外星生命可能就在我們身邊

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.

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.

Davies said the variant life forms - most likely tiny microbes - could still be hanging around "right under our noses - or even in our noses."

"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."

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.

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?"

So far, there's no answer. And ever finding one would be fraught with difficulties, as Davies himself acknowledged.

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.

"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.

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.

在過去50年中，科學家們尋遍蒼穹，希望發現來自外太空的無線信號，以期找到外星生命的一些跡象。但一位物理學家日前說，不能排除這樣一種可能性，即外星生命已“潛伏”在我們中間，甚至可能存在於我們體內。

知名科學作家、亞利桑那州立大學獲獎物理學家保羅•戴維斯於本週二稱，地球上的生命可能進化了不止一次，而是好幾次。

戴維斯說，生命變體形式——特別是極小的微生物——可能就出沒於“我們的鼻子底下甚至鼻子裏”。

他在倫敦皇家學會的一次研討會上說：“我們怎麼知道地球上的所有生命只有一個起源？我們對於微生物世界的瞭解只是一點皮毛而已。”皇家學會是英國的科學學會，享有很高聲望。

據美國“尋找外太空星球智慧生命項目”的主管吉爾•塔特說，有關外星微生物體可能隱居在地球上的觀點已經討論了一段時間。“尋找外太空星球智慧生命”項目主要監聽來自遙遠星球的聲音訊息，以判斷是否有外星文明存在。

她說，參與該項目的幾位科學家對探討這一觀點很感興趣。戴維斯在2007年發表於《科學美國人》的一篇文章中提出：“外星生命會不會就在我們身邊？”

到目前爲止，這一問題還沒有答案。戴維斯自己也承認，找到這樣一個生命十分困難。

地球上存在很多奇異的生物體，其中包括藏在深海中以化學品爲食的細菌和生存在滾燙的溫泉中的生物體。但這並不意味着它們是完全不同的生命形式。

戴維斯說：“它們到底要多怪異，才能說明它們是二次進化，而非生物系統中一個鮮爲人知的分支呢？”戴維斯指出，證明一種生物體不是“我們所知道的生命”的唯一辦法就是看它是否是由其他生命形式所沒有的外來元素組成的。

這樣的生物尚未發現。戴維斯還指出，目前世界上所有的細菌中，僅有不到1%得到了深入研究，因此尋找這些奇異生物體還需要大量時間。

Vocabulary:

scour: to search a place or thing thoroughly in order to find somebody/something （徹底地）搜尋，搜查，翻找（The police scoured the city for the robbers. 警察搜遍全城尋找搶竊犯。）

lurk: to exist unobserved or unsuspected 潛在（Danger lurks in that quiet river. 那條平靜的河裏潛在着危險。）

microbe: an extremely small living thing that you can only see under a microscope and that may cause disease 微生物

scratch the surface of :淺嘗輒止

fraught with: filled with something unpleasant 充滿（不愉快事物）的

genesis: the beginning or origin of something 開端；創始；起源