Tuesday, November 27, 2012

What Happens When A Theory Is Wrong?

This has happened a lot of times in the history of physics. However, we could be confronting one right now on a very prominent theory - Supersymmetry.

This article by Marcelo Gleiser briefly looks at how physics often proceeds, and what is the fate of Supersymmetry after so many searches for it have failed to produce anything it is predicting that is unique beyond the Standard Model.

Given the lack of data in support of supersymmetry after all these years, why is the theory still considered viable?

The complication comes from the way mathematical models depend on various adjustable parameters. For example, the decay rate of a particle may depend on its mass and the way it interacts with other particles; if certain types of decays aren't seen, parameters can be changed to reflect that. The model may be made to hide from available experiments. And given that technology has more concrete limits than the imagination of theorists, a model may always be beyond the detectable.

How, then, can such types of models be ruled out? Well, simpler versions may be ruled out when the tweaking of parameters becomes so extreme that the model loses its original motivation: it explains nothing and becomes too cumbersome. Or a forbidden particle is discovered. Then there are always the more complicated versions, with more parameters that are harder to rule out.

The point is that there isn't a clear-cut answer. The physicist Max Planck used to say that wrong ideas don't die out, their proponents do. It will be interesting to watch what will happen in the next few years with supersymmetry and its proponents if tests keep producing negative answers.
This will become even more interesting if the LHC sees no convincing evidence after it boots its collision energy in a couple of years. While I am certainly interested in the physics, I am equally fascinated to see how the high energy physics community, and the Supersymmetry advocates, handle the outcome that they will get from that run.

Zz.

1 comment:

coraifeartaigh said...

As you say, the point is that there isn't a clear-cut answer, because experiments over the next few years may only rule out the simplest models. So I don't understand the final cooment tha "it will be interesting to watch what will happen in the next few years with supersymmetry and its proponents if tests keep producing negative answers".
Not really - it just moves the focus from minimal models. Also, I think discussions like this benefit from a description of the motivation for SUSY in the first place