Wednesday, June 27, 2012

Murray Gell-Mann on testing superstring theory

A "Web of Stories" interviewer was under a visible influence of several crackpots who have polluted the science (and other) popular media in recent years so he asked Nobel laureate Murray Gell-Mann what he thought about the testing of superstring theory.

Murray Gell-Mann was obviously surprised by the question, thinking it was a strange one, and he enumerated some important successful postdictions (especially Einstein's equations derived from a deeper starting point) as well as some predictions waiting to be checked (SUSY: watch also Crucial tests of string theory).

He doesn't see anything wrong about superstring theory when it comes to testing. There's really no conceptual difference between the tests of this string theory and tests of older theories, e.g. those that Murray Gell-Mann became most famous for almost half a century ago.

In the interview, Gell-Mann has also defended the two main pillars of progress in high-energy physics – the theoretical extraction of the appropriate predictions; and the collider technology we must try to push to as high energies as possible.

In a different short video, Gell-Mann chastised Shelly Glashow for his hostile attitude towards string theory that Gell-Mann cannot understand. Glashow is a lot of fun, as I know from many social events in Greater Boston, but I can't understand it, either, even after I have used ex-his Harvard office for quite some time. ;-)

Gell-Mann also (partially) blames the completely wrong idea that superstring theory can't be tested on Glashow. One must carefully distinguish about direct tests of the "unified [Planckian] regime" and any tests of a theory; these are completely different questions. Glashow's attitude is even more paradoxical given his key contributions to grand unification in Yang-Mills theory which would also occur at (directly) inaccessible energy. Glashow is therefore a clear example of a person living in a wooden house not throwing termites. Why he should do that?

Gell-Mann and foundations of QM

In another video, Gell-Mann discusses Hugh Everett. Gell-Mann, Feynman, and others spent a part of their 1963-1964 years by thinking about the foundations of quantum mechanics and their conclusions didn't really differ from the "consistent histories" etc. that Gell-Mann (with Jim Hartle) was contributing to in recent decades, from 1984-1985.

He credits John Wheeler himself for the concept of "many worlds" while Everett was primarily interested in solving problems, not specifically in quantum mechanics, so he wasn't really disappointed by solving military problems in the rest of his life. At any rate, Gell-Mann didn't know about Everett; they reproduced some of the features. Like myself, it doesn't make sense to say that there are "other worlds that are equally real as ours".

See many other videos in the list at the bottom of this page which contains literally hundreds of several-minutes-long interviews with Gell-Mann. There are of course more than 7,000 other stories recorded by 166 other famous people on that website, too. You may try e.g. James Lovelock on his being a green skeptic (story 15).

Hat tip: Paul Halpern and B. Chimp Yen

Spain vs Portugal

Our, Czechia's quarterfinal conquerors, Portugal, are playing the semifinals of the Euro against Spain as I am typing these words. I can't stop thinking of Treaty of Tordesillas (1494). A Pope just wrote a one-page document and divided a planet, planet Earth, to two nations, Spain and Portugal, along a meridian that was chosen by randomly spinning a globe in his office. The paperwork used to be tolerable 500+ years ago. ;-)

In fact, they didn't talk about hemispheres: if you moved to the West from the demarcation meridian, it would always be Spanish; and the colony would be Portuguese anywhere to the East. Only decades later, Spaniards realized a conflict and argued that there was also an anti-meridian that helped to divide the world to two hemispheres.

At any rate, the reason why Brazil speaks Portuguese and occupies the Eastern corner of the South America boils down to the 1494 treaty. I was also intrigued by this 1502 Portuguese map, Cantino Planisphere:

Note the accurate shape of Africa – it is much more accurate than some obscure islands such as Great Britain. ;-) As you go further, the accuracy goes down and the map resembles an area settled by mysterious dragons. In some sense, this map is exactly "in the middle" of the explorers' mapping process. I believe that our current picture of the landscape of string theory is somewhat analogous. Lots of things that are very accurate in our minds, lots of sketches that are off, some identifications that shouldn't be there and some missed identifications that should be there, a few missing continents such as Australia ;-), but it is clear that we already know "much more than nothing".


  1. You are lucky to have known Gell-Mann personally. He is an amazingly clear-thinking and articulate man. Very few people can say exactly what they mean to say so clearly and so succinctly.

  2. Dear Gene, I agree with you but if you mean me, "knowing him personally" may be a bit of an overstatement. I've talked to him once - for ten minutes or so - at SidneyFest 2005...

  3. Gell-Mann endorsed Obama for President and repeatedly brought up climate change as an issue. Not as clear thinking as you claim?

  4. Dear David, I obviously disagree with him but the speech above doesn't look extraordinarily stupid to me. There are just very many folks I consider very smart and clear-thinking who just happen to take similar positions, for ideological reasons that may have been shaped by the environment.

    I personally don't consider conservative attitudes "rock solid science", however important they look to me.

    Concerning "reversing climate change", that's embarrassing but common and it's not necessarily the case that Gell-Mann has been the main driver of these three words in the letter... On the contrary, I think he wasn't.

  5. Lubos, I like your Higgs discovery countdown :-)...


  7. Gell-Mann says that string theory predicts SUSY. I thought that ST and SUSY are 2 independent but related things and even if SUSY won't be found at LHC, it wouldn't mean the end of ST. If that is really so, it is not a classical prediction that could falsify the theory. But of course if found, it would be another indicator that ST is probably true (the probability would be updated by the Bayesian formula)

  8. Dear Mephisto, your mistake – or deliberate demagogy? – must be very obvious to everyone who compares your first and second sentence.

    The first sentence correctly says that string theory predicts SUSY. The second sentence discusses whether SUSY is found by the LHC. In the following sentences, you pretend that the first two sentences talk about the same prediction but they're not. They're completely different things.

    There is nothing "unclassical" about string theory's prediction of SUSY. Atomic theory of matter also predicted that one could eventually isolate or observe individual atoms but it hadn't been known when it would occur. It finally did occur. The ignorance about some numbers didn't mean that the prediction didn't exist. It did exist. The case of string theory is totally analogous to this prediction of atomic theory – or any other prediction in the history of science.

  9. I meant to say that Gell-Mann has an amazingly un-muddled mind and an even more remarkable ability to express his thoughts clearly. This doesn't mean that he understands every issue or that he is always right.