2014年经济学人 天体物理 尘归尘土归土

Astrophysics

Dust to dust

A dramatic recent “discovery” in physics is looking rather dodgy

IN MARCH Chao-Lin Kuo, an astrophysicist at Stanford University, filmed himself knocking on the door of his colleague Andrei Linde. In the 1980s Dr Linde was one of several cosmologists who developed the theory of cosmic inflation, which holds that, in the first instants of its existence, the universe underwent a brief period of faster-than-light expansion.

Because inflation neatly¹ cleaves² several knotty³ problems in cosmology, many astrophysicists (though not all) subscribe⁴ to the theory. But direct, unambiguous evidence for it has been lacking. That was why Dr Kuo was visiting Dr Linde—to tell him that, thanks to the work of a telescope in Antarctica called BICEP-2, such evidence had now been found. After digesting the news, an emotional Dr Linde broke open a bottle of champagne⁵ to celebrate. The video has been viewed almost 3m times.

It now seems that Dr Kuo might have to make a new video, informing Dr Linde that he has wasted a bottle of bubbly. A paper just released by the team behind Planck, a European space telescope, casts serious doubt on the BICEP-2 result. What looked like a clear window back into the earliest moments of the universe might simply have been a faint glow from the diaphanous⁶ clouds of dust that exist between the stars.

The BICEP-2 team, led by John Kovac of Harvard University, had been studying the cosmic microwave background radiation (CMB)—a weak bath of radiation, left over from the Big Bang, that suffuses⁷ the universe. They were looking for evidence of primordial⁸ gravitational waves. These are ripples⁹ in the fabric¹⁰ of space, created, if the theory of inflation is correct, as the early universe was undergoing its post-creation growth spurt¹¹.

A dusty trail

Such waves should have left a distinctive¹², polarised mark imprinted¹³ upon the CMB. And, in a press conference on March 17th, that is exactly what the BICEP-2 team claimed to have found. It was the biggest news in physics since the discovery, in 2012, of the Higgs boson, and it was widely covered (including in The Economist). Not only would the BICEP result have confirmed the theory of inflation, but studying the gravitational waves it purported¹⁴ to have found would have given cosmologists a way to look back to the very earliest moments of the universe.

But gravitational waves are not the only things that BICEP-2 might have picked up. The Milky¹⁵ Way is filled with thin clouds of interstellar dust which, under the influence of the galaxy's magnetic field, scatter¹⁶ and polarise starlight. The BICEP team were confident that the contamination from the dust was small enough not to affect their detection of gravitational waves. But the behaviour of the dust is poorly understood, says Chris Lintott, an astronomer¹⁷ at Oxford¹⁸ University, and not everyone was convinced.

The Planck results suggest that they were right to be sceptical. The European telescope has just unveiled a map of dust density¹⁹ across the entire sky. It suggests that, contrary to the BICEP team's hopes, the signal from the dust is so strong that the telescope might well have seen no primordial gravity waves at all.

That, at least, is the most likely interpretation²⁰, but it is not the only one. The Planck team are careful to stop short of saying that their results are fatal to BICEP's claims, pointing out that applying their data to the BICEP results involves considerable “statistical and systematic²¹ uncertainties”. There are, in other words, a couple of glimmers²² of hope that signs of inflation have actually been seen. One is that the precise behaviour of the dust is still mysterious, which means the mathematical transformations²³ used to apply Planck's data to BICEP's results may turn out to be incorrect. And even if those maths are sound, statistics may ride to the rescue—for if the amount of radiation from the dust is at the lowest end of Planck's estimates, a small gravitational-wave signal may survive.

Rowing back on a triumphant²⁴ announcement about the first instants of creation may be a little embarrassing, but the saga²⁵ is a useful reminder²⁶ of how science works. There is no suggestion that anyone has behaved dishonourably. Admittedly, the BICEP team's original press conference looks, with hindsight, seriously overconfident. More information-sharing between the various gravitational wave-hunters, all of whom guard their data jealously, might have helped tone down the triumphalism. But science, ideally, proceeds by exactly this sort of good-faith argument and honourable²⁷ squabbling—until the weight of evidence forces one side to admit defeat.

