Jean-Baptiste Joseph Fourier

Mathematician and physicist — Jean-Baptiste Joseph Fourier (Auxerre 1768 – Paris 1830) was a French mathematician and physicist. Orphaned, he was educated by the Benedictines and became a teacher; he took part in Napoleon’s expedition to Egypt and later became prefect of Isère. His masterwork, the Théorie analytique de la chaleur (1822), studied the propagation of heat in solid bodies and introduced the tool that bears his name: the decomposition of any periodic function into a sum of sines and cosines. Fourier series and transforms are today indispensable in physics, engineering, acoustics and signal processing. He was also the first to intuit the greenhouse effect of the Earth’s atmosphere.

Trivia

In 1824 Fourier calculated that the Earth should be colder than it actually is and hypothesised that the atmosphere retains heat, formulating the first idea of the greenhouse effect.

Theories and contributions

• Fourier series — Any periodic function can be written as a sum of sines and cosines: $f(x)=\tfrac{a_0}{2}+\sum_n(a_n\cos nx+b_n\sin nx)$.
• Heat equation — Describes the diffusion of heat in time and space: $\partial_t u=\alpha\,\nabla^2 u$.
• Greenhouse effect — First hypothesis that the Earth’s atmosphere retains part of the radiation, warming the planet.

Featured in chapters

08b

Linked atoms

1 linked atoms.

08b Termologia

• Conduction