很久以前

Long long ago, we knew the periodic motion of a planet.

前, 们就知道行星的周期运动。

That was a great while ago.

那是前的。

An avocet has a long, strongly upcurved bill which contains a complex and highly specialized system of lamellae capable of filtering out small food items.

找一下网路上的资料，似乎也没有讨论他嘴上弯原因的文献，可能有前的，不过就不太好找。