Monthly Archives: March 2014

Demonstration, Discuss

Understanding the chain fountain

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Our chum Steve Mould has had a bit of a hit over the last few years with his chain fountain demo:

There have been arm-waving explanations (some more convincing than others), but recently John Biggins and Mark Warner in Cambridge have published a much more complete description of what’s going on.

Now, the video at the head of this post makes me wince a little, partly because I’m a snobby film-maker but also because the section from about 3:10 (about centripetal force) could, I think, be clearer. It’s not explicit, for example, that in the steady state the chain velocity must be the same all along the chain: that’s why the ‘ball being thrown straight upwards’ analogy works. It’s not that the ball is stationary at the top (if the ball’s path is arced like the chain’s, the ball isn’t stationary), it’s that the ball’s speed changes during its flight. The chain can’t do that.

There are several similar conceptual jumps which make sense only once you’ve understood the process, not whilst you’re in the process of understanding – a common mistake in academic scicomms, if I’m being snarky. You can see the result of these skipped steps in the comments thread at YouTube, which pretty much mirrors what I’d expect. That is: people tripping over precisely the parts the film covers poorly.

However, the torque argument for a force component from the beaker is lovely. The macaroni-on-a-string demo isn’t properly convincing as shown, but it does offer the beginnings of something terrific.

So, critical me thinks there’s better scicomms still to be done around this, but what delights me about the whole episode is that ‘proper’ physics is being done from a scicomms curiosity. It’s also a remainder that often science communicators stop just before the science gets properly interesting: we chicken out at the arm-waving stage rather than aiming for the greater satisfaction that comes from deeper understanding.

Bravo, Steve et al. There are precious few stories like this.

The Rutherford School Physics Partnership has a PDF of more chain problems, if you want to roll your sleeves up and get stuck in.

Demo: The Movie, Discuss

DEMO: The Movie – User’s manual

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It’s all well and good that we made a film, but what are you supposed to do with it?

Take a look at the discussion notes compiled by Alom and Mary Whitehouse at the University of York (PDF link). That document also includes a bunch of references (the film isn’t just us making stuff up you know, there’s research and everything!) along with Alom’s practical tips for performing demos.

DEMO is really intended to be watched in your own time, as a pick-me-up when the day-to-day grind has dulled your enthusiasm, or to reinforce and help clarify how you think about demonstrations. It’s a bit long, perhaps, to watch in a staff meeting or training course, though we’re already hearing reports of it being used that way.

With Alom’s previous film Why is Science Important? one thing that proved useful was having the film chunked up into individual scenes. DEMO has so many forward- and back-references we’re not sure that would be appropriate, however if you’d really like a specific scene pulled out, drop us a note in the comments here and we’ll see what we can do.

Alternatively, you can dissect the film yourself on YouTube. If you’re signed in, below the film you’ll see a button labelled ‘Remix this video!’. By the magic of Creative Commons licenses, pressing that button will pull the film into YouTube’s editor, allowing you to chop it up to your heart’s content. All we’d ask is that you include a link back to http://demothemovie.com in your film and its description, so people can find the full story.

Demonstration, Equipment

Ingenious, cheap way to investigate Boyle’s Law

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I’ve just taught Boyle’s Law to my Year 13s and made use of the standard apparatus for demonstrating how volume changes with pressure… only I didn’t use it to do a demonstration. It was a small class, so I thought I’d try something different: I presented the class with the apparatus, told them nothing about it, and challenged them to have a play with it and a) work out what it did, then b) use it to tell me something interesting about how the world works.

The students told me later that they liked the activity because it “made them think” and they seemed to have enjoyed the process of being free to discuss ideas and work together to solve the problem I had set. I think it was a successful activity (although I suspect some students got more out of it than others), however, I wish I could have had more sets of the equipment so they could have worked in even smaller groups or even individually to explore Boyle’s Law. Next year, I might use this – a cheap, ingenious way to allow students to arrive at Boyle’s Law through experimentation:

UPDATE: Since writing this, Bob Worley has been in touch to tell me of a similar approach from CLEAPSS to allow students to explore Boyle’s Law and Charles Law with guidance available here.

Demo: The Movie

DEMO: The trailer

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Alom and I made a movie, as the regular reader here might have worked out.

On Monday March 10th we’re having premiere events in London and York. The London one is invited guests only, sorry – but you can still get into the York screening at the National STEM Centre (free popcorn!). The movie will be online around the same time.

If you can’t make it to York… enjoy the trailer, and we hope you’ll find the film itself useful.

Demonstration

If the moon were 1 pixel…

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I’m not often a huge fan of computer-based demonstrations: if you’re going to show the reality of something, show it for real. However, when the thing you’re trying to show is abstract – like, for example, the immense scale of the solar system – then screen-based demos can make a lot of sense.

Take this fabulous side-scrolling solar system diagram, for example. It starts from the premise of the moon being 1 pixel high, and scales the rest of the solar system accordingly. Be warned: there’s a lot of scrolling involved.

A lot of scrolling.

The journey’s kept amusing by odd little snippets spaced between the planets in neptune-sized text, and the minimal design is particularly lovely. Hey, if you’re going to use a screen-based demo, use a good one.

(via everyone, but particularly Metafilter, where the comments thread also points to the impressive-looking Universe Sandbox. “Collide galaxies for fun.”)