What Greek astronomer used observations of the Sun's position at noon on the summer solstice at Alexandria and Syene to determine the circumference of the Earth?

Answer 1

n the 200s BC, Eratosthenes figured out a very clever method for measuring the size of the Earth. He heard about a well in Syene (in modern Egypt) where the sunshine reached the bottom only at noon in the summer solstice. So he knew exactly when the sun was directly overhead. Further north in Alexandria he put a stick straight up in the ground and measured the angle of its shadow at that precise moment as 7.2°. It meant that the distance from Syene to Alexandria was 7.2/360 of the Earth's circumference. Since he knew this distance, he could compute the circumference as 39250km, a diameter of about 12500km.n the 200s BC, Eratosthenes figured out a very clever method for measuring the size of the Earth. He heard about a well in Syene (in modern Egypt) where the sunshine reached the bottom only at noon in the summer solstice. So he knew exactly when the sun was directly overhead. Further north in Alexandria he put a stick straight up in the ground and measured the angle of its shadow at that precise moment as 7.2°. It meant that the distance from Syene to Alexandria was 7.2/360 of the Earth's circumference. Since he knew this distance, he could compute the circumference as 39250km, a diameter of about 12500km.

Answer 2

The earth's circumference is calculated by measuring the distance around the world at the equator.

Earth circumference can be approximated by taking earth's radius (6378 km) and multiplying by 2 pi, which gives 40,074 km. This is approximate because earth is not a perfect sphere.

Answer 3

Earth is not a perfect circle or sphere, and therefore does not have a set and unique circumference all the way round.

However, approximations through a single plane of the earth can be found by measuring angles and calculating from distances; for example, Eratosthenes estimated the circumference through Syene and Alexandria, by measuring the angles of parallel posts and knowing the distance between them. When one post has no shadow (and is "at vertical" the other has a shadow at an angle). By using the ration of this angle to the whole circle, you can figure the whole circumference from the section distance.

Answer 4

The name of the person to first do this has been lost to antiquity. It happened more than once, however. Many different cultures and civilizations had people who figured out how long it took the earth to orbit the sun. They did this by noting how long it took the constellations to return to their annual positions. There are ancient astronomical observatories in a number of locations around the world. The Egyptians were famous for building structures that could be used for this purpose. Stone Henge, in England, is an observatory. There are also stone piles in South America that were most likely used for astronomical observations.

Answer 5

Eratosthenes was able to calculate the approximate circumference of the earth. The difference in the angle between two cities along a curve. He multiplied the distance enough to equal 360 degrees. This made the circumference of the earth. But, of course it would be slightly off.

Answer 6

Eratosthenes was the first person to nearly correct the measurement of the earths

circumference.

Answer 7

Eratosthenes of Cyrene (Greek 276 BC

Answer 8

Eratosthenes