【Request】 Is the Earth really spherical?
We often hear that the earth is spherical, but is that true?
I will explain the shape of the earth in two parts.
In this article, we will take a look at the scientific background to reveal the shape of the Earth.
Flat Earth theory
Until a few hundred years before Christ, people thought of the Earth as a disk.
The idea that the earth is a disk is called Flat Earth theory.
It may seem hard to believe now, but back then, there was no technology that could give you a bird’s-eye view of the Earth like GPS, so it’s no wonder we’re imagining this kind of Earth.
Spherical Earth theory
At that time, while the flat earth theory was mainstream, a person advocated the theory that the earth was a sphere.
The idea that the earth is a sphere is called Spherical Earth theory.
It is said that Pythagoras, who is famous for discovering the Three Squares Theorem, first proposed the Earth Sphere Theory, but there seem to be various theories.
This led to the gradual spread of the globular theory.
Aristotle’s proof of Spherical Earth theory
Around the 4th century BC, a man named Aristotle claimed that the Earth was a sphere based on two observations.
Grounds 1: The shadow of the earth reflected on the moon during the lunar eclipse was round
The first reason is that during the lunar eclipse, the Earth’s shadow was round.
Aristotle realized that the Earth’s shadow on the moon was always round.
The fact that the shadow is always round means that from any angle it is a circle, meaning that the earth is a sphere.
Grounds 2: The altitude of the stars varied from place to place
The second reason is the altitude of the stars.
Altitude refers to the angle from the ground when an observer looks up at a star.
Now let’s compare how the stars look at different altitudes when the Earth is flat and when the Earth is spherical.
The assumption is that the stars are so far away from Earth that the light from them reaches in parallel wherever they are on Earth.
If the Earth were a flat disk, stars would be visible at the same altitude no matter where they were on Earth.
On the other hand, if the Earth is a sphere, the angle of the plane of the Earth as seen from the stars varies from place to place, so the altitude at which the stars are visible should also change.
So what was the actual observation?
The altitude at which the stars were visible varied from place to place.
Based on the above, Aristotle proved Spherical Earth theory.
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