I asked a professor of nanotechnology what they use to measure the unthinkable small distances of nanospace? He said it was the nanometre. This didn't help me very much. A nanometre is a billionth of a metre. I understood the idea but couldn't visualise what it meant. I said, "What is it roughly?" He thought for a moment and said, "A nanometre is roughly the distance that a man's beard grows in one second". I had never thought about what beards do in a second but they must do something. It takes them all day to grow about a milllimetre. They don't leap out of your face at eight o'clock in the morning. Beards are slow, languid things and our language reflects this. We do not say "as quick as a beard" or "as fast as a bristle". We now have a way of grasping of how slow they are - about a nanometre a second.

Autor: Ken Robinson