Armand Hippolyte Louis Fizeau


Armand Hippolyte Louis Fizeau was a great astronomer, inventor, and physicist. He is not one of the most famous people, but he has accomplished much during his days. He was the first person to take photographs of the Sun in 1845 on a daguerreotype, an early photograph invented by Louis-Jacques Dagguerre. He made the first reliable measurement of the speed of light and determination of the velocity of light[¹]. He was infatuated with light and how it worked. He debated that the Doppler effect should apply to any wave of motion with the respect of sound, especially while dealing with light. Hippolyte Fizeau was the first to invent an interferometer that measures waves of light by using interference patterns[4].
Photo courtesy of: Britannica
Photo courtesy of: Britannica

Insight and influences

Armand Hippolyte Louis Fizeau was born in Paris, France on September 23, 1819. His earliest projects involved improvements in photographic processes. He worked with his friend, J.B.L Foucault, who he met at College Stanislas while he was there[7]. They went to a free course on photographic techniques held by Louis-Jaques Daguerre. They watched Daguerre use his inventions of his own camera for thirty minutes. Fizeau and Foucault thought that it would be easier to take photographs if the subject did not have to remain still for such a long time. Together they worked on investigations involving the interference of light and heat. They replaced the iodine that Daguerre used with bromine and reduced the time to twenty seconds. He published the first results of the methods he used to find the speed of light in 1849. With the help of E. Gounelle, Fizeau measured the speed of electricity in 1850[1]. Using all of the advances he accomplished, Fizeau began studying the thermal expansion of solids. He used crystals as his prime experiment by applying the phenomena of the interference of light to the measurement of its dilatation.

Armand Hippolyte Louis Fizeau was the first born of Beatrice and Louis Fizeau[1]. Fizeau's father was the chair of internal medicine. Because of this, his family was socially prominent and wealthy. After his father’s death, Fizeau inherited an independent fortune to devote to science[2]. Being interested in his father's work, Fizeau wanted to follow in his footsteps, but the climate at the College Stanislas did not suit him due to his health[5]. He experienced migraines, which resulted in his loss of interest in medicine. He needed some time alone to refocus his thought. After spending some time traveling, he decided to go to the College de France to study physics. He studied under the famous astronomer Dominique-François Arago. Arago discovered Fizeau's potential and directed him to experimental physics. He studied with Regnault on optics at College de France and did a thorough analysis of his brother’s work at the Ecole Polytechnique through his notebooks. Through all of his study and experience with other physicists, Fizeau helped discover the Dopler effect. He also predicted the redshifting of electromagnetic waves almost six years before the proposal of the Doppler effect.

He married the daughter of the famous botonist Adrian de Jussieu. Therese Valentine de Jussieu and Fizeau had two daughters and one son. Fizeau attempted access into the Academy of Sciences in March of 1951. He was one of seven candidates to gain the membership. Foucault was also one of those candidates at that time but did not gain membership five years after Fizeau did in 1860. The Institut de France awarded the Triennial Grand Prix to Fizeau on July 9, 1856. One of Fizeau’s other awards includes the Rumford Medal of the Royal Society. He became the vice president of the Physics Section of the Academy of Science the president of the association the following year. Fizeau retired to his home near Jouarre after his beloved wife died at a young age. He rarely left his home even for meetings at the Academy.

Major Contributions

Armand Hippolyte Louis Fizeau enjoyed researching and experimenting with light and waves of light. He made the first estimate of the speed of light in 1849 and measured it to travel about 194,410 miles per second. He did this through placing a light five miles away from a mirror and set up a toothed wheel in front of the light. The light would travel through a gap between two of the teeth, reflect on the mirror and pass back through the gap between the next two teeth. This experiment allowed Fizeau to measure the speed of light through the speed that the wheel was moving.

Hippolyte Fizeau’s interferometer was similar to the Fabry-Perot interferometer. They both consist of two surfaces, but Fizeau’s interferometer surfaces do not totally reflect the light. His only reflected four percent to thirty percent of the light. However, he did this to keep secondary reflections away from the surfaces to make the experiment more accurate. He measured the beams with an angled beam splitter that captures the reference. Generally, scientists use Fizeau’s interferometer to measure the shape of an optical surface. These surfaces include a fabricated lens or a mirror that is compared to a reference piece that has the same shape.

Hippolyte Fizeau was the first person to take a picture of the Sun using a daguerrotype. A daguerrotype is one of the earliest ways to take photographs. Along with Focault, Fizeau was able to take a very detail oriented photograph of the sun’s surface. After experimenting with a creating a new interferometer, Fizeau had accurate knowledge of the interference of light waves and the interference patterns of heat waves. This knowledge helped contribute to the idea that light is not just a stream of particles, but more of a wave of light.

Hippolyte Fizeau had the idea that any wave of motion should contribute to the idea of the Doppler effect on sound, especially light. The Doppler effect is a shift in the frequency and wavelength of waves that results from a source moving with the respect of a medium, a receiving end of a source moving with the respect of a medium, or even a simple moving medium[6]. Fizeau discovered that the Doppler effect was flawed in a way that it cited that the reason for a star’s color was due to its shifting of red and blue color. Fizeau was the first to predict a light source that is moving toward the observer would be more toward the violet side of the spectrum because the waves would be pushed together and that if it was moving away, it would be more to the red end of the spectrum. Christian Johann Doppler, who created the Doppler effect, furthered this hypothesis[5].

