'No one dared question his results': How thermodynamics sparked a heated debate about Earth's age in the 19th century
(Image credit: Universal Images Group/Getty Images) With Carnot's vision, the way hot objects cool down began to be understood, raising hopes that the resolution of one particular problem might be imminent: the determination of the Earth's age.
Key points
- Were we to somehow guess how hot our planet was at birth, thermodynamics could then be used to tell us how much time had gone by for it to have cooled to its present temperature.
- His evidence was based on lead isotopic analysis that he used to calculate the age of the Canyon Diablo meteorite, which was discovered in Arizona in 1891.
- It gives us, humans, a way to understand how particles behave when there is a lot of them without needing to refer to each one of them individually.
Earth's true age was a subject of much debate among scientists in the 19th century.
Additional details
- Understanding the dynamics of heat meant a lot to nineteenth-century scientists — so much so that many saw in it the roots of a philosophy so universal and powerful that they thought it should guide us through all our lives.
- In this excerpt from "This Is Life: A Journey from Inside Your Body to Beyond Earth" (University of Chicago Press/Picador, 2026), author and physicist Christophe Galfard looks at the progression among scientists who were coming to realize that thermodynamics was an essential piece of this long-standing puzzle.
- A prominent scientist became so convinced that this was the case that he locked himself up in his house and overheated it, thus shielding himself from all mortal diseases (ageing and death included).
- He then calculated how long it would take it to cool down from being red hot to its present temperature, and declared that the Earth was something between 40 and 400 million years old.
- The experience was a true torture for the occasional guests who came to visit him, not to mention his wife, who had to endure it day and night.
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