Eratosthenes: What Is The Circumference Of The Earth?
Question: What is the circumference of the earth?
The circumference of the earth was at one time an interesting question and today an important piece of information. It is a question people have been trying to answer as early as 200 BC. Today, modern scientists and equipment – such as satellites and other similar devices – tell us the circumference of the earth is 40,075 kilometers when measured at the equator, and though the ancient peoples did not have access to such advanced technology and equipment, but instead were forced to use rather primitive methods to measure the circumference, their estimation of the answer was remarkably close to the true figure.
Eratosthenes, a Greek mathematician who lived around 200 BC, used an idea proposed by the philosopher and fellow Greek Aristotle to measure the circumference of the Earth. Aristotle’s idea was as follows: if the Earth was round, then stars in the distant night sky would appear in different positions to different observers at varying latitudes. Eratosthenes was able to use this concept in order to measure the circumference of the earth at two different locations: the city of Syene, Egypt, and the city of Alexandria, Egypt. …show more content…
During the summer solstice, the sun passes directly above Syene, Egypt, which is about 5,000 stadia away from Alexandria. At noon the same day, Eratosthenes measured the angular displacement of the sun from overhead at Alexandria. The displacement was 7.2 degrees, and since Eratosthenes knew there are 360 degrees in a circle, he was able to calculate that the displacement was 1/50 of a circle. With this information, Eratosthenes was able to use geometry, which shows that the ratio of 1/50 is the same as the ratio of the distance between the cities of Syene and Alexandria to the total circumference of the
The circumference of the earth was at one time an interesting question and today an important piece of information. It is a question people have been trying to answer as early as 200 BC. Today, modern scientists and equipment – such as satellites and other similar devices – tell us the circumference of the earth is 40,075 kilometers when measured at the equator, and though the ancient peoples did not have access to such advanced technology and equipment, but instead were forced to use rather primitive methods to measure the circumference, their estimation of the answer was remarkably close to the true figure.
Eratosthenes, a Greek mathematician who lived around 200 BC, used an idea proposed by the philosopher and fellow Greek Aristotle to measure the circumference of the Earth. Aristotle’s idea was as follows: if the Earth was round, then stars in the distant night sky would appear in different positions to different observers at varying latitudes. Eratosthenes was able to use this concept in order to measure the circumference of the earth at two different locations: the city of Syene, Egypt, and the city of Alexandria, Egypt. …show more content…
During the summer solstice, the sun passes directly above Syene, Egypt, which is about 5,000 stadia away from Alexandria. At noon the same day, Eratosthenes measured the angular displacement of the sun from overhead at Alexandria. The displacement was 7.2 degrees, and since Eratosthenes knew there are 360 degrees in a circle, he was able to calculate that the displacement was 1/50 of a circle. With this information, Eratosthenes was able to use geometry, which shows that the ratio of 1/50 is the same as the ratio of the distance between the cities of Syene and Alexandria to the total circumference of the