WHEELS APPEAR TO SPIN BACKWARDS - The wheels of the car moving forward, at first will appear to spin in one direction and as the speed of the car increases, its wheels will also rotate faster. At a certain point, the spin of the wheels appears to get slower and at some point, the rotation stops. But when it resumes, we see that the spin is in opposite direction. Due to this type of rotation, the car should be moving backward, isn’t it? But the car is moving forward. This phenomenon is known as The Wagon Wheel Effect. Most of the people, including you, are likely to see wagon wheel effect in movies or televisions. In movies or TV’s, the cameras record footage by capturing a series of images in a quick session and not recording it continuously. The cameras capture the images at a specified rate called “frame rate”. It is sometimes referred to as a reverse-rotation effect. But if the spoke somehow over-shoots, the wheel will appear to rotate in the right direction, but very, very slowly.

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Wheels Appear To Spin Backwards

Why do wheels appear to spin backwards at high speeds?

engineeringinsider

While standing on the footpath or while watching movies, have you ever wondered, why the wheels of the cars appear to spin backward when they are at high speeds?

Wheels

Let me explain why this happens with a short example. Suppose a car is moving forward and with time it is gaining momentum and speed.

While standing on the footpath or while watching movies, have you ever wondered, why the wheels of the cars appear to spin backward when they are at high speeds?

Wheels

Let me explain why this happens with a short example. Suppose a car is moving forward and with time it is gaining momentum and speed.

The wheels of the car moving forward, at first will appear to spin in one direction and as the speed of the car increases, its wheels will also rotate faster. But then, something weird happens.

At a certain point, the spin of the wheels appears to get slower and at some point, the rotation stops.

But when it resumes, we see that the spin is in opposite direction.

Due to this type of rotation, the car should be moving backward, isn’t it? But the car is moving forward. This phenomenon is known as The Wagon Wheel Effect.

Most of the people, including you, are likely to see wagon wheel effect in movies or televisions. Let us see why the effect appears to our eyes like this?

In movies or TV’s, the cameras record footage by capturing a series of images in a quick session and not recording it continuously.

The cameras capture the images at a specified rate called “frame rate”.

Many movie cameras have a frame rate of 24 frames per second, and when the frame rate of this camera matches with the frequency of a wheel’s spin (i.e. 24 revolutions per second), each of the wheel’s spoke completes a full revolution every 1/24 seconds, and due to this it ends up in the same position every time a frame is captured by the camera.

So, we can say that when a wheel seems to spin in the direction opposite to that of its actual rotation is because each spoke has come up a few degrees shy of the position it occupied when it was last imaged by the camera.

It is sometimes referred to as a reverse-rotation effect. But if the spoke somehow over-shoots, the wheel will appear to rotate in the right direction, but very, very slowly.

The appearance and effect of the effect also depend upon the exposure time of the camera and also the design of the wheel.

The optical illusion that we see requires nothing but a repeating motion that must be visible intermittently.

A similar phenomenon like this can be achieved with a strobe light, which gives rise to an effect called “stroboscopic effect”.

So now you know about the wagon wheel effect that you usually see on TV and movies.

The wagon wheel effect that we normal people see in the real world is not due to strobe of light or through the screen, but under constant lighting conditions. Presently, there are 2 hypotheses that give an explanation for this effect.

The first hypotheses were proposed by a neuroscientist Dave Purves and his colleagues in the year 1996.

The theory says that we humans perceive motion in a manner which is very similar to a movie camera i.e. by processing a series of visual episodes or like the sequential presentation of discrete scenes.

But in the year 2004, a researchers team led by neuroscientist David Eagleman explained with his tests that the 2 identical wheels spinning adjacent to one other often perceived their rotation as switching direction independently of one another.

This result of the Eagleman contradicts the Purves’ team’s discrete-frame processing model of human perception.

For a better explanation of motion reversal, Eagleman and his team concluded that motion reversal is a form of ‘perceptual rivalry’, a phenomenon by which the brain multiple interpretations of a visually ambiguous scene.

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