Why do car wheels spin backwards

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SUMMARY

The phenomenon of car wheels appearing to spin backwards is primarily attributed to the stroboscopic effect, which occurs when the frequency of light sources, such as electric lights at approximately 50Hz, interacts with the rotational speed of the wheel. This effect can also manifest in daylight due to the limitations of human visual perception, specifically the refresh rate of the human eye. The time it takes for a wheel or fan blade to rotate into a new position can create an optical illusion, leading to the perception of reverse motion.

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daniel_i_l
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Anyone who's looked at a spinning car wheel or fan notices that sometimes it looks as if the wheel/fan is spinning backwards. I was once told that this is because of the fact that the light shining on it, coming from an electric light source, turns on and off at a certain frequency (~50Hz) and therefore we get a stroboscopic effect.
But I see this effect even in daylight - which is constant. What could be the reason for this? Could it have to do with the rate that our eyes can "refresh" the picture sent to the brain?
Thanks.
 
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I think it has something to with the time taken for one fan blade to reach the position of the other one, being less than the time take taken for the light to reach your eyes. Granted I never really followed up on that explanation, but that was what I was told when I was young.
 

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