Galileo’s optical illusion

Galilleo illusion

In this illusion, the white coloured square against the black background, appears to be larger than the black coloured square on the white background. In actual fact, they are the same size. Our response to light makes it difficult to see that these squares occupy exactly the same area. The Italian astronomer Galileo first made a similar observation when looking at the planets. He found that Venus looked far larger than Jupiter (since it was the brighter of the two planets). Despite this, at second glance, looking through a telescope it is obvious that Jupiter is clearly the largest of the two planets.

This illusion can be explained by light sensitive neurons. A recent study showed that when the electrical signals between neurons were recorded using electrodes,  the neurons sensitive to light object gave a disproportionately greater response than those neurons sensitive to dark things. The heightened activity of these light sensitive neurons explains why our attention is shifted to the right, and why the white square appears much larger. Scientists working on this research believe that these light sensitive cells are within the eye itself, rather than in the brain. These cells are responsible for changing our perception of the image we are viewing. Research into this area has also sparked interest in problems with vision, which could potentially be explained by the imbalance in activity of these neurons.

 With regard to our visual system, this optical illusion tells us that under different conditions, things can be perceived much differently. It also tells us that sometimes our eyes and our brain are not always in complete agreement! What is interesting about this illusion is that the observed effect can  be essential for survival (particularly for predators in the wild).


One response to “Galileo’s optical illusion”

  1. Swathi Srinivasan says:

    This optical illusion is actually one of my personal favorites. You did a really great job explaining it too!

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