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散文:THE QUEST FOR EXTRATERRESTRIAL INTELLIGENCE

时间:2009-03-28 03:41来源:互联网 提供网友:龙xing天下   字体: [ ]
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Are we humans alone in the universe? Or is there intelligent life on other planets? These questions are not new. What is new, however, is the scientific attempt to discover whether or not other planets beyond our own have given birth to advanced civilizations. In the following article, the author describes the scientific means now available for investigating this possibility and discusses how probable it is that we are not alone in the universe.

THE QUEST FOR EXTRATERRESTRIAL INTELLIGENCE

Carl Sagan

Through all of our history we have pondered the stars and mused1 whether humanity is unique or if, somewhere else in the dark of the night sky, there are other beings who contemplate2 and wonder as we do, fellow thinkers in the cosmos3. Such beings might view themselves and the universe differently. Somewhere else there might be very exotic biologies and technologies and societies. In a cosmic setting vast and old beyond ordinary human understanding, we are a little lonely; and we ponder the ultimate significance, if any, of our tiny but exquisite4 blue planet.

The search for extraterrestrial intelligence is the search for a generally acceptable cosmic context for the human species. In the deepest sense, the search for extraterrestrial intelligence is a search for ourselves.

In the last few years -- in one-millionth the lifetime of our species on this planet -- we have achieved an extraordinary technological5 capability6 which enables us to seek out unimaginably distant civilizations even if they are no more advanced than we. That capability is called radio astronomy and involves single radio telescopes, collections or arrays of radio telescopes, sensitive radio detectors7, advanced computers for processing received date, and the imagination and skill of dedicated8 scientists. Radio astronomy has in the last decade opened a new window on the physical universe. It may also, if we are wise enough to make the effort, cast a profound light on the biological universe.

Some scientists working on the question of extraterrestrial intelligence, myself among them, have attempted to estimate the number of advanced technical civilizations -- defined operationally as societies capable of radio astronomy -- in the Milky9 Way Galaxy10. Such estimates are little better than guesses. They require assigning numerical values to quantities such as the numbers and ages of stars; the abundance of planetary systems and the likelihood of the origin of life, which we know less well; and the probability of the evolution of intelligent life and the lifetime of technical civilizations, about which we know very little indeed.

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 advanced civilization. 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.

Despite claims about ancient astronauts and unidentified flying objects, there is no firm evidence for past visitation 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 relatively11 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 electromagnetic spectrum12 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 which is radio.

The first serious attempt to listen for possible radio signals from other civilizations was carried out at the National Radio Astronomy Observatory13 in Greenbank, West Virginia, in 1959 and 1960. It was organized by Frank Drake, now at Cornel University, and was called Project Ozma, after the princess of the Land of Oz, a place very exotic, very distant and very difficult to reach. Drake examined two nearby stars for a few weeks with negative results. Positive results would have been astonishing because as we have seen, even rather optimistic estimates of the number of technical civilizations in the Galaxy imply that several hundred thousand stars must be examined in order to achieve success by random15 stellar selection.

Since Project Ozma, there have been six or eight other such programs, all at a rather modest level, in the United States, Canada and the Soviet16 Union. All results have been negative. The total number of individual stars examined to date in this way is less than a thousand. We have performed something like one tenth of one percent of the required effort.

However, there are signs that much more serious efforts may be mustered17 in the reasonably near future. Besides, hand in hand with the recent spectacular advances in radio technology, there has been a dramatic increase in the scientific and public respectability of the entire subject of extraterrestrial life. A clear sign of the new attitude is the Viking missions to Mars, which are to a significant extent dedicated to the search for life on another planet.

