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This illusion is called the “stroboscopic effect” and arises from the superposition of two periodic processes with the same or close and slowly changing phases relative to each other.
Example: if you see a car in a movie, the frame rate is 24 frames per second, the car's disk has 24 spokes and it makes 1 revolution per second, the movie will “slip” your eye only frames with equally standing spokes, that is, the spokes will seem to be standing. And at a slightly lower speed, the wheel will spin back.
But here's what's important: we need exactly TWO periodic processes. If it seems to you that all cars in reality (not in movies and not on video) have wheels spinning backwards, then either the light is flashing (for example, street lamps can flash at a frequency of 50 Hertz), or the second periodic process is in your head – but in this case you would go to the doctor, because this should not be!
Because it is. Your eyes don't deceive you. Forward movement obespechivaetsya movement of the wheels back. F1=-F2. Just as the development of one person is impossible without the degradation of another. This was confirmed by Newton. It is impossible not to notice that in the word 'back' there is a part of 'hell'. There's probably something supernatural about these laws of physics. But whether you believe it or not is up to you.
This is the result of a stroboscopic effect
It occurs due to the inertia of vision: in the mind of the observer, the visual image persists for some time after the picture that caused it disappears. Most often, the illusion of stationary wheels of a speeding car can be seen in movies. We detect the rotation of the wheel by the movement of its most noticeable parts, especially the spokes (or their relief imitation on car hoods). The film captures reality only at certain moments, and at a standard speed, it produces 24 images per second. If the wheels make one or more full revolutions in the interval between frames, it will seem to an outsider that they are standing still. If the wheels do a little more than one or several full revolutions, it will appear that they are rotating, but slower than the car is moving. A third option is also possible: if the wheels are a little short of the whole number of full revolutions, then the spokes “move back” and it seems that the wheels rotate in the opposite direction. In real life, this phenomenon can most often be observed on an evening street lit by lanterns that have a low-frequency pulsation. Our eye captures the “frame” only during the light pulse.
“Saccades” – the so-called periodic and uniform” twitching ” of the eyeball (down-up, down – up) – a little more often than once a second. In fact, our eyes “photograph” our surroundings, and discrete “snapshots”are sent to the brain (occipital region). From such mechanics. We, of course, can not notice this, because the brain “smoothes”.
We integrate this answer with the previous one and go to teach the hapless father and mother.
This effect is usually more noticeable in movies or under pulsing (artificial) lighting. It is called stroboscopic.
Briefly, its essence is as follows: a rotating wheel is symmetrical: its pattern repeats with some regularity. If we take pictures of the wheel at fixed time intervals, we will see an instantaneous image of the wheel turning at a certain angle. But by repeating its pattern, we will perceive it in the position closest to the previous one. In other words, if the next spoke of the wheel does not reach the position in which we previously saw its neighbor during the interval between images, we will think that the wheel has turned back.