And the adrenalin level goes up at 9am. I have only one class today, but a big one: first year physics for physicists, electrical engineers and computer scientists: a good group. One of them (why only one?) has solved the puzzle: we had calculated the point where the Earth's and sun's gravitational fields are equal but opposite. It is closer to the Earth than is the moon. A puzzle! If the moon falls into the sun, I had said, they are all responsible. A digression holds an interesting lesson about the web: one student had sought the answer on the site of a planetarium, but it has the moon's orbit wrong. Andrew, however, is right, and has resolved the paradox.

After writing to the planetarium, I do some work on an outreach project that a colleague and I are preparing for the centenary of relativity in June. (Part of it is up at www.phys.unsw.edu.au/~jw/time.html)

More outreach: a journalist who works for the Faculty of Science calls to talk about a story. Much research passes unnoticed by the media, but perhaps this story, about the effects of playing or not playing violins over extended periods, will attract a quirky but widespread readership. The scientific paper will appear at the end of April, so he will send a press release for 2 May.

A biological researcher in Canberra has an interesting question about cavitation in plants at sub-zero temperatures. I spend some time thinking about that and replying with a lateral thinking hypothesis with which I'm quite pleased. Something interesting might grow out of this idea. Then a reference for a recent PhD student, aiming for a better job.

A 12:30 meeting with a materials scientist working in industry who had read my web site on the physics of sailing. He has ideas for producing a new sail system, and wants to talk about it. How does this fit into my job? Well, a university has three main roles: it creates understanding (by research), it transmits understanding (by teaching) and it is a repository of understanding for the benefit of the community. So in the last role I have made this appointment. His ideas are interesting and I hope he ends up with a product.

After lunch, several tasks. Talking briefly to a PhD student about experiments that he is doing today. Assess an exam written by a colleague (is it fair, is it appropriate level?). Finding and setting up gear for an experiment that I am going to do next week.

I spend an hour or so on theory. In this problem, there is a simple linear effect and a less simple nonlinear effect, which are additive. But the calculations are ten times smaller than what we measure. We (the lab team) have been thinking about this for several weeks, on and off, since first we did the calculations. On one hand it's frustrating. On the other, it's fun: there's room to do the 'creation of understanding' I mentioned above. Today I tried a new idea. It didn't help, at least not yet. Bother. I haven't done much real research today and I haven't made much progress. But the occasional success, the thrill of being the first to see something or the first to understand it, that is why I chose this career.

A 3pm meeting about a teaching project goes well.

Then work on a paper describing a project on which six of us have worked. We are writing three large and moderately technical papers to describe it. But we are also making a short simple account for a generalist journal. I sent a first draft of this to the team a couple of days ago. I collect their comments and suggestions to make a new version, and redraw the figures in a simpler way.

From work I go to see Michael Frayn's play "Democracy", about Willy Brandt. Bob Hawke is in the next row, which is interesting for two reasons. First the parallels: Hawke and Brandt are social democrats, each succeeded a series of conservative regimes that had been first established by nondemocratic means, and both had strong personal followings. The other reason is that it's the second time I've seen Mr Hawke this week. On Tuesday, I went to the graduation of a student, part of the team for the paper I mentioned above. Bob Hawke was at the ceremony for the same reason. In all the time we knew him, the student in question had never mentioned that his mentor was the former prime minister.

A member of the expert panel plays a violin blindfold. This picture was taken during last year, part of the long term violin study mentioned in the diary.