These theories go beyond what we know experimentally already but explain some features of our universe that aren't really understood. Sometimes I invent new theories that solve certain problems, usually I'm working on someone else's, but the emphasis for me is always on testing them in an experiment. I don't actually do the experiments, thousands of people working at a few particle accelerators around the world do that. Usually I am taking a theory and asking "what is the smoking gun signature of this theory?", "Could the signature be confused with another theory and how do we tell them apart?", "How do you measure the theory's important parameters?". The most exciting question to ask (which has happened to be once, and I hope it will happen again) is "What the hell do those data mean? They look like a new discovery - what could it be?"

Often the sums are too hard or impossible to solve on paper, so then I resort to using a computer to calculate the relevant numbers. The job also involves some teaching, giving talks at conferences - sometimes in exotic places (hurrah), marking (groan) and the usual administrative stuff like applying for research grants etc. I also try to do at least one thing for public understanding of science a year. I think that if every scientist did this amount, it would be plenty. Sometimes it's telling the press what we've been up to recently, or it might be organising or demonstrating at an open day, for example.

Being an academic in this field is fun. We have autonomy over our research, which I believe leads to a more creative atmosphere. You get hired, and your mission is: "do some good research". Unlike many other fields you're not put on a project and you don't have some boss who's constantly on your back. The reason everyone still works so hard is that the field is highly competitive and it is difficult to even get post-doc positions. After a PhD, people travel the world being post-docs: getting hired for 2 year research contracts in each place. Places never re-hire their post-docs and so you have to move on. Typically, you need to do a few of these to get a permanent jon somewhere (I did 4, two in the UK, one in Switzerland and one in France). If you don't do a good amount of high quality research, you don't get a job next time. It's not an exaggeration to say that every postdoc position advertised has about a hundred applicants (actually, it's not as bad as it sounds because everyone makes quite a lot of applications).

I mostly work in small collaborations - 1 to 5 people, and usually have several projects on the go at once. Completion is fast - I usually complete say 4 projects a year, so they're pretty short term. This is nice because you get a little reward at the end - publishing the paper - and a sense of satisfaction. Now and again, when you think you're really onto something big, work gets very exciting. You can work on your own, but often you'll discuss something with another physicist at a conference, or email them a question about their paper, and suddenly you're collaborating with them on some project one of you has thought of. Often someone has an idea, but needs another with the right expertise and knowledge to perform some of the calculations. It's great to work with other people. So many good things come out of arguments, discussions etc that the whole is definitely bigger than the sum of the parts.

If what you're doing is some gigantic analytic computation, it is impossible to get everything correct, you'll miss a minus sign or a factor of 2. If you're working on your own, you have to do the calculation a second time without looking at the first. You invariably find the answer is different, so it's a question of tracking down the differences to find the mistakes. But it's easy for one person to make the same mistake twice, much less likely for two people doing the calculation independently.

In terms of the science itself, I'm mostly involved with the question: what are the smallest bits of matter, and how/why are they like they are? Of course this is the broad remit of particle physics, and it sometimes spills out into cosmology, for example when the particles we're discussing can constitute the universe's "dark" (missing) matter.

Why do you do it?

Direct immediate wealth creation is obviously not a primary aim. We can't tell what practical use any discoveries will be yet - history has taught us that. The discovery of the electron for example was a vital building block in modern science, and it's correct to say that modern technology, science or medicine would not be possible without it. But a hundred years ago, it was just an obscure tiny fundamental particle that Thompson found in his experiment. More recently, its antiparticle the positron was discovered, and that's used in medical scanning devices (positron emission tomography). There are many other examples.... But I feel that beyond any possible practical applications, it is a very human endeavour for us to explore the enviroment (ie the universe) in which we find ourselves. Anyway, I'm spouting my old funding body's propaganda now, so I'll shut up!