Last Thursday while browsing a popular NZ-based website an article caught my attention: ‘Scientists learn to levitate objects’. Images from Harry Potter films flashed before my eyes, and I thought this had to be something worth checking out. And it was, for two reasons. First, because the article is a surprisingly accurate piece of science writing for mainstream media, and secondly, it concerns a very curious quantum mechanical effect.
In my not-all-that-long science career I have come to the conclusion that you never trust a journalist to write a story about science. Usually they have an uncanny knack of removing all the key concepts and facts and replacing them with whatever fictional construction is required in order to support the message they wish to sensationalise. So I was pleasantly surprised when I refered to the original article by Steve Lamoreaux in the journal Nature and discovered that the journalist really had accurately portrayed the work that had been done. Admittedly, the title was a touch misleading, with the ‘objects’ in question likely to be not much bigger than molecules, but I can forgive that – I probably won’t have clicked on the article otherwise.
Which brings me on to the work itself. It concerns the Casimir force, which is decidedly strange. Its very existence is a result of quantum mechanics, can therefore be considered an experimental ‘proof’ of quantum theory. In a sense, the Casimir force is ‘something for nothing’; the idea is that ‘stuff’ can appear spontaneously out of a vacuum, so long as it only does so for a short period of time. This ‘stuff’ hangs around long enough to interact with objects surrounding the vacuum and in effect provide forces between them. In the case of this work, it is a repulsive force that can potentially levitate something.
Can something really come out of nothing? Let’s use an example from economics that is becoming depressingly familiar. There is talk in some countries of overnight interest rates dropping to zero. In that case, a bank can borrow money from its country’s central bank, overnight, for zero percent interest. It can take as much as it likes, so long as it pays all of it back exactly a short period of time later. Why bother? Because that keeps the bank functioning, and a functioning bank acts as a source of finance to business in general. No money is ‘created’ – it gets borrowed and repayed, but in a time-span just long enough to make a difference. That’s what’s happening (sort of) with the Casimir force.
Incidently, some people think that the universe exists because of one of these ‘borrow ‘stuff’ for a short time’ events. I’m far from convinced – the universe contains a whole lot of stuff, and it has existed for an awfully long time without having paid it back. The debt collectors seem long overdue.