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The American Association for the Advancement of Science

美国科学促进会



Is there anybody out there?

外面有人吗?

SEATTLE

西雅图

This year’s meeting of the AAAS featured the rhizosphere, human emotions, mapping body cells and the search for extraterrestrial intelligence

美国科学促进会今年的会议主要讨论了根际、人类情感、了解人体细胞以及寻找外星智慧生物

In 1990, a year into the journey to Jupiter of an American spacecraft called Galileo, Carl Sagan, a well-known astronomer, turned the probe’s instruments back towards Earth. He wanted to find out whether it was possible to detect evidence of life on the planet from a distance.

1990年,美国的伽利略号探测器驶向木星的第一年,著名天文学家卡尔·萨根使探测器的仪器转向地球。他想知道是否有可能从远处检测到这颗星球上有生命存在的证据。

Galileo took spectrographic measurements of sunlight streaming through Earth’s atmosphere and found methane and oxygen, both indicators of living processes. The probe also took photographs of Earth at different wavelengths and uncovered something called the “red edge”—a sharp change in the reflectance of the planet at red wavelengths, which Sagan ascribed to the presence of photosynthetic plant life on the surface.

伽利略号对穿过地球大气层的阳光进行光谱测量,发现了甲烷和氧气,这两者都是生命存在的证据。探测器还以不同的波长给地球拍摄了照片,发现了“红边”——以红色的波长拍摄时,地球的反射比会发生剧烈变化。萨根说该现象是因为地球表面有进行光合作用的植物。



SETI began 60 years ago with Project Ozma. This was led by Frank Drake, an astronomer at Cornell University. It was an attempt to listen for radio waves that might be coming from intelligent life in the vicinity of two nearby sun-like stars, Tau Ceti and Epsilon Eridani. Further projects along this line followed, but no little green men were detected. By the turn of the 21st century people were starting to lose interest and financial support for the endeavour was dwindling.

地外文明搜寻计划在60年前开启了奥兹玛计划。这一项目由康奈尔大学的天文学家法兰克·德雷克主事。奥兹玛计划试图收听可能来自附近两个类似太阳的恒星鲸鱼座的天仑五和波江座的天苑四的智慧生命发出的无线电波。随后进行了更多此类项目,但没有任何新发现。到21世纪之交,人们开始对这项工作失去兴趣,财政支持也在减少。

The tide turned, though, in 2009 with the launch of Kepler, an American probe designed to look for planets orbiting other stars. It found them. In spades. Astronomers have now confirmed the existence of more than 4,000 such exoplanets. Moreover, their models suggest that virtually every star has a planetary system. With so many potential habitats, and more being discovered every month, the prospects of finding alien life suddenly brightened.

然而,随着2009年开普勒的发射,这一趋势发生了转变。开普勒是美国旨在寻找环绕其他恒星运转的行星的探测器。它找到了这样的行星。确定无疑。现在,天文学家已经证实存在4000多颗这样的系外行星。而且,他们的模型表明,几乎每颗恒星都有一个行星系。潜在的栖息地如此之多,而且每个月都会有新的发现,寻找外星生命的前景突然变得光明。

They will brighten further with the launch, in 2021, of the James Webb Space Telescope and the opening of new observatories on the ground, such as the Extremely Large Telescope (ELT) in Chile. These will be able to repeat, for some nearby exoplanets, the first of Sagan’s experiments with Galileo—the search for biosignatures. But, even if they find them, exciting as that would be, it would say nothing about the crucial final letter in SETI, the “I” for intelligence.

随着2021年詹姆斯·韦伯太空望远镜的发射以及地面上新观测站的开放,例如智利的超级望远镜,发现外星生命的前景将进一步变得光明。这些新设备将能够对附近的一些系外行星进行萨根用伽利略号探测器进行的首次实验——寻找生物特征。但是,即使结果令人兴奋,真的找到了生物特征,也不能证明就存在地外文明搜寻计划的重要部分——文明。

The search for intelligence was boosted in 2015 with the launch of Breakthrough Listen, a project paid for by Yuri Milner, a software billionaire with a background in physics. This enterprise, on which Dr Siemion is chief scientist, is planned to last ten years and expected to cost $100m. It is intended to survey the 1m nearest stars in detail, scan the entire plane of Earth’s home galaxy, the Milky Way, and also listen for messages from the 100 closest galaxies. It is paying for astronomers interested in SETI to have time on more than a dozen big radio observatories around the world, and it collects in a day an amount of data that used previously to take a year to gather.

