Why do car wheels look like their going backwards (counterclockwise) when a fast car is moving forward?

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  • 1 decade ago
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    ok, this is a complicated answer.

    from what i've seen on tv scientists aren't exactly positive but their best guess is that our eyes are similar to video cameras. basically our eyes don't take in a continuous stream of 'video'. instead we take many snapshots and run them together quickly in our brain to create that 'video', similar to a video camera.

    that being said...

    (here's where it gets really complicated) suppose a wheel has 5 spokes on it. when our eyes take the first 'picture' a spoke is perfectly vertical. now suppose that when our eyes take the next 'picture' a spoke isn't to the right of its original position where it should be if the wheel is moving clockwise, but it is to the left of the original spoke. this would make it look like the wheel is going counterclockwise.

    even though the wheel is moving clockwise since it is moving a lot faster than our eyes take 'pictures' it is up to chance where the spokes will be arranged.

    if you stare at a the wheel long enough and if the speed of the wheel changes you'll actually see it switching between going clockwise and counterclockwise. the same is true of airplane propeller blades.

    sorry for the complicated response. if i could draw this on paper it would make a lot more sense.

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