Ideas: A History from Fire to Freud

Established in 1871, the laboratory opened its doors three years later. It was housed in a mock-Gothic building in Free School Lane, boasting a façade of six stone gables and a warren of small rooms connected, in Steven Weinberg’s words, ‘by an incomprehensible network of staircases and corridors’.² In the late nineteenth century, few people knew, exactly, what ‘physicists’ did. The term itself was relatively new. There was no such thing as a publicly funded physics laboratory – indeed, the idea of a physics laboratory at all was unheard-of. What is more, the state of physics was primitive by today’s standards. The discipline was taught at Cambridge as part of the mathematical tripos, which was intended to equip young men for high office in Britain and the British empire. In this system there was no place for research: physics was in effect a branch of mathematics and students were taught to learn how to solve problems, so as to equip them to become clergymen, lawyers, schoolteachers or civil servants (i.e., not physicists).

³ During the 1870s, however, as the four-way economic competition between Germany, France, the United States and Britain turned fiercer – mainly as a result of the unification of Germany, and the advances of the United States in the wake of the Civil War – the universities expanded and, with a new experimental physics laboratory being built in Berlin, Cambridge was reorganised. William Cavendish, the seventh duke of Devonshire, a landowner and an industrialist, whose ancestor Henry Cavendish had been an early authority on gravity, agreed to fund a laboratory provided the university promised to found a chair in experimental

physics. When it was opened, the Duke was presented with a letter, informing him (in elegant Latin), that the laboratory was to be named in his honour.⁴

The new laboratory became a success only after a few false starts. Having tried – and failed – to attract first William Thomson, later Lord Kelvin, from Glasgow (he was the man who, among other things, conceived the idea of absolute zero and contributed to the second law of thermodynamics), and second Hermann von Helmholtz, from Germany (who had scores of discoveries and insights to his credit, including an early notion of the quantum), Cambridge finally offered the directorship to James Clerk Maxwell, a Scot and a Cambridge graduate. This was fortuitous. Maxwell turned into what is generally regarded as ‘the greatest physicist between Newton and Einstein’.

⁵ Above all, Maxwell finalised the mathematical equations which provided a fundamental understanding of both electricity and magnetism. These explained the nature of light but also led the German physicist Heinrich Hertz at Karlsruhe in 1887 to identify electromagnetic waves, now known as radio.

Maxwell also established a research programme at the Cavendish, designed to devise an accurate standard of electrical measurement, in particular the unit of electrical resistance, the ohm. Because of the huge expansion of telegraphy in the 1850s and 1860s, this was a matter of international importance, and Maxwell’s initiative both boosted Britain to the head of this field, and at the same time established the Cavendish as pre-eminent in dealing with practical problems and devising new forms of instrumentation. It was this latter fact, as much as anything, that helped the laboratory play such a crucial role in the golden age of physics, between 1897 and 1933. Cavendish scientists were said to have ‘their brains in their fingertips’.⁶

Maxwell died in 1879 and was succeeded by Lord Rayleigh, who built on his work, but retired after five years to his estates in Essex. The directorship then passed, somewhat unexpectedly, to a twenty-eight-year-old, Joseph John Thomson, who had, despite his youth, already made a reputation in Cambridge as a mathematical physicist. Universally known as ‘J. J.’, Thomson, it can be said, kick-started the second scientific revolution, to create the world we have now. The first scientific revolution, it will be recalled from Chapter 23, occurred – roughly speaking – between the astronomical discoveries of Copernicus, released in 1543, and those of Isaac Newton, centring around gravity, and published in 1687 as Principia Mathematica. The second scientific revolution would revolve around new findings in physics, biology, and psychology.