2015年,突破聆听计划的推出推动了对地外文明的搜寻,该项目由拥有物理学背景的软件行业亿万富翁尤里·米尔纳出资。这项由西米翁博士担任首席科学家的事业计划持续十年,预计耗资1亿美元。它旨在详细调查距离最近的100万颗恒星,扫描地球所在星系银河系的整个平面,并收听来自最近的100个星系的讯息。突破聆听计划雇佣对地外文明搜寻计划感兴趣的天文学家在世界上十几个大型无线电天文台进行观测,一天之内收集以前要花费一年时间才能收集到的大量数据。

Hello?

你好?

Nor is Breakthrough Listen alone. On February 13th the SETI Institute, a not-for-profit organisation in California, and America’s National Radio Astronomy Observatory, announced a collaboration. The observatory operates the Very Large Array (VLA), a radio telescope in New Mexico that features in the film “Contact”. The collaboration allows SETI researchers to tap the entire stream of data the VLA records as it carries out its routine experiments.

突破聆听计划并不孤独。2月13日,位于加利福尼亚的非盈利组织地外文明搜寻计划研究所与美国国家射电天文台宣布了一项合作。该天文台运行着甚大天线阵,这是一组位于新墨西哥州的射电望远镜阵列,电影《超时空接触》中使用了它。这项合作使得地外文明搜寻计划研究所的研究人员可以在甚大阵进行常规实验时,利用它记录的整个数据流。

The partnership will become even more useful for SETI researchers if the VLA gets a proposed upgrade that would greatly enhance its sensitivity. This next-generation instrument would be good enough to detect electromagnetic radiation leaking from planets, similar to the television and radio channels that Sagan measured leaking from Earth.

如果甚大阵得到拟议的升级,将大大提高其灵敏度,这种合作关系将对研究所的研究人员更加有用。这个新一代的仪器将足以探测到从行星散播出的电磁辐射,类似于萨根测量到的从地球散播出的电视和无线电频道。

Nor, despite the importance of radio waves, will future SETI searches stick to that part of the spectrum. Alien civilisations might, for example, use laser flashes as optical beacons to signal their presence. If a nanosecond-long pulse of such light were pointed in the direction of Earth, it could be made energetic enough to seem brighter to human instruments than any of the stars in the same part of the sky.

尽管无线电波很重要,地外文明搜寻计划在未来的搜索也不会停留在这一种讯息上。例如,外星文明可能使用激光作为信标来表明他们的存在。如果这种光一纳秒长的脉冲射向地球的方向,在人类仪器看来,它的能量会强到比天空同一区域的任何星星都要亮。

Moreover, as observatories get better, astronomers will also be able to spot small, potentially pertinent features in and around exoplanets. These might be rings of satellites above a planet’s equator—or even structures surrounding a planetary system’s star, put there to capture that star’s light as a source of energy.

此外,随着天文台的升级,天文学家也将能够发现系外行星及其周围微小的、可能相关的特征。可能是某颗行星赤道上方的卫星环,甚至是环绕着某个行星系统的恒星的结构体,放置在那里用来收集该恒星的光作为能量来源。



Meanwhile, the Breakthrough Listen dataset continues to grow. In a study discussed in Seattle, a team of astronomers used it to look for radio transmissions from 20 stars in the so-called “Earth transit zone”—the part of the sky from which Earth itself would be detectable by the transit method. The hypothesis is that, if intelligent beings do exist in that region, they might thus have discovered Earth and be aiming transmissions at it. So far, the skies have been quiet. But SETI researchers are patient people. And they live in hope.

与此同时,突破聆听计划的数据集继续增长。在西雅图进行的一项研究中,一组天文学家用它来寻找“地球凌星带”中20颗恒星发出的无线电信号,在这片区域中,通过同样方法,地球自身也可以被探测到。研究人员们的假设是,如果该地区确实存在智慧生物,那么他们可能已经发现了地球并瞄准了地球传输讯息。到目前为止,天空一直很安静。但是地外文明搜寻计划的研究人员们很有耐心。他们充满了希望。