years ago they knew many things about the moon.

写成特殊疑问句为：How big was it?How far was it from the earth?写成陈述语序的宾语从句为：how big it was 就是说how big其到了引导从句的作用,主语it要放在表语was的前面；而How far was it from the earth?也是同样的道理。