These are pieces of paper on a screen… but why do they seem to be moving?.
This is a fun illusion that uses still images on a flashing background to create the illusion of movement!
By using a dark edge on one side, and a light edge on the other, the paper shapes appear to be moving in front of a screen that flashes between black and white. This is called (believe it or not) the 'phenomenal phenomenon'!
It uses a luminance contrast (different brightness) to create the illusion of not just side-to-side movement, but also expansion and contraction as well as rotation.
Credit: Takahiro Kawabe NTT Communication Science Laboratories
Look fixedly at the black cross in the center of the screen. You will see three things: a gap running around the circle of lilac discs; a green disc running around the circle of lilac discs in place of the gap; the green disc running around on the grey background, with the lilac discs having disappeared in sequence.
The illusion of motion is created by the way the lilac discs blink out in succession, one after the other (Phi Phenomenon). The green disc is a negative afterimage of the lilac disc, formed because of the cells in your retina becoming confused by the sudden lack of color in a given spot, instead signalling the "opposite" or complementary color. Finally, if you look at the center long enough, you'll find that the lilac circles fade out entirely, leaving only the green disc. This is because our eyes automatically discount blurry stimuli when staying still – the green disc is perceived as moving, and therefore remains in the visual field!
Clearly, there are two tables that have very different dimensions – one is a long rectangle while the other is almost a square… right? Nope!
The surfaces of the two tables are exactly the same in length and breadth!
Pair this gif with next slides – do not add this tex
Don’t believe it? Watch this proof.
This is one of the strongest illusions ever discovered – it even works on some animals!
Your brain automatically makes adjustments when it "thinks" an object’s size has been contracted because of viewing angle. Because the table on the left is (apparently) receding into the distance, your brain assumes it must actually be longer than the table on the right, which runs parallel to the viewer.
This is because it’s almost impossible for us to see the flat, 2-dimensional shapes that are actually on the screen – our brain automatically translates everything we see into 3 dimensions.
Such compensation by our brain for such perspective-dependent distortions can also explain why an object such as a coin appears circular, even when presented at an angle, so it actually projects an oval to the retina.