Why is it that when a vehicle is moving fast enough, it looks like the wheels are spinning backwards?


Why is it that when a vehicle is moving fast enough, it looks like the wheels are spinning backwards?

The receiver (your eyes or a camera) of the image…wheels rolling…can’t keep up with the actual speed of them. That’s why wheels on cars, stagecoaches, etc. on TV, look like they’re going backwards. The timing of the images on film (movies are a series of pictures) doesn’t coincide with the actual speed of the wheels turning.

It’s the same concept used in adjusting the timing belt on a car and using a ‘timing light’.

It’s all to do with how many frames the camera is taking and how fast the car is going. Every time the video takes a frame it shows the wheel at a certain place but in the next frame the wheel is in a slightly differant place just behind where it was in the previous frame and so on. So when you run the film it looks like the wheel is going backwards.

Because your eyes aren’t fast enough to keep up with the rotation of the spokes and the speed of the film frames .

That is why when they are filming while car is running down the road you can’t see them at all, but when they start slowing enough and the frames per second of the camera align, your eyes pick up the spokes because the wheel is in negative acceleration compared to the speed of the camera, so the wheels appear to be going backward

You need to have a camera going at a fixed rate of frames per second to notice this differential. Because if you don’t have a camera with film and you look at a car with just a naked eye, going by and it starts slowing for a red light you will NOT see the wheels appear to go backward because your eyes can only go so fast.

The camera makes all the difference

This is due to an Aliasing Error (Beat frequency) caused by sampling rate of the camera, has nothing to do with your eyes which run at about 15 frames per second, Maximum.

it is because our eyes are very slow….even we cannot see our fingers when we shake it very speedily….

Leave a Reply

Your email address will not be published. Required fields are marked *