He was then able to predict when the light and seasonal conditions would be virtually identical, and he and hundreds of Adams fans ventured to the spot at the appointed time. At 6:52 p.m. on September 15, 2005, Olson's colleague Doescher snapped a photograph that looks eerily similar to Adams' masterpiece. "In a project like this, the journey is its own reward," says Olson. "We not only got to walk in Adams' footsteps, we got to understand the circumstances under which he took the photograph. And the truth is, I think he was prepared. I think he knew that moment in nature was coming."
A starry sky in a work of art often catches Olson's eye—he is an astronomer, after all—and starts him thinking about how he might identify the stars and just when they were captured. "He brings the power of the stars to bear upon our understanding," says art historian Paul Tucker of the University of Massachusetts at Boston. Tucker teaches Olson's work in his class because "pinpointing the time period or a particular moment can have real bearing on the meaning of a picture."
Olson has tackled three van Gogh paintings, including White House at Night, one of more than 70 that van Gogh created in Auvers-sur-Oise in the weeks before he committed suicide, on July 29, 1890. (He hasn't published any findings on van Gogh's Starry Night, saying it's "not simple" to identify the stars in the painting.) When Olson and several of his students traveled to the town, about 20 miles outside Paris, they discovered that the house identified in most guidebooks as the one in the painting didn't have the right number of windows and faced the wrong direction. Once they found the right house—after walking every street in town—it was relatively easy to deduce from celestial calculations and weather reports that the star in the White House painting was actually the planet Venus as it appeared above the house near sunset on June 16, 1890.
Olson delved into Munch's best-known work, The Scream, in 1995. About the time Munch painted it, in 1893, the artist wrote himself a note—which Olson read with the help of Norwegian dictionaries—about a walk he had taken at sunset years earlier, on which "a flaming sword of blood slashed open the vault of heaven—the atmosphere turned to blood—with glaring tongues of fire...and truly I heard a great scream."
In Oslo, Olson located the road featured in a sketch for the painting. Details in it—a cliff, a road with a railing and an island in a fjord—indicated to Olson that Munch must have been facing southwest when he drew it. Olson concluded that the painting's blood-red sky was no metaphor but the extraordinary aftereffects of the 1883 eruption of Mount Krakatoa in Indonesia, which sent so much gas and ash into the atmosphere that skies were darkened or colored worldwide for many months.
Some Munch experts have challenged Olson's interpretation. Biographer Prideaux points out that Munch expressed contempt for realism in painting and "stated that his purpose was to paint the vision of the soul." Furthermore, "you'd hardly call the figure [in The Scream] realist, so why the sky?" And art historian Jeffery Howe of Boston College notes that Munch didn't paint The Scream until ten years after Krakatoa erupted. Howe admits that Munch "might have remembered the scene and painted it later," as the artist's note suggests, but Howe remains unpersuaded.
Olson insists his finding doesn't diminish Munch's creation. "How many people in Europe saw the Krakatoa twilights?" he says. "It would be hundreds of thousands, even millions. And how many people created a painting that people talk about more than a hundred years later? One. We think [our work] doesn't reduce Munch's greatness; it enhances it."
Olson now is working on an analysis of the skies in three other Munch paintings. After that, Claude Monet's Impression, Sunrise. In the 1970s, John Rewald, an Impressionist scholar, asked whether the painting's sunrise might actually be a sunset. Tucker tried his hand at the problem in 1984, consulting period maps and photographs of Le Havre, where Monet painted the piece, and concluded that the artist had indeed captured a sunrise. But, he said, "I would be more than happy to be corrected, and if [Olson] were able to bring scientific [and] astronomical issues to bear, all the better."
Whatever his findings, Olson's forays into art and literature are likely to keep stirring the debate about the sources of great art. His work may not change the way we see Munch or Adams or Chaucer, but it does tell us at least a bit about their three-dimensional worlds. And from there, we can see where the true genius begins.
Jennifer Drapkin is a senior editor at Mental Floss magazine. Sarah Zielinski is a Smithsonian assistant editor.