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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. |
这听起来很荒谬，但物理学家指出：随着宇宙膨胀的速度越来越快，最终通过望远镜看到的宇宙将比当今观测到的要小得多。那是因为在几千亿年，也许几万亿年后，除了我们的本星系团以外，所有其他的星系团都将飞离得太遥远，无异于永久性的消失。结果在那遥远的未来，研究宇宙史的天文学家们将无法搞到宇宙大爆炸的线索，也无从了解我们当今可以观察到的巨型星系团的存在。甚至宇宙大爆炸的微妙而又最可靠的迹象—微波背景辐射也将遥不可及。 |
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"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. |
凯斯西储大学的宇宙学家劳伦斯·克劳斯教授说：“那些星系团还在，但是空间膨胀的速度比光速还快，因此那些星系团的光线将永远无法到达我们地球。” |
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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. |
克劳斯指出，尽管宇宙间的速度极限是光速，但上述情况是有可能的，因为星系团本身实际上并不移动，而是诸星系团之间的空间将以大于光速的速度膨胀，致使光线无法横空穿过。 |
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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. |
有关这一主题，克劳斯和范德比尔特大学的物理学家理查德·谢勒合写了一篇论文，将发表在十月份出版的《相对论与引力杂志》上。 |
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Dark energy's to blame |
暗能量是罪魁祸首 |
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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. |
造成这一切的是宇宙中奇异而关键的组成部分，称为暗能量。暗能量是真空中不断增强一种趋势，这种趋势能够自行创造更多的真空。因此暗能量会驱散宇宙中任何未被引力束缚在一起的事物。 |
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No one can fully explain dark energy, but without it the universe we see today makes no sense. |
没人能够彻底地将暗能量解释清楚，但是若没有暗能量，我们现在看到的宇宙就无法理解了。 |
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"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. |
《宇宙的五个时期》一书的作者之一、密歇根大学的宇宙学家弗雷德·亚当斯教授说：“我们知道暗能量是遵循物理学的规律而产生，但不知道它到底是什么。” |
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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，天文学家所能够观察到的将只剩下我们的本星系团，其中的星系由引力束缚在一起，包括：银河系和仙女座、大小麦哲伦星系和其他几个小星系。这些星系足够紧密，相互之间的引力能够克服暗能量造成的膨胀力，所以它们能够聚集在一起，最终成为许多“岛宇宙”中的一个，然而这些“岛宇宙”之间再也无法探知彼此的存在。 |
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Within any of those islands, the visible universe will appear to be neither expanding nor contracting, but relatively small and static, Krauss says. |
克劳斯说，在其中任何一个“岛”中，可观测的宇宙将显得既不膨胀，也不收缩，相对来说范围小而处于静态。 |
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Some other event |
其它情况 |
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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." |
克劳斯指出，这次横跨时空的研究具有一种含意：即使今天的我们，或许也正在遭受障目之苦，却不自知。亚当斯同意克劳斯的观点，说：“事情可能会是这样的：早期宇宙中发生过某个情况，只是不可探知罢了。因此，所有的宇宙学家都应该特别谦逊，这一点很重要。” |
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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. |
亚当斯指出，甚至存在这样的可能性：在遥远的未来，暗能量本身也会发生变化。“我们总是认为宇宙将继续加速膨胀，”亚当斯说，“然而，甚至这个情况也有可能发生变化。” |
