Science, despite all its rigid laws and scrutiny towards empirical evidence, remains prone to mistakes and lapse of judgments on part of the researchers. In the early 19th century, Augustin Jean Fresnel, a French scientist ended up making a mistake that led him to be remembered years after his demise.
Fresnel has done modest work on gravitation and mechanics, along with offering scientific explanations for the natural phenomena of transmission, reflection, absorption and refraction. Newton was considered a pioneer on theories of light, his corpuscular theory maintained that light was based of particles, and with extensive experimentation Newton proved that light was indeed a ray. However, towards the 19th century, Newton’s theories were being challenged.
Thomas Young exhibited an experiment that allowed light to pass through two narrow slits with a small distance in between. The light didn’t travel like a corpuscle, but in fact, it exhibited a pattern of interference, with a pattern of dark and light bands. This pattern of bands was identified using two tunable parameters: the color of the light and the space between each slit.
If the blue light corresponded with the short wavelength light and the red light corresponded with the long wavelength light, it meant that light is travelling in a wave. Thus, Young’s experiments were only valid if light had a consistently wave-like nature of traveling.
It was hard to counter the successful experiments of Newton, and the theories of light became one of the most competitive subject amongst researchers and scientists towards the dawn of the 19th century. In 1818, the French Academy of Sciences organized a competition to offer scientific explanations for light, whether it is a wave or a particle, can it be tested and how can such tests be validated.
Young scientist Augustin Jean Fresnel, a trained civil engineer, decided to take part in this competition, and he invented a new wave theory that he was excited to reveal. His theory took inspired from the 17th century deductions of Huygens, and upon running some experiments, Fresnel was ready to exhibit the greatest mistake in the history of physics.
Fresnel’s entry was investigated and scrutinized by Simeon Poisson, the influential mathematician and physicist. Had light been a corpuscle, as Newton explained it to be, it would only travel in the form of a straight light, and if light was a wave, then it would create diffractions and interferences while travelling through a surface with barriers, edges or slits. Even though the general rule applies, various geometric configurations will bring about various patterns.
Simeon Poisson regarded light to have a monochrome color and a single wavelength according to Fresnel’s theory. Keeping this in mind, if light was to come across a spherical surface and create a cone-like form, according to Newton, the shadow must be circular with light in its surrounding. However, according to Fresnel’s theory, Poisson demonstrated that there can only be one bright point in the center of the show. Poisson cleverly conveyed the absurdity and irrationality of this prediction.
Poisson actively discarded and nullified the theory put forward by Fresnel because of its logically fallacious nature with the phrase: reductio ad absurdum. Poisson attempted to draw a conclusive prediction based on the light wave theory, which proved Fresnel’s prediction to be absurd and Newton’s theory prevailed as the accurate one.
However, this prediction by Poisson was the greatest mistake made in the history of Physics. No conclusion cannot be drawn without carrying an experiment. Physics is not a field that is based on assumptions, debates or arguments, but in fact, its strength lies in experimentation to reveal the true nature of the situation.
Luckily for Fresnel and for the evolution of Physics, the François Arago, the head of the committee judging the competition refused to let Poisson discard Fresnel’s work entirely. He took a hard lined stance to allow the process of scientific enquiry to unfold. Later, Arago went onto become an influential abolitionist and politician, and even the prime minister of France.
Arago performed the experiment himself by creating a spherical surface to pose as an obstacle, and exposing it to monochromatic like. A bright spot of light emerged at the center of the shadow, just as Fresnel’s theory had pointed out it would. Even though it sounded absurd and unlikely, the experiment proved Fresnel’s theory to be true.
This story reminds us that grave mistakes can occur in physics, science or any other discipline if we assume the answer without performing the relevant experiments to test our hypothesis. Physics is not a science that relies on theories, intuition or assumptions, and we must measure our assumptions through tests, observations and experiments.