When birds and airplanes are flying, they do not create a shadow on the ground because they are too small and too far away from the ground. However, this is not the complete explanation.
Many everyday objects that we encounter contain hidden scientific principles.
Have you ever noticed that when you place a pencil in a glass of water, it appears distorted and bent? Or have you realized that lightning always has a zig-zag shape? And did you know that submarines are always painted black?
Similarly, another phenomenon that caught my attention recently was the fact that airplanes and birds in flight seem to not cast a shadow. Have you ever thought about this? If so, do you know why? The same applies to birds.
But is this really true?
So… why can’t we see their shadows on the ground?
How Are Shadows Produced?
The process is quite simple. A shadow is formed when an opaque object (an object that does not allow light to pass through) obstructs the path of light. Since light travels in a straight line, a shadow is always produced when an object is placed in front of a light source.
This is a simple experiment that you can try at home: Take a light source, such as your smartphone’s flashlight, and position a piece of paper about one meter away from the light source.
Next, place a pencil in between the light source and the paper, so that it blocks the path of the light rays.
Observe how the shadow forms on the piece of paper.
As you move the pencil closer to the paper, the shadow becomes darker, more distinct, and well-defined. However, if you move the pencil towards the light source (or away from the paper), the shadow becomes diffuse and less defined, eventually seeming to disappear completely.
This is exactly what happens with airplanes and birds in flight.
Why Can’t We See the Shadows of Flying Airplanes and Birds?
Any opaque object that stands between a light source and a “screen,” in this case the ground, will always create a shadow. Therefore, the question “Why don’t airplanes cast a shadow on the ground?” is fundamentally incorrect.
Airplanes and birds in flight do cast shadows.
The correct question would be: “Why can’t we perceive the shadow of a flying airplane on the ground?”
Have you ever seen the shadow of an airplane on the ground? (Photo Credit: joo830908/Shutterstock)
There are two reasons why we do not see the shadows of flying airplanes.
Airplanes fly at a very high altitude of 35,000-40,000 feet, which is why their shadows are not visible from the ground. Even if the airplane flies lower, you still won’t be able to see its shadow. However, during takeoff and landing, when the plane is just a few dozen feet off the ground, its shadow becomes visible. This is because the airplane is too small compared to the light source, the sun, and its distance from the earth’s surface. Birds also cannot cast a well-defined shadow due to their small size. In contrast, a massive asteroid passing by Earth would create a visible shadow on the ground. This principle is also seen in solar and lunar eclipses, where the shadow of the moon is cast on the sun. Therefore, flying airplanes do cast shadows, but they are so scattered that they are virtually invisible to us on the ground.