"What if everything is an illusion and nothing exists? In that case, I definitely overpaid for my carpet."- Woody Allen -What you see isn’t always what you get!Since ancient times, humans have known that immediate perception is not a reading of physical reality. Vision is the most creative act that a human being is capable of. Seeing is depicting the world on the living canvas of our mind. As we depict well only what we really know, our mind is both the canvas and the artist. In this creative process, the eyes represent nothing other than a medium with which our mind interprets and reconstructs our near environment. Some illusions teach us to doubt and to question the many appearances of the reality - they are a kind of school of life!We have five main senses – sight, hearing, taste, touch and smell – but about 75 per cent of the information humans receive about our environment comes from our sight, making it the most ‘important’ of the five senses. The vision depends, obviously, on the EYES to see (with optic receptors called rods and cones) and on the BRAIN to make sense of what we see. The optic nerve at the back of the eye connects to the central nervous system in the brain. The brain receives electrical impulses (stimuli) from our eyes which are interpreted as SIGHT, but the brain adds two extra ingredients to the received image: memory and interpretation (in short, perception). Sometimes the brain is deceived by information received from the eyes. Visual illusions are caused when differences occur between our perceptions or expectations and the image seen by the eye. Actually, there are particular illusions which deceive the human visual system into perceiving something that is not present, or incorrectly perceiving what is present. Optical illusions can be roughly categorized as physical illusions, physiological illusions and cognitive illusions.Apparent MovementsThe diagram below is static. However, when you stare (not too close!) at it, at a given time the 3 coloredconcentric rings seem to glow and to rotate around the central sphere...
Disappearing/Appearing Cheshire CatFocus your attention on the blue point to make the Cheshire cat vanish!Stare at the center of the diagram below. Keeping your gaze fixed on the center, move your head backwards and forwards. You may see the orange rings rotate counterwise!How many cubes do you see simultaneously... One or two cubes?Can you perceive when the spinning mask becomes concave? Impressive, isn't it?
(en: open source - Confederation Day - Switzerland & archimedes)
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