John Herapath

Who was John Herapath?

John Herapath was an English physicist who gave a partial account of the kinetic theory of gases in 1820 though it was neglected by the scientific community at the time.

Herapath's scientific interests started with an attempt to provide a mechanistic explanation for gravity. Motivated by his search for a mechanical explanation of gravitation, he started to consider how a system of colliding particles could give rise to action at a distance. In considering the effect of the high temperatures near the Sun on his gravific particles he was led to a relationship between temperature and particle velocity.

Herapath postulated that the momentum of a particle in a gas is a measure of the absolute temperature of the gas. He used momentum, rather than the kinetic energy on which the later established theory is based, as it seemed to him to avoid some difficulties around whether elastic collisions were possible between indivisible atoms. Apparently ignorant of Daniel Bernoulli's work, he was led to the incorrect, but suggestive, relationship that expresses the product of pressure P and volume V as proportional to the square of his true temperature.