Definition of scaling

It is regrettable that we cannot study the effects of scaling by building super-sized elephants. Nevertheless, we can approach the problem in a different way, and in this regard we have much to learn from the engineer who continually solves the problems of building taller skyscrapers, longer bridges, bigger ships, and so on. Indeed, the need for changes in the size or scale of things has given rise to an entire branch of engineering known as scaling. For our purposes here, we shall use the definition that scaling deals with the structural and functional consequences of changes in size or scale among otherwise similar organisms.

If we increase the size of a brick house, we know that we need heavier foundations and thicker walls. There are practical limits to the size of brick houses, however, for the walls must be made thicker and thicker as house size increases. Eventually we meet an ultimate limit to further increases, dictated by the strength of brick. In the design of a skyscraper the engineer therefore changes the material in the main supporting structures; he uses steel rather than brick. In this case the constraint on a further increase in size is overcome by a change in material.

Another avenue is also open to the engineer: He can change to a new design. The construction of long bridges gives an example.