The Earth is spherical, so why do people perceive it as flat?

Since ancient times, it has been known that the Earth is round. This has been repeatedly confirmed by photographs of our planet taken from space. But why do people, while standing on the surface of our planet, perceive it as flat? The answer lies in perspective; after all, humans are relatively small beings living on a massive sphere, as noted by Space.

The average height of an adult is between 1.5 and 2 meters. If one stands, like a circus performer, on a large ball with a diameter of 1 meter, it becomes evident that this ball curves in all directions, confirming its round shape.

However, if a fly were to be placed on this ball, its view would be significantly smaller than that of an adult, as the insect would only be a few millimeters above the surface of the ball. Due to its tiny size, the fly would never be able to see the entire ball, as it is too close to the surface.

The diameter of the Earth is nearly 12.8 million meters, so even a very tall person, standing at 2 meters, will have a limited view. The human eye cannot perceive the size and shape of the immense sphere on which it resides. Even ascending to the peak of the tallest mountain, Everest (8,850 m), one still cannot see that the Earth is spherical.

One can only confirm that our planet is round by ascending to an altitude of at least 10 km above its surface. This is because the length of the horizon visible to a person depends on the height at which they are positioned.

When on the surface of the Earth, if there are no obstructions to the view, people can only see approximately 4.8 km of the horizon. This means they cannot perceive the curvature of the Earth, much like the fly on a much larger ball. To fully ascertain that our planet is spherical, one needs to ascend much higher than 10 km. A flight to several hundred kilometers above the Earth's surface is required.

On the other hand, it is important to understand that the Earth is not a perfectly round shape. In reality, our planet is a slightly flattened spheroid. This means that the Earth is a bit wider at the equator. The reason for this is related to the Earth's rotation around its axis, which creates a centrifugal force. This is the same force that would cause a person to fly off a spinning carousel if they do not hold on. It is this centrifugal force that creates a slight bulge at the equator.

Mountains and oceanic depressions also slightly distort the shape of our planet. They cause minor changes in the strength of the Earth's gravitational field, which is the force that pulls everything toward the center of the planet.