Question

Who calculated the actual circumference of the earth in the 3rd century CE?
A) Ptolemy
B) Plato
C) Aristotle
D) Eratosthenes

Answer 1

Hint: The circumference of the Earth is the distance around it. The circumference of the earth is 40,007,863 kilometres when measured around the poles (24,859.734 mi). It is 40,075.017 kilometres around the Equator (24,901.461 mi)

Complete answer:
Now let us loo at the given options:
Option A-Claudius Ptolemy was a Greek mathematician, astronomer, natural philosopher, geographer, and astrologer who authored a number of scientific treatises, three of which were influential in subsequent Byzantine, Islamic, and Western European science.This is an incorrect option

Option B-Plato was an Athenian philosopher who founded the Platonist school of thought and the Academy, the first institution of higher learning in the Western world, during the Classical period in Ancient Greece.This is also an incorrect option.

Option C- During the Classical period in Ancient Greece, Aristotle was a Greek philosopher and polymath. He was the founder of the Lyceum, the Peripatetic school of philosophy, and the Aristotelian legacy, and was taught by Plato.This is also an incorrect option.

Option D-In the third century CE, Eratosthenes measured the real circumference of the earth. He was a Greek poet, astronomer, and science scholar. His work is similar to what is now known as geography research, and he pioneered terminology that is still used today.

The calculation of the Earth's diameter is the most notable of Eratosthenes' results, who determined that the meridian is 252,000 stadia long, with an error on the real value of between 2.4 percent and +0.8 percent (assuming a value for the stadion between 155 and 160 metres). In a book called On the Measure of the Earth, which has not been preserved, Eratosthenes mentioned his arc measurement technique.

According to the same Cleomedes, Eratosthenes' method was actually more complex, and his intention was to present a simplified version of the one mentioned in Eratosthenes' text. The method was based on many surveying trips carried out by experienced bematists whose task it was to precisely calculate the extent of Egypt's territory for agricultural and taxation purposes.

Furthermore, the fact that Eratosthenes' measure exactly equals 252,000 stadia may be deliberate, given that it is a number that can be divided by all natural numbers from 1 to 10: Some historians believe Eratosthenes modified the 250,000 value written by Cleomedes to this new value to simplify calculations; others believe Eratosthenes changed the 250,000 value written by Cleomedes to this new value to simplify calculations. On the other hand, according to Pliny, who writes about the stadion "according to Eratosthenes' ratio," Eratosthenes introduced a new length unit based on the length of the meridian. Eratosthenes measured the real circumference of the earth.

Note: The angle of a shadow cast by a stick at noon on the summer solstice in Alexandria was found to be around 7.2 degrees, or about 1/50 of a full circle, by Eratosthenes. He realised that if he knew the distance between Alexandria and Syene, calculating the circumference of the Earth would be easy.