Venus puzzle solved: Why naked-eye sees illusion in sky


planetsizesnasaIt’s an illusion that intrigued Galileo four centuries ago: When you look into the night sky with your naked-eye, Venus seems much bigger than the huge Jupiter. But if you use a telescope, Jupiter retains his throne as ruler of the planets.

Venus is nearer to us, you say. Um, yes. But that alone can’t account for the difference, scientists all the way back to the 16th century astronomer realized. Venus appears to have a “radiant crown,” Galileo noted, which boosted the planet’s appearance. Why?

Now researchers from State University of New York’s College of Optometry report that they have solved the mystery of Venus’ crown. The answer lies in the way humans perceive  light objects against dark backgrounds.

White spots on a black background look bigger than same-sized black spots on white background, the scientists report in Proceedings of the National Academy of Sciences.

“We live in a bright world,” says Jose-Manuel Alonso, a lead author of the study. “Most of our lives are in a brightly illuminated world. We are exposed to images that have a bright background.”

Alonso and his colleagues show how the light and dark stimuli are separately processed by channels in the retina of the eye and the thalamus in the brain.

Venus is wearing her bright crown because a light object looks blurred and is magnified by human cells, making the whole ‘star’ appear bigger.

Read more here.