Galileo's Optical Illusion Mystery Solved by Neuroscientists [VIDEO]

First Posted: Feb 12, 2014 08:55 AM EST

A team of neuroscientists have finally figured out the secret behind the visual illusion that baffled Galileo and several other scientists for decades.

Galileo Galilei, the Italian astronomer and physicist was baffled when he figured that Venus looked much larger than Jupiter when viewed with the naked eye but vice-versa when viewed by a telescope. This mystery puzzled several scientists for decades. But in a new study neuroscientists have identified the visual illusion that was first discovered by Galileo.

They revealed that the illusion occurs because of the way human perceive brightness and darkness.

This new findings deepens our understanding on how the brain views white and black objects. This study was led by Jens Kremkow and collaborators in laboratories of Jose Manuel Alonso and Qasim Zaidi at the State University of New York College of Optometry.

Galileo was fascinated by the fact that the appearance of the planet was linked to how one looked at it- with naked eyes or with a telescope. When Venus was seen directly with naked eyes, the planet seemed to expand and develop a radiant crown. It looked about 8-10 times larger than Jupiter, even if Jupiter was four times bigger in reality.

Galileo then realized that the illusion was not something that was created by the object but was something that was created by the eyes. Though he understood this fact he failed to find out the mechanism lying under this.

He considered, "Either because their light is refracted in the moisture that covers the pupil, or because it is reflected from the edges of the eyelids and these reflected rays are diffused over the pupil, or for some other reason."

Several decades later scientists following Galileo went ahead to pursue his assumption. But this still didn't explain why Venus looked larger than Jupiter when viewed with naked eyes.

Herman von Helmholtz, the 19th Century German physician and physicist explained that there was more to the illusion than just the 'eye'. This was later described in Helmholtz in his Treatise on Physiological Optics.

In the current study, the researchers focused at how neurons in the visual system of the brain responded differently to dark versus light stimuli.

They discovered that dark stimuli results in neural response that represents the accurate size while light stimuli shows a non linear and exaggerated result making the stimuli appear larger.

White spots against a black backdrop look bigger than the same sized black spots placed on a white backdrop.

On seeing how neurons are interconnected in the retina and brain, the researchers discovered that illusion is derived from the origin of vision in the photoreceptors of the eye.

The finding was published in the Proceedings of the National Academy of Science.


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