BBC BLOGS - Gregory's First Law

Archives for February 2011

The story behind "invisibility cloaks"

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David Gregory | 13:39 UK time, Thursday, 3 February 2011


Sometimes you get wind of a paper in a scientific journal and you know it's going to be of great interest to your audience but at the same time you have no idea how you are going to film and explain it. The University of Birmingham's "invisibility cloak" was a perfect example of this. This is the story of how we took a tricky tale from lab to limelight.

As is often the case with science stories once the paper revealing the research was accepted by a journal for publication then an embargoed press release was sent out. You can read the press release from The University of Birmingham here and the paper itself here [subscription required]

But chatting to the press office in the University it was pretty clear science journalists weren't beating down their doors on this one. There's a couple of reasons for that; first, exciting though talk of an "invisibility cloak" is, as a reporter the reality just doesn't match up to that. Secondly the images of the invisibility effect in action were not that exciting. Can you spot the "invisibility cloak" working in the above picture? (*Answer at the bottom of the post)

But to his credit my Producer was very keen and had faith we would overcome these problems and we swung into action. The scientists involved also thought long and hard about the needs of tv and came up with a nice panda-based demonstration. This is the "fat minute" explainer I put together for the BBC News website that makes use of it.

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As you can see the calcite crystal "cloak" is pretty visible itself which is obviously a problem and the use of more efficient crystals is difficult as they turn out to be poisonous. It also only works for polarised light as you can see from the filter in the video. But this research does have significant advantages over existing attempts at invisibility in the lab which have so far involved extremely expensive materials that take an age to fabricate and usually only make invisible things that are too small to see with the human eye anyway.

This crystal "cloak" also works with visible light (well polarised visible light) and the effect isn't restricted to a single viewing angle. The discussion of the paper itself does conclude that this research;

"...paves the way for future practical cloaking devices"

And once we did the story on Midlands Today and Radio 5 Live then it was picked up by everyone else. Channel Four News even used the Harry Potter and Star Trek footage I just didn't have time to fit in. It's a good example of a story everyone knew about thanks to the embargo but avoided because it just looked too hard to tell. Thanks to a pushy producer, a well told story and a clever new demonstration created by the scientists themselves it eventually got the exposure the science really deserved.

*It's the first picture. Obviously! Basically the lack of any distortion makes it look like the crystal has a flat bottom. In fact of course it has a slight bump where you can hide your top secret paperclip. That bump is distorting things in the second picture.

How bad is light pollution where you live?

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David Gregory | 16:59 UK time, Wednesday, 2 February 2011


Time exposure photograph of polar stars during a meteor shower. The circular streaks of light result from the rotation of the Earth in relation to the fixed stars. The diagonal line across the trails is the track of a Perseid meteor. Photographed over the rim of Nicola River canyon, British Columbia, Canada, in August.

Tonight I'm reporting on plans to turn off the lights on a section of the M5 between junctions 2 and 4. The Highways Agency say this will help them reduce their carbon footprint. Although it will also produce a multimillion pound saving on their electricity bill. You can read more about this story here.

In science terms, what's exciting about this move is the prospect of it becoming widespread and so reducing light pollution across the Midlands. Making stargazing a slightly more rewarding experience for those of us who live in more urban areas. Every little helps!

At the moment the Council for the Protection of Rural England is running a star gazing survey to investigate just how bad light pollution has become. You can read more about the problems here and take part in the survey here. And if you're an amateur astronomer let us know just how bad the light pollution is where you are in the comments.

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