All posts by Jonathan Sanderson

Science film-maker, writer, director and consultant.

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.)

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.

MAKE | Maker Faire UK: Interview with Artist Giles Walker

I want ScienceDemo.org to be about demos, yes, but also about issues surrounding demos – how and why we do them, to whom, and to what end. So here we go. Make have an interview with a guy who’s exhibiting pole-dancing, CCTV-headed robots at Maker Faire UK this weekend. Worth a read:

MAKE | Maker Faire UK: Interview with Artist Giles Walker.

One of the things we discuss rather a lot in science communication circles is how to shift science and engineering further into mainstream culture. While the likes of Festival of the Spoken Nerd are taking great strides, it’s still notable that, for example, the ‘Cultural Olympiad’ surrounding last year’s London Olympics laughed all over the idea that STEM could be ‘cultural.’

This is one of the reasons I think Maker Faire is important. I’ve said before that while many STEM engagement projects are about STEM as career choice, Maker Faire comes from a completely different community and set of sensibilities. If it’s about STEM at all, it’s about STEM as lifestyle choice.

Maker Faire is chaotic, noisy, messy, and more than a little bewildering. It’s also joyous, inspiring, friendly, and pleasantly challenging. In my opinion it should be required reading on scicomms MSc courses, precisely because of that anarchic joy – it’s what happens when you take similar ideas to public engagement but develop them with a completely different group of people coming from a completely different viewpoint. In many ways, I prefer their interpretation of how things could be.

There’s a danger, I think, of the Cheltenham Science Festival and its ilk coming to represent ‘authorised’ science communication, and anything else being regarded with an air of suspicion (sometimes, when I’m hanging out with the London scicomms set, I wonder if this has already happened). There’s an orthodoxy to the sector which risks becoming bland. Maker Faire is doing a different job for a different audience, but the approach is so radical I think everyone should see it. Yet the usual scicomms community is notable largely for its absence. What should be worrying for them, I think, is how little they’re missed.

We’re not going to take STEM into mainstream culture unless we take the cultural sector seriously, and come to understand it on its own terms. Maker Faire UK is by far the best place to see the collision and interaction of the ‘two cultures.’ It’s a huge hit regionally, but I wish more of the opinion-makers and leaders made the arduous journey north to see it for themselves, and have their assumptions challenged.

Maker Faire UK runs April 27/28th at the Centre for Life, Newcastle. Details.

 

Status report

A brief post so you don’t think we’ve expired after the excitement of Pendulum Week, which was pretty much launch round here.

This is always likely to be a niche blog for a small audience, where by ‘small’ we mean, potentially, ‘millions of teachers and informal educators worldwide’. So I’m pretty darn delighted we’ve drawn well over a thousand page views so far. As sites go that’s pretty crap, but for what’s currently a spare-time/hobby project by a couple of obscure specialists it’s a decent start.

We’ll continue bringing you joyous demo links and musings on the art and craft. We’ve several more theme weeks planned (not yet sure of the schedule for those, though), and a few guest and contributing posters lined up to save you from our particular blether.

One thing I do want to do is find a more appropriate theme than this, specifically one which does a better job of surfacing comments. There’s ‘minimalist’ and there’s plain invisible. So if the site looks completely different on your next visit, that’ll be me trying out some alternatives.

Meanwhile – do drop us a line with your favourite demos, or your thoughts. There’s a contact form at the foot of the page.

Pendulums [6] – Coriolis Effect

Enough of the deep-and-meaningful musings, I’m going to wrap up Pendulum Week with perhaps my favourite pendulum demo of all time. “Foucault’s!“, I hear you cry?

Well, firstly: no need to be rude. Second: actually, no. Well, sort-of no. Which is to say, yes. Ish. Only without the… er… pendulum. Look, here it is:

…and I’ll let you, dear reader, work out what to do with this one. Lovely demo.