Through many of Fizeau’s experiments with light traveling through water and air, he was able to measure the velocity of light as it passed through a liquid. One of the experiments included splitting one beam into two and shining one in water and the other in the air. He used another rotating-gear-and-mirror system and was able to calculate and measure the velocities. Because the speed of light was greater in the air than in the water, his wave theory of light was experimentally proven. Later scientists looked at both sides of the physicist’s work and grew closer to the understanding of the phenomenon. The merging of the two men’s work resulted in the Doppler-Fizeau shift, which is the shifting of light[5].

Affect and Effect

Louis-Jacques Daguerre held a free course in Paris to show his new advances on photographic techniques. When Fizeau and Facault were still friends, the two of them left to attend this showing. They colaborated together to patten the photographic techniques invented by Daguerre. They improved the photographic time by over twenty eight minutes[1]. These advances helped scientists and photographers further develop cameras and other photographic lenses for more effective technologies. The world now has higher definition cameras, which make photos more intiricate and appealing to the eye. Without Fizeau and Facault's advances, high definition would not be as great as it is.

Christian Johann Doppler created the Doppler effect in 1842[6]. Fizeau analyzed the light waves in the Doppler effect. Fizeau's improvement is sometimes reffered to the Doppler-Fizeau shift[10]. Fizeau's ideas on wavelength relating to the velocity of light led to an amendment to the Doppler effect. Without these ideas, sound sources would be more difficult to predict. Sound sources can help find locations of lost objects. By relating sound to light, Fizeau was able to calculate sound to improve the laws on the Doppler effect. These advances are important to scientists, police officers, fire fighters, and those that help find people stuck in emergency situations like on September 11,


Jean Bernard Léon Facault was Fizeau's best friend during his lifetime. They worked together on Daguerre's photographic techniques. They both attempted to calculate the velocity of the speed of light. After a personal dispute between the two, they both went their own ways and worked separately on the same subject. After attempting to calculate the speed of light, the two of them arrived with different answers. Through many experiments, Fizeau's calculation was found more accurate than Facault's. When comparing the two, Fizeau always seemed to trump over Facault in all of their accomplishments. Fizeau was accepted into the Academy of Sciences before Facault and he was also Vice President and President a year later.

Fizeau worked under the famous astronomer and physicist, Dominique-François Arago at the College de France. Arago put Fizeau on the right track for his studies. Arago planted the thought in Fizeau's head to make him so obsessed with the interference of light waves. He proposed that one had to measure the speed of light to prove its wave nature. This started Fizeau on his quest to find the speed of light. Arago was the first to propose an experiment to find the speed of light, but Fizeau was the one that actually performed it, along with Facault, who was his friend at the time in 1845. They had made the first terrestrial measurement no more than two years later than the experiment was performed. However, they also came to the hypothesis that light would travel faster in water if it in fact were made up of particles. It also said that if it were a wave, it would travel faster in the air[5]. If Arago had not put Fizeau on the right track, then Fizeau would not have made all of the advances that he discovered. Fizeau did a lot of the things that benefitted science. Arago was about the most important person Fizeau's life in relation to physics and other sciences.

The Things He Left Behind

Diagram Courtesy of: Encyclopedia Britannica
Diagram Courtesy of: Encyclopedia Britannica

Armand Hippolyte Louis Fizeau will always be remembered for his cogwheel experiment to measure the speed of light. Arago originally created the cogwheel experiment, but he never officially went through with the experiment [5]. The cogwheel experiment involved a light, mirror, and toothed wheel, also called a cogwheel. He set the mirror five miles, or eight kilometers, away from the wheel. The time it took the wheel to move a width of one of the teeth was compared and set equal to the time it took the light to travel through the tooth, to the mirror, and back again. After finding the accurate measurement, he tested again and came up with evidence for the discovery that light travels faster in the air than in the water [11]. Although Fizeau accomplished much during his lifetime, the most important thing that he ever did was measure the speed of light through this experiment. Fizeau's amendment of the Doppler effect was very important to science, but not many recognize him in the invention. He had to argue that the Doppler effect should apply to light and any other wave of motion, with respect to sound. He used the evidence of the travel of light through the air as his argument. His improvement of the Doppler effect renamed it to the Doppler-Fizeau effect or the Doppler-Fizeau shift, along with its advances with red and blue shifting [5]. Fizeau could not have accomplished this without knowing what the speed of light was. The speed of light helped him come to the conclusion that the color spectrum of a star depends on its motion, but not knowing how far away it was by using his value for the speed of light, it would have been difficult to keep up his argument.
Fizeau's other great accomplishment involved the patten of Louis-Jaques Daguerre's photographic invention of one of the first cameras. With the help of this paten, the time it takes to take a picture is dramatically decreased, in partial credit to Fizeau and his partner and friend, Facault. Through the advances of the daguerreotype, they were able to take the first photograph of the sun[1]. This first photograph helped scientists better understand the concept of how the sun worked based on what it looked like. The photo revealed evidence for Galileo’s discovery of the sunspot, through which there were tiny dots on the photograph. The advances made by Fizeau not only helped scientists working in the field of physics, but also scientists working with astronomy.