I think the answer you are looking for is parallax. Hipparchus used parallax to not only measure the distance from the sun, but also the moon. Although he was off my a couple hundred yards or so he actually measured the moon before the sun.
Answer: Emperor Wuzong of the late Tang dynasty greatly disliked Buddhism because it was foreign, because the monks didn't pay taxes, and because it was becoming a very, very powerful force in China. In 845, he began the repression of Chinese Buddhism.