That could happen soon: the Planck and BICEP teams have pooled their data and are working on a joint²⁸ paper, expected to be published in the next few months. Information from other gravity-wave hunting experiments—including some run by the BICEP team themselves—will shed extra light, too. It is not yet impossible that Dr Kovac and his colleagues will be proved right after all. But at this point it would take a brave cosmologist to bet on it.

From the print edition: Science and technology

1 neatly   

adv.整洁地，干净地，灵巧地，熟练地

参考例句：

• Sailors know how to wind up a long rope neatly.水手们知道怎样把一条大绳利落地缠好。
• The child's dress is neatly gathered at the neck.那孩子的衣服在领口处打着整齐的皱褶。

2 cleaves   

v.劈开，剁开，割开( cleave的第三人称单数 )

参考例句：

• This wood cleaves easily. 这木材好劈。 来自《现代英汉综合大词典》
• The water cleaves the banks away like a knife. 河水象一把刀似的，把两岸削掉。 来自辞典例句

3 knotty   

adj.有结的，多节的，多瘤的，棘手的

参考例句：

• Under his leadership,many knotty problems were smoothly solved.在他的领导下，许多伤脑筋的问题都迎刃而解。
• She met with a lot of knotty problems.她碰上了许多棘手的问题。

4 subscribe   

vi.(to)订阅，订购；同意；vt.捐助，赞助

参考例句：

• I heartily subscribe to that sentiment.我十分赞同那个观点。
• The magazine is trying to get more readers to subscribe.该杂志正大力发展新订户。

5 champagne   

n.香槟酒；微黄色

参考例句：

• There were two glasses of champagne on the tray.托盘里有两杯香槟酒。
• They sat there swilling champagne.他们坐在那里大喝香槟酒。

6 diaphanous   

adj.(布)精致的，半透明的

参考例句：

• She was wearing a dress of diaphanous silk.她穿着一件薄如蝉翼的绸服。
• We have only a diaphanous hope of success.我们只有隐约的成功希望。

7 suffuses   

v.（指颜色、水气等）弥漫于，布满( suffuse的第三人称单数 )

参考例句：

• A rosy glow that suffuses snow-covered mountain peaks at a clear day. 她困恼的最顶点出现在一个覆盖著冰雪的纽西兰山上一时的无力感。 来自互联网

8 primordial   

adj.原始的；最初的

参考例句：

• It is the primordial force that propels us forward.它是推动我们前进的原始动力。
• The Neanderthal Man is one of our primordial ancestors.的尼安德特人是我们的原始祖先之一.

9 ripples   

逐渐扩散的感觉( ripple的名词复数 )

参考例句：

• The moon danced on the ripples. 月亮在涟漪上舞动。
• The sea leaves ripples on the sand. 海水在沙滩上留下了波痕。

10 fabric   

n.织物，织品，布；构造，结构，组织

参考例句：

• The fabric will spot easily.这种织品很容易玷污。
• I don't like the pattern on the fabric.我不喜欢那块布料上的图案。

11 spurt   

v.喷出；突然进发；突然兴隆

参考例句：

• He put in a spurt at the beginning of the eighth lap.他进入第八圈时便开始冲刺。
• After a silence, Molly let her anger spurt out.沉默了一会儿，莫莉的怒气便迸发了出来。

12 distinctive   

adj.特别的，有特色的，与众不同的

参考例句：

• She has a very distinctive way of walking.她走路的样子与别人很不相同。
• This bird has several distinctive features.这个鸟具有几种突出的特征。

13 imprinted   

v.盖印（imprint的过去式与过去分词形式）

参考例句：

• The terrible scenes were indelibly imprinted on his mind. 那些恐怖场面深深地铭刻在他的心中。
• The scene was imprinted on my mind. 那个场面铭刻在我的心中。 来自《简明英汉词典》

