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William Thomson (later Lord Kelvin) was born June 26, 1824 in Belfast, Ireland, and was part of a large family whose mother died when he was six. His father taught Kelvin and his brothers mathematics to a level beyond that of university courses of the time. Kelvi ....

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.... This work contained his ideas and version of the second law of thermodynamics as well as James Joule’s idea of the mechanical equivalent of heat. This idea claimed that heat and motion were combined, which now is taken as second nature. At the time, heat was thought to have been a fluid of some kind. Kelvin also maintained an interest in the age of the sun and calculated values for it. He assumed that the sun produced its radiant energy from the gravitational potential of matter falling into the sun. In collaboration with Hermann von Helmholtz, he calculated and published in 1853 a value of 50 million years. He also had an interest in the age o ....