The Greatest Mistake In The History Of Physics

The Greatest Mistake In The History Of Physics

“Poisson attempted to disprove Fresnel’s theory by showing that it led to a logical fallacy: reductio ad absurdum. Poisson’s idea was to derive a prediction made by the light-as-a-wave theory that would have such an absurd consequence that it must be false. If the prediction was absurd, the wave theory of light must be false. Newton was right; Fresnel was wrong. Case closed.

Except, that itself is the greatest mistake in the history of physics! You cannot draw a conclusion, no matter how obvious it seems, without performing the crucial experiment. Physics is not decided by elegance, by beauty, by the straightforwardness of arguments, or by debate. It is settled by appealing to nature itself, and that means performing the relevant experiment.”

It’s now been 200 years since one of the most embarrassing moments in the history of physics. The famed scientist Simeon Poisson, at a conference on the nature of light, discounted one of the entrant’s theories because its predictions were completely absurd. He attempted to have the contestant, a young civil engineer named Fresnel, laughed out of the competition because his theory predicted that, at the center of a shadow, a bright spot of light should appear. Yet Poisson made these moves without ever performing the experiment that would decide whether Fresnel was right or wrong!

You can’t do that in science, no matter how sure you are that you know what is or isn’t absurd. Nature must decide. And that, in science, is always the lesson.