It sounds crazy, but as the universe expands faster and faster, it will eventually get to a point where the cosmos seen through a telescope will look a lot smaller than today, say physicists. That's because in a few hundred billion, or perhaps a few trillion years, all but our local group of galaxies will have moved so far away they will be lost forever. As a result, any cosmologists of that distant time who try to figure out the history of the universe will have no clue to the Big Bang or the existence of the vast clusters of galaxies we can see today.Not even the microwave background radiation, the subtle and surest sign of the Big Bang, will remain within reach. 

 這聽起來很荒謬，但物理學(xué)家指出：隨著宇宙膨脹的速度越來越快，最終通過望遠(yuǎn)鏡看到的宇宙將比當(dāng)今觀測(cè)到的要小得多。那是因?yàn)樵趲浊|年，也許幾萬億年后，除了我們的本星系團(tuán)以外，所有其他的星系團(tuán)都將飛離得太遙遠(yuǎn)，無異于永久性的消失。結(jié)果在那遙遠(yuǎn)的未來，研究宇宙史的天文學(xué)家們將無法搞到宇宙大爆炸的線索，也無從了解我們當(dāng)今可以觀察到的巨型星系團(tuán)的存在。甚至宇宙大爆炸的微妙而又最可靠的跡象—微波背景輻射也將遙不可及。

 "They'll still be out there," says cosmologist Professor Lawrence Krauss of Case Western Reserve University."But space will be expanding faster than the speed of light," and so the light from those galaxies will never reach us again.

 凱斯西儲(chǔ)大學(xué)的宇宙學(xué)家勞倫斯·克勞斯教授說：“那些星系團(tuán)還在，但是空間膨脹的速度比光速還快，因此那些星系團(tuán)的光線將永遠(yuǎn)無法到達(dá)我們地球?！?/SPAN>

 This is possible despite the universal speed limit being that of light, Krauss says, because the galactic clusters won't actually be moving. It's the space between them that will be expanding at a rate faster than light can traverse it.

 克勞斯指出，盡管宇宙間的速度極限是光速，但上述情況是有可能的，因?yàn)樾窍祱F(tuán)本身實(shí)際上并不移動(dòng)，而是諸星系團(tuán)之間的空間將以大于光速的速度膨脹，致使光線無法橫空穿過。

 Krauss and Vanderbilt University physicist Professor Richard Scherrer have written a paper on the topic, which will appear in the October issue of the Journal of Relativity and Gravitation.

 有關(guān)這一主題，克勞斯和范德比爾特大學(xué)的物理學(xué)家理查德·謝勒合寫了一篇論文，將發(fā)表在十月份出版的《相對(duì)論與引力雜志》上。

 Dark energy's to blame

 暗能量是罪魁禍?zhǔn)?/SPAN>

 The cause of all this is the bizarre but critical component of the universe called dark energy. Dark energy is the growing tendency of empty space to spontaneously create more empty space, thereby distancing anything in the universe that's not bound together with gravity.

 造成這一切的是宇宙中奇異而關(guān)鍵的組成部分，稱為暗能量。暗能量是真空中不斷增強(qiáng)一種趨勢(shì)，這種趨勢(shì)能夠自行創(chuàng)造更多的真空。因此暗能量會(huì)驅(qū)散宇宙中任何未被引力束縛在一起的事物。

 No one can fully explain dark energy, but without it the universe we see today makes no sense.

 沒人能夠徹底地將暗能量解釋清楚，但是若沒有暗能量，我們現(xiàn)在看到的宇宙就無法理解了。

 "We know it's allowed [by physics], but we have no idea what it is," says University of Michigan cosmologist Professor Fred Adams, co-author of the book The Five Ages of the Universe.

 《宇宙的五個(gè)時(shí)期》一書的作者之一、密歇根大學(xué)的宇宙學(xué)家弗雷德·亞當(dāng)斯教授說：“我們知道暗能量是遵循物理學(xué)的規(guī)律而產(chǎn)生，但不知道它到底是什么?！?/SPAN>

 By the year 3,000,000,000,000, all that will be left for astronomers to observe will be the stuff that today makes up our gravitationally bound 'local group' of galaxies: the Milky Way and Andromeda, the Large and Small Magellanic Clouds, and a few other puny galaxies.These are all close enough that their gravity overcomes the expansion of dark energy, and so they can stick together and eventually become one of many 'island universes' that can no longer detect each other.

 到公元3,000,000,000,000年，天文學(xué)家所能夠觀察到的將只剩下我們的本星系團(tuán)，其中的星系由引力束縛在一起，包括：銀河系和仙女座、大小麥哲倫星系和其他幾個(gè)小星系。這些星系足夠緊密，相互之間的引力能夠克服暗能量造成的膨脹力，所以它們能夠聚集在一起，最終成為許多“島宇宙”中的一個(gè)，然而這些“島宇宙”之間再也無法探知彼此的存在。

 Within any of those islands, the visible universe will appear to be neither expanding nor contracting, but relatively small and static, Krauss says.

 克勞斯說，在其中任何一個(gè)“島”中，可觀測(cè)的宇宙將顯得既不膨脹，也不收縮，相對(duì)來說范圍小而處于靜態(tài)。

 Some other event

 其它情況

 One implication of this time-travelling exercise, says Krauss, is that even today we may be suffering from similar blinders and don't know it. Adams agrees."It could be there's some event that happened in the early universe that's [undetectable]," says Adams. "It's very important for all cosmologists to be very humble."

 克勞斯指出，這次橫跨時(shí)空的研究具有一種含意：即使今天的我們，或許也正在遭受障目之苦，卻不自知。亞當(dāng)斯同意克勞斯的觀點(diǎn)，說：“事情可能會(huì)是這樣的：早期宇宙中發(fā)生過某個(gè)情況，只是不可探知罷了。因此，所有的宇宙學(xué)家都應(yīng)該特別謙遜，這一點(diǎn)很重要。”

 There's even the possibility that dark energy itself will change in the distant future, says Adams. "We're always assuming that the universe will continue accelerating," Adams says. But even that might change.

 亞當(dāng)斯指出，甚至存在這樣的可能性：在遙遠(yuǎn)的未來，暗能量本身也會(huì)發(fā)生變化?！拔覀兛偸钦J(rèn)為宇宙將繼續(xù)加速膨脹，”亞當(dāng)斯說，“然而，甚至這個(gè)情況也有可能發(fā)生變化?！?/SPAN>