評論
打印
When we do the arithmetic, the sorts of numbers we come up with are, characteristically, around a million technical civilizations. A million civilizations is a breathtakingly large number, and it is exhilarating to imagine the diversity, lifestyles and commerce of those million worlds. But the Milky Way Galaxy contains some 250 billion stars, and even with a million civilizations, less than one star in 200,000 would have a planet inhabited by an advancedcivilization. Since we have little idea which stars are likely candidates, we will have to examine a very large number of them. Such considerations suggest that the quest for extraterrestrial intelligence may require a significant effort.
計算結果，我們得出的具有典型意義的數字是有大約一百萬個技術文明社會。這可是個大得令人咋舌的數目。想像一下這百萬個世界的千姿百態、各種生活方式和商業往來，真令人興奮不已。然而，銀河系大約有二千五百億顆恒星，即便有百萬個文明世界，平均每二十萬顆恒星中，也僅有一顆不到的恒星，其周圍的一顆行星上存在著先進的文明社會。由于不知道哪些星球上存在這種可能性，我們不得不進行大量的觀察。這表明，搜尋外星人需要作出巨大的努力。
Despite claims about ancient astronauts and unidentified flying objects, there is no firm evidence for past visitations of the Earth by other civilizations. We are restricted to remote signaling and, of the long-distance techniques available to our technology, radio is by far the best. Radio telescopes are relatively inexpensive; radio signals travel at the speed of light, faster than which nothing can go; and the use of radio for communication is not a short-sighted or anthropocentric activity. Radio represents a large part of the electromagneticspectrum and any technical civilization anywhere in the Galaxy will have discovered radio early -- just as in the last few centuries we have explored the entire electromagnetic spectrum from short gamma rays to very long radio waves. Advanced civilizations might very well use some other means of communication with their peers. But if they wish to communicate with backward or emerging civilizations, there are only a few obvious methods, the chief of whichis radio.
盡管有人聲稱見過古代的太空人和來歷不明的飛行物體，但并無確切證據證實別的文明世界的來客曾經訪問過地球。我們目前只限于遠距離信號的使用，而在我們的技術所能掌握的長距離通訊手段中，無線電是最佳的一種。相對說來，射電望遠鏡并不貴;無線電能以光速發送，其他任何東西都無法做到比它更快;采用無線電作通訊工具不是短視的或以人類為宇宙中心的行為。無線電包括了大部分電磁波譜，所以銀河系中任何地方的技術文明社會，該早已發現了無線電技術了——如同我們在近幾個世紀中，對包括短的γ射線到長的無線電波在內的整個電磁波譜進行過探測一樣。先進的文明世界相互間很可能采用別的方法進行通訊聯系。可是，如果他們想和其他落后的或發展中的文明社會聯絡的話，就只有幾種顯而易見的辦法，而其中為主的就是無線電。
