MOST people think of the empty space between the stars as being, well, empty. But it is not. It is actually filled with gas. Admittedly, at an average density of 100-1,000 molecules per cubic centimetre (compared with 100 billion billion in air at sea level), it is a pretty thin gas. But space is big, so altogether there is quite a lot of it.大多数人们指出星星之间就是空无一物，但事实并非如此。实质上有气体致密其中。

诚然，分子平均值密度10^2-10^3/cm^3的气体十分平流层（海平面处是10^26/cm^3）。不过由于空间很辽阔，气体分子总体数量是相当可观的。Most of it, about 92%, is hydrogen. A further 8% is helium, which is chemically inert. But a tiny fraction—less than one-tenth of a percent—consists of molecules with other elements, such as oxygen, carbon and nitrogen, in them. Though these other elements are a mere soupon of the interstellar soup, they do give it real flavour.大部分（大约92%）的气体是氢，另外8%是惰性气体氦。还有一小部分（不多达千分之一）由氧、碳、氮等其他元素包含的分子。

虽然这些元素意味着是“星际浓汤”严重的调料，但它们显然加添了汤的味道。Signs of life生命的迹象So far about 180 types of these molecular ingredients have been detected in space from their microwave spectra—the energy produced when molecules rotate around their chemical bonds. There are two reasons for wanting to study them. One is that these molecules are probably the precursors of life. The other is that the rarefied nature of astrochemistry changes the way processes work. It means the individual steps in chemical reactions can be disentangled from one another in a way that is hard—and sometimes impossible—on Earth. And it allows reactions to happen that are unknown on Earth.到目前为止，人们早已通过微波谱线观测出约180种分子成分。分子绕行其化学键转动时，分子能级不会再次发生转变，从而产生微波谱线。

研究微波谱线有两个原因。一是分子有可能是生命的预兆。二是天体化学其平流层的属性不会转变化学反应的过程。

人们可以用这种方式把化学反应中独立国家的一步从彼此步骤间分离出来，有时这在地球上很难构建。并且还有有可能再次发生人类不得而知的化学反应。Now the astrochemists have a new tool: the Atacama Large Millimetre/submillimetre Array (ALMA) in northern Chile. It was officially opened on March 13th but has already been making discoveries, including the most intense bursts of star birth in the early universe. ALMA consists of 66 dishes and is the world’s most powerful radio telescope. At a cost of $1.3 billion it should provide a hundredfold increase in sensitivity and resolution over the best older instruments.现在天体化学家有了新的工具：阿塔卡马大型毫米/亚毫米波天线阵（ALMA，坐落于智利北部）。3月13日ALMA月运作，到现在早已有了找到，例如宇宙早期恒星问世最白热化的愈演愈烈。

ALMA有66台天线，是世界上最强大的射电望远镜。花费13亿美元毕竟不会使灵敏度分辨率比过去最差的仪器还要好百倍。Those older telescopes had to focus on nebulae, where the interstellar gas is most concentrated (a familiar one, visible through binoculars, is the gas cloud around the stars that make up Orion’s sword). And older telescopes can detect only strong, simple signals of the sort emitted by small molecules like carbon monoxide and hydrogen cyanide, which have two and three atoms respectively. Spotting more complex substances was almost impossible because their rotational energy is scattered by their numerous bonds across a wide range of frequencies.以往的望远镜必需注目星云，那里是星际气体最集中于之处。一个能用双筒望远镜看见的典例是气体环绕着恒星所构成的猎户座的”剑”。

并且杨家望远镜不能观测到一氧化碳（双原子）、氢氰化物（三原子）等小分子释放出来的强劲的，非常简单的信号。而辨别更加简单的物质完全不有可能，大量化学键占据很长的频率范围，以至于转动能被衍射掉。

ALMA, by contrast, can detect such things routinely. It has already identified glycolaldehyde and acetone, molecules that have eight and ten atoms respectively. In particular, ALMA’s masters, a consortium of research agencies from Canada, Chile, Europe, Japan, Taiwan and the United States, hope to find simple sugars and organic acids—molecules most researchers in the field believe were needed to get life going on Earth.忽略ALMA可以只能观测到这些信号：它早已检验出有了乙醇醛（8原子分子）和丙酮（10原子分子）。尤其的，由加拿大、智利、欧洲、日本、台湾及美国的财团构成的研究机构掌控ALMA，期望以此找寻非常简单的糖类和有机酸——该领域大多数研究人员指出它们是地球上生命的必须之物。The ability to study chemical reactions stage by stage will be equally important. High-school chemistry lessons, with their neat equations transforming, say, 2H + O into 2HO, miss out a plethora of intermediate steps such as (in this case) the formation of hydroxyl, OH. In a lab, these intermediates are often too short-lived to be detectable. But in space an intermediate may hang around a long time before it encounters its partner in the next stage of a reaction. ALMA can see the microwave traces of such intermediates, and thus gain a better understanding of them.需要研究化学反应中的每一步某种程度很最重要。

高中化学课上非常简单的反应方程式省略了大量的中间步骤。例如2H + O = 2HO就没反映构成羟基（OH）的过程。实验室里，这些中间过程十分一段时间，人们无法观测。

不过在太空中，一个中间过程不会持续很长时间，直到遇到下一步反应的搭挡。ALMA可以看见这些中间过程的微波轨迹，因此研究者可以更佳的理解这些过程。There are also completely new reactions to discover. Anthony Remijan, of America’s National Radio Astronomy Observatory, who is one of the astronomers putting ALMA through its paces, is studying the formation of methyl formate, a compound widely used on Earth in applications from insulation to insecticides. Usually it is synthesised either from methanol and formic acid, or methanol and carbon monoxide. But there is, in theory, a third route that uses formic acid and an unstable substance made from methanol and hydrogen. This has not been seen in an Earthly laboratory, but Dr Remijan thinks it is an important pathway in space, and ALMA should soon tell him if he is right.还有全新的反应尚待人们找到。美国国家射电天文台的Anthony Remijan是将ALMA引进这个方向的天文学家中的一员。

他正在研究甲酸甲酯的构成过程。从绝缘体到杀虫剂，可以说道地球上四处都是甲酸甲酯。

一般来说它由甲醇和甲酸，或甲醇和一氧化碳制备。但是在理论上，还可以用于甲酸和一种不稳定的物质来生产甲酸甲酯。（不稳定的物质则由甲醇和氢来构成。

）这还没在地球上的实验室中找到，但Remijan博士指出在太空中这是一个最重要的过程。ALMA应当迅速就不会告诉他他否准确。Probably, that particular discovery will have no practical consequences. The known syntheses are effective, and methyl formate is already cheap. But it will prove a principle about using the cosmos as a chemistry laboratory,and the hope is that similar findings about other molecules that are harder to make may allow chemical engineers at home to reformulate their processes.If that happens, the test tube in the sky really will have proved its worth.或许，上述尤其的找到会产生简单效果。甲酸甲酯熟悉的制备方法很有效地，而且它很低廉。

但是，这证明了一个理念：用宇宙当作化学实验室。期望有关其他较难生产的分子的类似于找到需要让化学工程师在家里重新制定它们的制备过程。如果可以，天空中的试管显然有其价值。

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