Scientists use forensic astronomy to unlock secret of Monet's work

Claude Monet's The Cliff, Etretat: Sunset is the only one in the series that includes the disc of the sun.

If someone asked you what Claude Monet, the artist, was doing at 4.53pm on February 5, 1883 you might struggle to answer: but a group of academics believe they could now tell you.

The French impressionist was standing at his easel, overlooking cliffs at Etretat in Normandy, capturing the watery winter rays of the fading sunset.

For the past 131 years, his work The Cliff, Etretat: Sunset has held a secret which has now been unlocked by a group of astronomers and physicists.

The Texas State University team applied a practice known as forensic astronomy to the painting, studying the tides and alignment of the sun to pinpoint the exact moment Monet was trying to capture. Donald Olson, an astronomer and professor of physics, said: "We like to use astronomy to show students how science can solve real-world puzzles."

Monet made a series of paintings featuring the same stretch of the Normandy coast during his three-week visit to the area during the winter of 1883. With The Cliff, Etretat: Sunset, the artist painted a rock formation known as the Falaise d'Aval, together with the arch Porte d'Aval, overlapping a tall rock spire known as the Aiguille that stands just offshore. It is the only one in the series that includes the disc of the sun. To determine on which days in February the sun would have set in the correct location for Monet to capture it in his painting, the team of researchers travelled from Texas to France. The team found that the view matched the scene depicted in Etretat: Sunset at only one location - a spot 388m from the Porte d'Amont on a rocky beach under an overhanging cliff.

The Texas State researchers then used planetarium software to compare the modern sky with that of the 19th century and calculated that the sun would have set along that path on February 5, 1883. That date matches the sun's position, the weather and the tide level in the painting.

The team used the height of the Aiguille formation to calculate the exact time from the altitude of the sun above the horizon. "We were able to determine the month, day, hour and precise minute - accurate to plus or minus one minute - when Monet was inspired by that beautiful scene," Olson said.