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Flip Tanedo | USLHC | USA

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Theory Grad Student Q&A (Part 2)

Welcome to part 2 of my “theory grad student Q&A!”

If it’s ‘theoretical,’ then it’s not “real” science, is it?

On the contrary! My friends doing biology always tease me about this, saying that I’m not ‘really’ doing science since I don’t wear a lab coat. (News flash: even experimental particle physicists don’t wear lab coats!)

The reality is that the program of particle physics naturally requires an interplay between theory and experiment. This is all part of the scientific method. Our current model of particle physics, the Standard Model, is the result of decades of joint theoretical and experimental progress.

A lot of the work on the theoretical end involves making hypotheses for how to extend the Standard Model to address perceived theoretical limitations. These hypotheses make predictions and are tested by experimentalists at facilities like the LHC or through indirect measurements in astrophysics and cosmology. These experiments, in turn, may support or refute our hypotheses, leading us to further refine (or throw out!) our ideas. It’s even more exciting, however, when experiments discover something totally unexpected — that’s when theorists really get to play with the structure of our models.

There’s a bit of a myth that the goal of theoretical physics is to come up with ideas with no regard to actual reality. This is not true! Physicists, even the theorists, all ultimately care about nature and are constrained and motivated by experiment.

Why is physics divided into theoretical and experimental branches?

This is an excellent question and I unfortunately don’t have a complete answer, and perhaps the other US LHC bloggers have different takes on this.  Physics is the only science where there is a clear distinction between those who do ‘theoretical’ research and those who do ‘experimental’ research. Whenever I think about the relation of physics to other sciences, I’m always reminded of this comic from XKCD:

Image from XKCD.com.

Image from XKCD.com with permission.

I think a big part of the reason for this separation of theory and experiment is that physics really studies the forefront of what can be probed experimentally, either  the extremely small (particles) or the extremely large (the cosmos). On the experimental side this requires a lot of specalization to find clever ways to study nature at scales so far removed from what we’re used to.  On the theory side, we use a lot of insight from the mathematical structure of our theories. (Historically a lot of this mathematics was developed for physics!) This requires a investment in a very different set of skills.

I should emphasize, however, but the key qualities of a good experimentalist and a good theorist are the same: creativity, enthusiasm, and curiosity.

To the best of my knowledge, the last example of a physicist to really make great progress in theory and experiment was Enrico Fermi, whose Nobel prize in [experimental] nuclear physics stands among a long list of accomplishments in quantum theory and statistical mechanics. On the other side of the spectrum is the unabashed theorist Wolfgang Pauli, who earned the reputation of jinxing any experiment he came near*.

(* — Many theoretically-inclined physics students will use this as an excuse when plodding their way through undergraduate lab courses.)