The Way Things Work Now

VERYTHING A MACHINE DOES is in accordance with a set of principles or scientific laws. To see the way a machine works, you can take the covers off and look inside. But to understand what goes on, you need to get to know the principles that govern its actions. The machines in this and the following parts of this book are therefore grouped by their principles rather than by their uses. This produces some interesting neighbours: the plough rubs shoulders with the zipper, for example, and the hydroelectric power station with the dentist’s drill. They may be vastly different in scale and have different purposes, but when seen in terms of principles, they work in the same way.