Ludwig Boltzmann
Boltzmann, Ludwig (1844-1906), an Austrian physicist, made a major contribution to the foundation and development of statistical mechanics, the study of temperature, pressure, and related phenomena by a mathematical analysis of movements of molecules that are assumed to obey the laws of mechanics.
The son of an Austrian taxation official, Ludwig Eduard Boltzmann grew up in Wels and Linz. He earned his doctorate in 1866 from the University of Vienna. His doctoral thesis, written under the direction of Josef Stefan, was on the kinetic theory of gases. He began his academic career the following year with an appointment at the Physikalisches Institut in Vienna, which was followed by a series of professorial positions in different related disciplines. He left a professorship in theoretical physics at the University of Graz (1869-1873), in southeast Austria, for a professorship in mathematics at the University of Vienna (1873-1876), and then returned to the University of Graz (1876-1879) as a professor of experimental physics. After serving as director of the Physikalisches Institut (1879-1889), Boltzmann took a position as professor of theoretical physics at the University of Munich. In 1894, he returned to Vienna as professor of theoretical physics at the university, succeeding his mentor, Josef Stefan. The following year, Ernst Mach (whose name today is used to measure the speed of sound, as the Mach I) was appointed to the chair of history and philosophy of science at Vienna. The two men not only were scientific opponents, with Boltzmann championing the point of view of the “atomists” and Mach of the “energeticists,” but also were on bad personal terms. Boltzmann's dislike of working alongside Mach led him to move to the University of Leipzig in 1900, where he became professor of theoretical physics. Even though the move made him the colleague of his most vigorous scientific opponent, Wilhelm Ostwald, Boltzmann and Ostwald had a good personal relationship. Nonetheless, a bout of severe depression led Boltzmann to make a suicide attempt while in Leipzig.
Boltzmann at least partly in jest, attributed his peripatetic nature to the fact that he was born during the dying hours of a Mardi Gras ball. He recognized early on that he was subject to what today is called bipolar disorder, characterized by periods of mania alternating with periods of depression, usually separated by lengthy intervals of normal mood. How much of his depression was attributable to chemical imbalances and how much to the lack of acceptance of his ideas can never be known for sure.
After Mach's retirement from the University of Vienna in 1901, Boltzmann returned there in 1902 to his chair of theoretical physics, which had remained unfilled in the interim. The university also honored him with a second chair, which Mach had just vacated. Responsible now for teaching Mach's course in the philosophy of science, Boltzmann became famous as a lecturer in this field. The audience for his lectures soon grew too large to be accommodated in the largest available lecture hall. Boltzmann's reputation even reached the imperial court, and Austrian emperor Franz Josef invited him to the royal palace.
Boltzmann is best known for establishing statistical mechanics, the branch of science independently invented by the American mathematical physicist Josiah Willard Gibbs. Their work connected the properties and behavior of molecules, atoms, or elementary particles with the large-scale properties of the substances of which they are the building blocks. Boltzmann used probability to describe how atomic properties determine the properties of matter.
Over the course of his career, Boltzmann made significant contributions to mechanics, dynamics, and electromagnetism, all of which were being developed during his student years. He was one of the first European scientists to recognize the importance of Scottish physicist James Clerk Maxwell's research in the field of electromagnetism. Theory of Electricity and Magnetism, a book based on Boltzmann's lectures on Maxwell's theories, which was published in 1897 with a preface by Boltzmann, helped disseminate Maxwell's work.
Boltzmann's first published paper (1865) was stimulated by a lecture given by Josef Stefan on electrical theory. Three years later, he published a paper on thermal equilibrium in gases, which both cited and extended Maxwell's work on this topic. In 1871, he obtained an equation for the distribution of atoms due to collision. According to this equation, which became known as the Maxwell-Boltzmann distribution, the average amount of energy required for atomic motion in all directions is equal. In 1884, Boltzmann expanded on the work of his mentor by demonstrating how the empirical law for black-body radiation that Stefan formulated in 1879 could be derived from the principles of thermodynamics. According to the Stefan-Boltzmann law, the total energy radiated from a black body is proportional to the fourth power of its absolute temperature. The law is illustrated by the fact that a blue star that is the same size as a red star is very much brighter. In the 1890's, Boltzmann derived the second law of thermodynamics from the principles of mechanics. He asserted that entropy increases almost always, rather than always.
Many scientists rejected Boltmann's ideas. At an 1895 scientific meeting in the German seaport city of Lübeck, a heated debate took place between Boltzmann and Wilhelm Ostwald. Asserting that Boltzmann was wrong when he said that everything could be explained with suitable equations, Ostwald said, “The actual irreversibility of natural phenomena thus proves the existence of processes that cannot be described by mechanical equations, and with this the verdict on scientific materialism is settled.” Boltzmann and his backers countered with a strong and vocal opposition. A youthful eyewitness to the debate, physicist Arnold Sommerfeld, compared the ensuing argument to “the battle of the bull [Boltzmann] with the supple fighter [Ostwald].” According to Sommerfeld, Boltzmann's arguments were convincing, and the young mathematicians in attendance sided with Boltzmann.
Ostwald continued, however, as spokesman of those European scientists who failed to fully understand the statistical basis for Boltzmann's ideas. Despite the fact that Ernst Mach did not get along well with Boltzmann, he felt the tone of the scientific debates was overly heated and tried to reconcile the two schools of thought.
In 1904, Boltzmann traveled to the United States, where he lectured on applied mathematics at the St. Louis World's Fair. He went on to California, where he visited Stanford University and the University of California at Berkeley. During this visit. Boltzmann learned about new discoveries concerning radiation that would shortly validate his theories. Upon his return to Austria, he continued to defend his belief in atomic structure.
Despite his vigorous rebuttals, however, many scientists continued to challenge his theories, and he worried that his life's work was on the verge of collapse. In 1906, suffering from illness and depression, Boltzmann committed suicide. He died before seeing his work confirmed by scientific discoveries of the 1900's that proved atomic theory.
In recent years, Boltzmann has been recognized as a pioneer of quantum mechanics. By introducing the theory of probability into his statistical interpretation of the second law of thermodynamics, he broke with the classical idea that fundamental laws have to be strictly deterministic. In an 1872 paper, Boltzmann introduced the idea of discrete energy levels. At a scientific meeting in Halle, Germany, in 1891, Boltzmann anticipated by just under a decade Max Karl Ernst Ludwig Planck's law that assumed the quantization of energy. In Boltzmann's lectures on natural philosophy in 1903, he anticipated Albert Einstein's theory of special relativity by treating space and time coordinates equally.