Extended life was not the only observable difference between the two groups.

VOA: special.2009.09.01

It has no observable nationality at all, does it?

那么这本，并没有显示出任何的异国色彩，不是吗？

耶鲁公开课 - 现代诗歌课程节选

They are not observable.

是无法观察到的。

耶鲁公开课 - 死亡课程节选