My favorite “wrong” scientific theory is from the eighteenth century: It’s the so-called caloric theory of heat.
In the eighteenth and nineteenth centuries, steam engines proliferated. However, many of these engines were clumsy and inefficient, consuming vast quantities of expensive fuel.
A better explanation of how these engines work, how they process heat and ultimately convert it to mechanical energy, was badly needed. But it was not easily attained.
There was the phlogiston theory of combustion: a presumed substance that is released by things that burn, but absorbed by living plants. This theory was rejected by Lavoisier who developed a theory of combustion based on oxygen instead. But Lavoisier then proposed another invisible substance as an explanation of heat: the caloric. This was a substance that was supposed to be conserved, flowing from hot things to cold things.
This theory is not as nonsensical as it might appear today. In fact, it led to some significant successes, including the work of Sadi Carnot on the foundations of thermodynamics, and even improved theoretical estimates of the speed of sound.
Over the nineteenth century, it became evident that heat is not conserved. (E.g., a mechanical process can continue to generate heat without ever running out of “caloric”). Eventually, the presumed conservation law of caloric was absorbed into the modern concept of energy conservation. But it took many more decades before modern axiomatic thermodynamics, or better yet, statistical thermodynamics were born in the second half of the nineteenth century.
Now let me emphasize: the need was great. Tons of money was involved. And some of the finest scientific minds were trying to tackle the problem. Yet it still took many, many decades before the modern theory was born.
To me, the caloric theory teaches humility. Yes, we are smart apes. But not nearly as smart as we sometimes think. Even when the need is great and our finest minds are working on a problem, sometimes it takes generations to find the right answers. But the history of the caloric should also be a reminder to those who impatiently ask, “why can’t scientists figure out already?”
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