经济学人下载:桌面上的天体物理学 怎样建立一个多元宇宙

Science and technology
科学技术

Table-top astrophysics
桌面上的天体物理学

How to build a multiverse
怎样建立一个多元宇宙

Small models of cosmic phenomena are shedding light on the real thing
宇宙现象的一些小模型反映了真相

THE heavens do not lend themselves to poking and prodding.
天空不会帮助任何企图研究它的行为。

Astronomers therefore have no choice but to rely on whatever data the cosmos deigns to throw at them.
因此，天文学家们只能听天由命，任何宇宙透露出的一些数据，他们都当做宝贝一样。

And they have learnt a lot this way.
不过他们通过这种方式也学到了很多。

Thus you can even study chemistry in space that would be impossible in a laboratory.
因此，人们甚至能在太空中研究化学，而这在实验室是无法做到的。

Some astronomers, though, are dissatisfied with being passive observers. Real scientists, they think, do experiments.
虽然，一些天文学家们对成为被动的观察者很是不满，他们认为真正的科学家应该是有所行动的。

It is impossible—not to mention inadvisable—to get close enough to a star or a black hole to manipulate it experimentally.
要想接近一颗星或者一个黑洞，进行实验性地操作是不可能的，其实也是不可取的。

But some think it might be possible to make meaningful analogues of such things, and even of the universe itself, and experiment on those instead.
但是，一些人认为，如果进行类似方面，甚至宇宙方面的有意义的研究，而不是试验，是有可能的。

Ben Murdin of the University of Surrey, for example, has been making white dwarfs.
比如说，萨里大学的本-穆迪一直在制作白矮星。

A white dwarf is the stellar equivalent of a shrunken but feisty old-age pensioner.
从某种程度上说，白矮星是一颗虽然已经萎缩，但仍旧不服老的高龄恒星。

It has run out of fuel and is contracting and cooling as it heads towards oblivion—but taking its time about it.
当它正慢慢淡出宇宙这个大家庭时，它的动力已渐渐耗尽，而且正在缩小，渐渐变冷，但是还是值得花些时间的。

As they shrink white dwarfs pack a mass up to eight times the sun's into a volume the size of Earth.
当它们缩小时，这些白矮星把自己相当于八个太阳那么大的个头压缩到了地球这么大的个头。

A consequence of stuffing so much matter into so little space is that white dwarfs have powerful magnetic fields.
把如此之大的东西压缩到了这么小空间的结果是，白矮星拥有强大的磁场。

Many aspects of a white dwarf's mechanics, including how long it will last, are thought to depend on its magnetism.
天文学家认为，白矮星形成过程的许多问题，包括它会存在多久，都基于它的磁场。

But it is hard to measure.
但是这是无法衡量的。

To make estimates, scientists examine the light a white dwarf emits for telltale patterns left by stellar ingredients like hydrogen.
为了做出这方面的估计，科学家们检测了白矮星发出的光，这种光正说明了这种问题的某种方式，是由组成恒星的元素，比如氢产生的。

They then compare this spectrum with a theory, based on calculations from first principles, of how magnetic fields effect light emitted by hydrogen.
然后，他们把测得的光谱与理论计算得到的结果进行了比较，这种理论是基于氢怎样产生磁场效应区域的第一原则得到的。

The predictions agree with experiments up to the strongest fields mankind can muster—about 1,000 tesla, generated in a thermonuclear detonator.
结果，预测与试验完全一致—即达到人类在这个领域最高水准，能够在热核雷管中产生1000特斯拉的磁感应。

The problem is that the theory puts white dwarfs' magnetic fields at 100,000 tesla or more, well beyond humanity's reach.
问题是，这个第一原则认为白矮星的磁场强度可以达到100,000特斯拉或者更多，远远超过了人类的极限。

Dr Murdin built his own little white dwarf to see if the theory looked good.
穆迪博士建造了他自己的小白矮星，想弄明白这种理论是否真的正确。

It consists of a silicon crystal sprinkled with phosphorus atoms.
这个小白矮星由布满磷原子的硅晶体组成。

A silicon atom has four electrons in its outer shell.
一个硅原子外有四个电子。

In a crystal, all four are used to bind it to neighbouring atoms.
在晶体中，所有的四个电子都是与其相邻的原子紧紧捆绑在一起。

Phosphorus has five outer electrons.
磷原子外有5个电子。

Insert a phosphorus atom into the silicon lattice and you are left with an unused electron.
把一个磷原子嵌入到硅晶格中，那还剩下一个电子。

Since phosphorus also has one more proton in its nucleus than silicon does, taken together the extra particles resemble a hydrogen atom: a single electron tethered to a single proton.
因为磷的细胞核中比硅还多一个质子，把多余的质子、电子收集起来，这和氢原子的结构很相似：一个独立的电子捆绑着一个独立的质子。

However, the extra electron is much less tightly held by the extra proton in this pseudo-hydrogen than it would be in real hydrogen.
然而，在这个山寨版的氢中，这个额外的电子与额外质子的结合并不如真正氢原子中那么紧密。

