Born to perceive a flat world: scientists explain why we fail to recognize the Earth's curvature.

Since ancient times, the Earth has been regarded as a spherical body, a concept supported by both observations and scientific research. Despite this understanding, the planet's vast size compared to human scales makes its curvature imperceptible in everyday life. This has led to numerous theories, including the one suggesting that our planet is a flat disk; however, there are many scientific explanations that refute the illusion of such a shape, as noted by The Conversation.

This phenomenon of perceiving the Earth as flat is dictated by perspective: a person who is 1 meter 82 centimeters tall observes a massive sphere with a diameter of over 12,000 kilometers while standing just a few meters above its surface, explains Kelly R. McGregor, a professor of geology at Macalester College. This limited viewpoint, akin to a fly on a ball, prevents a person from seeing the Earth's curvature from ground level. To perceive the curvature of the Earth, one must ascend significantly higher, notes Professor McGregor.

At altitudes exceeding 10 kilometers, the planet's horizon begins to exhibit its slight curvature. This effect is barely noticeable from passenger airplanes but is most apparent from space, where astronauts and satellites capture the complete spherical shape of the Earth. However, even these views emphasize that the Earth is not a perfect sphere but an oblate spheroid. The equatorial bulge, caused by the centrifugal forces of the Earth's rotation, results in its slightly flattened shape at the poles.

Topographical features further complicate the Earth's shape, says McGregor. Mountains and oceanic trenches contribute to minor deviations in the planet's gravitational field, which is the subject of study in geodesy. This discipline is crucial for applications such as sea-level mapping and infrastructure design worldwide.

Physicist Neil deGrasse Tyson has discussed how natural processes cause celestial bodies, like planets and stars, to take on a rounded shape, as gravity pulls mass toward a central point. From an observational standpoint, human experience is limited to a horizon that typically extends about five kilometers at most on flat terrain. This restricted field of vision explains why the Earth appears flat in everyday scenarios to everyone on it.

Even at the summit of Mount Everest, the earthly expanses already exceed the observer's viewpoint. Interestingly, this topic highlights the importance of perspective and scale in understanding many celestial phenomena, states McGregor. Although modern technology allows us to glimpse the true shape of the Earth, it also underscores the challenges of conveying the grandeur of planetary science in an accessible manner, which helps to prevent the emergence of many fantastical theories that nevertheless have numerous adherents.