Laplace gave the theory of bodies so heavy that they would not let even light escape. This theory needs light to have a mass and hence is compatible with the corpuscular theory. So how did Laplace feel when the corpuscular theory was proved false by Thomas Young a decade later?


1 Answer 1


Short answer: Pierre-Simon Laplace was skeptic of Thomas Young, but he had to go silent after the works of Augustin-Jean Fresnel and François Arago.

Long answer

Laplace was the reference for the theory of corpuscular light. As you have mentioned, in 1796 Laplace considered that light may not be able to escape a start if the density is large enough, making some bodies invisible. Four years later, Young published his famous double slit experiment.

Now, all French opticians at the time were big followers of Laplace (Jean-Baptiste Biot, Etienne-Louis Malus, Arago, Siméon Denis Poisson and so on). When Young publishes his experiment and his defense for wave theory, historical sources (see reference below) tells us about how Young's result was received in France:

In France, however, Young's work was almost completely ignored. Not a word about it can be found in Haüy's Traité de physique of 1806 or Biot's longer Traité of 1816. Nor did the French corpuscularians respond in print to Young's detailed critique of Laplace's theory of extraordinary refraction in the Quarterly Review for 1809 or his criticism of Biot's theory of mobile polarization in the same magazine in 1814. In fact, Biot seems to have summed up the French attitude toward Young in a letter to Brewster in 1816:

I very much esteem the merit and talent of this distinguished scientist, but you will permit me to tell you that his witness has no more weight here than the authority of Aristotle against the observations of Galileo on motion... Even if his theory, which I do not know at all, were true...

Some French corpuscularians read Young only in private, like Malus (from the Malus' law of polarization). Other would clearly defect, like Arago (from the Arago spot, see below) in 1813.

With respect to Laplace, he seems to have kept his corpuscularian position but leaving the criticism to others. It would be the work of Fresnel that would change everything in France. Fresnel was already showing how diffraction could be explained with waves, but many were skeptics. In 1817, a commission made from the most prestigious French physicist of the time, including Laplace, proposed diffraction as the subject of the biannual physics prize competition:

The wording of the contest made it clear that the commissioners sought a corpuscular explanation of diffraction.

Fresnel who during this time was trying to fix all the problems of his wave theory, profited on the occasion and participated. Fresnel's work was so clear that the commission had no option but to give him the prize in 1819 even if his theory was not corpuscular. Laplace who read Arago's report on a follow-up work of Fresnel that explained double refraction, said that he

declared that he put this research above everything that had been communicated to the Académie in a long time.

Another great battle was that of Arago vs. Poisson. Poisson calculated that if wave theory was true, there would be diffraction (Arago) spot through a circular disk, very different from corpuscular theory that predicted no light around the edges. Arago took the challenge. His experiment, showed Poisson's corpuscular theory wrong in 1819. This in part, led to the acceptance of Fresnel as the winner of the contest.

Thus, a new set of scientists (including Fresnel and Arago) was rising and taking positions of power in the French Science Academy, creating an anti-Laplacian coalition:

By 1823, therefore, the anti-Laplace faction was in control of the Académie, and Arago, its leader, was in the dominant position that Laplace had occupied a decade earlier. As a critic of Arago has put it:

Laplace was reduced to silence, M. Biot absented himself from the Institut for several years and M. Arago remained master of the battlefield.


The quotes have been taking from this fantastic document:

There is a whole chapter on Biot vs. Fresnel. Biot was the main advocate of corpuscular theory, after Laplace. On a motion by Laplace, Biot tried to counter Fresnel.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.