"It is difficult to make predictions", goes the old joke, "especially about the future." However, there is one way in which we can predict the rate of change. It is called Moore's Law, named after Gordon Moore the founder of the computer chip company Intel. More than 50 years ago, he observed that the computing power that was available at a fixed price doubled every 18 months or so. This was based on the number of transistors that could be fixed on a chip.