Timestamps are handy. They show up on things like receipts, emails, and text messages (ahem, drunken text messages). There aren’t timestamps for everything, though, and before the digital age they just didn’t exist. But researchers at Texas State University won’t take no for an answer.
Astrophysicist Donald Olson and his team came up with the idea of being able to date a series of paintings created by Claude Monet by examining astronomical and geophysical data. The paintings, made during a three-week trip to Normandy, France, in the winter of 1883, depict different seascapes and skies that gave researchers clues to work on. Etretat, sunset (above) is the only painting in the series that contains a sunset, so during a site visit to Normandy, Olson and his team took angular “declination” measurements to determine the path that the sun would have borrowed to appear to the right of the distinctive rock formation in the painting. Later, they used those measurements and planetarium software to compare the modern sky to the 1883 sky and calculate when the sun would have traveled that path.
Assuming a margin of error, the scientists estimated that Monet created the painting between February 3 and 7. Then they got a little boost. Monet wrote letters during his trip, including the days of this range – and apparently he was very mindful of the tides. Using information from these missives, along with historical weather data and tide charts, researchers were able to identify February 5, 1883 at 4:53 p.m. local time as the time Monet was painting, plus or minus one minute. The results are published in the February issue of Sky & Telescope.
This type of work, known as astronomical chronology, is often criticized for relying on imprecise and unreliable landmarks. In a 2003 article, for example, astronomy historian John Steele wrote that astronomical dating “can easily produce precise and impressive results based on invalid assumptions – results so precise and impressive that they cannot not be questioned by researchers from other fields”.
So maybe it’s not the exact date and time? Who knows. Since little depends on the accuracy of this date, other than the emotional stability of art historians, it seems that the real value of this type of inquiry comes from the creative use of a range of sources of data and the development of new tactics for interdisciplinary research. Plus, it creates a sense of cool immediacy to imagine Monet painting this particular work at 4:53 p.m. on a Monday in 1883.