This weaker grasp means that it takes much less magnetism to make a given change in the pseudo-hydrogen's spectrum than it would for real hydrogen.
这种越来越弱的结合意味着，如果要让这个山寨版频谱产生一个额定的变化，它所需要的磁场比真正的氢少得多。

So when Dr Murdin placed the crystal in a 30-tesla magnet at Radboud University in the Netherlands, he was mimicking the conditions in a 100,000-tesla white dwarf.
因此，当穆迪博士这个晶体放到一个30特斯拉的磁体中时，因为他在格尔福德的实验室缺少必要的设备，他是在模仿一个100,000特斯拉磁场强度的白矮星所处环境。

And the spectrum came out looking just the way the theory predicted.
结果得到的频谱与理论预测的看起来很像。

A black hole in a bath
浴缸中的黑洞

Creating a star in a laboratory is small beer compared with creating a black hole.
在实验室中建立一颗星星，相比于建立一个黑洞简直就是不值一提。

This is an object that is so massive and dense that not even light can flee its gravitational field.
黑洞是一个很庞大，密度很高的物体，甚至连光都无法逃脱它的引力场。

Looking inside one is therefore, by definition, impossible.
因此，向里面看—就是字面意思上的看—一眼都是不可能的。

All the more reason to try, says Silke Weinfurtner of the International School for Advanced Studies, in Trieste, Italy.
所有的，越来越的理由都让人们想试试建立一个山寨版的黑洞—意大利里雅斯特国际高级学院的西尔克-威福特纳这样表示。

Dr Weinfurtner plans to make her black hole in the bath.
威福特纳博士计划在浴缸中建立一个她的黑洞。

The bath in question, properly called a flume, is a water-filled receptacle 3 metres by 1.5 metres and 50cm deep, across which carefully crafted trains of ripples can pass.
这里说到的浴缸，更应该称之为水槽，因为它是一个3米乘1.5米，50厘米深的装满水的容器，横跨其中的是精心制作的涟波车队。

In the middle of the tank is a plug hole.
在这个水槽中有一个泄水孔。

If the water going down the hole rotates faster than the ripples can propagate, the ripples which stray beyond the aqueous event horizon will not make it out.
如果水旋转至水孔的速度快于涟波扩散的速度，那么超过水的黑洞边境—是黑洞的不归路--的涟波就不会让水漫出来的。

They are sucked down the drain.
水将会被吸到下水道里。

Then the researchers will check whether the simulacrum affects water waves in a way analogous to that which general relativity predicts for light—itself a wave—approaching an astrophysical black hole.
到时，研究者会检查这个模拟物，是否会以一种与广义相对论预测的光，接近天体物理学黑洞类似的方式影响水波。

According to Albert Einstein's theory, a region immediately outside the event horizon of a rotating black hole will be dragged round by the rotation.
根据爱因斯坦理论，一个靠近旋转黑洞边界的外部区域会在这个旋涡的影响下也转动起来。

Any wave that enters this region but does not stray past the event horizon should be deflected and come out with more energy than it carried on the way in.
任何进入这个区域，没能穿越过去的光波会发生偏离，并且将会带着比它接近这里时更多的能量出现。

To detect this super-radiant scattering, as the effect is called, Dr Weinfurtner will add fluorescent dye to the water and illuminate the surface waves with lasers.
为了检测这种越辐射的辐射—这种效应被这样称谓，威福特纳博士会在水中加入荧光染料，资助用激光照亮表面的水波。

The waves, often no bigger than one millimetre, can then be detected using high-definition cameras.
这些往往不会超过1毫米的水波，届时可以通过高清度摄像机拍下来。

Stefano Liberati, Dr Weinfurtner's colleague in Trieste, reserves the greatest enthusiasm for another aspect of the experiment.
威福特纳博士在里雅斯特的同事，斯特凡诺-莱伯拉蒂对这个试验的另一个方面表现出了极大的热情。

It might, if the researchers are lucky enough, offer clues to the nature of space-time.
如果研究者们运气好的话，这可能会是研究空间-时间本质的一个线索。

Could the cosmic fabric be made up of discrete chunks, atoms of space if you like, rather than being continuous, as is assumed by relativity?
宇宙的会是由一块块的独立物质，空间微粒—如果你愿意相信的话--组成，而不是像相对论认为连接在一起的吗？

This problem has perplexed physicists for decades.
这个问题已经困扰了物理学家们数十年了。

Many suspect black holes hold the answer, because they are sites where continuous relativity meets chunky quantum physics.
他们中的许多人猜测，黑洞就是答案，因为黑洞是连续性相对论与厚实量子物理学都无法研究出真相的地方。

Waterborne holes serve as a proxy.
水面上的洞就代表了这种现象。

Water is, after all, made up of just such discrete chunks: molecules of H2O.
毕竟，水是由类似上述的一个个分散的物质组成：水分子。

