Theorists and Experimentalists in Physics

Regular readers of his blog (Sid and Doris Bonkers) will know that here at Maynooth University there are two Physics departments, one the Department of Theoretical Physics (of which I am a Faculty member) and the other the Department of Experimental Physics. These two units are in the same building but have so far have been largely separate in terms of teaching and research; Experimental Physics (EP) is somewhat larger in terms of staff and student numbers than Theoretical Physics (TP).

For instance, when students enter on our General Science degree programme they have to choose four subjects in the first year, including Mathematics (much as I did when I did my Natural Sciences degree at Cambridge back in the day). Picking `double physics’ (i.e. Experimental Physics and Theoretical Physics) uses up two of those choices, whereas Physics was a single choice in the first year of my degree. In the second year of this programme students do three subjects so can continue with both Theoretical and Experimental Physics (and another) , as they can in Year 3 where they do two subjects, and in Year 4 where they can do a single Major in either TP or EP or a double Major doing a bit of both.

To confuse matters still further, the Department of Theoretical Physics only changed its name from the Department of Mathematical Physics relatively recently and some of our documentation still carries that title. Quite often I get asked what’s the difference between Theoretical Physics and Mathematical Physics? As far as Maynooth is concerned we basically use those terms interchangeably and, although it might appear a little confusing at first, having both terms scattered around our webpages means that Google searches for both `Mathematical Physics’ and `Theoretical Physics’ will find us.

The Wikipedia page for Theoretical Physics begins

Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experimental tools to probe these phenomena.

This is what Wikipedia says about Experimental Physics:

Experimental physics is the category of disciplines and sub-disciplines in the field of physics that are concerned with the observation of physical phenomena and experiments. Methods vary from discipline to discipline, from simple experiments and observations, such as the Cavendish experiment, to more complicated ones, such as the Large Hadron Collider.

I count myself as a theoretical physicist (that’s what I did in Part II at Cambridge, anyway) though I do work a lot with data and many of the researchers in my discipline (cosmology) actually work at the interface between theory and experiment, so the distinction between theorists and experimentalists is perhaps not a very useful one.

As a matter of fact I think there’s a good case for theoretical physicists to have at least some experience of practical experimental work. There are two reasons for this:

  1. to understand about errors in measurement and how to treat them properly using statistical methods;
  2. to learn how easy it is to break expensive laboratory equipment.

In the past during Open Days I have asked the audience of prospective physics students if they could name a famous physicist. Most popular among the responses were the names you would have guessed: Einstein, Hawking, Feynman, Dirac, Newton, Schrodinger, and some perhaps less familiar names such as Leonard Susskind and Brian Greene. Every single one of these is (or was) a theorist of some kind. This is confirmed by the fact that many potential students mention similar names in the personal statements they write in support of their university applications. For better or worse, it seems that to some potential students at least Physics largely means Theoretical (or Mathematical) Physics.

Although it is probably good for our recruitment that there are so many high-profile theoretical physicists, it probably says more about how little the general public knows about what physics actually is and how it really works. No doubt there are many prospective students who are primarily drawn to laboratory work just as there are many drawn to theoretical calculations. But there are probably others whose interests encompass both. For me the important thing is the interplay between theory and experiment (or observation), as it is in that aspect where the whole exceeds the sum of the parts.

Anyway, this year we’ve been thinking very hard about bringing about closer cooperation between the two Physics Departments at Maynooth. It remains to be seen precisely what form that closer cooperation will take but I think it’s a good idea in principle. In fact in the Open Day at Maynooth coming up on Saturday 24th April there will, for the first time ever, be a joint talk by the Departments of Theoretical Physics and Experimental Physics. I’m looking forward to seeing how that goes!

18 Responses to “Theorists and Experimentalists in Physics”

  1. I’ve long been struck by the fact that the most famous scientists of all (such as Einstein and Hawking) tend to be in very esoteric fields. I sometimes wonder if this suggests that the public quite like the sound of mysterious, crazy-sounding stuff that they don’t expect to understand…

    • There’s probably something to that. On the other hand, though his image is that of the typical absent-minded professor, Einstein was actually a very practical man, as his work at the patent office shows. He also had a few of his own patents, for things like refrigerators and compasses.

    • telescoper Says:

      I wrote about this in my little books about Einstein and Hawking. There are people who don’t seem to mind if they don’t understand the work of such people. What they really want to do is marvel at them, perhaps it feels good for some of us to feel that there are people cleverer than ourselves. I dare say there are people who feel the opposite, and resent people cleverer than themselves.

  2. Perhaps there’s an element of selection bias in the students you come across as a theoretician at Open Days?
    I’d argue that Newton was an experimentalist too – prisms and poking needles in his eyes, before he went into management (of the Mint), for example. Perhaps too, experimental physicists are just so well known that they are not thought of as physicists – Celsius, Fahrenheit, Kelvin, Joule… plus Archimedes and his ilk?

    • telescoper Says:

      Almost certainly there is a selection effect, but if you think about most popular science books about physics they are nearly all by theorists…

    • Anton Garrett Says:

      Did you know that he was a leader of the right side of an argument about how to respond to the monetary crisis of the 1690s? A pioneer of economics too, which might be why he got the Mint job at the end of that decade.

  3. Can’t wait to hear your discussion tomorrow 🙂

  4. Has there ever been any discussion on merging the two departments and just having a single Department of Physics ? We had separate Pure Mathematics, Applied Mathematics and Theoretical Physics, and Pure and Applied Physics Departments many years ago, which were subsequently merged into one School.

  5. In astrophysics, Chandrasekhar is a good example of the theoretician. He told me once (I was a very young student) that he did not see himself as an astronomer. He talked about discussion he had has with Jan Oort about this. The word ‘experimental’ has never really caught on in astronomy. In the solar system we ‘explore’, and further away we ‘observe’. I have a great respect for people who can mix theory and experiment.

    • telescoper Says:

      There is a difference between observational and experimental, but the people who develop instrumentation for astronomy are definitely experimentalists and it is they that have driven much of the progress in astronomy and cosmology over the last few decades.

      • True. The observations are instrumentation driven. There have been two nobel prizes for astronomy instrumentation (interferomery and CCDs). That is not normally called ‘experimental’. Would computational astrophysics be ‘experimental’, as it also involves impressive development work?

      • Anton Garrett Says:

        I’d say the difference is that experimentalists can perturb a system in specific ways and observe its response. Astronomers can’t do that for obvious reasons.

    • One often hears of CMB experiments. That seems a misnomer; they are observations. (OK, some of them might be experimenting until they get things right.)

      • Looked up a dictionary which defined an experiment as:

        …a scientific procedure undertaken to make a discovery, test a hypothesis, or demonstrate a known fact…

        So if you do an observation as a scientific procedure then its an experiment; presumably if you just do an observation (e.g. look at the moon through a telescope) then its just an observation….

  6. Anton Garrett Says:

    I enjoyed practical physics a lot more at A-level than at university. But school chemistry practicals were even more fun!

  7. […] few hours today involved with our Open Day at Maynooth University, including – as I mentioned here – giving a presentation about Theoretical Physics to complement one about Experimental […]

  8. […] Lest anyone gets the wrong idea about my view of the Experimental versus Theoretical Physics divide, let me repeat some thoughts I posted a while ago. […]

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