For the past 50 years, scientists have scoured the skies for radio signals from beyond our planet, hoping for some sign of extraterrestrial life. But one physicist says there's no reason alien life couldn't already be lurking among us - or maybe even in us.
在曩昔50年中，科学家们寻遍天穹，期望发现来自外太空的无线信号，以期找到外星生命的一些痕迹。但一位物理学家日前说，不能扫除这样一种或许性，即外星生命已“埋伏”在咱们中心，乃至或许存在于咱们体内。
Paul Davies, an award-winning Arizona State University physicist known for his popular science writing said Tuesday that life may have developed on Earth not once but several times.
闻名科学作家、亚利桑那州立大学获奖物理学家保罗•戴维斯于本周二称，地球上的生命或许进化了不止一次，而是好几次。
Davies said the variant life forms - most likely tiny microbes - could still be hanging around "right under our noses - or even in our noses."
戴维斯说，生命变体方式——特别是极小的微生物——或许就出没于“咱们的鼻子底下乃至鼻子里”。
"How do we know all life on earth descended from a single origin?" he told a conference at London's prestigious Royal Society, which serves as Britain's academy of sciences. "We've just scratched the surface of the microbial world."
他在伦敦皇家学会的一次研讨会上说：“咱们怎样知道地球上的一切生命只要一个来源？咱们关于微生物国际的了解仅仅一点皮裘罢了。”皇家学会是英国的科学学会，享有很高威望。
The idea that alien micro-organisms could be hiding out here on earth has been discussed for a while, according to Jill Tarter, the director of the US SETI project, which listens for signals from civilizations based around distant stars.
据美国“寻觅外太空星球才智生命项目”的主管吉尔•塔特说，有关外星微生物体或许隐居在地球上的观念现已评论了一段时刻。“寻觅外太空星球才智生命”项目首要监听来自悠远星球的声响消息，以判别是否有外星文明存在。
She said several of the scientists involved in the project were interested in pursuing the notion, which Davies earlier laid out in a 2007 article published in Scientific American in which he asked: "Are aliens among us?"
她说，参加该项意图几位科学家对讨论这一观念很感兴趣。戴维斯在2007年发表于《科学美国人》的一篇文章中提出：“外星生命会不会就在咱们身边？”
So far, there's no answer. And ever finding one would be fraught with difficulties, as Davies himself acknowledged.
到现在为止，这一问题还没有答案。戴维斯自己也供认，找到这样一个生命好不容易。
Unusual organisms abound - including chemical-eating bacteria which hide out deep in the ocean and organisms that thrive in boiling-hot springs - but that doesn't mean they're different life forms entirely.
地球上存在许多奇特的生物体，其间包含藏在深海中以化学品为食的细菌和生存在滚烫的温泉中的生物体。但这并不意味着它们是彻底不同的生命方式。
"How weird do they have to be suggest a second genesis as opposed to just an obscure branch of the family tree?" he said. Davies suggested that the only way to prove an organism wasn't "life as we know it" was if it were built using exotic elements which no other form of life had.
戴维斯说：“它们究竟要多奇怪，才干阐明它们是二次进化，而非生物体系中一个不为人知的分支呢？”戴维斯指出，证明一种生物体不是“咱们所知道的生命”的仅有方法便是看它是否是由其他生命方式所没有的外来元素组成的。
Such organisms have yet to be found. Davies also noted that less than 1 percent of all the world's bacteria had been comprehensively studied - leaving plenty of time to find unusual organisms.
这样的生物没有发现。戴维斯还指出，现在国际上一切的细菌中，仅有不到1%得到了深入研究，因而寻觅这些奇特生物体还需要很多时刻。
