Linde's speech at Strings 08 banquet

The task of entertaining the audience at the end of the Strings 08 banquet at UniMail was accomplished with spirit by Andrei Linde. He started by saying that he was going to make a discourse in the Georgian-Russian fashion, but maybe it was not appropriate... He said that after our visit at the United Nations on Monday, he was seeing two goals of utmost importance: 1). world peace, and 2). experimental evidence for string theory.

Given that we live in an expanding universe, in a few billion years the galaxies will be beyond each other's horizon, and so there will be no intergalactic war any more. First problem solved.

He addressed the second problem with a succession of anecdotes from various famous physicists. One of them was about a Russian scientist (something in Z... I forgot) that once told physicists which were discouraged by the absence of experimental evidences in favour of baryon asymmetry that the fact that parallel lines do not intersect was actually an evidence (he quickly explained what he meant but I couldn't get it). "That is another type of evidence," Andrei said.

Then he talked about Murray Gell-Mann who asked one of his students to measure the height of a tower with a barometer. One week later the student came back and said that he had found three ways of doing it: The first option was to go to the top of the tower, attach a rope to the barometer, slide it down, and then measure the length of the rope. "Myeaaah. What is the second way?" Murray asked. The second option was to go to the top of the tower, throw the barometer down, and count the time it takes to reach the ground. "That is not really what I expected..." The student's third way was to go to the superintendent and tell him: "This barometer is worth about 30 €. It is yours if you tell me the height of the tower."

Andrei's point was that in order to get evidence for string theory, we need to use the barometer in a clever way (measuring the pressure difference at the top and bottom of the tower). There
is no straightforward way to do it (like the first two solutions of the naive student), and all the superintendents left the universe about 13.7 billion years ago (that is, at its creation).

And this clever way is to think about dolphins (not fishes: dolphins!). Dolphins live in water because it is the place where they can live, just as we live on the ground because we can live here. The tiny value of the cosmological constant can be explained in this way, but only at the condition that there exist a huge number of possible universes with different values of it. (Huge as in 10^500, which journalists, as they cannot typeset exponents, write as 10,500... "Anyway: big number.") Yes: anthropic reasoning. [I thought about David Gross at that point, who certainly won't miss on Friday to repeat his warning of last year's conference in Madrid: "Do not give up!"]

Andrei ended his discourse by saying that he could have proposed a toast for the LHC, the biggest machine ever built -- but that would have been too banal. Then for string theory -- not surprising enough. He had to be surprising (Georgian-Russian style!). He finally drank a toast to "You, the people that are making string theory, because we enjoy working together and learning." I found this apparition of a human, relational factor indeed quite surprising in such a context (although it would have been completely trivial in many other contexts).

In summary, Andrei's discourse operated two shifts:

• A shift from the dream of a unique and unambiguous explanation of everything to the acknowledgement of the relevance of environmental determination.

• A shift from a machine or a theory to mutual enjoyment.