James Clerk Maxwell was one the greatest theoretical physicists of the nineteenth century. He was born in Edinburgh and studied at the Edinburgh Academy (where he was nicknamed 'Dafty') and the University of Edinburgh where he remained until 1849. He then moved to Cambridge University where, in 1850, he worked on the three-colour theory proposed by Thomas Young. He confirmed Young's theory that colour-blindness was due to damage of the cones in the retina and that there were three types of cone, one for each primary colour. He also explained how, through subtraction and addition, other colours could be formed from these three colours and in 1861 produced the first colour photograph 'of a piece of tartan ribbon' It was generated using three coloured filters, red, blue and green, a technique now widely used to produce colour photographs, prints and television pictures.
In 1856 he became Professor of Natural Philosophy at Marischal College, Aberdeen, where he began to investigate theoretically the rings of Saturn. After proving that a solid or liquid ring around the planet would collapse, he correctly predicted that the ring was composed of a number of small objects orbiting the planet. His statistical approach to this problem was to became particularly useful when he began investigating the kinetic theory of gases.
In 1860 he moved to King's College, London, but left after his father died in 1865. He returned to his family home in Scotland and continued his research there until 1871 when he returned to Cambridge, where he set up the famous Cavendish Laboratory, which opened in 1874. Since 1855 he had spent many years researching electromagnetic radiation and he summed up this work in the publication 'Treatise on Electricity and Magnetism' (1873). Here he explained all of the known effects of electromagnetism and provided a number of equations that described the electromagnetic field. On the basis of these equations Maxwell deduced the existence of electromagnetic waves and found that they travelled at the speed of light. He proposed that light consisted of electromagnetic waves, stating that it was composed of electric and magnetic fields that vibrate perpendicular to their direction of propagation. He also suggested that electromagnetic waves existed beyond infrared and ultraviolet, and that they could be generated in the laboratory. Unfortunately, his untimely death meant that he didn't see his prediction verified in 1888, when Hertz produced radiowaves.
Among Maxwell's other great contributions was the development of a mathematical formulation of the kinetic theory of gases. He based his initial research on two things; the first was Rudolf Clausius' model of a gas as an ensemble of molecules that vibrate and collide with each other and with their container. The second aspect was his success in mathematically solving the problem of Saturn's rings. He used this statistical approach on gas molecules, developing a formula that described the relationship between the speeds of the molecules in a gas and the temperature, viscosity and diffusion of the gas. He argued that temperature of a gas is dependent on the vibration of the gas molecules. After conducting a series of experiments with his wife into the viscosity of gases, he changed the kinetic theory, suggesting that the gas molecules were subject to repulsive forces, rather than elastic collisions. It was a view that confirmed the laws of partial pressure, diffusion and the viscosity-temperature relationship. Maxwell's theory did not however, explain fully all the properties of a gas and in 1868 Ludwig Boltzmann modified the theory again, developing the Maxwell-Boltzmann distribution. The two men then set about fine tuning the theory until it was complete. Through his mathematical power and the quality of his intuition, Maxwell made such profound contributions to a wide range of topics in physics that he may be fairly considered as the most important figure in theoretical physics between Newton and Einstein.
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