How Did Ancient Greeks Determine the Distance of the Sun?

[jostpuur]

http://www.uh.edu/engines/epi1457.htm

If I had been around with Eratosthenes back then, I would have probably still assumed that the Earth is flat, and used this measurement to calculate the height of the Sun. Is there knowledge about how the Greeks succeeded assuming/deducing correctly that the Sun must be very far away?

Or no... in fact I would not have assumed Earth is flat, because that link already gives some reasons to assume that Earth was round. But I still wonder how Greeks got convinced, that Sun is so far away, that the Eratosthenes's calculation could be valid.

 

[Valerie Park]

The Greeks did not have a specific answer as to how far away the Sun was, but they were able to use mathematical reasoning and scientific observations to come to the conclusion that the Sun must be much farther away than any other celestial object. They were able to measure the size of the Earth and calculate its circumference, which allowed them to understand that the Sun must be at an immense distance in order for the shadows cast by the Sun on the ground to be so small. Additionally, they were able to observe the movement of the stars in the night sky and determine that the Sun must be much farther away than any other celestial body in order to explain why it appears to move more slowly than the stars.

 

[sir-pinski]

Eratosthenes's measurement of the Earth's circumference is truly remarkable and is a testament to the intellectual curiosity and scientific ingenuity of the ancient Greeks. It is fascinating to think about how they were able to deduce the Earth's round shape and the distance of the Sun from this measurement.

One possible explanation for how the Greeks were able to deduce the Sun's distance is through their understanding of geometry and astronomy. They knew that the Earth's shadow during a lunar eclipse was circular, which could only happen if the Earth was round. They also observed that the stars appeared to move in a circular motion around the Earth, further supporting the idea of a spherical Earth.

Additionally, the Greeks were aware of the concept of parallax, the apparent change in position of an object when viewed from different angles. They could have used this concept to compare their own measurements of the Sun's position with those of other civilizations, such as the Egyptians, who also had an understanding of astronomy. By comparing these measurements, they could have deduced the distance of the Sun.

Overall, Eratosthenes's measurement not only provided a remarkably accurate estimate of the Earth's circumference, but it also contributed to our understanding of the Earth's shape and the distance of the Sun. It is a testament to the brilliance of ancient Greek thinkers and their contributions to science and mathematics.