ABSTRACT

The uncertainty about the ultimate nature of matter is of course much older than physics. Indian and Greek philosophers already disputed whether matter was granular or continuous, made of atoms or made of symmetries. But their theories were based on pure thinking, without much input from Nature itself. Gases where only elastic scattering among molecules and with the confining boundaries occurs are called ideal gases. Noble gases are a particularly good example. John Dalton, of modest origins and educated by Quakers, was appointed teacher of mathematics and natural philosophy in 1793 at the “New College” in Manchester, a dissenting academy not conforming to the Church of England. The discovery of Brownian motion by the botanist Robert Brown in 1827 could have lent strong support to the atomist view, but passed almost unnoticed by physicists.