it's not magic, it's science!

As a higher level university student, you are allowed to undertake tutoring and other teaching opportunities. I think having teaching responsibilities is great, although it can be difficult - it is very true that you find out just how much you know about a subject by trying to teach it to someone. So far I've been a tutor in a first-year physics tutorial and lab, both of which were great experiences and lots of fun! My school also gets involved with many outreach activities, which are pivotal to ensuring that as many people as possible are exposed to the insights and wonders of physics.

At the moment I'm involved as a science advisor for a children's TV show, one of probably a number of advisors that rotate from week to week. Every week, the (awesome) 9 year old host goes through a science topic, aimed primarily at a pre-school audience. His motto, and possibly the tagline of the segment, is: "It's not magic, it's science!" You can probably guess from the audience what the emphasis of the show is - it's all about making science fun through various activities designed to engage kids, as well as keeping the science accurate as possible.

So far I've helped out with one shoot - the theme was exploding soda cans, or basically exploring the nature of carbonation in soft drinks. The science of it was actually a little bit tricky, admittedly, because it deals with the controversial suggestion that tapping a soda can after shaking it will reduce the amount of foam when the can is opened. The overall consensus from the Internet is that this is a myth (see here or here), however most of these debunkers deal with "tapping the top of a soda can".

In this episode, it is suggested that, after shaking a can, flicking (not tapping) the sides of a can will detach carbonated bubbles forming on the side of the can and allow them to float to the top, escaping as gas rather than liquid when the can is opened. The main cause of soft drink overflowing when shaken is thought to be the expansion of the volume of these carbonated bubbles due to the sudden pressure gradient (high pressure in the can, low pressure outside), so this suggestion is not unreasonable. It is generally believed, however, that it is time rather than human influence which best settles a shaken can, and that people tapping is simply increasing the time for the liquid to settle rather than having a true influence. This is not proven, however!

As science advisor, the reason I thought this was tricky is because it's not something with an easy answer. Most things in science don't have easy answers, to be fair. But you have to be careful when there is no strong consensus, such as in the case of soft drink shaking, because you don't want to be responsible for purporting something that's not true! The goal of science is to try and find the truth about physical processes, as objectively as possible; a good scientist has to make a solid argument in favour of their hypothesis, but at the same time should consider arguments against their stance because it is only through understanding objections that you can explain why your hypothesis is more convincing.

I did some tests with my brother and his friend - we bought a 24 pack of lemonade and did some tapping experiments. The results of this were inconclusive, and if anything it seemed like tapping the can either slightly increased or decreased the foaming. In other words, the results were consistent with zero effect! However, I then found a website which fairly confidently stated this did have an effect. The difference here was that it was flicking, not tapping, that was central to the success of the technique. I have since tried this, and watched the director of the show try it, and I have to say, it seems pretty convincing. It looks like it may actually work - though I doubt anyone is going to write a journal article in the near future explaining why.

What I have to say at the end of this is in support of the motto of the Royal Society: "nullius in verba". It means "take no one's word for it" - and that's what I say to you reading this. Try the soft drink experiment yourself. Take two cans, shake them an equal amount, and flick one of them around the sides of the can before opening them at the same time. Do it more than once - see if there is a trend. That's the only way you can believe anything yourself, by verifying it. It's the best conception of the scientific method. And if you do try it, let me know how you go! Post on the forum or drop me an email, I'd be really interested to see how it pans out.

Remember: "It's not magic, it's science!" And that's what science is about, in the end - delving into the unknown and the mysterious, and trying to make sense of it. I think it's great that the scientific method is not limited by age, but by a desire to explore, experiment and explain. Go do some science!

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