Physicist and astronomer — Sir James Hopwood Jeans (Ormskirk, 1877 – Dorking, 1946) was a British physicist, astronomer and mathematician. Trained at Cambridge, he made significant contributions to radiation theory, gas dynamics and cosmogony. Together with Lord Rayleigh he formulated the Rayleigh–Jeans law for blackbody radiation, valid at low frequencies: its failure at high frequencies — the so-called “ultraviolet catastrophe” — was one of the problems that led Planck to quantum theory. In astrophysics he introduced the criterion establishing when a cloud of gas can gravitationally collapse to form stars. He was also a celebrated science populariser, author of highly successful books.

Theories and contributions

  • Rayleigh–Jeans law — Describes the spectral density of blackbody radiation at low frequencies: u(ν,T)=8πν2c3kBTu(\nu,T) = \dfrac{8\pi \nu^2}{c^3} k_B T; its failure at high frequencies is the ultraviolet catastrophe.
  • Jeans mass — Critical mass beyond which a cloud of gas collapses under its own gravity, forming stars.

Linked atoms

1 linked atoms.

21 Introduzione alla meccanica quantistica