All posts by Alom Shaha

Simple accelerometer and circular motion

I’ve just started teaching circular motion to my Year 12s. There are some obvious demonstrations you can do when teaching this topic, such as spinning a bucket of water around your head, but I’m somewhat ashamed to admit that I’ve only just discovered the floating cork accelerometer which can be used to illustrate a key idea for this topic. Watch the video to see what I mean.

Massive thank you to my colleague Ronan McDonald for making the big accelerometer and volunteering to get dizzy.

[Edit 18/6/2013 – this post inspired a lively discussion at the Institute of Physics PTNC mailing list for physics teachers, which is a hidden gem of a community and a list every teacher of physics should at least be aware of. Sign up via the web interface. Thanks to everyone who cross-posted their comments here.

Joe Rowling had a nice blog post a few days before this, too – well worth a look if circular motion is your thing.


Ben Craven’s arch demo

Science communication legend Ben Craven was in London over the weekend, giving me the chance to grab a quick bite with him while he waited for his train at King’s Cross. It also gave him time to show me a surprising demo related to his love of arches and for me to try out filming on my new iPhone 5. The picture quality is way better than my crappy old iPhone 3GS but the sound is problematic for doing something like this. Might need to invest in a lavalier mic of some sort…

[Oh, I see: requisitioning equipment via the blog. That’s your game, is it? Tsk. – Ed.]

Flames and Shadows

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.

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?


A simple tip for any science communicator, or indeed teacher, intending to perform a demonstration to an audience:

Make sure it works.

That’s it.

It’s such obvious advice it almost goes without saying. Almost, but not quite. Sometimes we become so confident in our performance skills that we forget the basics, and this post is prompted by my having seen two prominent UK science communicators recently do demos which didn’t work.

I’m not going to mention any names and I’ll leave the details vague: this isn’t intended as a personal attack. I’m much more interested in how the demonstration failures felt from where I was sitting at the time – in the audience.

I’m going to try to do a demonstration which never works.”

One of the first bits of advice you’ll receive as a performer is: never apologise. The above line called that to mind, along with the obvious response: “Well, why are you going to do it?”. My hope was that famous science communicator #1 was joking for effect, but he proceeded to spend several minutes of an otherwise fascinating and engaging lecture on an incomprehensible demo involving members of the audience having to stand up and sit down according to a set of instructions neither they nor the rest of the audience seemed to understand.

As best I can tell, the ‘demonstration’ failed to illuminate the bit of science it was meant to illustrate. Certainly, it added nothing to an explanation which had already been provided with a diagram. The lecturer even admitted as much. So why include the demonstration at all?

Perhaps because we’re so enslaved to the notion that we must entertain our audiences with demonstrations that we’ll shoehorn one in if there’d otherwise be too much exposition. Or perhaps the lecture was simply too short otherwise.

From the audience’s perspective, all the demonstration achieved was a measure of audience embarrassment.

Famous science communicator #2 did a demo which simply didn’t work. It was supposed to illustrate that chemicals of a certain family were all good fuels, and it involved separating the wick from the wax of a tea-light. The wick was then squirted with body cream and lit: the body cream would melt, flow up the wick, vaporise and burn.

It didn’t.

The wick caught fire, but it didn’t melt the body cream and it certainly didn’t work as a candle. So, again, an under-prepared demonstration which made the audience uncomfortable, except that communicator #2 proceeded as if it had. The lecture – a team effort – carried on without him, and he distracted me as I watched him continue trying to make it work. He was clearly puzzled as to why it hadn’t.

Prior to doing the demo, science communicator #2 had joked that he had only purchased the cream a few minutes before the lecture, making light of his under preparation. And that was the problem, obviously – he hadn’t checked his demo. He’s a busy man, but I think the audience deserve better. So did the non-geek friend with whom I attended the lecture, who was unimpressed by this demonstration and a number of other shortcomings which we’ll cover in later posts.

Most science communicators are scientists themselves, and we’re accustomed to the idea that science doesn’t always, well… work. Our audiences, however, often aren’t as comfortable with the nuances of statistical repeatability. Every time a demo doesn’t work, we risk the inference that science doesn’t work. Dangerous.

In a classroom situation, however, discussing with your audience (students) why they think the demo didn’t work and – time permitting – trying to fix it can be tremendously instructive.