But along with the burgeoning18 dedication19 to a serious search, a slightly negative note has emerged which is nevertheless very interesting. A few scientists have lately asked a curious question: If extraterrestrial intelligence is abundant, why have we not already seen its manifestations20? Skeptics also ask why there is no clear evidence of extraterrestrial visits to Earth. We have already launched slow and modest interstellar spacecraft. A society more advance than ours should be able to ply14 the spaces between the stars conveniently if not effortlessly. Over millions of years such societies should have established colonies, which might themselves launch interstellar expeditions. Why are they not here? The temptation is to deduce that there are at most a few advanced extraterrestrial civilizations -- either because statistically21 we are one of the first technical civilizations to have emerged or because it is the fate of all such civilizations to destroy themselves before they are much further along than we.

It seems to me that such despair is quite premature22. All such arguments depend on our correctly surmising23 the intentions of beings far more advanced than ourselves, and when examined more closely I think these arguments reveal a range of interesting human conceits24. Why do we expect that it will be easy to recognize the manifestations of very advanced civilizations? Is our situation not closer to that of members of an isolated25 society in the Amazon basin, say, who lack the tools to detect the powerful international radio and television traffic that is all around them? Also, there is a wide range of incompletely understood phenomena26 in astronomy. Might the modulation27 of pulsars or the energy source of quasars, for example, have a technological origin? Or perhaps there is a galactic ethic28 of noninterference with backward or emerging civilizations. Perhaps there is a waiting time before contact is considered appropriate, so as to give us a fair opportunity to destroy ourselves first, if we are so inclined. Perhaps all societies significantly more advanced than our own have achieved an effective personal immortality29 and lose the motivation for interstellar gallivanting, which may, for all we know, be a typical urge only of adolescent civilizations. Perhaps mature civilizations do not wish to pollute the cosmos. There is a very long list of such "perhapses," few of which we are in a position to evaluate with any degree of assurance.

The question of extraterrestrial civilizations seems to me entirely30 open. Personally, I think it far more difficult to understand a universe in which we are the only technological civilization, or one of a very few, than to conceive of a cosmos brining over with intelligent life. Many aspects of the problem are, fortunately, amenable31 to experimental verification. We can search for planets of other stars, seek simple forms of life on such nearby planets as Mars, and perform more extensive laboratory studies on the chemistry of the origin of life. We can investigate more deeply the evolution of organisms and societies. The problem cries out for a long-term, open-minded, systematic32 search, with nature as the only arbitor of what is or is not likely .


