Experiments with metamaterials simulates the beginning of the universe and suggests that time travel is likely a quantum impossibility...
（注：所谓metamaterial是“具有天然材料所不具备的超常物理性质的人工复合结构或复合材料”，但目前仍没有确定定义）
You may want to delay your plans a little more to build that time machine. Laboratory scientists have developed a sort of mini Big Bang suggesting that, ultimately, time travel is an unlikely possibility.
也许你制作时间机器的计划又要推迟了吧。实验物理学家通过迷你大爆炸表明，时间旅行似乎不太可能。
In a new study, Igor Smolyaninov and Yu-Ju Hung, University of Maryland, simulated the birth of the universe using advanced materials that allow the bending of light in unusual ways. The device created is based on the idea that "time's arrow," pointing forward, cannot bend over backwards to undo events that have already occurred.
马里兰大学Igor Smolyaninov和Yu-Ju Hung在一项新的研究中，通过使用先进材料引起光的弯曲来模拟宇宙起源。这个装置是基于单向的“时间线”制造的，即过去已经发生的事不能消除。
For the time being, time travel is still not possible in real life and, according to Smolyaninov, such material suggests that this will never be possible.
Smolyaninov表示，目前时间旅行在现实生活中仍无法实现，而这样的材料表明它也许永远无法实现。
New material temporarily replaces time and space
新材料暂时代替时间和空间
The new Big Bang simulator is tiny - its width is only a few fractions of centimeters (20 micrometers). It was constructed from alternating strips of plastic gold and fitted so as to create a metamaterial, a substance produced artificially for the manipulation of light.
这个新模拟的大爆炸是迷你型的，其宽度只有厘米的几千分之一（20微米）。它是一种塑料高分子链中掺金制成的材料，科学家由此能人工控制光。
In recent years, researchers have been using metamaterials to create devices previously only possible in fiction, like invisible cloaks and "super-lenses" that allow scientists to "see" structures smaller than the wavelengths of visible light.
近年来，研究者已经使用了很多超材料来制造以前只会出现在科幻小说里的装置，比如隐形斗篷和“超透镜”——能够让科学家看到比可见光波长还小的结构。
Metamaterials have also aroused the interest of astronomers who recently used the alien substances to create artificial black holes and multiuniverse simulators.
超材料同时引起了天文学家的兴趣。他们最近用奇异物质制造了人工黑洞和平行宇宙模型。
According Smolyaninov and Hung, the material developed by them is a reasonable representation of our universe, particularly the early universe at the time of Big Bang - around 13.7 billion years ago.
而据Smolyaninov和 Hung介绍，他们研发的材料能够很好地展示我们的宇宙，特别是大爆炸（大约137亿年前）早期的婴儿宇宙。
Due to the unique way such material causes light to bend, the equations that describe the passage of a particle through time are similar to those that describe the movement of photons and of similar quantum particles called plasmons - created from waves of free electrons - through the material.
由于能够通过这种材料使光弯曲，描述粒子时间上的运动方程和描述光子和等离子体的方程是类似的，可由材料里自由电子的波函数得到。
In this way, the metamaterial serves as a model for our universe: the horizontal movement in the metamaterial is analogous to the movement through the three dimensions of space, while vertical movement represents the movement through time.
通过这种方法，超材料可以作为我们宇宙的模型加以研究：在材料里的水平运动类比于三维空间里的运动，而垂直运动就代表了时间运动。
The universe is too cluttered to allow the reversal of time?
宇宙已经太满了，不允许时间反演？
For the experiment, the scientists used a green laser beam to cause an event similar to the Big Bang in the metamaterial. The laser caused the atoms to generate bursts of gold plasmons.
在此实验中，科学家在材料中使用了绿激光制作类似大爆炸的环境。激光轰击材料产生金原子等离子体。
Such plasmons radiated outwards from a single point, just as scientists imagine that the particles would have done after the Big Bang. The researchers found that the trajectory of plasmons became increasingly disorganized as they strayed. The finding is consistent with the second law of thermodynamics, which says - excluding any kind of intervention - the systems have the tendency to become more disordered with the passage of time, a phenomenon known as entropy.
该等离子体的辐射是单向的，正如科学家预计大爆炸后粒子的运动一样。研究者发现当等离子体辐射开来，其轨迹是杂乱无章的。这和热力学第二定律是一致的，该定律说，没有任何干扰，随着时间推演体系总是有更混乱的趋势，即熵增现象。（注：这里用的是第三种表述，即不可逆热力过程中熵的微增量总是大于零。）
In the toy model, a complete revolution of a plasmon exactly along the same path would be equivalent to time travel. But since the plasmon is lost in such a way - due in part to entropy - it wouldn't be possible to make the complete turn.
