BALTIMORE, Maryland – Mario Livio tossed his car keys in the air. They rose ever more slowly, paused, shining, at the top of their arc, and then in accordance with everything our Galilean ape brains have ever learned to expect, crashed back down into his hand.
馬力歐‧李維歐把汽車鑰匙拋到空中。鑰匙上升速度漸慢，到弧線頂端停一下，接著墜回他手中，正合我們這些伽利略類人猿腦袋學會預測的情況。

That was the whole problem, explained Dr. Livio, a theorist at the Space Telescope Science Institute here on the Johns Hopkins campus.
但那也正是整個問題所在，李維歐博士解釋道。他是馬里蘭州約翰霍浦金斯巴爾的摩校區太空望遠鏡科學研究所的理論專家。

A decade ago, astronomers discovered that what is true for your car keys is not true for the galaxies. Having been impelled apart by the force of the Big Bang, the galaxies, in defiance of cosmic gravity, are picking up speed on a dash toward eternity. If they were keys, they would be shooting for the ceiling.
10年前，天文學家發現，對你的汽車鑰匙為真的現象，對整個銀河卻不見得為真。銀河被大爆炸力道炸開，不理會宇宙重力，而是向永恆奔去，速度愈來愈快。如果它們就是那串鑰匙，會向天花板射去。

“That is how shocking this was,” Dr. Livio said.
「那是令人驚異之處，」李維歐博士說。

It is still shocking. Although cosmologists have adopted a cute name, dark energy, for whatever is driving this apparently antigravitational behavior on the part of the universe, nobody claims to understand why it is happening, or its implications for the future of the universe and of the life within it. It has led some cosmologists to the verge of abandoning their fondest dream: a theory that can account for the universe and everything about it in a single breath.
它還是很驚人。雖然宇宙論者為宇宙間這種顯然違反重力的行為取了「黑暗能量」這個俏名稱，但沒有人敢聲稱了解為何有此現象，或它與宇宙未來及其內部生命有何關聯。它逼得部分宇宙論者幾乎放棄他們最鍾愛的夢想：一個能一口氣解釋宇宙及每個相關問題的理論。

“The discovery of dark energy has greatly changed how we think about the laws of nature,” said Edward Witten, a theorist at the Institute for Advanced Study in Princeton, New Jersey.
「黑暗能量的發現，大幅改變我們對自然定律的想法，」愛德華‧維登說。他是新澤西州普林斯頓高等研究所的理論家。

This fall, NASA and the U.S. Department of Energy plan to invite proposals for a $600 million satellite mission devoted to dark energy. But some scientists fear that might not be enough. When astronomers and physicists gathered at the Space Telescope Science Institute recently to take stock of the revolution, their despair of getting an answer to the dark energy mystery anytime soon, if ever, was palpable.
今秋，美國太空總署和美國源部計畫斥資6億美元，為一項專門研究黑暗能量的衛星任務公開徵求企畫案。不過，有些科學家擔心經費可能不夠。天文學和物理學家最近在太空望遠鏡科學研究所討論此一革命性創舉，對近期內是否能解開黑暗能量之謎，絕望之情溢於言表。

Cosmologists have recently arrived at a robust but dark consensus regarding our cosmos. It was born 13.7 billion years ago in the Big Bang. By weight it is 4 percent atoms and 22 percent so-called dark matter of unknown identity–perhaps elementary particles that will be discovered at the Large Hadron Collider starting up outside Geneva this year. That leaves 74 percent for the weight of whatever began causing the cosmos to accelerate about five billion years ago.
宇宙論者最近才對我們的宇宙，達成一個堅固卻黑暗的共識。宇宙在137億年前的大爆炸中誕生。依重量，4%是原子，22%是身分不明的所謂黑暗物質，或許就是今年在日內瓦市郊啟用的大強子對撞機即將發現的基本粒子也說不定。剩下的74%，不管叫什麼，約從50億年前就已造成宇宙加速。

As far as astronomers can tell, there is no relation between dark matter, the particles, and dark energy other than the name, but you never know. There is in fact a simple explanation for the dark energy, Dr. Witten pointed out, one whose tangled history goes all the way back to Einstein, but it is also the most troubling.
據天文學家所知，黑暗物質、粒子和黑暗能量，彼此除了名字外，並無任何淵源，但這只有天曉得。維登博士指出，黑暗能量其實有一個單純的解釋，且其糾結的歷史可一直上溯到愛因斯坦，但那也是最令人困惑的地方。

In 1917, Einstein invented the cosmological constant, a sort of cosmic repulsion to balance gravity and keep the universe in balance. He abandoned his constant when the universe was discovered to be expanding, but quantum physics resurrected it by showing that empty space should be foaming with energy that had the properties of Einstein’s constant.
1917年，愛因斯坦發明宇宙常數，約莫是一種平衡重力，維持宇宙平衡的排斥作用。宇宙被發現逐漸在膨脹時，他放棄了他的常數，但量子物理學又顯示虛無的太空，應充滿具備愛因斯坦常數特質的能量，常數於是起死回生。

