Through his black and white photographs, Ansel Adams managed to immortalize some of the most spectacular landscapes in the United States before they were invaded by economic development and tourism. But Adams was never very meticulous taking notes, and it is still unclear when some of his most famous images were taken, such as this snapshot of Mount Denali next to a quiet Wonder Lake.
To solve the mystery, an astronomer named Donald Olson decided to look at the sky. Famous for proposing that the colors of The Scream by Edvard Munch are a description of the Norwegian sky at the time of the eruption of Krakatoa , Olson is dedicated to deciphering cultural puzzles through a process he calls “forensic astronomy”. In the case of Adams’ photo, he was lucky enough to find an image taken the night before in which the rising moon can be seen on Mount Denali.After studying the glacial cirques and other topographical features of the landscape, Olson and his assistant wrote a computer program to determine the exact coordinates from which the photographer made the capture. Next, they used the position and phase of the moon in the photo to find out the exact time it was taken: 20:28 on July 14, 1948. With that data, and knowing that the image of Denali and Wonder Lake had been taken the next day, Olson already had what he was looking for.
Thanks to the shadows cast on the mountain, he calculated the position of the sun and discovered the precise moment when Adams had taken the photograph of Denali and Wonder Lake. It was July 15, 1948 at 3:42 in the morning, local time in Alaska. All the details of the process that led him to that relief are described in the book Further Adventures of the Celestial Sleuth: Using Astronomy to Solve More Mysteries in Art, History, and Literature that has been published this year.