Capturing the sun, calculating the speed of light

On April 2, 1845, French physicists Armand-Hippolyte-Louis Fizeau and Jean-Bernard-Leon Foucault came together to produce the first surviving detailed daguerreotype photographs of the surface of the sun. A few years later, the duo came together to measure the speed of light. A.S.Ganesh tells you how Fizeau and Foucault captured the sun and calculated the speed of light…

If we want to click a picture of the sun, we pick up a camera or a smartphone and snap it in all its magnificence. While it is as easy as that currently, capturing the sun was no easy feat even a couple of centuries ago.

In fact it was only on April 2, 1845 that the first surviving detailed photographs of the surface of the sun were taken. French physicists Armand-Hippolyte-Louis Fizeau and Jean-Bernard-Leon Foucault were the two men who made it happen.

The son of a physicist, physician, and professor of medicine, Fizeau was born in Paris in 1819. The fact that Fizeau's father left him a fortune meant that he was free to pursue his own interests, without having to worry about making a living. Even though he initially wished to be a physician like his father, he eventually focused on scientific research, choosing to study astronomy.

Foucault was born in the same year and in the same city as Fizeau. The son of a publisher, Foucault was a rather timid boy and enjoyed limited success academically. After receiving most of his education at home, he enrolled in medical school as his mother wanted him to become a doctor. That didn't last long, however, as the mere sight of blood freaked him and he dropped out.

What Foucault lacked through formal training, he made up with his dexterity, intuitive understanding of nature, and an ability to build gadgets. Once he left medical school, he set out on his new career by working as a lab assistant.

Fizeau and Foucault came together through their interest in the Daguerre photographic process that had been recently invented. Even though photography was still in its infancy and its mainstream use in astronomy was still decades away, Fizeau and Foucault decided to turn their camera towards the sun.

While they came together for this project late in the 1830s, adapting the then existing photographic process to astronomy was no easy feat. It took them years, but on April 2, 1845, they succeeded in what they set out to do - capturing the sun in considerable detail. These images are the first surviving detailed daguerreotype photographs of the surface of the sun.