Why Do Planes Appear Slowly In The Sky?

While walking on the road or traveling in a car, imagine an airplane you see when you look up at the sky. You'd probably be thinking how slow it seems to go from here. Have you ever wondered why?
 Why Do Planes Appear Slowly In The Sky?
READING NOW Why Do Planes Appear Slowly In The Sky?

Likewise, when traveling by plane, you may feel as if you are passing distant objects very slowly. Average passenger planes at an altitude of 8,500-10,500 meters and traveling at a speed of 900-1020 km/h may seem slow to you.

The reason for this situation is completely related to the way our perception works. It even has a name in the literature.

We perceive nearby objects as moving “faster”.

For example, while driving, we see roadside trees (nearby object) as moving fast, and distant objects such as the Sun or Moon as slow moving.

Whereas, a passenger plane is actually moving quite fast as seen in this video.

The name of this condition in the literature is “motion parallax”. Think of your field of view as a frame, in which objects moving at a constant speed across that frame are perceived to be moving faster when they are closer than when they are at a farther distance.

This is what’s called “motion parallax”. This phenomenon is true with respect to the moving object itself, or relative to the observer moving relative to the object (us who is looking at the plane while traveling in a car).

The percentage of our field of view also causes us to perceive the distance the object moves differently.

The effect is due to the distance the object moves compared to the percentage of our field of view. For example, in the image above, an object 100 meters away can move 20 meters in a given direction and only moves through 25% of the field of view.

However, a 20 meter displacement on an object only 40 meters away causes the object to be completely out of sight.

In short, thanks to motion parallax, we perceive a distant aircraft as slower.

Thus, we perceive objects close to us as moving faster than distant objects. In order to determine this distance, we rely on visual cues and motion parallax is formed.

Sources: Science Direct, Science Focus, The Naked Scientist

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