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sciencesoup:

The Venus Spokes Illusion

19^th century American astronomer Percival Lowell is infamous for his claim that the surface of Mars is covered with an intricate system of non-natural canals, but it is less well known that he also reported controversial observations about Venus. From his observatory atop a remote mountain in Arizona, Lowell claimed to see a central dark spot on the cloud-shrouded planet, with an intricate systems of ‘spokes’ coming out of it. Lowell confidently sketched his discovery, saying they were beyond the possibility of an illusion and envisioning them as permanent surface features, but no one else could see them—and so, understandably, the astronomical community was skeptical. Lowell argued for many years that their technology was simply inferior to his own remote mountainous set-up, but as the years went on, no other evidence was produced, and Lowell’s passionate claims were dismissed. The mystery of what he really saw was finally solved in 2003, when an optometrist Sherman Schultz suggested that the spokes Lowell saw were actually the shadow of his own blood vessels cast onto his retina. So, instead of mapping other planets, Lowell actually spent part of his career mapping the structure of his own eye.