Using little more than clever trigonometry, it’s possible to estimate:

- the circumference of the earth
- the ratio of distance earth to the sun : earth to the moon
- the ratio of size of the sun and the moon.

and for that matter, all of these stats were known in (IIRC) ancient Greece.

Has it been proven that the same thing could have been done with measuring the speed of light (a little high school math + some measuring tools available BCE)?