CONCEPT
The Two Clouds Lecture
Lord Kelvin’s April 1900 address to the
Royal Institution—in which the most celebrated physicist of his age refused to declare the science finished and instead pointed, with uncanny precision, at two unexplained anomalies that would become relativity and quantum mechanics—is the standing model for how an expert ought to forecast: not from confident destination but from honest cartography of present ignorance.
In April 1900, the seventy-five-year-old Lord Kelvin delivered a lecture at the Royal Institution in London with a title that has aged extraordinarily well: “Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light.” Far from announcing a finished physics—as the popular legend insists he did—Kelvin stood before his audience and pointed at two unresolved anomalies, two “clouds” hanging over the otherwise clear edifice of classical physics, which he could not dispel. The first was the Michelson-Morley result—the failure to detect the Earth’s motion through the luminiferous ether—which Einstein’s special relativity would resolve within five years. The second was an anomaly in the theory of heat radiation that classical physics could not explain; it would be dispersed by the quantum theory, born the same year in Max Planck’s work.
Kelvin had put