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[经济学人] [2010-04-15]Signs of life 生命的迹象(完整版)

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发表于 2010-4-29 03:59 | 显示全部楼层 |阅读模式
Is it time for a new approach to finding extraterrestrials?

该是用新方法去搜寻外星生命的时候了吧?

IN THE Cascade mountains of California, north of Lassen Peak, astronomers are looking for aliens. The Allen Telescope Array (mostly paid for by Paul Allen, co-founder of Microsoft) consists of 42 dish antennas,each six metres across,scattered across the countryside. When the array is complete, it will have 350 dishes that, by acting in concert, will have the power of a single instrument 700 metres across.

在加州的喀斯喀特山脉(位于拉森火山以北),天文学家们正在寻找着外星生命。艾伦望远镜阵列(主要是由微软的创始人之一的保罗艾伦出资建立的)由42个碟形天线组成,每一个天线有六米宽,它们遍布乡村。当这个阵列完成的时候,它将包含350个碟形天线——这些天线行动一致,到那时每一个装置的功率覆盖范围将达到700米。

The Allen telescope is looking for aliens the traditional way: by searching for radio signals that have either been sent out deliberately, or leaked into space accidentally, as human radio signals are. The search for extraterrestrial intelligence, or SETI, is a 50-year-old idea. Much progress has been made in locating Earthlike planets (see article) but about 1,000 star systems have also been subject to serious radio scrutiny. The Allen array will increase the number to 1m within a decade.

艾伦望远镜正在用最传统的方式搜寻着地外文明:即通过寻找那些被故意的或者是无意中泄露到宇宙空间里的无线电信号(的蛛丝马迹),(但)这些无线电信号(必须)是像人类发射的无线电信号一样(译者注释:这里之所以说是“像人类发射的那样的无线电信号”指的是那些有别于宇宙背景辐射的智慧生命发出的信号)。用这个方法搜索地外文明(英文为SETI),已是一个有50年历史的构想了。这项工程的很多进展是通过锁定像地球一样的行星来确立的,但是只有大约一千个星系受到严密的观察。艾伦望远镜阵将会在未来的10年中将这个数字提高到到一百万。

That is an impressive number but some think this is the wrong approach. Paul Davies, a physicist at Arizona State University, points out that widespread radio communications may prove a short-lived historical phenomenon on Earth. Humans are, after all, increasingly using fibre optics to talk to each other. Moreover, many modern radio devices (such as mobile phones) rely on a technique called “spread spectrum” encoding. It uses signals that look like background noise, except to a receiver equipped with the right unscrambling code. Humans figured this out within a century of inventing radio technology, so aliens might have done the same. Radio signals that are clearly artificial in origin may, then, be only a transient sign of civilisation. So it might make sense to widen the search by looking for other telltales.

虽然这是一个令人印象深刻的数字,但另一些人还是认为这是一种错误的方式。亚利桑那州立大学的物理学家保罗?戴维斯指出在地球上(被)广泛(应用的)无线电通讯可能被证明只是一个相对短暂的历史现象。毕竟人类已经在渐渐的使用光纤技术(来取代上文中提到的无线电技术)。而且,现在(使用的)无线电通讯装置(比如手机)所依赖的主要是一种叫做“扩展频谱”的通讯编码方式。这使得人类发出的无线电信号看起来像是宇宙中(杂乱无序)的背景辐射,但对装有解码装置的接收装置除外(译者注释:这句活的意思是说装有解码装置的接收器能认出这种信号不是宇宙中的背景辐射)。人类只不过用了不到一百年的时间发明了无线通讯技术,外星智慧生命可能和我们一样。即经过(智慧生物)处理过的无线电信号可能只是(漫长的)文明史中的一个短期的现象。所以我们(搜寻宇宙中其他智慧生命)的路子最好拓得更广一些。

The truth is out there

真相(其实)就在那里

Dick Carrigan, a retired particle physicist, has enumerated several suggestions for such signs in a paper posted recently on arXiv, an online repository of scientific papers. His first idea is to look for pollution in the atmospheres of promising planets. This is an extension of the idea of looking for signs of life in atmospheres. It would be obvious to anyone who turned a spectroscope on Earth, for example, that something odd was going on. Air that is 21% oxygen, one of the most reactive elements in the periodic table, suggests the gas is being freshly minted—as it is, by photosynthesis.

迪克?卡里根是一位退休的粒子物理学家,他在一篇被列入aiXiv(一个在线的科学论文数据库)的论文中列举了一些针对这些迹象的几点建议。他的基本构想是观察那些“可能”的星球(译注:这里的“可能的星球”指的那些可能有条件演化出生命的星球)的大气“污染物”。这种构想是一种延伸即在大气中寻找生命构想的延伸。这(种方法)对在地球上任何一个会使用分光镜的人来说是显而易见的——例如,我们可能会(在那个星球上)发现某些“怪异”的进程可能在继续。氧气约占空气体积的21%,而氧在元素周期表中又是最活跃的元素之一,这些(“怪异”的)进程可能暗示出(在那个星球上)一种气体(作者暗指这种气体是在地球的生命赖以生存的氧气)可能正在通过光合作用(慢慢的)被形成。

In February this year Mark Swain of the Jet Propulsion Laboratory in California and his colleagues reported that they had developed a new technique for calibrating data arriving at ordinary ground-based telescopes, allowing them to identify the components of an extrasolar atmosphere. They used it to detect methane in the atmosphere of a planet nearly 63 light-years away. In the past only space-based
telescopes could manage this trick—and they are ludicrously expensive.

