Back in the late 19th century, impressionist artist Claude Monet captured this striking sunset on the Normandy Coast. Now, thanks to the work of forensic astronomers, we known the precise moment it happened: February 5th, 1883 — at exactly 4:53 PM.
Art historians know that Monet visited this stretch of the Normandy coast, called Étretat, during a three week visit in 1883. During this time, he painted the Falaise d'Aval cliff and the arch Porte d'Aval — a tall, needle-shaped rock spire known as Aiguille (the Needle).
But unlike those paintings, "Étretat: Sunset" contains a distinct feature: a low, setting sun just right of the landforms. It's the only canvas that includes the disk of the sun set against fixed objects.
Looking to pinpoint the exact date and time of the sunset, a team of forensic astronomers from Texas State traveled to France to find the exact physical location where Monet must have stood while making the painting. Though astronomers, the researchers set about the task in a way that could hardly be considered rocket science. Writing in San Marcos Mercury, Jayme Blashke explains:
The research team made extensive topographic measurements of the terrain at Étretat. To determine the exact locations where Monet stood, they walked systematically from one end of the beach to the other at low tide, armed with postcard-size reproductions of about a dozen Monet paintings of the area. They located the precise vantage points from which Monet created the various paintings.
The researchers found that the view matched the scene at only one possible location — a spot 425 yards from the Porte d'Amont on a rocky beach under an overhanging cliff (interestingly, this was not the spot claimed by some art historians).
That being done, science did the rest:
The researchers used planetarium software to compare the modern sky to that of the 19th century. Since the Texas State team visited in the summer, the sun was out of position to replicate the sunset from Monet's painting. The waxing crescent moon, however, offered a convenient stand-in during the early evening hours, and star-fields became visible after moonset. By determining an astronomical coordinate called declination for the moon and stars, they were able to calculate the sun would have set along that path on Feb. 5, 1883. Allowing for some uncertainty, the researchers concluded that the correct date must fall in the range between Feb. 3 and Feb. 7, 1883.
The group then combed through letters Monet wrote during his retreat, along with weather records and tide tables. Through a process of steady elimination, the researchers settled on one possible date and time that matched the sun's position, the weather, and the tide level in the painting: February 5, 1883 at 4:53 p.m. local mean time. Give or take a minute.
[ More at San Marcos Mercury | h/t The Verge]