Terrific interview with Harry White of Techniquest, about science centres and informal engagement in general. Harry’s one of the old-hand caring professionals, and it shows in his fulsome replies. There are interesting parallels between his approach to hands-on exhibits, and mine to video.

I also have a little to add about Laithwaite’s levitation demo, mentioned towards the end of the article and pictured left. The late Bill Coates, in the lower right corner of the picture, told me the story that they had, in fact, turned the thing on in rehearsals (which would have been earlier in the day, or possibly the day before recording). It worked superbly, the ball thrumming up to clear the induction coil by a good few inches, and starting to rotate gently as the eddy currents did their thing.

Witnesses were called, and a growing crowd added to the general excitement. After a period of congratulation and elation, thoughts turned to bringing the ball safely down again. This was a problem, since thoughts had not turned in this direction previously. The ball was light, but might conceivably have damaged either itself or the induction coil had the coil simply been turned off.

Also, by this time, the ball was both spinning at a considerable rate and heating up to dangerous temperatures. It was, after all, the secondary in an air-core transformer.

The eventual solution involved nothing more advanced than a bunch of BBC stagehands wearing gloves, but I still love the image of delighted physicists lurching from ‘It works!’ to ‘Oh bother!’

The ball hung for years from the rafters of the Royal Institution’s Prep Lab. I never saw the induction coil, but the ball did find other uses. Most recently, to my knowledge, I used it to cast modrock hemispheres for models of the gas giant planets and the sun for Malcolm Longair’s 1990 Christmas Lectures. At one point the ball fell off its little stand, putting a palm-sized dent in the otherwise-perfect shell. I’ve never forgiven myself.

I don’t know where the ball is now. I hope it hasn’t shared the fate of many other vintage props, of being chucked during renovation work.

(Via Paul and Flossie)