Janssen revolver

In the mid-nineteenth century, one of the scientific challenges of the moment was to determine with the greatest accuracy possible the distance between the Earth and the Sun, the so-called Astronomical Unit, which indicates the size of the Solar System.

With this data and applying the laws of Kepler, which describe the behavior of planetary orbits, the distance with the rest of the planets of the Solar System could be obtained.

The Venus transit in 1874 was a unique opportunity, which was why more than sixty co-ordinated expeditions from up to ten different countries were dispatched to locations in China, Vietnam, New Caledonia, some Pacific islands and Japan.

As the exact moment in which the transit of Venus would take place was impossible to predict, he added a watch set to create a sequence of images.

The revolver recorded 48 photographs in 72 seconds in a daguerreotype, material that was no longer used but was ideal for the sunlight that was presented in the situation, since it could capture the light in a great time of exposure and obtain clearer results.

Four years previously, Eadweard Muybridge was the first to record the movement of living beings, in The Horse in Motion, with 12 serialized cameras that allowed him to play and even project those photographs in a row.