The Shrivelling Apple

Put an apple on a windowsill and leave it for a month. The inside shrinks, the skin does not, and it wrinkles. For about seventy years, that was the best available scientific explanation for the Himalayas. Episode 2 of The Slow Machine is about a good theory — simple, mathematical, and wrong. A cooling, shrinking Earth with mountains for wrinkles. Lord Kelvin, the monarch of British physics, using it to put a clock on the age of the world, and Charles Darwin losing sleep over the answer. Eduard Suess in Vienna, who brought clean water to a city with cholera and then wrote the face of the whole Earth in four volumes. And the fossils that would not behave: a seed fern on four continents, and a freshwater reptile the size of a cat on both sides of the South Atlantic and nowhere else. The Slow Machine is a nine-part series on how we found out that the continents move, and why almost every clue came from an instrument built for something else entirely. Next time: Episode 3, "Two Facts That Cored the Apple" — how mountains turned out to be icebergs, and how the most certain number in nineteenth-century science was off by a factor of a hundred. — Guest voices: Derek M (Lord Kelvin) and Alex John (Eduard Suess), both found on Fiverr. Every quotation is listed with its source on this episode's page at theslowmachine.com. Written and narrated by Michael Goddard. Music composed with Suno. Sound effects from freesound.org, all Creative Commons 0. Every voice in this series is human.