If a way could be found to transfer heat to the polar regions they could support large populations just as the temperate countries do. Fortunately man has been more successful in making use of the natural methods of heat transfer on a smaller scale. A quantity of heat is useless if it is where it is not needed. It may be useful if it can be moved to another place. Heat, by its very nature, helps to make this possible.
Heat always travels, or flows, from a high temperature to a low temperature.
It can do this by three different methods. These are called conduction, convection, and radiation. If one part of a body is heated by direct contact with a source of heat, the neighboring parts become heated successively. Thus, as shown in the diagram, if a metal rod is placed in a burner, heat travels along the rod by conduction. This may be explained by the kinetic theory of matter.