点击收听单词发音收听单词发音  

1 mused 0affe9d5c3a243690cca6d4248d41a85     
v.沉思,冥想( muse的过去式和过去分词 );沉思自语说(某事)
参考例句:
  • \"I wonder if I shall ever see them again, \"he mused. “我不知道是否还可以再见到他们,”他沉思自问。 来自《简明英汉词典》
  • \"Where are we going from here?\" mused one of Rutherford's guests. 卢瑟福的一位客人忍不住说道:‘我们这是在干什么?” 来自英汉非文学 - 科学史
2 contemplate PaXyl     
vt.盘算,计议;周密考虑;注视,凝视
参考例句:
  • The possibility of war is too horrifying to contemplate.战争的可能性太可怕了,真不堪细想。
  • The consequences would be too ghastly to contemplate.后果不堪设想。
3 cosmos pn2yT     
n.宇宙;秩序,和谐
参考例句:
  • Our world is but a small part of the cosmos.我们的世界仅仅是宇宙的一小部分而已。
  • Is there any other intelligent life elsewhere in the cosmos?在宇宙的其他星球上还存在别的有智慧的生物吗?
4 exquisite zhez1     
adj.精美的;敏锐的;剧烈的,感觉强烈的
参考例句:
  • I was admiring the exquisite workmanship in the mosaic.我当时正在欣赏镶嵌画的精致做工。
  • I still remember the exquisite pleasure I experienced in Bali.我依然记得在巴厘岛所经历的那种剧烈的快感。
5 technological gqiwY     
adj.技术的;工艺的
参考例句:
  • A successful company must keep up with the pace of technological change.一家成功的公司必须得跟上技术变革的步伐。
  • Today,the pace of life is increasing with technological advancements.当今, 随着科技进步,生活节奏不断增快。
6 capability JsGzZ     
n.能力;才能;(pl)可发展的能力或特性等
参考例句:
  • She has the capability to become a very fine actress.她有潜力成为杰出演员。
  • Organizing a whole department is beyond his capability.组织整个部门是他能力以外的事。
7 detectors bff80b364ed19e1821aa038fae38df83     
探测器( detector的名词复数 )
参考例句:
  • The report advocated that all buildings be fitted with smoke detectors. 报告主张所有的建筑物都应安装烟火探测器。
  • This is heady wine for experimenters using these neutrino detectors. 对于使用中微子探测器的实验工作者,这是令人兴奋的美酒。 来自英汉非文学 - 科技
8 dedicated duHzy2     
adj.一心一意的;献身的;热诚的
参考例句:
  • He dedicated his life to the cause of education.他献身于教育事业。
  • His whole energies are dedicated to improve the design.他的全部精力都放在改进这项设计上了。
9 milky JD0xg     
adj.牛奶的,多奶的;乳白色的
参考例句:
  • Alexander always has milky coffee at lunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
  • I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。
10 galaxy OhoxB     
n.星系;银河系;一群(杰出或著名的人物)
参考例句:
  • The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。
  • The company has a galaxy of talent.该公司拥有一批优秀的人才。
11 relatively bkqzS3     
adv.比较...地,相对地
参考例句:
  • The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
  • The operation was relatively painless.手术相对来说不痛。
12 spectrum Trhy6     
n.谱,光谱,频谱;范围,幅度,系列
参考例句:
  • This is a kind of atomic spectrum.这是一种原子光谱。
  • We have known much of the constitution of the solar spectrum.关于太阳光谱的构成,我们已了解不少。
13 observatory hRgzP     
n.天文台,气象台,瞭望台,观测台
参考例句:
  • Guy's house was close to the observatory.盖伊的房子离天文台很近。
  • Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。
14 ply DOqxa     
v.(搬运工等)等候顾客,弯曲
参考例句:
  • Taxis licensed to ply for hire at the railway station.许可计程车在火车站候客。
  • Ferryboats ply across the English Channel.渡船定期往返于英吉利海峡。
15 random HT9xd     
adj.随机的;任意的;n.偶然的(或随便的)行动
参考例句:
  • The list is arranged in a random order.名单排列不分先后。
  • On random inspection the meat was found to be bad.经抽查,发现肉变质了。
16 Soviet Sw9wR     
adj.苏联的,苏维埃的;n.苏维埃
参考例句:
  • Zhukov was a marshal of the former Soviet Union.朱可夫是前苏联的一位元帅。
  • Germany began to attack the Soviet Union in 1941.德国在1941年开始进攻苏联。
17 mustered 3659918c9e43f26cfb450ce83b0cbb0b     
v.集合,召集,集结(尤指部队)( muster的过去式和过去分词 );(自他人处)搜集某事物;聚集;激发
参考例句:
