John Herapath

from Wikipedia, the free encyclopedia

John Herapath (born May 30, 1790 in Bristol , † February 24, 1868 in Lewisham ) was an English physicist and astronomer who partially anticipated the kinetic gas theory , but what was hardly noticed by his contemporaries and he as an amateur scientist who himself In addition, he was not committed to experimental research, but primarily to theoretical speculation, was considered an outsider in Great Britain.

Life

Herapath was the son of a malt maker and cousin of the doctor and chemist William Bird Herapath . He was mostly self-taught and had studied French classical works in physics, mathematics and astronomy in particular. In 1815 he married and in the same year gave up his profession as a malt manufacturer and opened a private school for mathematics, which did not go well. In 1837 he had eleven children. From 1829 he began to be interested in the then new railway and he began to write articles about it. In 1836 Herapath became the editor of The Railway Magazine (today Railway Gazette International and not to be confused with the magazine of the same name, which was first published in 1897), which gave him the limited opportunity to publish his scientific ideas. The magazine (known as Herapath's Railway and Commercial Journal) was successful at the time.

plant

Herapath's scientific work began with astronomical work and the attempt to find a mechanical explanation of gravitation . Following Isaac Newton's speculations about gravitation as a result of density differences in the ether, he came to the conclusion that the gravitational force must be temperature-dependent, which led him to occupy himself with statistical mechanics. He came to the conclusion that there must be a connection between temperature and particle speed.

Herapath postulated that the momentum of a particle in a gas is nothing more than a measurement of the temperature of the gas. In contrast to the later kinetic gas theory, he preferred to use the concept of momentum over that of kinetic energy in order to avoid existing problems with concepts such as elastic and inelastic collisions. Although he obviously did not know the work of Daniel Bernoulli (who, with his Hydrodynamica of 1738 and the interpretation of heat as internal motion, is also considered the forerunner of the kinetic gas theory), he was led to the obvious, but not entirely correct, assumption that the product of the The pressure P and the volume V are proportional to the square of what he called the “correct temperature”. However, the correct relationship is proportional to absolute temperature, not its square. The error resulted from the identification of the pulse with the temperature.

He developed his theory from 1814 and submitted his ideas to the Royal Society in 1820. Herapath's work, however, was rejected by Sir Humphry Davy because he did not agree with absolute zero temperature, as Herapath's theory had to exist. In 1821, however, Herapath managed to publish his work in the Annals of Philosophy , a journal in which u. a. and Michael Faraday posts created. However, the work seemed to arouse little interest among his contemporaries. The exception was James Prescott Joule , who published a brief outline of the work in 1848. Meanwhile, Herapath launched a campaign against Davy and the Royal Society in The Times newspaper .

In 1836, on the basis of his gas theory, he calculated the mean speed of particles in a gas and, from this, the speed of sound (a result that he announced as early as 1832 at the meeting of the British Association for the Advancement of Science). Joule reproduced these results, but is wrongly commonly referred to as the originator.

He revised his theories in the 1840s, based primarily on the experimental work of Thomas Graham and Henri Victor Regnault , and published them in his two-volume Mathematical Physics in 1847 . James Clerk Maxwell , who is considered the founder of the kinetic gas theory, praised Herapath as a forerunner in his work On the Dynamical Theory of Gases (1866)

On January 7, 1831, Herapath, who was also involved in astronomy, discovered the Great Comet of 1831 .

Fonts

literature

  • Stephen Brush : The development of the kinetic theory of gases I. John Herapath. In: Annals of Science. Volume 13, 1957, p. 188.
  • Stephen Brush (Ed.): Mathematical physics and selected papers of John Herapath. Johnson Reprint Corporation, New York 1972.
  • Stephen Brush: The kind of motion we call heat. North Holland 1976.
  • Stephen Brush, Article John Herapath in Dictionary of Scientific Biography

Web links

Individual evidence

  1. A preliminary note on this was published in 1816
  2. Philosophical Transactions of the Royal Society, Volume 157, 1867, Niven (ed.), The scientific papers of James Clerk Maxwell, Cambridge University Press, Volume 2, 1890, p. 28. He points out that, despite the flawedness of his theory Herapath applied them in many cases to numerical values ​​of experiments and his speculations were always ingenious and contributed a lot to the elucidation of the problems treated ( This author however, has applied his theory to the numerical results of experiment in many cases, and his speculations are always ingenious , and often throw much real light to the questions treated ).
  3. ^ J. Herapath: Comet seen, January 7, 1831. In: Monthly Notices of the Royal Astronomical Society. Vol. 2, 1831, pp. 6-7. ( bibcode : 1831MNRAS ... 2 .... 6H ).