Читать книгу Heat-Its Role in Wildland Fire - Clive M. Countryman - Страница 6

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Everyone knows how heat feels, and is well aware of its many applications in daily life. Heat from the sun is the basic control of our weather, and this heat is also essential in the growing of food crops and other vegetation. Without the sun's heat, life could not exist on the earth.

Through the science of thermodynamics, heat has a place in many of the industrial processes that bring us the conveniences of modern life. But as recently as 200 years ago, the true nature of heat was not understood. In the early days of science the phenomena associated with heat were ascribed to a mystical and intangible fluid called "caloric." This fluid was believed to have the power of penetrating and expanding materials, sometimes melting or dissolving them, and converting some substances to vapor. Heat produced by friction or the compression of gases was attributed to stored caloric that was squeezed or ground out of the material. The caloric fluid was considered intangible, since even the most careful experiments in adding or subtracting heat by nondestructive heating or cooling of a substance failed to produce any changes in its weight.