James Clerk Maxwell and the Electrodynamic Theory of Light

James Clerk Maxwell and the Electrodynamic Theory of Light

1 About James Maxwell's life

The Scottish physicist James Clerk Maxwell (1831-1879) is widely considered to have been one of the most significant figures of the 19^th century. As a child, Maxwell was enrolled in the Edinburgh Academy; he spent his free time "drawing curious diagrams and making rough mechanical models".

These pursuits bore signs of talent and originality. Encouraged by his father, the fourteen-year-old Maxwell produced his first publication: a paper describing a simple mechanical means of drawing mathematical curves with a piece of string.

This combination of algebraic mathematics with elements of geometry would remain a distinctive feature of Maxwell's work. After graduating from Cambridge in 1854, he turned his attention towards electrical science. He completed and unified the laws of electricity and of magnetism set down by Ampère, Gauss and Faraday. Maxwell modifies Ampère's Law by adding a single term to it. This was what was needed to make the laws consistent with the conservation of charge. However, the     addition of this term led to a remarkable prediction: the existence of electromagnetic waves. Maxwell's formulation of electricity and magnetism was published in A Treatise on Electricity and Magnetism (1873), which included the formulas today known as the Maxwell Equations. With the full set of equations, he was able to calculate the speed of these waves. He found that their speed was a constant, independent of the nature of the electric and magnetic fields.

What Maxwell found was that electromagnetic waves travelled at the speed of light. Thus, the Maxwell equations not only unify the theories of electricity and the magnetism, but of optics as well. In other words, electricity, magnetism, and light could all be understood as aspects of a single object: the electromagnetic field.

As a consequence, the Maxwell equations made the physical prediction that "light travels with the same speed, in all directions".

With the German physicist Rudolf Julius Emanuel Clausius (1822-1888), he developed the Kinetic theory of gases. His studies of this theory led him to propose the Maxwell's demon paradox. Maxwell's demon (termed a "finite being by Maxwell") is a tiny hypothetical creature that can see individual molecules. He can make heat flow from a cold body to a hot one by opening a door whenever a molecule with above average kinetic energy approaches from the cold body, or below average kinetic energy approaches from the hot body, then quickly closing it. This process appears to violate the Second Law of Thermodynamics, according to which it is impossible for a self -acting machine to convey heat from one body to another at a higher temperature, however , it was used by Maxwell to show that the Second Law of Thermodynamics is a statistical law describing the properties of a large number of particles.

Maxwell made numerous other contributions to the advancement of science. He argued that the rings of Saturn were small individual particles, performed experiments which showed that viscosity varied directly with temperature.

Refutes Evolutionary Thinking

Maxwell strongly opposed Darwin's theory of evolution, which was becoming popular at that time. He believed that the speculations involved in evolutionary thinking contradicted scientific evidence. In a paper he presented to the British Association for the Advancement of Science in 1873, he said: "No theory of evolution can be formed to account for the similarity of molecules, for evolution necessarily implies continuous change.. The exact equality of each molecule to all others of the same kind gives it . the essential character of a manufactured article, and precludes the idea of its being eternal and self-existent."

Maxwell was able to refute evolutionary thinking in another important way. He mathematically disproved the nebular hypothesis proposed in 1796 by French atheist, Laplace. Laplace suggested that the solar system began as a cloud of gas which contracted over millions of years to produce planets and so on. Laplace claimed there was thus no need for a Creator. This philosophy was eagerly embraced by the opponents of Christianity.

However, Maxwell demonstrated two major flaws in Laplace's theory, and proved mathematically that such a process could not occur. Laplace's theory was subsequently discarded.

Maxwell was convinced that scientific investigation and the teachings of the Bible were not only compatible but should be linked together. This was reflected in a prayer found among his notes: "Almighty God, Who hast created man in Thine own image, and made him a living soul that he might seek after Thee, and have dominion over Thy creatures, teach us to study the works of Thy hands, that we may subdue the earth to our use, and strengthen the reason for Thy service; so to receive Thy blessed Word, that we may believe on Him Whom Thou hast sent, to give us the knowledge of salvation and the remission of our sins. All of which we ask in the name of the same Jesus Christ, our Lord."

Maxwell died of abdominal cancer at Cambridge on November 5, 1879, aged 48. He was greatly respected by those he had known and with whom he had worked. One of his close colleagues wrote: "We his contemporaries at college, have seen in him high powers of mind and great capacity and original views, conjoined with deep humility before his God, reverent submission to His will, and hearty belief in the love and atonement of that Divine Saviour Who was his portion and comforter in trouble and sickness."

The 1888 announcement by the German physicist Heinrich Hertz (1857-1894) that he had transmitted and received electromagnetic waves was almost universally received as a glorious confirmation of Maxwell's work, and secured Maxwell's status within popular and scientific culture as a Victorian physicist without equal.