Alas, all attempts to calculate the amount of this energy come up with an unrealistically huge number, enough energy to blow away the contents of the cosmos like leaves in a storm before stars or galaxies could form. Nothing could live there.
天哪，所有計算此一能量的企圖，都得出一個難以想像的巨大數字，其能量之大，足以像狂風掃落葉般，在星星或星雲形成前，就將宇宙的內容吹光。沒有任何東西可以立足。

Something was missing in physicists’ understanding of physics, the logic went. The constant was really zero for deep reasons that, when revealed, would lead physicists closer to an understanding of what they call “the vacuum,” that is to say, the structure of reality.
就物理學家對物理的理解，一定有東西不見了，這種邏輯繼續推論著。宇宙常數應該真的是零，最大的理由在於一旦現身，將使物理學家對他們所謂的「真空」，亦即現實的結構，有進一步的理解。

“It seems now that the answer is not really zero,” Dr. Witten said.
「現在看來，答案似乎不真的是零，」維登博士說。

Einstein’s constant is the most economical explanation for dark energy, Dr. Witten said. The others, involving new force fields or tinkering with Einstein’s gravity, raise more questions than they answer. But if dark energy is the cosmological constant, it is smaller than predicted by a shocking factor of 10⁶⁰.
愛因斯坦的常數是黑暗能量最精簡的解說，維登博士說。其他的解說，包括新力場說或修補愛因斯坦的重力說，新增的問題比解答的還多。不過，如果黑暗能量真是宇宙常數，應該比預期的小，且小了驚人的10的60次方。

Dr. Witten suggested that maybe physicists should give up trying to explain that number and look instead for a theory that generates all kinds of universes.
維登博士認為，也許物理學家應該放棄解釋這個常數，轉而尋找一個能盡解所有宇宙之謎的理論。

That idea has been given mathematical form by string theory, which portrays the constituents of nature as tiny wriggling strings, an elegant idea that in principle explains all the forces of nature but in practice leads to at least 10⁵⁰⁰ potential universes.
那個構想用數學形式表現，也就是弦論，把自然的構成物看成許多細小蠕動的弦。這個高明的理論，原則上可解釋自然界所有力量，但實際上卻可導向至少10的500次方個可能的宇宙。

Dr. Witten allowed that dark energy might have transformed this fecundity from a vice into a virtue, a way to generate universes where you can find any cosmological constant you want. We just live in one where life is possible. “This interpretation of string theory might be close to the truth,” Dr. Witten said. But that truth comes at a cost.
維登博士同意，黑暗能量也許讓這種多產的能力，從邪惡轉變為一種美德，成為一種產生眾多宇宙的方式，你要找多少個宇宙常數都沒問題。我們正好住在一個生命能夠存在的宇宙。「弦論這種詮釋，可能很接近真實，」維登博士說。但那個真實是有代價的。

“Before the discovery of the dark energy, quantum physicists tended to assume that the ‘vacuum’ we live in has some deep meaning that reflects nature’s deepest secrets,” Dr. Witten said. But if ours is only one of a zillion in a haystack, there is nothing special about it.
「發現黑暗能量之前，量子物理學家傾向假定我們居住的『真空』有反映自然最深沉秘密的重大意義，」維登博士說。但是，如果我們的宇宙只是乾草堆裡的一根毫芒，那就毫無特別之處。

It could still turn out that dark energy is some as-yet-undiscovered “fifth force,” say, or the result of not understanding gravity.
黑暗能量仍有可能變成某些尚待被發現的「第五力量」，或不為人知的重力結果。

“I’d be happy if that happened,” Dr. Witten said. “Our reward would be to go back to where we were, not understanding the cosmological constant.”
「如果那種事情真的發生，我會高興，」維登博士說。「我們的報酬將是回到從前，回到對宇宙常數毫無所悉的時代。」

關鍵字句

Galaxy指大星團及所屬充斥宇宙的物質，或稱星雲、小宇宙；宇宙中，這種星團不計其數。Gala希臘文milk之意，所以galaxy也是milky way，但泛指包括太陽系在內的整個銀河系則為The Milky Way galaxy，必須大寫。文中提及的the galaxies應是一般的星團或星雲。

第三段，what is true for your car keys is not true for...是一種邏輯語法（logic syntax），整個what子句是個「真」（true）命題敘述（descriptive proposition），與述部（predicate）的「假」（not true / false）命題相對。用白話說，就是「汽車鑰匙是這樣，星團卻不見得」。

作者指出， 部分宇宙論者（cosmologists）希望能有一種足以解釋宇宙萬象（account for the universe）的理論，但這個美夢在10年前卻因黑暗能量（dark energy）的發現而幻滅。原來宇宙自137億年前因大爆炸（the Big Bang）而生，星團便不斷受黑暗能量排擠，向外膨脹，奔向永恆（dash toward eternity），就連物理學大師愛因斯坦也承認宇宙不斷在膨脹，被迫放棄他在1917年發明，認為宇宙會趨於均衡的宇宙常數（cosmological constant ）。

有趣的是， 量子物理學家（quantum physics）卻證明了空空的太空（empty space）裡面，其實充滿具備宇宙常數特質的能量，讓這個愛因斯坦的棄嬰起死回生（resurrected）。

原文參照：
http://www.nytimes.com/2008/06/03/science/03dark.html

2008-06-17/聯合報/G6版/UNITED DAILY NEWS 蔡繼光 原文請見6月17日紐時周報六版頭條