

:-)

[wurzel]

5. Quarks are "paired" because they are the two ends of a single string?

But I understood that three quarks make a particle. So where is the other end of the string for the third quark? It was said that "locality" couldn't be tested. Until Bell came along.

[pmbryant]

6. I'd be hesitant about taking the string analogy too literally

Anyway, some particles are made up of 2 quarks, while other more famous ones (protons, neutrons) are made up on 3 quarks.

My particle physics is a bit rusty, so I'd better stop here.

--Peter

[wurzel]

7. American scientists are scandalously careless when the talk to laymen.

The double use of the word "theory" has gotten them into all kinds of trouble. They claim there are six "colors" of quarks that always appear in "pairs" So when physicists say there are "three quarks" to a particle they may really mean there are three "pairs of quarks". It is hard to tell. The failure of the scientific community to be consistent in explaining what they do is causing the public to turn away and underfund science here. The future will be in Europe and India. When people once used the word "fundamental" it was connected with physics. Now the word is connected with religion.

[pmbryant]

8. You're right it is all very confusing & often poorly related to the public

Again, I'm a bit rusty, so this explalantion may not be perfect, but I believe the "pairs" of quark colors you mention are not the same as "pairs" of quarks in the same particle. The former is just referring to certain colors of quarks having similar properties to each other, I think. But that just demonstrates your point that inconsistent use of terminology is very confusing.

I believe protons and neutrons are made up of 3 quarks, not 3 "pairs" of quarks.

The problem is not merely with the scientific community, but frequently with American science journalism, of which most is extremely amateurish. (Dennis Overbye, who wrote the article in the original post, is one of the very few masters.) Is it really any better in Europe and India?

--Peter

[wurzel]

9. It is better I think because there are more "interviews".

BBC Radio has dozens of scientific programs, available over the "Internet", where scientists are routinely interviewed and questioned to clarify their answers. But the BBC is into cuts now so who knows about the future. The only program like this is "Science Friday" on NPR.

If there really are only three quarks then my original question still stands. It was the first time I had ever heard the idea that two quarks were the end of a single string. I wonder what else I don't know? Maybe I will E-mail the BBC.

[Donkeyboy75]

11. You're right, bryant

It's a rare article indeed that accurately describes any sort of scientific news.