by Jeremy Berlin 
At 7:35 am on November 13, 1872, in the port city of Le Havre, France, the art world changed forever. Claude Monet gazed out his hotel window and began to paint what he saw. The result was “Impression, Soleil Levant”–and the birth of a movement.
How do we know exactly when [French] Impressionism began? Because of Donald Olson, a Texas State University astrophysicist who uses astronomy to solve art and literary mysteries. When art historian Geraldine Lefebvre and Marmottan Monet Museum deputy director Marianne Mathieu asked Olson to help determine the painting’s provenance, the self-styled “celestial sleuth” began by poring over maps and photos to identify Monet’s hotel and room. Then he turned to astronomy–using the rising sun and the moon to determine the tide, season, and time of day–and consulted digitized 19th-century weather observations. The final clues were the smoke plumes in the painting, showing the wind blowing east to west.
Those findings–plus the “72” by Monet’s signature–closed the case and put a precise time stamp on a timeless work of art.
 Jeremy Berlin, “Dawn of Impressionism,” National Geographic, April 2015.