James Clerk Maxwell is regarded by most modern physicists as the scientist of the 19th century who had the greatest influence on 20th-century physics; he is ranked with Sir Isaac Newton and Albert Einstein for the fundamental nature of his contributions. In 1931, at the 100th anniversary of Maxwell's birth, Einstein described the change in the conception of reality in physics that resulted from Maxwell's work as "the most profound and the most fruitful that physics has experienced since the time of Newton." The concept of electromagnetic radiation originated with Maxwell, and his field equations, based on Michael Faraday's observations of the electric and magnetic lines of force, paved the way for Einstein's special theory of relativity, which established the equivalence of mass and energy. Maxwell's ideas also ushered in the other major innovation of 20th-century physics, the quantum theory. His description of electromagnetic radiation led to the development (according to classical theory) of the ultimately unsatisfactory law of heat radiation, which prompted Max Planck's formulation of the quantum hypothesis--i.e., the theory that radiant-heat energy is emitted only in finite amounts, or quanta. The interaction between electromagnetic radiation and matter, integral to Planck's hypothesis, in turn has played a central role in the development of the theory of the structure of atoms and molecules.

BIBLIOGRAPHY: Maxwell's works include Theory of Heat, 3rd ed. (1872, reprinted 1970), and A Treatise on Electricity and Magnetism, 3rd ed., 2 vol. (1892, reissued 1954). Maxwell's original papers are collected in W.D. NIVEN (ed.), The Scientific Papers of James Clerk Maxwell, 2 vol. (1890, reissued 2 vol. in 1, 1965).

Furthermore, John notes an interesting historical parallel:
Newton was born in the same year that Galileo died. Einstein was born in the same year (1879) that Maxwell (alas only 48) died.