1. The Limited Human Field of View

One of the primary reasons the Earth appears flat is the limitation of our field of view. The human eye can only see a short distance before objects disappear beyond the horizon. This horizon appears as a straight line, creating an illusion of flatness. Since we usually navigate and live on relatively small-scale areas compared to the Earth’s vast size, we do not experience its curvature directly.

2. The Immense Size of Earth

The Earth has a circumference of about 40,075 kilometers (24,901 miles). Given its enormous scale, any curvature is negligible over small distances. To detect a noticeable curve, one would need to travel hundreds of miles or gain a high-altitude vantage point, such as from an airplane or spacecraft.

3. The Horizon and Atmospheric Refraction

The horizon is the apparent boundary between the Earth and the sky. Due to the Earth’s curvature, objects moving away from us gradually disappear bottom-first, a phenomenon that can be observed with ships on the ocean. However, atmospheric refraction, where light bends as it passes through different layers of the atmosphere, can distort this perception, further contributing to the flat-Earth illusion.

4. The Law of Perspective

Objects that are extremely far away, such as mountains or distant buildings, appear to shrink and eventually merge with the horizon. This effect makes it seem as though everything lies on a flat plane rather than a curved surface.

5. Gravity’s Role in Perception

Gravity pulls everything toward the Earth’s center, creating a sensation of standing on a flat surface. Since we experience the force of gravity uniformly in all directions, we lack a direct, intuitive sense of the Earth’s curvature under normal circumstances.

6. Airplane and High-Altitude Observations

From an airplane flying at high altitudes, passengers can observe a slight curvature of the horizon. Astronauts aboard the International Space Station (ISS) or lunar missions have captured clear images of the Earth’s round shape. These perspectives confirm that the flat appearance of the Earth from the ground is an optical illusion.

Scientific Evidence of Earth’s Spherical Shape

While the illusion of a flat Earth is compelling at ground level, multiple scientific methods and observations confirm its true shape:

• Eratosthenes’ Experiment (3rd Century BCE): By measuring the angle of shadows in two different locations, the Greek mathematician Eratosthenes calculated the Earth’s circumference with remarkable accuracy.
• Satellite Imagery: Modern satellites provide continuous images of a spherical Earth.
• Lunar Eclipses: The Earth’s round shadow cast on the Moon during an eclipse confirms its curvature.
• Time Zones: The variation in time across different locations on Earth is only possible due to its curved surface.