A Brief History of Ideas About Energy

Theories about energy started to become important when machines started to become important in industry. In order to make more efficient machines it became important to know about theories of heat and work. Important milestones are listed below.

1705 – Thomas Newcomen built the first steam engine.

1764 - James Watt built a more efficient steam engine.

1760 – Joseph Black showed that heat and temperature were distinct things. He developed the caloric theory of heat, which viewed heat as an invisible weightless fluid that flowed out of hot objects and into cold objects. This theory could not however, explain why truning a stick inside a hole in a log could generare enough heat to start a fire.

1798 – Count Rumford demonstrated by boring a cannon, that it was possible to generate enough heat to boil water. By taking measurements, he showed that the cannon continued to heat up long after it should have run out of caloric liquid.

1837 – James Joule began a series of experiments. He demonstrated that the heating effect of electricity varies as the square of the current, but his most famous experiment demonstrated that turning a paddle in a container of water heated the water, and showed that all the work done in turning the paddle was turned into heat energy in the water. He accumulated evidence to demonstrate that energy was conserved overall in all processes. This is 'The Law of Conservation of Energy'.

1859 – James Clerk Maxwell showed that thermal or heat energy is really the random motion of atpoms and molecules. This is part of the kinetic theory of gases.

1905 – Einstein's Special Theory of Relativity implied that mass was a form of energy. The theory implied the modification of the law of conservation of energy so that it became a law of conservation of mass plus energy.

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