Hendrik Antoon Lorentz | Biography

Lorentz was born in Arnhem, Holland, on July 18, 1853. At the age of seventeen, he entered the University of Leyden and earned his bachelor's degree a year later. He then returned home and studied on his own for the doctorate, supporting himself by teaching classes at night. He received his degree in 1875 and was appointed to the chair of theoretical physics at Leyden at the age of twenty-four. He remained in this position throughout his academic career. Lorentz's doctoral thesis was entitled The Theory of Reflection and Refraction of Light. It dealt with unsolved problems of James Clerk Maxwell's theory of electromagnetism, the behavior of light at boundaries between two media. Lorentz showed how Maxwell's equations could be modified to deal with such conditions. Lorentz next attacked the problem of the transmission of light through the ether. According to Maxwell, an electromagnetic wave is caused by the oscillation of electric charges. But what is the source of the charges that oscillated to produce light? Lorentz suggested that atoms in the ether consist of electrically charged particles. He referred to these particles as "electrons," although these are not the same as the electrons later discovered by Joseph J. Thomson. Lorentz added a term to Maxwell's equations to account for the force of the magnetic field on these "electrons." If this theory were correct, Lorentz suggested, then the properties of light should be affected by an external magnetic field. That field should influence the behavior of the "electrons " that propagate light. Lorentz's graduate student, Pieter Zeeman (1865-1943), investigated this questions and found that, indeed, the spectral lines of an element undergo a change in the presence of a magnetic field. This phenomenon came to be known as the Zeeman effect. For their contributions to the study of the effects of magnetic fields on radiation, Lorentz and Zeeman shared the 1902 Nobel Prize for physics. Lorentz next considered the negative results obtained by Albert Abraham Michelson and Edward Morley in their experiment on the speed of light. He suggested that those results could be explained by assuming that matter, consisting of "electrons," decreases in length as it moves. The faster it moves, the more the matter (and the "electrons" of which it is made) is shortened. At everyday velocities, this shortening is much too small to be observed. But at velocities close to the speed of light, the shortening becomes significant. And, at the speed of light, the linear dimension of an object becomes zero. One consequence of this idea, then, is that nothing can move faster than the speed of light since no object can have a negative length. This conclusion is similar to one derived somewhat later by Albert Einstein in his special theory of relativity. Lorentz's conclusion was also similar to one proposed by the Irish physicist, George F. FitzGerald (1851-1901), in 1895. Lorentz went on, however, to point out that the shortening of an object in motion should produce another effect. As an "electron" approaches the speed of light, he said, its volume would become smaller and smaller until, at the speed of light, it becomes zero. Since Lorentz believed that the mass of an object depends on its volume, this change means that the "electron's" mass (and that of matter) increases with velocity. Experiments carried out in 1900 showed this conclusion to be correct. Lorentz was active throughout his life in professional and national organizations and activities. He chaired a committee, for example, formed to find a way of draining the Zuider Zee and crating new land for Holland. He died in Haarlem on February 4, 1928. During his funeral, six days later, all telegraph and telephone services in the nation were stopped for three minutes in honor of his contributions to science and country.