Heat — Jean-Baptiste-Joseph Fourier

Jean-Baptiste-Joseph Fourier proposed a theory that describes the relationship between temperature and heat content and how heat moves by conduction. He also was the first, in 1824, to describe the main components of the heat balance for the Earth. The heat balance drives weather and climate, and climate models used to investigate climate change are based on heat balance calculations. In this work, Fourier also described the phenomenon that we now know as the greenhouse effect; although at the time Fourier did not really understand what causes it to happen.

Fourier proposed his theory of heat conduction in the form of a differential equation, for which he also developed a general solution based on infinite series of sine and cosine functions. Fourier’s work stimulated a lot of interest among his contemporaries, particularly Simon Laplace. Fourier’s theory extended the scope of mathematical analysis, which was central to Laplace’s program for French science. As it turns out, Fourier’s mathematical theory also describes a variety of other phenomena, such as molecular diffusion, turbulent dispersion, and groundwater flow, and his series solution, now known as the Fourier series, has proven to be a very useful way of characterizing quantities that vary over time or in space. And so, Fourier’s work on heat flow remains as important today as when it was first introduced 200 years ago.

Jean-Baptiste-Joseph Fourier, physicist, is one of the 72 scientists and engineers named on the Eiffel Tower.