### Doubt, Strings, and CO2

When is it OK to doubt the experts?

Let me rephrase that: Does it ever make sense to doubt the experts?

We are often faced with conclusions from scientists or other experts which seem profoundly counterintuitive or offensive to our general world view. So when should we listen to our intuition and when should we just bow to those considered "experts?" The answer, as always, is "it depends." Consider a few test cases.

One of my fellow graduate students once told me about his clever scheme for extracting otherwise unavailable energy. It had only one problem - it didn't square with the second law of thermodynamics.

Was he crazy to doubt the experts? Yes, I think he was. There are so many lines of logic and so much experimental evidence for the second law that it is almost certainly unassailable. I seem to recall that he never did get his degree, but he did become a successful engineer and rather wealthy - but not from his energy extraction scheme.

The vast majority of climate scientists and students of the atmosphere believe that the CO2 that we are pumping into the atmosphere is causing an extremely dangerous global warming. A tiny minority of such scientists, and a horde of other nuts take the opposite view. Many thoughtful people look at the argument and wonder what they should believe.

The above question presents an extreme case, because not quite all the doubters can be dismissed as guys who can't do the arithmetic - Richard Lindzen being the archtype. Moreover, the evidence consists of a not quite unequivocal time series and the results of some of the most complex models in existence, all of which have known and unknown limitations. Finally, the consequences of choosing wrongly are potentially very severe or catastrophic.

Regular readers know my choice - I will go with the experts, mainly because the vast majority of the critics really can't, or won't, do the arithmetic. They mostly make trivially obvious or absurd errors. I tend to trust my analysis of that point, because even though I'm not an expert, I have done research in closely related fields. For a true layman, the case is much more difficult - such a person can mainly just listen to pro and con and try to decide who seems more trustworthy.

My last example is string theory. This theory is so complex and difficult that only a very few people - probably a few thousand at most - have any kind of detailed understanding of it. Even among professional physicists, any kind of detailed comprehension is very rare. It's easy for outsiders to imagine that string theorists are a kind of priesthood consumed by a fanatical devotion to their religion.

What's wrong with that last idea? Several things, actually. Firstly, there are several powerful arguments that suggest that string theory may be on the right track: it seems an expression of the unification of relativity and quantum mechanics, the beauty of some remarkable mathematical results, the fact that it seems to be a natural extension of the most powerful ideas of twentieth century physics. From a different perspective, there is the fact that for a generation string theory attracted many or even most of the most brilliant physics students.

It one critical way, the string theory (ST) situation differs fundamentally from the question of anthropogenic global warming (AGW). Almost nothing depends on your decision, if decide you do. Unless you sit on the funding board of some institution funding physics research, or on the tenure committee of some physics department, nothing at all.

For the rest of us, we can afford to wait until string theory either makes some testable predictions or proves hopelessly incapable of making such predictions. In the meantime, we can afford to be fans, critics, or merely indifferent. The future can decide whether string theory was the most brilliant inspired guess in the history of physics or just a particularly challenging new kind of chess.