  • We mustered what support we could for the plan. 我们极尽所能为这项计划寻求支持。
  • The troops mustered on the square. 部队已在广场上集合。 来自《简明英汉词典》
18 burgeoning f8b25401f10e765adc759ee165d5c1c5     
adj.迅速成长的,迅速发展的v.发芽,抽枝( burgeon的现在分词 );迅速发展;发(芽),抽(枝)
参考例句:
  • Our company's business is burgeoning now. 我们公司的业务现在发展很迅速。 来自《简明英汉词典》
  • These efforts were insufficient to contain the burgeoning crisis. 这些努力不足以抑制迅速扩散的危机。 来自辞典例句
19 dedication pxMx9     
n.奉献,献身,致力,题献,献辞
参考例句:
  • We admire her courage,compassion and dedication.我们钦佩她的勇气、爱心和奉献精神。
  • Her dedication to her work was admirable.她对工作的奉献精神可钦可佩。
20 manifestations 630b7ac2a729f8638c572ec034f8688f     
n.表示,显示(manifestation的复数形式)
参考例句:
  • These were manifestations of the darker side of his character. 这些是他性格阴暗面的表现。 来自《简明英汉词典》
  • To be wordly-wise and play safe is one of the manifestations of liberalism. 明哲保身是自由主义的表现之一。 来自《现代汉英综合大词典》
21 statistically Yuxwa     
ad.根据统计数据来看,从统计学的观点来看
参考例句:
  • The sample of building permits is larger and therefore, statistically satisfying. 建筑许可数的样本比较大,所以统计数据更令人满意。
  • The results of each test would have to be statistically independent. 每次试验的结果在统计上必须是独立的。
22 premature FPfxV     
adj.比预期时间早的;不成熟的,仓促的
参考例句:
  • It is yet premature to predict the possible outcome of the dialogue.预言这次对话可能有什么结果为时尚早。
  • The premature baby is doing well.那个早产的婴儿很健康。
23 surmising 752029aaed28b24da1dc70fa8b606ee6     
v.臆测,推断( surmise的现在分词 );揣测;猜想
参考例句:
  • Fanny's heart beat quick, and she felt quite unequal to surmising or soliciting any more. 范妮的心跳得快了起来,她不敢猜测她往下讲些什么,也不敢求她再往下讲。 来自辞典例句
24 conceits 50b473c5317ed4d9da6788be9cdeb3a8     
高傲( conceit的名词复数 ); 自以为; 巧妙的词语; 别出心裁的比喻
参考例句:
  • He jotted down the conceits of his idle hours. 他记下了闲暇时想到的一些看法。
  • The most grotesque fantastic conceits haunted him in his bed at night. 夜晚躺在床上的时候,各种离奇怪诞的幻想纷至沓来。
25 isolated bqmzTd     
adj.与世隔绝的
参考例句:
  • His bad behaviour was just an isolated incident. 他的不良行为只是个别事件。
  • Patients with the disease should be isolated. 这种病的患者应予以隔离。
26 phenomena 8N9xp     
n.现象
参考例句:
  • Ade couldn't relate the phenomena with any theory he knew.艾德无法用他所知道的任何理论来解释这种现象。
  • The object of these experiments was to find the connection,if any,between the two phenomena.这些实验的目的就是探索这两种现象之间的联系,如果存在着任何联系的话。
27 modulation mEixk     
n.调制
参考例句:
  • The soft modulation of her voice soothed the infant. 她柔和的声调使婴儿安静了。
  • Frequency modulation does not allow static to creep in. 频率调制不允许静电干扰混入。
28 ethic ziGz4     
n.道德标准,行为准则
参考例句:
  • They instilled the work ethic into their children.他们在孩子们的心中注入了职业道德的理念。
  • The connotation of education ethic is rooted in human nature's mobility.教育伦理的内涵根源于人本性的变动性。
29 immortality hkuys     
n.不死,不朽
参考例句:
  • belief in the immortality of the soul 灵魂不灭的信念
  • It was like having immortality while you were still alive. 仿佛是当你仍然活着的时候就得到了永生。
30 entirely entirely     
ad.全部地,完整地;完全地,彻底地
参考例句:
  • The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
  • His life was entirely given up to the educational work. 他的一生统统献给了教育工作。
31 amenable pLUy3     
adj.经得起检验的;顺从的;对负有义务的
参考例句:
  • His scientific discoveries are amenable to the laws of physics.他在科学上的发现经得起物理定律的检验。
  • He is amenable to counsel.他这人听劝。
32 systematic SqMwo     
adj.有系统的,有计划的,有方法的
参考例句:
  • The way he works isn't very systematic.他的工作不是很有条理。
  • The teacher made a systematic work of teaching.这个教师进行系统的教学工作。
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