Fortunately, the ancient Greeks were able to refute the statement about flat Earth long before the advent of satellites and rockets, and for this they needed only common sense, and not any technology.
Idea of the spherical Earth
More than 2300 years ago, lived a great thinker named Aristotle, who became best known for his polemic with Plato. Aristotle was well versed not only in politics, poetry, theater, music, the natural sciences and philosophy, but he was also a child prodigy in astronomy. Other ancient Greek thinkers hinted at the idea of a spherical Earth with the help of vague poetic utterances (among them Plato and Pythagoras), but Aristotle was the first who could formulate it.
What is the subject of the treatise of Aristotle
In the treatise "On Heaven", written back in 350 BC. He explained: "Again, our observations of the stars make it obvious not only that the Earth is round, but also that this circle is large, because even a small change in position to the south or north causes a clear change in the horizon."
"Indeed, in Egypt and in the vicinity of Cyprus you can see some stars that are not visible in the northern regions; and stars that can not be seen in the north are very different in these regions. All this shows that the Earth is round in shape, and also that it is a sphere of a large size. "
Eratosthenes calculations
Thus, we understand how this idea arose, but we should thank Eratosthenes for developing this theory. Eratosthenes was a librarian, mathematician, poet, historian, astronomer and "father of geography".
Approximately in 250 BC. e. he noted that the wells and pillars in the city of Siena (now Aswan in Egypt) do not cast shadows at noon during the summer solstice, as the Sun is directly overhead. But at the same time and the same day in Alexandria, located about 800 kilometers from Siena, these shadows were long and elongated.
Eratosthenes knew that the Sun is a massive object, and its rays that hit the Earth must be relatively parallel. So why were the shadows so different? He decided that this would be impossible if the Earth was flat, hence it should have a spherical shape. In fact, Eratosthenes was able to find out that the angle of the sun's rays is about 7 degrees, so he managed to make a surprisingly accurate estimate of the size of our planet.
Needless to say, the rejection of this idea did not become something new in the modern era of celebrities and social networks. The idea of a spherical Earth was tried earlier to refute, and did it both brilliant medieval Islamic scholars and pseudoscientists of the XIX century.
