Why do the spokes of a wheel seem to rotate in the opposite direction to that of the wheel?

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Why do the spokes of a wheel seem to rotate in the opposite direction to that of the wheel?

In: Physics

Because sometimes they turn with a frequency that sometimes slightly mismatches the “frequency” that we look… i guess there was a video on youtube. When you look at the rotating circle with, it speeds up to 1 RPM, 2 RPMs, and so on, and, when it seems like it’s turning backward, it means that your eyes miss some of it’s movement, en only see like 99%, but every single time… and it looks like turning opposite direction…

The term that describes it is “Aliasing”. It’s most prominent on TV programmes where 30 frames per second are not enough to capture a wheel spinning and what you see is out of step with the movement of the wheel.

Say the wheel is turning forwards 75% of a full turn, if you don’t see how much the wheel actually rotated, it would seem like it just moved 25% the way backwards

Typically the spokes on a wheel make it work with smaller percentages than that, otherwise it would only work on really fast moving wheels

This is what happens when you film, you take a picture every interval, usually 1/30th of a second and you can’t see what happens on between

It can also happen with the naked eye at night, because street lights flicker 60 or 50 times a second, so you can’t see the wheels very well when they are flickering