.................with apologies to Alistair Cook

Thursday, 23 October 2008

Danger! High energy X-rays! From Sellotape?

Nuclear fission from Sellotape?

As usual, the excellent Nature production editors nail a story with a succinct one-liner: "How weird is that?".

Very. It turns out that ordinary sticky tape - Sellotape in the UK, Scotch tape in the US, Durex in Australia (well, once upon a time) - emits high energy X-rays when you pull some off the roll. In fact, enough are given off under the right circumstances to form an X-ray image of an experimenter's finger -- although as the right circumstances involve a high grade vacuum, don't send off for the lead codpiece before wrapping your Christmas presents just yet.

But the phenomenon is very real. It's an example of one of my very favourite bits of quotidian weirdness, triboluminescence. This is the habit of some compounds, including sugar, of emitting light when crushed: if you take a Trebor mint and a pair of pliers into a dark room and let your eyes adjust, you can check this for yourself. (I did as a kid and have been a big fan ever since.)

That light is not due to heat or sparks of static electricity, at least not as we normally know it. In fact, nobody's quite sure what happens: the leading theory is that the disruption of molecular bonds results in a sudden localised distribution of positive and negative charges, which snap back into neutrality with a burst of photons. And this makes some sense, given that charges changing speed are the way light comes about.

But X-rays? To make them normally, we have to use tons of energy to accelerate electrons in vacuum to very high velocities and smash them into carefully constructed targets. There are no known low-energy producers, and only the most exotic solid-state emitters.

So finding X-rays streaming out of a 99p roll of sticky tape by the application of thumb and finger is akin to discovering a nest of dragons behind the Pick'n'Mix counter in Woolworths. The researchers were "a little bit scared" when they first realised what was happening - they were checking a Russian report from 1953, which first noted the effect - but have now decided that there's no danger in everyday tape use.

They're now decidedly excited, but comprehensively baffled. Given that nobody quite understands the long-observed sugar crushing experience, this new variation - far removed from anything else in a physicist's experience - is utterly bewildering. But investigations are underway, with an intriguing codicil that the mechanism may be good enough to trigger nuclear fusion.

Gotta love that physics.

(Via ZDNet UK Blogs - Rupert's Diary.)