Question

How did early astronomers figure out how large the Earth really was?

Thank you! :-)

Answer 1

Yes, see here:

http://www.astro.washington.edu/courses/labs/eratosthenes/rung1.html

The ancient Greeks also measured the distance to the Moon:

http://www.astro.washington.edu/courses/labs/eratosthenes/rung2.html

They also attempted to measure the distance to the Sun:

http://www.astro.washington.edu/courses/labs/eratosthenes/rung3.html

but they could not obtain a accurate figure for this.

Answer 2

Check this article.

http://en.wikipedia.org/wiki/History_of_geodesy