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每当我们瞭望遥远的宇宙时,常常会联想到自己身在大海中的一条船上。远离陆地,我们的视线可以向各个方向延伸到二三十公里外的海平线,这距离取决于甲板的高度。这个以轮船为中心、海平线为周长的圆圈,就标志着眼睛能否看到的界限。在你看来,这条海平线就围住了所有存在的水,而你刚巧位于它的中心。但经验证明这是错误的。在开阔的海面上,你可以航行几个小时或者几天几夜,而周围仍然是浩瀚的水面。自然,与刚巧处于你的视野之内的部分相比,海洋大得多!
Whenever we look at the distant universe, we often think of ourselves as a ship in the sea. Far from land, our line of sight can be extended in all directions to a flat line 20 to 30 kilometers away, depending on the height of the deck. This circle, centered on the ship and the perimeter of the sea level line, marks the boundaries of whether the eyes can see it. In your opinion, this sea level line encloses all existing water, and you happen to be in its center. However, experience shows that this is wrong. On the open sea, you can sail for hours or days and nights while the surrounding water is still vast. Naturally, the ocean is much bigger than the part that happens to be in your field of vision!