This is a #linocut of French #mathematician & #physicist Joseph Fourier (1768-1830) 🐡🧪🎢🧮 #histsci remembered for his work on Fourier series, Fourier transforms, Fourier’s law of conduction, Fourier analysis & harmonic analysis & their use to solve heat transfer problems & credited with proposing 🧵1/
the greenhouse effect as early as 1824.
Being a commoner he could not seek a commission in the scientific corps of the army but took a military lectureship in math. He took a prominent part in promoting the French Revolution in his district & was briefly imprisoned by the Terror. In 1795 he was 🧵2/
appointed to École Normale & later succeeded Lagrange at École Polytechnique. He accompanied Napoleon as scientific adviser on his Egyptian expedition in 1798 & in 1801 Napoleon appointed him Prefect of the Department of Isère in Grenoble. There he began to experiment on the propagation of heat. 🧵3
In 1820 he published his theorem on polynomial real roots, that a polynomial with real coefficients has a real root between any 2 consecutive zeros of its derivative (corollary of a theorem by Budan known as Fourier’s theorem). In 1822 he succeeded Delambre as Permanent Secretary of the French 🧵4/
Academy of Sciences &published his heat flow research which included his important claim that any function of a variable, continuous or discontinuous, can be expanded in a series of sines of multiples of the variable. The idea is true (with some conditions, discovered by Dirichlet) & a breakthrough.
This is the foundation for what we call the Fourier transform, an invaluable tool in math, physics & engineering. During the 1820s he realized that the Earth, at its distance from the Sun should be colder if it is only heated by solar radiation. He wrongly thought Earth must receive significant 🧵6/
radiation from interstellar space but he did consider the correct answer that the atmosphere acts as an insulator - the first conception of what we know as the greenhouse effect.
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