今年二月美国加州喷气动力实验室的马克?思文和他的同事们报告说他们已经发展出了一项新的技术,这项技术可以帮助通过分析地球上的望眼镜接收到的数据来鉴定出自太阳系之外的行星的大气主要组成成分。他们用这种技术去判断在63光年以外的行星的大气中是否含有甲烷气体。而在过去这种判断只能基于在太空中的望远镜来完成,而且花费相当的昂贵。

Dr Carrigan says that besides looking for oxygen, astronomers should seek molecules such as
chlorofluorocarbons (CFCs) which would be unequivocal signs of technology, since no natural process on
Earth creates them. (Although if CFCs were as damaging as they are on Earth, they too might be transient
technologies.)

卡里根博士说包括寻找氧元素在内,天文学家们也应该搜寻分子级别的能代表文明成果的氟氯烃,因为仅就地球上来讲氟氯烃还不能被自然演化出来(译注:这能通过人工的创造)。(但是氟氯烃如果在那个星球上同样具有破坏力,那么它同样可能成为短暂的的技术)

Instead of looking for the earliest signs of industrialisation, then, perhaps the thing to do is to let the imagination run riot and ask what technology might do to a solar system if it had tens or hundreds of thousands of years to work its magic. This is the realm of science fiction, of course. But the best sci-fi is grounded in reality.

此外,与忙着寻找(外星的)工业化痕迹不同的是,或许我们应该做的是让想象力天马行空并,并且问问什么样的技术能对太阳系起作用,如果有几万甚至几十万年去施展这项技术的魔力的话。当然,这或许是科幻小说的领域,但是最好的科学幻想是以事实作为依据的。

One famous work of science fiction is “Ringworld”, by Larry Niven. This book, which describes the descendants of a civilisation that has converted the material in its planets into a giant ringlike structure around its sun, was inspired by Freeman Dyson’s idea that a truly technologically advanced species would endeavour to capture as much light as possible by building a spherical shell around its central star. Such so-called Dyson spheres would, if they exist, reradiate captured energy (after some of it had been put to good use) as heat—infra-red radiation.

《环形世界》是一部著名的科幻小说,作者是拉瑞·尼文。这本书描写的是一个文明的后裔们改变了他们星球的物质结构,把它变成了一个环绕着他们的“太阳”巨大的环形结构——这是受到弗里曼?戴森的构想的启发。戴森认为技术上先进的物种应该通过建立围绕恒星的球壳来竭力捕捉光亮。这种别称作戴森球壳的东东,如果它们存在,它将再辐射俘获的能量(在一些能量被充分利用之后)就像热量,例如红外辐射。

So far, few astronomers have conducted searches for Dyson spheres—and none has been successful. But Dr Carrigan still thinks it is worth trying. He has been cataloguing possible candidates from the Infrared Astronomical Satellite, a collaboration between America, Britain and the Netherlands that conducted the first space-based survey of the entire sky at infra-red wavelengths and located hundreds of thousands of sources. On his website he offers tips for amateur cosmic archaeologists who wish to hunt for Dyson spheres. An investigation of SETI signals from the 13 “least implausible Dyson sphere candidates” is planned for the Allen telescope.

目前为止,几个天文学家已经开始了对道森球体的搜寻工作,但是一无所获。但是卡里根博士依然相信这值得一试。他通过红外天文观测卫星和一个合作计划已经为可能的资源编了目。这个合作是以美国,英国和荷兰之间引导的第一个以天基为基础的通过红外波段的对整个天空的调查并且已经锁定了数以十万计的可能资源。在他的网站上他为希望找到道森球体的宇宙考古爱好者提供各种各样的小贴士。艾伦望远镜正在计划对13颗以置信的最有可能的候选星做搜寻外星文明痕迹的调查。

Any civilisation that has built a Dyson sphere will have to have been around for a long time, of course— and in the very long run its star will start to change in unpleasant ways, ballooning to form a red giant. Another signature of advanced technology would be an attempt to slow this process down. Red giants are created when a star exhausts its supply of hydrogen at its core, with the result that the inner layer
contracts and the outer layers expand, forming a redder and much larger star. If the star’s outer layers could be mixed into the core, that would slow the process of inflation down. And, presumably, a sufficiently advanced civilisation would try to do that if it could.

当然,任何能建造出道森球体的文明一定演化了很长时间,在这个漫长的时间中它的恒星可能已经发生了不良的改变,即膨胀成了一颗(濒临死亡)的红巨星。另一个先进文明的迹象是减慢(恒星的)这个变化过程即让他慢下来。红巨星是当恒星核心的氢元素耗尽了的时候形成的,与此同时它的内部开始塌缩并且外部开始膨胀,构成了一个更红的更大的星星。如果这颗星星的外层能被核心的引力束缚住那么这个衰变即膨胀的过程就可能被减缓。一个足够先进的文明如果它有这个能力它一定会试图做到这一点的。

Such a star would look odd, though. It would be bluer than it should be and would be of a type known to astronomers as a “blue straggler”. Although, again, there are perfectly natural reasons these might form.The universe, though, is an ancient place, so many civilisations could be very old indeed. Perhaps, then, it will be a sign like this—of a technological civilisation millions of years old—that is seen, rather than some upstart that has not even got its radio waves under control.

这样的恒星可能看起来怪怪的。但是,它会比它本来的颜色看起来更蓝一些并且可以被天文学家作为一颗“蓝离散星”所发觉。虽然一些自然的力量就可以创造出这种形式。不过宇宙是一个足够大的地方,很多文明可能比我们想象的还要老。或许我们有一天会发现这样一个信号—— 一个有数百万念历史的工业文明——至少看起来是,这总比一个刚刚起步的还没有学会控制无线电的文明要好。
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发表于 2010-4-29 04:29 | 显示全部楼层
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