Age of Invention: The Idea of Energy

It’s been a busy few weeks for me, research-wise. My last few posts have been less frequent than usual, but all the more researched and detailed for it. My last post, on why the non-electric telegraph wasn’t invented earlier, was supposed to be a very quick one. But after a few days it had ballooned to 5,000 words. A fun rabbit-hole to dive down, but a distraction nonetheless — because for months my focus has really been on the history of energy.

I’m still piecing a lot of disparate strands together, but it’s been very striking to me just how late our understanding of concepts like force, work, efficiency, heat, and energy took shape. It was not really until the mid-nineteenth century, for example, with the experiments of John Prescott Joule, William Thomson (later Baron Kelvin), and others that the laws of thermodynamics began to be worked out concretely.

Even though Sadi Carnot intuited many of the core concepts as early as the 1820s, he did so while thinking of heat as a fluid called “caloric” — just like most other scientists at the time. Even in the 1850s, when Joule’s ideas had already been widely publicised, the likes of Isambard Kingdom Brunel and Robert Stephenson were still talking in terms of caloric when discussing the performance of steam- and hot air engines. And yet, despite using flawed theories, steam engines underwent substantial improvement in thermal efficiency.