Kisah Eratosthenes, Orang Pertama yang Mengukur Keliling Bumi

Summary

The video explores how Eratosthenes, a brilliant scholar from ancient Greece, calculated the Earth's circumference over 2,000 years ago. Using the unique phenomenon of a shadowless well in Aswan during the summer solstice, Eratosthenes measured the angle of the sun at two locations—Alexandria and Aswan—and used this to determine the Earth's size. With the help of a foot-measuring assistant and the Pythagorean theorem, he calculated the circumference to be approximately 40,000 km, remarkably close to modern measurements. His method demonstrates the power of curiosity and ingenuity in ancient science.

Takeaways

• 😀 Eratosthenes, a Greek scholar born in 276 BC, is famous for calculating the Earth's circumference.
• 😀 The Earth was imagined as a circle by Eratosthenes to estimate its circumference using geometry.
• 😀 He worked as the head of the Alexandria Library, one of the most prestigious positions of his time.
• 😀 The idea for measuring the Earth's circumference came from a phenomenon observed in Aswan, Egypt, where the sun cast no shadow at noon during the Summer Solstice.
• 😀 Eratosthenes measured the angle of the sun's rays by comparing the shadow length in Alexandria with the shadow at noon in Aswan.
• 😀 By applying the Pythagorean theorem and understanding the geometry of the situation, Eratosthenes calculated the Earth's circumference.
• 😀 Eratosthenes used a shadow length and pole height to form a right triangle, using the Pythagorean theorem to solve for unknown values.
• 😀 The angle formed by the sun's rays in Alexandria was 7.21 degrees, which was used in the calculation.
• 😀 To measure the distance between Alexandria and Aswan, Eratosthenes employed the help of a trained individual who used foot measurement (stadia).
• 😀 Eratosthenes concluded that the Earth's circumference was about 40,000 km, which is very close to the modern measurement of 40,070 km at the equator.

Q & A

Who was Eratosthenes and what role did he play in measuring the Earth's circumference?

Eratosthenes was a Greek scholar born in 276 BC in Libya, who became the head of the Library of Alexandria. He is famous for being the first person to measure the Earth's circumference accurately using basic geometry and observational data.

What unique phenomenon did Eratosthenes learn about from a traveler?

Eratosthenes heard about a phenomenon occurring in the city of Aswan (formerly known as Shen), where, during the Summer Solstice, the sun was directly overhead and cast no shadow in a well. This observation sparked his curiosity about the Earth's circumference.

Why was the location of Aswan significant to Eratosthenes' measurement of the Earth's circumference?

Aswan's location at 23.5 degrees North Latitude was crucial because it allowed Eratosthenes to use the angle of the sun’s rays and the shadow of a pole to calculate the Earth's circumference, as the city experiences no shadow during the solstice.

What method did Eratosthenes use to calculate the circumference of the Earth?

Eratosthenes used geometry. He compared the angle of the sun's rays at two locations (Alexandria and Aswan) and the distance between the cities. Using the Pythagorean theorem and the angular difference, he was able to estimate the Earth's circumference.

What role did the pole and its shadow play in Eratosthenes' calculation?

The height of the pole and the length of its shadow in Alexandria helped Eratosthenes determine the angle of the sun's rays. This angle, along with the distance between Alexandria and Aswan, formed the basis of his calculation.

What was the unit of measurement used to determine the distance between Alexandria and Aswan?

The unit of measurement used was the 'stadia.' Eratosthenes recruited a man named Bamesthes, who was trained to measure distances using his own footsteps, to measure the distance between the two cities.

How did Eratosthenes estimate the Earth's circumference using the distance between Alexandria and Aswan?

Eratosthenes used the ratio of the angular difference between the two cities (7.21 degrees) to 360 degrees. By comparing this ratio with the distance between the cities, he was able to estimate the Earth's total circumference.

What was the estimated circumference of the Earth calculated by Eratosthenes?

Eratosthenes estimated the Earth's circumference to be 250,000 stadia, which is approximately 40,000 kilometers.

How accurate was Eratosthenes' calculation of the Earth's circumference?

Eratosthenes' calculation was remarkably accurate. The current accepted value for the Earth's circumference at the equator is around 40,070 kilometers, very close to his estimate of 40,000 kilometers.

Why was Eratosthenes' method considered groundbreaking in his time?

Eratosthenes' method was groundbreaking because he used simple geometry, observation, and logic to calculate the Earth's circumference, which was a major scientific achievement for his time, especially given the limited technology available.