14 purported   

adj.传说的，谣传的v.声称是…，（装得）像是…的样子( purport的过去式和过去分词 )

参考例句：

• the scene of the purported crime 传闻中的罪案发生地点
• The film purported to represent the lives of ordinary people. 这部影片声称旨在表现普通人的生活。 来自《简明英汉词典》

15 milky   

adj.牛奶的，多奶的；乳白色的

参考例句：

• Alexander always has milky coffee at lunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
• I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。

16 scatter   

vt.撒，驱散，散开；散布/播；vi.分散，消散

参考例句：

• You pile everything up and scatter things around.你把东西乱堆乱放。
• Small villages scatter at the foot of the mountain.村庄零零落落地散布在山脚下。

17 astronomer   

n.天文学家

参考例句：

• A new star attracted the notice of the astronomer.新发现的一颗星引起了那位天文学家的注意。
• He is reputed to have been a good astronomer.他以一个优秀的天文学者闻名于世。

18 Oxford   

n.牛津（英国城市）

参考例句：

• At present he has become a Professor of Chemistry at Oxford.他现在已是牛津大学的化学教授了。
• This is where the road to Oxford joins the road to London.这是去牛津的路与去伦敦的路的汇合处。

19 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。

20 interpretation   

n.解释，说明，描述；艺术处理

参考例句：

• His statement admits of one interpretation only.他的话只有一种解释。
• Analysis and interpretation is a very personal thing.分析与说明是个很主观的事情。

21 systematic   

adj.有系统的，有计划的，有方法的

参考例句：

• The way he works isn't very systematic.他的工作不是很有条理。
• The teacher made a systematic work of teaching.这个教师进行系统的教学工作。

22 glimmers   

n.微光，闪光( glimmer的名词复数 )v.发闪光，发微光( glimmer的第三人称单数 )

参考例句：

• A faint lamp glimmers at the end of the passage. 一盏昏暗的灯在走廊尽头发出微弱的光线。 来自互联网
• The first glimmers of an export-led revival are apparent. 拉动出库复苏的第一缕曙光正出现。 来自互联网

23 transformations   

n.变化( transformation的名词复数 )；转换；转换；变换

参考例句：

• Energy transformations go on constantly, all about us. 在我们周围，能量始终在不停地转换着。 来自辞典例句
• On the average, such transformations balance out. 平均起来，这种转化可以互相抵消。 来自辞典例句

24 triumphant   

adj.胜利的，成功的；狂欢的，喜悦的

参考例句：

• The army made a triumphant entry into the enemy's capital.部队胜利地进入了敌方首都。
• There was a positively triumphant note in her voice.她的声音里带有一种极为得意的语气。

25 saga   

n.(尤指中世纪北欧海盗的)故事，英雄传奇

参考例句：

• The saga of Flight 19 is probably the most repeated story about the Bermuda Triangle.飞行19中队的传说或许是有关百慕大三角最重复的故事。
• The novel depicts the saga of a family.小说描绘了一个家族的传奇故事。

26 reminder   

n.提醒物，纪念品；暗示，提示

参考例句：

• I have had another reminder from the library.我又收到图书馆的催还单。
• It always took a final reminder to get her to pay her share of the rent.总是得发给她一份最后催缴通知，她才付应该交的房租。

27 honourable   

adj.可敬的；荣誉的，光荣的

参考例句：

• I don't think I am worthy of such an honourable title.这样的光荣称号，我可担当不起。
• I hope to find an honourable way of settling difficulties.我希望设法找到一个体面的办法以摆脱困境。

28 joint   

adj.联合的，共同的；n.关节，接合处；v.连接，贴合

参考例句：

• I had a bad fall,which put my shoulder out of joint.我重重地摔了一跤，肩膀脫臼了。
• We wrote a letter in joint names.我们联名写了封信。