2024-01-12 23:00:00
Provided by Getty Image Bank
Nowadays, there is a lot of evidence that the Earth is round, but in the past, many people believed that the Earth was flat. How did ancient people figure out that the Earth was round?
● In the past, it was believed that the Earth was flat?
I am researching stars and space at the Korea Astronomy and Space Science Institute. Every year, I fly to overseas conferences and meet various scientists. The conference is an event where scientists from all over the world who are researching the same field come together to introduce their newly discovered research results. Scientists from all over the world share their research at academic conferences, become friends, and collaborate on research.
Flying around the world is a natural thing these days. However, just 150 years ago, few people from Korea traveled to Europe or the United States. Before Ferdinand Magellan succeeded in circumnavigating the world in 1519, no one had ever circumnavigated the Earth. Many people even believed that the Earth was flat.
Take a look at the map called ‘Cheonhado’ made in Joseon in the early 18th century. The world depicted in this map of the world is shaped like a wide, flat disk. This shows that people in ancient times probably thought the Earth was flat. The map of the world contains the entire world known at the time, but strangely enough, the shapes of the land and sea depicted on the map, as well as the names and locations of the countries shown on the map, are all different from reality.
Cheonhado is a map containing the thoughts of ancient people who might not explore the entire world themselves, but only imagined the world through legends or word of mouth from other people.
Cheonhado: A world map made in a circular form during the late Joseon Dynasty. It was produced in various ways in the late Joseon Dynasty and widely distributed to the civilian public. It is currently stored at the National Museum of Korea. Provided by the National Museum of Korea
● The size of the Earth illuminated by a single wooden stick?
Not everyone in the past thought the Earth was flat. 2,400 years ago, the Greek philosopher Aristotle noticed that stars that were clearly visible in Egypt were not visible in other areas farther north. And he argued that this might only happen if the ground was curved into a ball. Aristotle also assumed that the Earth was shaped like a ball because the shadow the Earth casts on the Moon during a lunar eclipse was round.
A lunar eclipse phenomenon is representative evidence that the Earth is round. The fact that the Earth’s shadow on the moon is round shows that the Earth is shaped like a ball. offered by Tomruen
About 100 years later, scientists were able to measure the size of the ball-shaped Earth with great precision. The philosopher Eratosthenes was the director of the Library of Alexandria, Egypt, which had the largest collection of books in the world at the time. One day he heard a fascinating story regarding a city called Aswan at the southern tip of Egypt.
There is a deep well in that city. If you look into the well at noon on the summer solstice, the longest day of the year, the well does not receive any sunlight and appears dark. The direction from which the sunlight shines and the direction from which the well was opened are completely different. This phenomenon occurred because sunlight was completely blocked by people looking at the well.
The restored Library of Alexandria, Egypt and Eratosthenes (bottom right). Provided by Wikimedia
After hearing this story, Eratosthenes became curious regarding how the sunlight shines at noon on the summer solstice in Alexandria, where he lived. He asked an expert who was measuring the size of the land precisely at the time to examine the shadow. The engineer placed a straight stick on the ground and measured the length of the shadow. The angle of sunlight hitting Alexandria at noon on the summer solstice was regarding 7.
Through this fact, Eratosthenes discovered that if a line was drawn from the center of the Earth to Alexandria and Aswan, the angle formed by the two lines would also be 7. If you know this angle and the distance from Alexandria to Aswan, you can determine the circumference of the Earth. The size of the Earth calculated by Eratosthenes was accurate enough to be only 2% different from the value we know today.
Like this, the reason we can now travel around the world by plane is because scholars like Aristotle and Eratothenes have discovered the shape and size of the Earth since ancient times.
Seongwook Hong, Senior Researcher, Korea Astronomy and Space Science Institute
※Introduction of the author
Seongwook Hong, Senior Researcher, Korea Astronomy and Space Science Institute He is an astronomer who studies cosmology and extraterrestrial life at the Korea Astronomy and Space Science Institute. He is researching the cosmic macrostructure, the largest structure in the universe, using computer simulations and artificial intelligence. He currently serves as a senior researcher at the Theoretical Astronomy Center of the Korea Astronomical Research Institute.
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