Download Maxwell, James Clerk (1831

Maxwell, James Clerk (1831-1879). Maxwell is generally regarded as the foremost
physicist of the 19th century. He is best known for his influential theory of
electromagnetism, but he made important contributions to other areas of physics as well.
Maxwell was born on 13 June 1831 in Edinburgh, Scotland, and raised at his parents’
country estate near the village of Parton. As a wee lad, Maxwell showed remarkable
curiosity, continually inquiring about the workings of things and pursuing his own
investigations. His mother was responsible for his education until her death in 1839.
Maxwell was then sent, after two difficult years with a private tutor, to Edinburgh
academy where he was initially teased for his rural ways. Maxwell persevered, however,
and eventually became a budding scholar, publishing a paper (1846) on a method for
drawing oval curves. As a student at Edinburgh University (1847-50) and Cambridge
University (1850-54), Maxwell read widely and was respected for his quick mind and
physical intuition. He remained at Cambridge for two years after graduation, obtaining a
fellowship from Trinity College in 1855, and held professorships at Marischal College in
Aberdeen (1856-60) and King’s College in London (1860-1865). On the death of his
father in 1865, Maxwell returned to the family estate in Scotland where he continued his
research and farmed. He was appointed first professor of experimental physics at
Cambridge University in 1871, and he planned and developed Cambridge’s newly
established Cavendish Laboratory. Maxwell’s research was mainly on electromagnetism
(1854-79), the kinetic theory of gases (1859-79), color vision (1849-70), and the structure
of Saturn’s rings (1855-59).
The close relationship between electricity and magnetism was known well before
Maxwell’s interest in it. Hans Christian Oersted demonstrated the effect of an electric
current on a magnetic compass in 1820, and Michael Faraday showed that a moving
magnet could induce an electric current in 1831. In his first paper on electromagnetism
(1856), Maxwell explored an analogy (suggested by William Thomson, later Lord
Kelvin) between streamlines in fluid flow and the lines of electric or magnetic force
proposed by Faraday. A second paper (1861-2) developed a mechanical model of an
all-pervading medium (the ether) in which the electric and magnetic fields would
conform to known experimental results. Near the end of this paper, Maxwell calculated
the propagation speed of transverse electromagnetic waves in this hypothetical ether,
noted that this speed closely matched the experimentally known speed of light (first
determined by Armand Fizeau in 1849), and concluded that light consists of such waves.
In subsequent publications, including his Treatise on Electricity and Magnetism (1873),
Maxwell further developed and extended his electromagnetic theory.
In his work on the kinetic theory of gases, Maxwell was the first to apply statistical
methods to physical processes (1860), deriving a probability distribution for the velocities
of molecules in a gas. He used this distribution to investigate gas properties such as
diffusion and viscosity, and (with his wife, Katherine) performed experiments on gas
viscosity (1865) that led to further theoretical advances. Using devices of his own
invention, Maxwell resurrected Thomas Young’s three-receptor theory of color vision
(by showing that any color can be visually matched by appropriate proportions of three
primary colors) and established that color blindness is caused by deficiencies in one or
more receptors. He also projected the first color photograph (of a Scottish tartan) in 1861.
The structure of Saturn’s rings was announced as the theme of the 1855 Adams prize
competition at Cambridge. In response, Maxwell showed that solid or fluid rings would
disintegrate and that the rings are stable only if they consist of many small particles; he
won the prize and went on to write more on the topic.
Maxwell’s electromagnetic theory furthered science in many critical ways. It unified the
phenomena of electricity, magnetism, and light, suggested types of electromagnetic
radiation (e.g., radio waves, discovered by Heinrich Hertz in 1888) other than light, and
advanced the physical concept of a field. The unsuccessful search for Maxwell’s ether,
whose existence was made doubtful by an experiment of Albert Michelson and Edward
Morley in 1887, led directly to Albert Einstein’s special theory of relativity; however,
Maxwell’s electromagnetic equations were not overturned by Einstein’s theory and, in
fact, supported it. Maxwell was adept at using analogies (such as his mechanical model of
the ether) without tying his conclusions to them. Moreover, electromagnetic radiation
(specifically thermal radiation) as well as the molecular concepts and statistical methods
employed by Maxwell (and Ludwig Boltzmann) in the kinetic theory of gases played
significant roles in the development of quantum mechanics.
C. W. F. Everitt, James Clerk Maxwell: Physicist and Natural Philosopher, 1975.
Martin Goldman, The Demon in the Aether: the Story of James Clerk Maxwell, 1983.