Discoveries of genuine changes on the lunar surface are never within the reach of the average amateur observer . 月面真实变化的发现从来不是一般业余天文学家力所能及的。
The moon is nearly inexhaustible test field for the abilities of an observer and for the quality of his instrument . 月球几乎永远是检验观测者能力和望远镜质量的理想场所。
It took an outside observer like you or me to see that he was the interpreter of twentieth-century man . 只有你我这样的圈外人，旁观者清，才看得出他体现了二十世纪人的精神。
Each observer is correct in his own frame of reference, but simultaneity is not an absolute concept . 每一个观察者在他所处的参照系中都是正确的，但同时性并不是一个绝对的概念。
The light reflected and refracted several times by a droplet and then finally returned to the observer is therefore white . 光由粒子反射和折射数次，最后到达观察者，所以是白色的。
The impartial observer had to acknowledge that his lack of regulation culture did not seem to impede him in any way . 不抱偏见的观察家不得不承认，缺乏正规教育看来并未给他造成障碍。
Whether or not two events at different space points are simultaneous depends on the state of motion of the observer . 在不同的空间点上发生的两个事件是否同时，取决于观察者的运动状态。
An observer on our galaxy or on any other would get this illusion of his neighbors fleeing in all directions . 在我们或在其他任何星系上的观测者会产生这种错觉--他的邻居正在向各方向逃散。
At the lead bombardier dropped his bomb, the pilots, observers and radiomen in the other planes shouted, "release! " 领炸员投下炸弹，其他各机的飞机员、观察员、无线电员也都跟着大喊“投弹！”
During the 1960s and early 1970s, many governments and observers were concerned about wide-spread shortages of food . 在60年代和70年代初期，许多国家的政府和观察家对粮食的普遍短缺都深表关注。
