James Clerk Maxwell (1831 - 1879)
Contributions: Electricity, electromagnetism, thermodynamics, astrophysics, optics:
- Astrophysics of Gaseous Nebulae: Maxwell published in 1859 his outstanding essay, On the Stability of Saturn's Rings, in which he concluded that Saturn rings could not be completely solid or fluid. Maxwell showed that the rings' stability could be achieved only on the condition that the rings consisted a large number of small solid particles. In this essay he also disproved mathematically the nebular hypothesis of his time which stated that the solar system was formed through the condensation of a purely gaseous nebula without any solid particles present. For this, Maxwell was awarded the Adams prize the same year in Cambridge.
- Kinetic Theory of Gases: In 1866, Maxwell formulated, independently from Ludwig Boltzmann, the Maxwell-Boltzmann kinetic theory of gases. His formula was called the Maxwell-Boltzmann distribution and described particle (molecule) velocity in gases at any given temperature. According to Maxwell's kinetic theory, temperatures and heat are related only to molecular movement. This approach clarified and simplified the previous laws of thermodynamics by interpreting observations in a simpler way. As a result of his work on thermodynamics he suggested a thought experiment known as Maxwell's demon which demonstrated his views regarding the Second Law of Thermodynamics.
- Color Photography: Maxwell suggested a method of creating color photographs by using red, green, and blue (RGB) filters. In his experiments he photographed an colored object three times, each time with a different RGB colored filter in front of the camera lens. The three images were developed and then projected onto a screen by three different projectors, each equipped with the same color filter used to take the respective image. When brought into register (the correct alignment), the three images formed a full color image. Nevertheless the resulting image colors were to some extent unnatural, because the filters passed also light outside the visible spectrum of light, the principle was fully demonstrated.
- Maxwell's Equations: However, Maxwell's most important scientific contribution was to the field of electricity and magnetism: a set of differential equations which are now known as Maxwell's equations, and describe the properties of electric and magnetic fields and their interactions with matter. Maxwell used his equations to show that electric and magnetic fields are two complementary components of electromagnetic fields. He also showed that electric and magnetic fields travel through empty space, in the form of waves, at a constant velocity of 3.0 × 108 m/s (which predicted the speed of light c) and also proposed that light was a form of electromagnetic radiation.