Who, when and how first determined the size of the globe? Detailed answer

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Who, when and how first determined the size of the globe? Detailed answer

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Who, when and how first determined the size of the globe?

The dimensions of the globe were first estimated around 240 BC by Eratosthenes of Cyrene (c. 276-194 BC).

Working in the famous Library of Alexandria, he discovered an old papyrus, from which he subtracted that in the south of Egypt, in Siena (present-day Aswan), at noon on June 21, a vertical pole does not cast a shadow, the reflection of the Sun can be seen at the bottom of the deepest wells, and therefore, The sun is directly overhead. Eratosthenes was not too lazy to check whether a vertical pole casts a shadow at noon on June 21 in Alexandria.

Finding out what was casting, he measured the length of the shadow. If the Earth is flat, then both in Syene and in Alexandria the sun's rays should fall on the Earth at the same angle and the shadows cast by the pole should have the same length. If this is not the case, then the surface of the Earth is curved, and the more its curvature, the greater should be the difference in the length of the shadows.

The length of the shadow measured by Eratosthenes in Alexandria showed that the angular distance between Alexandria and Syene should be about 7 degrees (if you mentally continue the poles installed vertically in these cities to the center of the Earth, they will intersect at an angle of 7 degrees). Eratosthenes hired a man who measured the distance between the indicated cities with steps, and it amounted to 5 thousand Greek stadia. Since 7 degrees is approximately 1/50 of a full circle (360 degrees), then the length of a full circle should be equal to 250 thousand stages, Eratosthenes reasoned. And then the radius of the globe is 40 stadia.

Translating this value into modern measures of length (the ancient Greek stage is 175 meters), we get that the radius of the globe is 7 thousand kilometers. Eratosthenes' estimates were surprisingly accurate for those times; according to modern data, the average radius of the Earth is 6371 kilometers.

Author: Kondrashov A.P.

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The English meteorologist Clement Wragg, who worked in Australia, was the first to name tropical cyclones. At first he called them the names of mythological monsters and the letters of the Greek alphabet, and then he began to assign the names of local politicians, who especially annoyed him. However, the international practice of naming hurricanes arose after World War II, when the Americans decided to use female names for this purpose. But numerous feminist protests eventually led to the fact that in 1979 the World Meteorological Organization approved a new procedure for naming tropical cyclones by both female and male names.

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