Pendulums [5] – Not Resonance

As Pendulum Week continues here you’ll have noticed a pattern building up: that pendulums crop up in all sorts of demonstrations, but it’s often rather tricky to pin down satisfying explanations for their behaviour. Pendulums appear simple and straightforward to grasp, which is usually a good sign for demonstration tools as we want audiences to engage with ideas or behaviour and not be distracted by unfamiliar apparatus. However, I wonder if it’s possible that pendulums are too simple, in that their apparent simplicity seems to lull us into forgetting their subtleties.

Heck, unless you’re in that sin θ ≈ θ small-amplitude space you haven’t even, technically, got simple harmonic motion. Most of the time, pendulums don’t even swing like, well, pendulums. Ouch.

It feels like it ought to be possible to link pendulum demonstrations together in a neat story. A mass on the end of a string is about as simple as physics apparatus gets, surely there’s a delightful sequence of demos which can build successively, one on the other, to arrive at something complex and surprising and revealing about the world? That’s got to be possible, right?

Perhaps it is, but the origin of this series of posts lay in my noticing that pendulum demos aren’t alike, and the distinctions seem to me to be of the subtle-and-confusing kind rather than the subtle-but-illuminating kind.

Probably the best attempt I’ve seen to navigate the resulting swamp was by my colleague Marty Jopson, who made this film for the first series of Science Shack (skip to 2:40 for the start of the show):

Marty and I were co-producers on the series, and if I remember correctly he won awards for this show. I wasn’t, I should say, much involved with this episode (harrumph), but it’s still worth a watch. It gets into some of the subtleties about resonance and synchronisation that we’ve seen in this series of posts.

Pendulums [4] – Synchronisation

In the previous post, pendulums of the same length (and hence the same natural frequency) oscillated each other. Here, the point is that the pendulums are of slightly different lengths. And yet:

Comprehensive notes can be found in what appears to be the original source of this demo, Bryan Daniels’ senior project at Ohio Wesleyan University.

To my mind this demo isn’t an example of resonance… and that’s a thought we’ll pick up in the next post in this series. Meanwhile, please do share your favourite pendulum demos in the comments. Or, you know, any pendulum-related anecdotes – there’ll never be a better time for those.

Pendulums [3] – Coupled Pendulums

Pendulum Week heats up with… coupled pendulums:

(First embed, doubtless of many to come, from the prolific Brady Haran at Nottingham.)

Look in any of those interminable/popular[delete as applicable] ‘Exciting Fun Science Things to Do on a Rainy Day! Science!‘ books and you’ll likely find this old standby, more commonly done with potatoes rather than creme eggs.

It’s not one of my favourites, partly because I think it needs careful performance to appear as amazing as is usually claimed, but also because the subtlety of explanation required hardly seems worth the effort. This film, for example, doesn’t tell us very much. The explanation bit goes:

“There are little forces as [the connecting string] goes out of line that pull from one to the other, transferring energy from [the first pendulum] … over to that one, and then back again.”

Hmm. All that’s doing is describing what we see and replacing the word ‘swing’ with ‘energy,’ and I’m not a big fan of using ‘energy’ as an arm-wave explanation. Robert Winston’s book, snarkily linked above, explains pendulum movement in terms of gravity and momentum, then adds:

“If two pendulums are attached to the same piece of string, they pass their motion back and forth between each other. One pendulum swings, pulling the string it’s hanging from to and fro. This transfers energy to the second pendulum, which starts swinging itself.”

…which, again, is a reasonable description. Is it an explanation, though? I’m unconvinced.

Neither of these ‘explanations’ has begun to cover why it matters that the pendulums are the same length, let alone pesky details like: the demo still works if the connecting string is perfectly taut, when the driving force is delivered by torsion at the suspension point rather than lateral displacement.

But when you try to write a more satisfying explanation you end up in a bit of a mess. I know I did when I wrote this demo into a children’s TV series back in about 1998. A satisfactory explanation has to include (or at least skirt around) energy exchange, mechanical impedance, and resonant frequency – the sheer amount of physics required is, to my mind, beyond what the demo itself will support.

Better, I think, is this variation:

…which is much more clearly about resonance. The inverted spring pendulums also break the visual connection with the phase demonstration in the previous post in this series, which I think would reduce the risk of confusion were one to attempt linking several of these demos together.