Scientists have considered flying away from Earth to fully view our planet’s spherical shape. So, how far would they need to go?
The Earth is Round
Interestingly, as far back as 2,000 years ago, even without satellites or modern technology, humans knew that the Earth was spherical.
The Ancient Greeks were the first to believe in the spherical shape of the Earth even before having any evidence to prove it. The renowned mathematician and philosopher Pythagoras was the first to hypothesize that the Earth is spherical around 500 BC. Pythagoras argued that, in his view, a sphere is the most perfect shape.
Many believed in the spherical Earth long before Christ. (Image: Sohu)
A century later, the philosopher Plato also expressed a similar opinion. However, the person who truly provided evidence for the spherical nature of the Earth was the Greek philosopher Aristotle. He presented several pieces of evidence in his book “On the Heavens” written around 350 BC. According to Aristotle, we can only see the shadow of the Earth on the Moon during lunar eclipses, and it always appears spherical regardless of Earth’s position in its rotation.
In another argument, he noted that the positions of stars would differ when viewed from different locations on Earth. For instance, stars visible in Egypt cannot be seen in Cyprus, which is 1,000 km away. This demonstrates that the Earth is not only round but is indeed a sphere.
In ancient Europe, there was also a widespread belief in the spherical nature of the Earth. Particularly after explorer Ferdinand Magellan’s expedition around the globe, many became more convinced of the existence of the spherical Earth theory.
How Can We Confirm the Earth is Spherical?
Many believe that observing coastlines can confirm that the Earth is spherical. However, scientists state that this method cannot observe the outline of Earth’s curvature.
Even using a telescope to observe the ocean, one cannot prove this argument. You can clearly see the coastline with a telescope, but on land, you would only see a horizon. Nevertheless, regardless of where you stand, you are on a segment of the Earth, and your view is limited; the curvature of the Earth varies, and the distances between segments are also different.
Our Earth is not flat or empty everywhere, so verifying that surfaces are uniformly curved is very challenging. (Image: Sohu)
This limitation of segments can only prove that the Earth has a curved surface but cannot show whether other areas are curved.
Our Earth is not flat or empty everywhere; it also has mountainous terrains and plateaus, making it very difficult to verify that surfaces are uniformly curved. Similarly, scientists have stated that even if a person stands on the highest mountain in the world, Mount Everest, they still cannot see the entire Earth.
How Far Must One Go from Earth to See its Spherical Shape?
While sitting on an airplane, we can see mountains and the ground below appearing flat and square. The typical altitude of airplanes ranges from 7,000 to 12,000 meters. However, according to what the human eye sees while flying, this altitude is still insufficient to clearly discern the spherical shape of the Earth. Given the Earth’s massive size, with a radius of over 6,000 km, an airplane flying at 10,000 meters cannot capture the full panorama.
So, what does Earth look like to astronauts when they fly into space?
Neil Armstrong saw the Earth as a complete sphere when standing on the Moon. (Image: Sohu)
According to many astronauts’ descriptions, at an altitude of 118 km above sea level, they can see a pale blue star in their view. This height can be considered the boundary between Earth and space. Beyond this altitude, it is clear that, from a human perspective, the Earth appears as a sphere.
American astronaut Neil Armstrong once recounted that while standing on the Moon, he saw the Earth as a complete sphere and was awestruck by the sight before him.
In fact, at an altitude of 1,000 km above the Earth’s surface, astronauts can see a larger arc of Earth’s edge through the windows. If the altitude is increased to 2,000 km, at this distance, astronauts can clearly see the curvature of the Earth. Naturally, at a distance of about 400 km from the Earth’s surface, such as at the International Space Station, astronauts can easily see the Earth as a clearly defined sphere.
