This is a lovely demo shown to me by Andreas Tober, the Physics technician at Alleyn’s School in Dulwich, London (which also happens to be the secondary school I attended. I left shortly before Andreas started, but we’ve somehow managed to become friends anyway. Gotta love the internet). I think this is a lovely, simple way to introduce the idea of absorption spectra. I will definitely be using it in my physics teaching next year.
Monthly Archives: May 2013
Demos in the Royal Society
Speaking of Michael de Podesta (see comments on previous post. Also: autocorrect wants to transmogricate ‘Podesta’ to ‘Pedestal’), he’s blogging the development of the NPL’s stand for the Royal Society Summer Exhibition. Well worth keeping an eye on for some background about what goes into a good demo. Knowing Michael, there’ll be some extremely subtle and smart thinking involved.
(Michael presented some of our physics demo films, shot in one of the archive rooms at the NPL‘s kind invitation.)
Whose demo is it?
I would really like to take credit for “The Alom Shaha Motor” and “Alom Shaha’s jellybaby wave machine” because they’re two of my favorite demonstrations to use in class, but I can only wish that I had had the ingenuity to devise either of them. I’ve put my own spin on a few demos but the only thing I think I’ve invented from scratch was something to illustrate how the Mercator map projection works for an Adam Hart-Davis TV programme.
I’ve no idea who invented the simple electric motor demo, so that person is not credited in the film Jonathan and I made for our series of physics demonstration films for the National STEM Centre and IOP. But we do know who invented the jelly babywave machine… well, kind-of.
The first jellybaby wave machine was built for the Children’s ITV series The Big Bang, produced by Jonathan back in 2004. Whilst working at the Royal Institution years earlier, he’d seen a wave machine made of wood and metal. He’d wanted to recreate it in a way that children watching the show could build, and with his colleagues David Pitt and Luke Donnellan, came up with the now-famous jellybaby version. 150,000 or so young TV viewers would have seen it when that particular episode of The Big Bang was broadcast.
Surprisingly – perhaps because it was only shown on children’s TV in the days before YouTube – it didn’t become widely used by science teachers, even though it really is a fantastic way of introducing wave phenomena in the classroom. So Jonathan and I are delighted that the more recent film we made seems to have taken it into classrooms all over the world. Videos are a great way of sharing science demonstrations and it’s wonderful that the internet allows teachers and science communicators to find ones that are new to them, but I think it’s a bit of a shame that we rarely acknowledge the originators of these wonderful things we call demos. So, two questions to you, dear reader:
- Can you name any classic demonstrations for which you know the inventor?
- Do you claim to have invented any demo yourself?
How not to do the methane bubbles demo
Funnily enough, only today Paul and I were discussing the importance of jeopardy in demos, and how the ‘best’ moments (particularly for children’s audiences) are often when things ‘go wrong.’ This isn’t quite what we had in mind.
What I don’t understand is why the bubbles are being lit on the ceiling. Typically, the methane bubble demo is done with a volunteer’s hands well wetted with the soap solution, and the bubbles lit on their hands. The perceived jeopardy is very much to the volunteer. It’s a lovely routine for building trust and establishing the purpose of exploring science (you get to do things to the world that are worth doing, and nobody dies). Setting up the demo in the way shown here is, I think, less impressive and less useful.
Still, at least the fire suppression works.
(via io9.org)
Imploding Can
The imploding can demo is an old classic, often done with an old square-sided oil tin though I’m personally rather partial to the Coke can version. This, however, is something else. Commentary around the web suggests the method used here is to steam-clean the tank then seal the valves while it’s still full of steam. Which sounds plausible, and it’s not ridiculous to suspect this has been done as part of an industrial safety course.
Years ago I remember talking to David Jones about trying this – he’d long fancied having a go with a petrol tanker lorry. Even for TV the costs had looked prohibitive, and I never did find him an end-of-life tanker to play with. There’s also the minor issue of disposal to consider. But at least we can now be reasonably confident we could have made it work.
One concern, though: I’m not 100% convinced by the video. It’s from an interlaced source so it’s hard to tell for sure, but frame-by-framing the implosion makes it look to me like it’s been sped up somewhat. That said, the movement of the bogies looks appropriate. Ah, YouTube, you do so tease us with your ripped-off sources and your dodgy recompression.
Are demos in decline?
As hands-on science communicators, we live and breathe our demos. We hone, improvise and improve them over years, even decades. Few things please us more than an evening in good company discussing and dissecting the demos that work and why. In our world, science communicators usually have a favourite demo or five.
I work with a lot of new science communicators. Many of them are top class new graduates with a science background, and I love to ask them ‘What’s your favourite demo?’. It’s fascinating to this jaded old sock. Gone, alas, are the days where every week brought an exciting new concept for me to play with. I can share this excitement vicariously, of course. I get to delight other people afresh, but I love the extra insight I get quizzing someone who’s new to this world. With bright eyes and keen minds what are they looking for in a good old-fashioned demonstration?
What I find interesting is that in the last few years not as many of our new recruits seem confident in their answers. I find myself giving hints as to what I mean by ‘demonstration’ – not an experiment, a practical nor a trick: a science demonstration.
Are they simply unfamiliar with this jargon or is something more sinister afoot?
Is the delight of the demonstration becoming a dark art, practiced more by a growing band of science communicators but less by teachers and lecturers? Perhaps demonstrations are seen as entertaining quirks in a social context, shared via Facebook and YouTube, and not as teaching tools in an academic world.
I may be reading too much into this, of course. My sample is small and could represent a gentle blip within the boundaries of standard deviation with no rhyme, reason nor correlation. I’d be interested to hear if others have noticed a trend.