Thursday, 17 July 2014

Hairy is the New Black

While the news has been dominated by people watching ear-biters kick a ball about, or bombing other people’s families, or travelling in search of work, or trying to stop people travelling in search of work, a few — just a few — have been doing more creative and interesting things. One rarely hears about this on radio news, but the other day one little item caught my attention.

The ‘Black Body’, like the frictionless surface or the non-resistant conductor, is one of those ideal, perfect, non-existent things which scientists posit to make the theory, especially the maths, simpler: a genuinely, ‘scientifically’ Black Body would absorb all light (or heat) reaching it, and so be entirely featureless. (We see things by the light they reflect.) It would be just as featureless if one heated it up to the point where it emitted light itself, and you can ‘see’ something like ‘Black-Body Radiation’ when you look into the centre of a well-established coal fire, which is why people used to talk of seeing faces (or whatever) while gazing dreamily into the fire: the featurelessness gets one’s imagination going.

One might think that the Black Body could remain a ‘mere’ convenient scientific fiction; that to try to find or make one would be to miss the point, like those hopelessly materialistic people who thought the Philosopher’s Stone and the Holy Grail were actual physical objects, and rushed around looking for them.

But in fact a Black Body, or at least a really, ‘scientifically’ black surface, could be useful: For instance, there is a telescope floating around in space which is trying to pick up very faint light (or other electromagnetic radiation) from very distant objects, and it is distracted by light reflected from its own surfaces. It would be handy to coat it with something entirely non-reflecting.

Such a thing is one step nearer, in the form of what one might call hairy paint. The hairs are in fact nano-tubes of carbon: very tiny, very thin tubes. Coating something with a load of these, all standing upright, (I don’t know how they do that bit) renders it almost completely non-reflective. The scientist/technician interviewed about this on BBC World Service was, unlike most of his kind, a good explainer and came up with a fine analogy: a surface thus coated is like the ground in a dense forest. Anyone who has walked in a dense forest of tall trees on a hot bright summer’s day will know how cool and dark it is: the heat and light are absorbed by the trees on the way down and in, so that very little light reaches the ground, and so very very little is reflected back out again.

As I said, this was the only interesting, non-trivial, non-horrific item on the news the other day. I find it cheering that, not I hope in ignorance but rather in spite of the awful things that are happening in so many places, there are people who carry on with scientific and technical research and experiment.

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