The Physics Of Predicting Everything : 13.7: Cosmos And Culture Here's my problem: I've been writing about fundamental physics for more decades than I care to admit, and hardly ever have I heard — or even read — a physicist claiming that one theory can explain everything.
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The Physics Of Predicting Everything

Too complex for string theory. Torsten Silz/AFP/Getty Images hide caption

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Torsten Silz/AFP/Getty Images

Too complex for string theory.

Torsten Silz/AFP/Getty Images

My fellow bloggers are waging the good fight against the idea of reductionism -- the idea that the universe can be explained by an equation on a T-shirt -- and that physicists believe there is some "Theory of Everything" that would do just that. Also, against the related idea that physicists somehow believe they can predict what will happen in the future based on this theory, or others.

Here's my problem: I've been writing about fundamental physics for more decades than I care to admit, and hardly ever have I heard -- or even read -- a physicist claim any such thing(s).

I'm not a scientist, so I come to this from a somewhat different perspective than my colleagues. Adam says that this claim -- that a theory describing the most fundamental level of reality (particles or strings or whatever) is all that you need to describe planets and people -- still holds a lot of currency in the halls he walks.

I'm sure that's true. But the physicists and cosmologists I talk with make it pretty clear that understanding the fundamental forces and particles will tell us nothing about love, music or even the brain of a snail, not even a single neuron. These things are simply too complex. So where does the notion that they think they can explain the universe on a T-shirt come from?

I fear part of the problem comes, oops, from exactly what I do: popularization. It's common for much to get lost in translation when "science" gets out of the hallways and labs and into the media.

Here's a telling (and personal) horror story on how this misunderstanding gets ingrained in the public consciousness. In the 1980s, I wrote a story about string theory for The New York Times Magazine. It was mainly about the mathematics, though much of that got cut. The story began as a profile of Edward Witten, one of the most prominent physicists of the day (and still today).

Everything was fine with the piece until the Times decided to make it into a cover story. Then someone in the higher reaches of the paper looked at it and wanted to include an idea he'd heard about, if memory serves, at a party: the "theory of everything" (which was equated in someone's mind with string theory).

I knew Ed Witten would hardly claim that string theory is a "theory of everything." But because the editors were now so keen on the idea, I had to ask him. His answer was something along the lines of: The only physicists who talk about a "theory of everything" are those who have no real physics to do.

The cover line on the magazine? "A Theory of Everything."

As for prediction, I'll never forget the late physicist Phil Morrison telling me how fundamental physics can't even predict the path of a drop of water flowing over a fall. There are too many interacting parts. And even if you somehow put all the relevant information into a computer that could calculate the drop's path, the very gravitational presence of a computer so big could throw the calculation off. Computers have gotten a lot smaller since then, but the argument holds.

One often hears the term "the theory predicts"; but this kind of prediction is not about gazing into the future. It's about looking for what already exists in the present. If your theory is right and it "predicts" that there should be a black hole sitting in the center of your galaxy, and you find that black hole, then you've found a good piece of evidence to support your theory. But theory predicted what was already there, not what was going to come into being.