初中语文课本第三册中有一篇民间故事,题目叫《牛郎织女》。这篇课文的结尾说:“每年七月七日,成群的喜鹊在天河上边搭一座桥,让牛郎织女在桥上会面。”牛郎织女真的能在鹊桥相会吗? 天文学家告诉我们,牵牛星和织女星是两颗恒星,它们的位置是不变的,两颗星相距十万光年。(光年,就是光走一年的距离,约等于94605亿公里。)也就是说,任何时候在牵牛星上接收到的织女星上的光都是它十六年前发出来的。人们知道,电波传递的速度几乎和光速一样,如果在牛郎织女之间安上电话,让牛郎给织女通话,织女要在十六年后才能听到,而要听到织女的回话,就要等到三十二年以后。世界上哪有这么多的喜鹊来给他们搭桥呢? There is a folk story in the third volume of junior middle school textbooks, entitled “The Cowherd and the Weaver.” At the end of this text: “On July 7th each year, groups of magpies ride a bridge over the Milky Way and allow the Cowherd and the Weaver to meet on the bridge.” Can the Cowherd and the Weaver actually meet in the Bridge? Astronomers tell us that Star and Vega are two stars, their position is unchanged, and the two stars are separated by 100,000 light years. (The light year is the distance that light travels for one year, which is equal to approximately 9460.5 billion kilometers.) In other words, the light received by Vega at any time on the Altair was sent out 16 years ago. People know that the speed of transmission of radio waves is almost the same as the speed of light. If a phone call is made between the cowherds and weavers to allow the cowherd to talk to the Weaver, weaving girls can hear it only after 16 years. To hear the Weaving Woman’s reply, we must wait until Thirty-two years later. How can there be so many magpies in the world to bridge them?