此模型中，等离子体沿着同一路径的运动等价于时间旅行。但是并没有发现这一现象，这是因为熵不允许完全相同的路径。
The result, described in a paper published this month, suggests that the particles in our universe may also be unable to move backward in time.该研究结果已于本月发表，表明我们宇宙的粒子也许同样不能在时间上逆向运动。
Smolyaninov admits that the experiment is far from perfect: "I'm not sure how much of it can be applied to real life."
Smolyaninov承认该实验远称不上完美：“我不确定它在现实世界是否适用。”
Andreas Albrecht, a cosmologist at the University of California who was not part of the study, has doubts that such a metamaterial is a sufficiently accurate representation of the early universe.
加利福尼亚大学宇宙学家Andreas Albrecht没有参与此项目，他对这种超材料能否有效的代表早期宇宙很是怀疑。
For Albrecht, the Big Bang simulator created by the researchers is an interesting achievement, but he does not believe that it will teach something about the universe that was not already known from empirical data or models based on equations and computer simulations.
在Albrecht看来，研究者制作的大爆炸模型是个有趣的尝试，但是他不相信这个模型能告诉我们宇宙更多的信息，毕竟通过实验数据和电脑模拟都没有让我们完全了解宇宙。
"We have much better models of the universe that we can create with regular PCs. So for me, this material offers no understanding of the universe that cannot be reached by a more direct form," said Albrecht.
Albrecht认为：“通过常规的电脑模拟我们都能做出更好的宇宙模型。所以我以为，我们的宇宙是不可直接了解，他们的材料并不能让我们走的更远。”
Time travel may be imperceptible
时间旅行也许是不可感知的
Although the new experiment - and our daily experience - apparently eliminates the possibility of time travel, there are still many questions about the universe, so physicists can imagine scenarios in which time travel is possible.
虽然这个新实验和我们日常生活经历都显然消除了时间旅行的可能性，但是关于宇宙我们仍有太多疑问，所以物理学家开始设想在何种情况下时间旅行是可行的。
For example, the laws of physics may vary depending on where one finds oneself in the cosmos, and maybe the Earth is one way in the universe where there is an increase of entropy, which might make time travel impossible to take place.
比如，物理定律也许在宇宙不同的地方是不一样的（注：可以参见伽莫夫的科幻名著《台球》，而此文中理解成平行宇宙的物理定律也可，这里涉及的问题就是物理定律的普适性问题），也许地球所在宇宙是一个熵增的宇宙，是不允许时间旅行的。
"Perhaps life itself is present in this way where there exists an increase of entropy, since we need the existence of the arrow of time," Albrecht said. As Albert Einstein once quipped, "Time exists so everything does not happen all at once."
“也许我们目前生活的宇宙就是熵增的宇宙，因为我们需要时间之箭的存在。”Albrecht说。正如爱因斯坦说的：“因为时间存在所以任何事情都不能同时发生。”
Moreover, Albrecht says he also could imagine a universe where entropy occurs in increasing and decreasing cycles.
此外，Albrecht说他构想了一个熵增熵减循环往复的宇宙。
If entropy is not consistent with the hypothetical universe, he says that then the arrow of time could go backwards and events like a broken cup could become whole again, or reverse aging in humans would not only be possible, but natural.如果在他的假设宇宙熵增不是确定的，那么时间之箭就会倒退，那些类似摔坏的杯子重新复合或者人类换老还童的事情就不是不可能，而是很自然的了。
The inhabitants of such a universe probably would not even realize such inadequacies.生活在那样一个宇宙的居民也不会觉得那是什么不正常的吧。
"If that happens, we simply would change our idea about what is past and what is the future, without noticing anything special."
“如果那真的发生了，我们只需改变我们的观念就好了，什么是过去，什么又是未来."
译者评价：类似这样的实验过去就有很多，但是对现实当中的时间旅行的确没有什么帮助，译者小时候想的第一个问题就是如果时间旅行可行为什么我们现在看不到那些穿梭者。关于熵增的问题译者也曾YY过：http://blog.sina.com.cn/s/blog_5323507f0100ho2k.html，但是那时并没有意识到热统和时间旅行的关系。而关于平行宇宙也只是物理学家的幻想，难以证实，国内王晋康的《泡泡》是讲述不同宇宙物理规则的好故事。爱因斯坦曾说：宇宙最不可理解的地方在于它是可理解的（The most incomprehensible thing about the world is that it is comprehensible.）平行世界也是包含了人类美好的愿景的。最后给几张关于时间之箭的图片，就不翻译了。
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