I used to worry about going into schools to talk, since I figured I'd be no good at dealing with naughty students (despite working at a University). I've long realised that it's not that hard - at least not as a guest speaker, so I wasn't too worried, and indeed it turned out fine. In fact, I found, as I always do, that the pupils were interested, they paid attention, and asked lots of interesting questions. One of these was related to a picture of the JET fusion reactor in Oxfordshire which showed it both in action (with a hot plasma of hydrogen isotopes) and out of action (to see the apparatus without all that hot plasma). One of the students asked, "how did they take the picture when it was switched on?" and I had to admit that I didn't really know. It's a good question: The temperature inside the reactor when it is on is exceedingly high and would destroy a camera. The answer I gave (with a caveat that it might be wrong) was that the plasma is contained in a magnetic field, which keeps it away from the walls, and a camera could be attached near the wall and away from the plasma. It's probably the right answer, but I don't know (if anyone does, please comment!). But that's one of the nice things about giving these talks - I get a combination of questions that make me think and comments that inform me of things I didn't know.
One of the best comments I have got when giving the talk was about the medical imaging technique which is these days known as MRI ("Magnetic Resonance Imaging") and used to be known as NMR ("Nuclear Magnetic Resonance"). I ask, as I usually do, if anyone in the audience knows the difference. Usually noone answers, and I explain that there is no difference, except that the word "nuclear" was removed to avoid worrying people that there was something nuclear about the technique. One time that I gave the talk, and told this story, someone came up to me at the end and said that actually the reason that they changed the name was because "NMR" sounds too much like "enema" and that people would get confused about what they were going in to hospital for. I told this story on Friday, and I thought that I got some glowering looks from the teachers. Oh well. It's a good story. I don't know if it's true though.
P.S. I'm glad that when this post is mirrored on facebook that people comment. I'd rather, though, that you'd do it on the original blog post so that everyone can see the comments and comment on the comments whether they are looking on facebook or not. Thanks!