在我們還是孩子的時候就已經注意到這個現象了：無論我們跑得多快，月亮都會跟著我們，就算開車都甩不掉它。其實道理很簡單，因為它離我們太遠了。
According to astronomers, the reason why the Moon and the Sunseemto be following us is because they are so far away. The Moon,forexample, is about 240,000 miles away; the Sun about 93millionmiles. And no matter how fast we drive, we just cantpassthem.
When you drive by a stand of trees or a series of telephonepolesnear the road, you pass them very quickly. So you see roadsidetsfirst ahead of you, then next to you, and finally behindyou,receding into the rear-view mirror.
But when you drive (or stroll) by the Moon, its adifferentstory. Because the Moon is so far away, the angle you viewit fromwill change very little as you move along. So mile aftermile, theMoon will remain in roughly the same spot of sky. And justas youcant pass the Moon, neither can you shake the presence oftheSun, planets, or stars. Even very distant mountain rangesappearnearly stationary as we drive by. And far-away farms andcityskylines seem to move by very slowly.
Since we cant pass the Moon, we cant pass itsreflection,either. When you walk along the beach at night, theriver ofmoonlight reflected off the water moves center along withyou. Tryto wade out into the moonlight, and youll find itremainstantalizingly out of reach, just as a shimmeringpatch-of-watermirage retreats down the road as you drive towardit.
When you stand on the beach, moonlight bounces off the waterandinto your eyes at a nearly fixed angle. As long as the Moon isinthe same spot of sky and the water level doesnt rise or fallmuch,the angle of reflection will remain roughly the same. So ifyou cansee the entire ribbon of moonlight, your eyes are at justthe centerborder=1 Height to intercept the rays of light bouncingoff the water fromthe horizon to the beach.
Once you wade out into the water, however, youve also movedyoureyes. The moonlight bouncing from the water at your feetdoesntstrike your eyes; instead, it shoots center past you at alowerborder=1 Height. So the water at your feet looks dark.
Friends on the beach behind you, however, will see youstandingcenter in the moonlight road, and could even snap a pictureof it.So to bathe in moonlight, simply sit down in the water, whereyoureyes can catch the silvery light at the center angle.
Meanwhile, just as every car on the road thinks the Moonisfollowing it, every walker on the beach sees his (her) ownribbonof moonlight, stretching towards the horizon.
rear-view mirror: 後視鏡
stationary: 固定的
（實習編輯：顧萍）