百年相對論 愛因斯坦爲宇宙立法(2)

Designing a Universe

設計一個宇宙

Like most of his colleagues at the time, Einstein considered the universe to consist of a cloud of stars, the Milky Way, surrounded by vast space. What was beyond? Was the universe infinite? And if so, what stopped a star from drifting so far that it would have nothing to relate to?

就像他當時的大多數同事一樣，愛因斯坦認爲宇宙由大量恆星、銀河及周圍的廣闊空間組成。宇宙之外有什麼？宇宙是無限的嗎？如果是這樣的話，什麼能阻止一顆恆星漂移到與所有物體脫離聯繫的距離？

To avoid such problems, Einstein set out in 1917 to design a universe without boundaries. In his model, space is bent around to meet itself, like the side of a tin can.

爲了避免此類問題，愛因斯坦在1917年建立了無限宇宙模型。在他設立的模型中，空間就像錫罐的側面一樣，能夠彎曲觸碰到自己。

“I have committed another suggestion with respect to gravitation which exposes me to the danger of being confined to the nut house,” he confided to a friend.

他向一名朋友傾訴，“我提出另一個有關引力的建議，這使我面臨被關進瘋人院的風險。”

This got rid of the need for troublesome boundaries. But this universe was unstable, and the cylinder would collapse if something didn’t hold its sides apart.

這就不需要設置令人煩惱的邊界了。但這個宇宙並不穩定，如果某種東西沒有將兩邊撐住，這個圓柱就會坍縮。

That something was a fudge factor added to the equations Einstein called the cosmological constant. Physically, this new term, denoted by the Greek letter lambda, represented a long-range repulsive force.

這種東西就是愛因斯坦在自己的公式中插入的一種被他稱爲“宇宙常數”的容差係數。從物理學來看，這個由希臘字母“蘭布達”(λ)指代的新名詞代表着遠距離的排斥力。

The happy result, Einstein thought, was a static universe of the type nearly everybody believed they lived in and in which geometry was strictly determined by matter.

愛因斯坦認爲，皆大歡喜的結果就是一個靜態宇宙，幾乎所有人都認爲他們生活在這樣一個宇宙中，其中的幾何形態完全由物質決定。

But it didn’t last. Willem de Sitter, a Dutch astronomer, came up with his own solution describing a universe that had no matter at all and was flying apart.

但這沒能站住腳。荷蘭天文學家威廉·德西特(Willem de Sitter)提出了自己的解答，他描述了一個根本不存在物質且正在飛散的宇宙。

“It would be unsatisfactory, in my opinion,” Einstein grumbled, “if a world without matter were possible.”

“我認爲，如果說一個沒有物質的世界是可能存在的，”愛因斯坦抱怨稱。“這是無法令人滿意的。”

And then Edwin Hubble discovered that the universe really was expanding.

後來，埃德溫·哈勃(Edwin Hubble)發現，宇宙確實在不斷膨脹。

If the cosmological constant couldn’t keep the universe still, then forget about it and Mach’s Principle, Einstein said. “It dates back to the time in which one thought that the ‘ponderable bodies’ are the only physically real entities,” he later wrote to the British cosmologist Felix Pirani.

愛因斯坦表示，既然這個宇宙常數不能使宇宙保持靜態，那就別考慮它以及馬赫原理了。他後來給英國宇宙學家費利克斯 ·皮拉尼(Felix Pirani)寫信稱，“這可以追溯到人們認爲‘有重量的物質’是唯一真實存在的實體的時候。”

But it was too late. Quantum mechanics soon invested empty space with energy. In 1998 astronomers discovered that dark energy, acting just like the cosmological constant, seems to be blowing space-time apart, just as in de Sitter’s universe.

但爲時已晚。量子力學很快就表明，真空中存在很多能量。1998年，天文學家發現暗能量就像宇宙常數一樣，似乎將空間與時間分離，與德西特描述的宇宙相似。

In fact, most cosmologists agree today that not quite all motion is relative and that space-time does have an existence independent of matter, though it is anything but static and absolute. The best example are gravitational waves, ripples of compression and stretching speeding through empty space at the speed of light.

實際上，大多數宇宙學家如今同意這個觀點，即並不是所有運動都是相對的，時空的確獨立於物質存在，儘管它不是靜態和絕對的。最好的例子就是引力波——以光速超速穿過真空的一波波引力壓縮和伸展。

Einstein was back and forth on this. In 1916, he told Schwarzschild they did not exist, then published a paper saying they did. In 1936, he and his assistant did the same flip-flop again.

愛因斯坦在整個問題上搖擺不定。他在1916年告訴史瓦西，引力波並不存在，後來又發表論文稱它存在。他和助手在1936年再次改變觀點。

Nobody said this was easy, even for Einstein.

沒人認爲這很簡單，即使是對愛因斯坦來說。

He set out to do one thing, namely make all motion relative, Michel Janssen, a science historian at the University of Minnesota, told a Princeton gathering this month. He failed, but in the process succeeded in doing something very interesting, unifying the effects of acceleration and gravity.

明尼蘇達大學(University of Minnesota)科學史學家米歇爾·詹森(Michel Janssen)本月在普林斯頓大學參加聚會時表示，愛因斯坦開始做一件事情，就是使所有運動成爲相對的。他失敗了，但他在這個過程中成功地做了一些有趣的事情，將加速度與引力的效應統一起來。

The story goes to show, he said, that Bob Dylan was right when he sang “there’s no success like failure,” but wrong that “failure is no success at all.”

他表示，這個故事說明，鮑勃·迪倫(BobDylan)那句“沒有像失敗這樣的成功”是對的，但“失敗根本不是成功”是錯誤的。

Einstein’s greatest success came in 1919, when Arthur Eddington did the experiment that Freundlich had set out to do, and ascertained that lights in the heavens were all askew during an eclipse, bent by the sun’s dark gravity, just as Einstein had predicted.

愛因斯坦在1919年取得了巨大成功，當時亞瑟·愛丁頓(Arthur Eddington)做了弗羅因德利希之前開始做的實驗，他發現，正如愛因斯坦預測的那樣，出現日食時，天空中的光線在太陽的暗引力下發生彎曲，出現偏斜。

Asked what he would have done if general relativity had failed, Einstein said, “Then I would have been sorry for the dear Lord. The theory is correct.”

被問及如果廣義相對論失敗了，他會做什麼時，愛因斯坦曾說，“那我會替敬愛的主感到難過。這個理論是正確的。”

And still the champ.

而且直到今天還是最棒的。