Условие:
The Law of Energy Conservation Heat, this most active, powerful and mysterious phenomenon of Nature. was once a really challenging problem to physicists-professionals as well as non-professionals. Among the first investigators of the problem were people of all walks of life: the peer of France Laplace and the English manufacturer of beer Joule [dsu:1], the French philosopher and writer Voltair and the English acrobat, musician and physicist Young, the War Minister Rumford and the French doctor Paul Marat, the leader of the French Revolution. The first to estimate the mechanical equivalent of heat was Robert Mayer (1842). Soon afterwards it was also proposed by Joule and later by von Helmholtz, a physiologist and a physicist. The same idea, though not so clearly expressed. seems to have occurred to at least five other physicists or engincers. The approaches of the three principal discoverers were different. Mayer was led to the conception by general philosophical considerations of a cosmical kind. He was struck by the analogy between the energy gained by bodics falling under gravity and the heat given off by compressed gases. Joule was led to the idea first by experiments aimed at finding out how far the new electric motor could become a practical source of power. Helmholtz in 1847, by an attempt to generalize the Newtonian conception of motion to that of a large number of bodies acting under mutual attraction, showed that the sum of force and tension, what we would now call kinetic and potential energy, remained the same. This is the principle of conservation of energy in its most formal sense. but it was important in that it reconciled the new doctrines of heat with the older ones of mechanics, a process that was to be largely completed by William Thomson (later Lord Kelvin), a friend of both Joule and Helmholtz, in his paper The Dynamical Equivalent of Heat (1851).