As wavelengths fall—equivalent to rising energy—waves reach a point where the size of molecules may begin to influence how they behave.
随着波长的减小—相当于光波能量的增加，当波长达到一定的值时，水分子的大小可能会开始影响水波的行为。

If Dr Weinfurtner and Dr Liberati observe some strange behaviour around their event horizons, theorists will be thrilled.
如果威福特纳博士和莱伯拉蒂博士能够观察到这些水波的黑洞边界周围的一些奇怪表现时，那么理论学家们会兴奋不已。

and home-brewed universes
自家制作的宇宙

Even benchtop black holes, though, are nothing compared with the ambitions of Igor Smolyaninov of the University of Maryland.
即使是桌面上的黑洞，但是也无法与马里兰大学的伊戈尔-斯莫利亚尼诺夫的雄心相比。

For Dr Smolyaninov wants to create entire universes.
因为，斯莫利亚尼诺夫想创造一个完整的宇宙。

The way light travels through the four dimensions of space-time is mathematically akin to how it moves through metamaterial.
从数学的角度看，光穿越四维空间的方式与它穿透超材料的方式很接近。

These are substances with features measured in nanometres, or billionths of a metre, which let them bend light in unusual ways.
这些材料是以纳米为单位，或者是以一米的十亿分之一为单位的特别物质，所以可以以特别的方式改变光的方向。

For example they can force light to skirt along the outside of an object, hiding it from view as if behind an invisibility cloak.
比如说，它们可以让光波绕开一个物体的外围，就好像隐藏在一个隐形斗篷的后面，让人无法看到它。

Space-time, too, bends light, in ways that depend on how mass is distributed within it.
时空也同样可以改变光的方向，改变方式取决于这个空间质量的分配方式。

In principle, then, metamaterials ought to be able to mimic how light moves not just through the space-time scientists on Earth are familiar with, but also other possible space-times to which they do not, and never will, have access.
原则上讲，超材料应该不仅能够模拟地球科学家们熟悉的光波穿越时空，而且可以模拟光穿越其它可能存在的，地球科学家们无法触及，也可能永远无法打开的时空。

Two years ago Dr Smolyaninov suggested an experiment with various metamaterials, corresponding to universes with different properties lashed together into a home-brewed multiverse.
两年前，斯莫利亚尼诺夫曾建议用不同的超材料进行试验，相当于把拥有各种特性的宇宙集中到了自家创造的宇宙中。

In a paper to be published inOptics Express, he and his colleagues report that they have succeeded.
他和他的同事在光学快报上发表了一篇论文，称他们的试验取得了成功。

Rather than fine-tune metamaterial to exact specifications, which is finicky and expensive, the researchers used nanoparticles of cobalt, which are relatively easy to get hold of, and suspended them in kerosene.
研究者并没有对超材料的具体规格进行微调，因为这样既繁杂又增加成本，他们使用了钴的纳米粒子，这个相对而言容易得到，可以把它们暂时存放在煤油中。

They then applied a magnetic field which, thanks to cobalt's ferromagnetic nature, arranged the particles into thin columns.
然后，根据钴的铁磁性，他们应用一个磁场把这些粒子安置到了薄薄的柱子中。

In space-time terms the length of the columns is time and the two axes perpendicular to the length represent the three spatial dimensions in a real universe.
在时空的术语中，这种柱子的长度就表示，时间和两个垂直于距离的轴代表着真实宇宙中的三维空间。

To build his multiverse, Dr Smolyaninov added slightly less cobalt to the kerosene, about 8% by volume, than was needed to maintain stable nanocolumns.
为了创建他的多元宇宙，斯莫利亚尼诺夫博士在煤油中加了些钴，大概是总体积的8%，这比稳定纳米柱的需要量略少。

Natural fluctuations in the density of the fluid then lead to the spontaneous erection of transient nanocolumns—equivalent to space-times popping up only to fizzle and re-emerge elsewhere in the multiverse.
在这个液体浓中的自然流动，会导致临时纳米柱的自发性的直立—相当于时空突然出现，却只能以失败结束，但是会在这个多元宇宙中的某个其它地方再次出现。

They could be detected by their effect on polarised light shone through the material.
要想探测到它们，可以通过它们在极化光通过物质时所施加的影响来检测。

Whether all this ingenuity unravels any cosmic truth is uncertain.
所有这种独出心裁是否能解开宇宙的真相，还不确定。

Cliff Burgess, a theorist at Perimeter Institute for Theoretical Physics in Ontario, has his doubts.
安大略省周边物理理论研究所的克里夫-伯吉斯是一位理论学家，他还对此存有疑问。

But he thinks that such experiments are nevertheless worth pursuing.
但是，他认为，这些试验还是值得一试的。

Like tap-dancing snakes, he says, the point is not that they do it well, it is that they do it at all.
他说，就像跳踢踏舞的蛇一样，关键不是他们做得非常好，而是他们已经在做了。