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Astrophysics
天體物理
Dust to dust
塵歸塵，土歸土
A dramatic recent “discovery” in physics is looking rather dodgy
近期，物理學中的一項戲劇性發現看上出非常模糊
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.
三月，斯坦福大學天體物理學家郭兆林拍下了自己造訪同事Andrei Linde的一幕。上世紀80年代，Linden博士是少有的幾位發展了宇宙膨脹論的宇宙學家。宇宙膨脹論認為，在其出現的那一瞬間，宇宙經歷了一段超光速膨脹。
Because inflation neatly cleaves several knotty problems in cosmology, many astrophysicists (though not all) subscribe 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 champagne to celebrate. The video has been viewed almost 3m times.
因為膨脹論能完整解釋宇宙學中的一些難題，許多天體物理學家都傾向于該理論。但是膨脹論仍缺乏直接、清晰的證據。這正是郭博士拜訪Linde博士的原因—在南極洲的BICEP-2天文望遠鏡發現了這種證據。收到消息后，Linde博士開了一瓶香檳來慶祝。這段視頻已經被瀏覽了將近300萬次。
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 diaphanous clouds of dust that exist between the stars.
現在好像郭博士不得不再做一個視頻，告訴Linde博士他浪費了一瓶香檳。新近有文獻報道稱，歐洲的普朗克天文望遠鏡拍到了對BICEP研究構成重大質疑的結果。回溯到宇宙最初時間，看上去似乎是清晰的窗戶的圖像可能僅僅是恒星間的透明灰云折射的淡淡光芒。
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 suffuses the universe. They were looking for evidence of primordial gravitational waves. These are ripples in the fabric of space, created, if the theory of inflation is correct, as the early universe was undergoing its post-creation growth spurt.
由哈佛大學John Kovac領導的BICEP-2小組長期研究宇宙微波背景輻射，即一種由大爆炸產生的微弱輻射，彌漫在宇宙中。他們在找尋原始引力波的證據。如果膨脹論是正確的的話，那么這種由宇宙在初創后迸發過程中產生的波會存在于空間架構中。
A dusty trail
布滿塵埃的小徑
Such waves should have left a distinctive, polarised mark imprinted 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 purported to have found would have given cosmologists a way to look back to the very earliest moments of the universe.
這種波應該在宇宙微波輻射背景上留下了一個獨特的、極化的記號。并且，在3月17日的新聞發布會上，BICEP-2小組宣布發現的，正是這個記號。這是從2012年希格斯玻色子發現以來，物理學界最大的新聞，并廣為傳播（包括《經濟學人》）。BICEP的結果不僅確認了膨脹論這么簡單，研究他們宣稱所發現的引力波，將為宇宙學家提供一條回溯宇宙最開始的時刻的方法。
But gravitational waves are not the only things that BICEP-2 might have picked up. The Milky Way is filled with thin clouds of interstellar dust which, under the influence of the galaxy's magnetic field, scatter 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 astronomer at Oxford University, and not everyone was convinced.
但是引力波并不是BICEP-2發現的唯一一件事情。銀河中遍布的星級塵埃，在星系磁場的作用下，散射或極化星光。BICEP小組相信，灰塵的污染非常小，不足以影響其對引力波的測定。但是牛津大學的天文學家Chris Lintott稱，對灰塵行跡我們理解不足，而且無法令所有人信服。
The Planck results suggest that they were right to be sceptical. The European telescope has just unveiled a map of dust density 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.
Planck小組的結果說明，懷疑論者是正確的。歐洲天文望遠鏡最近提出了一份整個天空中的灰塵的密度分布圖。分布圖顯示，同BICEP小組的假定相反，灰塵發出的信號很強，天文望遠鏡甚至無法檢測到任何的原始引力波。
That, at least, is the most likely interpretation, 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 systematic uncertainties”. There are, in other words, a couple of glimmers 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 transformations 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.
至少這是最有可能的解釋。但卻不是唯一的。普朗克小組謹慎地不曾宣稱他們的結果對BICEP小組的聲明有顛覆效果，而是指出，將他們所獲得的數據應用于BICEP的結論中會產生可觀的“統計學和系統上的不確定性”。換句話說，有些閃爍有望作為膨脹論確實存在的證據。一方面，灰塵行跡的精確表述依然是個謎，也就是說，將普朗克小組的數據轉換為BICEP結果的數學過程可能是錯誤的。而且即使這些數學轉換可靠，數據也可能出現問題。因為如果灰塵的輻射數量處在普朗克小組估計的最低端，可能會有一點點引力波信號留存。
Rowing back on a triumphant announcement about the first instants of creation may be a little embarrassing, but the saga is a useful reminder 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 honourable squabbling—until the weight of evidence forces one side to admit defeat.
收回早期的勝利宣言可能有點尷尬，但是這個冒險非常恰當地提醒了我們，科學工作者的工作方式。沒人會覺得誰的表現有愧其身份。固然，BICEP小組最初的新聞發布會，事后來看，過度自信了。在各種引力波守望者當中共享貢多信息可能有助于緩和這種勝利主義，可惜他們都視自己的數據如命根子。但是，想象中的科學，正是通過這種善意的爭論和尊重彼此的吵鬧，直到證據的分量迫使一方承認失敗。
That could happen soon: the Planck and BICEP teams have pooled their data and are working on a joint 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.
這一幕可能很快上演：普朗克小組和BICEP小組已將各自的數據湊到一起，并聯合撰寫論文，預計將于接下來的幾個月中發表。通過其他引力波探測實驗，包括BICEP小組自己的，將會擺脫多余的光。可能最終Kovac博士及其同事無法自圓其說。但在這一時刻，需要勇敢的天文學家站出來孤注一擲。
From the print edition: Science and technology
原文出自《經濟學人》 翻譯：趙興昊
譯文屬譯生譯世
