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:

  1. Can you name any classic demonstrations for which you know the inventor?
  2. Do you claim to have invented any demo yourself?

9 thoughts on “Whose demo is it?”

  1. What’s interesting about the wave machine is that I don’t really claim to have invented it (despite what Michael cheekily implies). It’s clearly an adaptation of earlier work, and I just called the Ri’s historian Frank James to check what he knows about their original. He believes it was made by Bill Coates and Lawrence Bragg, which puts it in the 1950s.

    What’s interesting, though, is that earlier models in the Ri’s collection – from Tyndall’s era – are based on a mechanical cam arrangement. Unlike the later model they can’t show reflection or interference (heck, the jelly baby version can show wavepacket dispersion!).

    The torsion-spring-with-outriders was a hugely clever and subtle design, and it may well be that Bragg and Coates came up with it.

  2. Mmmm. Demonstrations I think I may have invented or re-invented:

    1. The electric sausage. Pepperami suspended from a wire and caused to swing around by using a ‘rubbed’ balloon. Can also be extended to the electric anything – including a guitar! But I only claim first use of a sausage!

    2.The use of wine glasses to demonstrate the emission of light. Individual glasses when hit give out a unique pure tone cf the line spectra of atoms but when held together emit a dull spread of frequency cf the continuous spectrum of a hot solid.

    3.The demonstration of the magnetic properties of terbium. Child find terbium on a string is weakly attracted to big magnet. When cooled to 77 K terbium is ripped out child’s hand.

    4. Putting dry ice powder inside balloons (molecular capture devices) and allowing children to hold the balloons as they inflate. Heat transfer through rubber is so low this is quite safe.

    5. The curie point of iron. A paperclip on the end of a copper wire held in a burner near a big magnet. When cold the paperclip is held away from the vertical and when hot the paperclip falls down. This seems so obvious I can’t believe I invented it.

    And then there is the Gherkinator – a device for passing mains current through a gherkin that causes one end to glow yellow. I saw Simon Singh do this – but did he invent it?

  3. Demos that are my own, crivens, that’s a tough one.
    I’m better at putting my own twist on existing demonstrations.
    There are a couple that I’ve thought are mine at first, then realised they already existed.
    There are a few that I think are completely mine, or at least a case of independent discovery.

    1.The hull shapes of the Endurance and Fram, made of wire and aluminium foil, floated on water and crushed by ‘surface ice’. One crumpled and sank, the other lifted clear of the danger. Cute props, but are hardly likely to set the world alight.

    2.The other involves a set of garden jenga, which I may well write up for this blog sometime.

    3.Not a demonstration, but I’ve not seen this: http://www.exhibitfiles.org/stick_it_pointillism2 done anywhere else.

    There may be others, I’d need to think. As to Michael’s comments.

    My first memory of the dry ice balloon is pre 2000 at Techniquest, by the then Education Director, Bill Dines. It’s a great demonstration. I loved it then and love it now. I’d be thrilled to have come up with it.

    I first saw the glowing gherkin over a decade ago, but I know we weren’t first. A little searching (thanks James Piercy) brings up:
    Sodium D Line Emissions from Pickles” by J.R. Appling, F.J. Yonke, R.A. Edgington, and S. Jacobs, in Journal of Chemical Education, volume 70, number 3 (March, 1993), pages 250-251.

    So it is at least a decade older than that.

    I wonder what other fabulously quirky references are hiding away for us to find.

  4. The problem or possibly the beauty of demos is that you think you have invented something and then you find some crazy american or Victorian got there first.

    I came up with using a diode as a solar cell independently, but I am sure that is how solar cells were invented, so it isn’t really an invention.


    I don’t know if anyone else has used margerine to model planet s forming cores, though I don’t know if they would want to

    Similarly making mountains from lard

    Me and some of my friends came up with ground effect protractors, whilst avoiding being sent outside by the dinner ladies, but I am pretty sure we weren’t the first

    Making a lens from a lemonade bottle and water, is prerry obvious, so I doubt I got there first

    I am pretty sure other people were making hot air balloons with toasters before me, but I came up with it on my own,

    I am fairly sure I came up with using glow sticks to show rates of reation with different temperatures, but I think I wasn’t first


    Though I have no evidence that I wasn’t the first to build a repeating vacuum bazooka…

    And I think I have come up with various new science centre exhibits, though I haven’t built them all yet, or gone to enough science centres to know if they are actually new.

    Broadly completely new demos are pretty unusual, as they are by definition relatively simple, so the creative leap isn’ that big, most innovation comes when there are new problems to solve or new materials/devices to use, and mostly we are teaching the same stuff as Fraday…

    by the way those optical illusions are cool Elin.

  5. Thinking about it didn’t farady invent the Alom-Shaha motor?
    Though I guess he used weaker magnets and more mercury

    Which again gets to the point of how do you define inventing a demo… everything since Faraday was probably in fairly small steps, but the modern design is far cheaper, more convenient and less poisonous than the original version.

    1. I don’t know how to define inventing a demo, but I know it when I see it.

      So for want of a better name, the Alom Shaha motor (who ever invented it) is dramatically – and I mean that in the sense of drama – different from Faraday’s motor, even though they are recognisably similar.

      It may be that if Faraday had access to AA batteries, NdFeB Magnets he would have invented this. He might even have thought it obvious. But for me it is the dramatic shock of placing these everyday items together and re-discovering the motor that makes this is a new demo.

      It might be just a change of meaning over time. Perhaps when people saw Faraday’s original demo they too gasped – but then for them a bowl of mercury might have been a commonplace. For people today it is oddity in itself and other things – which would have been rarities in Faraday’s time – have become commonplace. If the Alom Shaha Motor demo had required a bowl of mercury or some unfamiliar component it would have lost its dramatic power.

      Forgive the long-winded-ness – one glass of wine too many 🙂

Leave a Reply

Your email address will not be published. Required fields are marked *