撰文 | Frank Wilczek (麻省理工學院教授、2004年諾貝爾獎得主）
翻譯 | 胡風、梁丁當
獲得今年諾貝爾物理學獎的研究解釋了宇宙是如何從初期的均勻狀態中，演化出我們今天所觀察到的複雜性的。
Prize-winning research shows how the universe evolved from its uniform beginnings to the complexity we observe today.
2019年的諾貝爾物理學獎頒給了詹姆斯·皮布爾斯 （James Peebles）、米歇爾·馬約爾（Michel Mayor）和迪迪埃·奎洛茲（Didier Queloz）。其中，皮布爾斯因對宇宙物理理論的貢獻獨享一半獎金，而馬約爾和奎洛茲因為發現了繞著類日恆星運動的太陽系外行星而共享另一半獎金。
Last week, the Nobel Prize in Physics went to James Peebles for theoretical contributions to physical cosmology, along with Michel Mayor and Didier Queloz for their work on exoplanets-distant planets that orbit stars other than our sun.
這些方向的研究從不同的角度幫助我們認識宇宙以及地球在宇宙中的位置。現代宇宙學表明，宇宙在誕生初期具有驚人的簡單性和均勻性。系外行星的發現則揭示出了當前宇宙的複雜性與多樣性。兩者的對比引發出一個很大的疑問：宇宙的複雜性是如何從均勻性中產生的？
These lines of research both shed light on the universe and our position in it, but they do so from very different perspectives. Modern physical cosmology reveals that the universe started out amazingly simple and homogeneous, while the study of exoplanets reveals that at present it is complex and diverse. That contrast poses a big question: How did the complexity emerge?
在宇宙歷史的初期，所有的物質都處於一種高溫、緻密、 近乎均勻的狀態，並且迅速膨脹。這是標準宇宙大爆炸模型的核心思想。它能夠解釋許多天文觀測結果，包括遙遠星系遠離我們的速度，以及不同化學元素的相對丰度。
Early in the history of the universe, all the matter in it was hot, dense and very nearly uniform. It was also rapidly expanding. Those ideas are the heart of the standard Big Bang model, which lets us account for many observations, including the fact that distant galaxies are moving away from us and the relative abundance of different chemical elements.
尤其值得一提的是，該模型預測宇宙中還殘存著大爆炸的餘暉--即充滿了整個宇宙空間的微波背景輻射。所以不出意外，這個餘暉被觀測到了，為我們展示了早期宇宙的概貌。皮布爾斯先生將這些證據結合起來，構建出一個連貫的宇宙歷史框架，闡明了它們是如何影響星系的大小、形狀和分布的。
Notably, the model predicted the existence of a lingering Big Bang afterglow-the so-called microwave background radiation that fills all space. That afterglow was duly observed, providing a snapshot of the early universe. Mr. Peebles pulled those lines of evidence together into a coherent scenario of the history of the universe and spelled out its consequences for the size, shape and distribution of galaxies.
充盈著早期宇宙的熾熱氣體的分子運動與化學組成完全是隨機的，非常接近物理學家們稱之為「 完全熱平衡」的狀態。一般來說，當系統達到了熱平衡後，就會一直處於這個態：始終保持一種均勻單調的狀態，不會衍生出任何結構乃至生命。
The early hot gas that filled the universe was completely random in its molecular motions and chemical mixing. It was, to a very good approximation, in the condition physicists call 「complete thermal equilibrium.」 Ordinarily, once systems reach complete thermal equilibrium they stay there. They remain uniform and featureless; they do not develop structure or 「come to life.」
幸運的是，我們的宇宙逃脫了這種悲慘的命運。在萬有引力對廣袤時空的作用下，均勻態不再穩定，物質更加傾向於聚集在一起。於是，在引力的作用下，高度均勻的宇宙逐漸四分五裂開來，形成了巨大的類雲狀結構。
Our universe escaped that dismal fate primarily because gravity, acting over vast reaches of space and time, makes uniformity unstable. Gravity wants things to clump. Thus the material in the universe, at first highly uniform, fragmented under the influence of gravity into vast cloudlike structures.
剛開始，這些雲還很稀薄飄渺。隨著時間的推移，其中的物質在引力的持續影響下進一步發生凝聚。宇宙因而逐漸演化成今天的形態--在廣袤、虛無的宇宙空間中零星散落著一個個星系，其中分布著恆星和行星。
At first the clouds were tenuous and wispy, but over time, under the continuing influence of gravity, their material condensed further. The matter in the universe gradually evolved into its present configuration: galaxies hosting stars and planets, all separated by yawning regions of nearly empty space.
構成行星的物質溫度較低，密度較高。它們繼續在一個新的層次上進行分化並衍生出更多的形式--形成複雜的化合物，甚至是形成智慧生命。由於行星相對較小，本身又不發光，我們很難從遙遠的距離探測到它們的存在。馬約爾先生和奎洛茲先生開創了系外行星探測技術的先河。從此以後，系外行星的探索不再只是科幻小說的情節。它迅速興起為一個蓬勃發展的、由數據驅動的科技領域。
Planetary matter, cool and dense, then began to host another level of fragmentation and diversification: the emergence of complex chemistry, and even—in at least one case—intelligent life. Because planets are relatively small and emit no light of their own, it is very hard to detect them from far away. Mr. Mayor and Mr. Queloz pioneered the delicate technologies that have quickly taken exoplanetary astronomy from science fiction into a thriving, data-driven enterprise.
我們現在這個複雜宇宙大概就是這樣形成的。人類已經建立了標準宇宙學來描述這一過程，雖然還有許多關鍵的細節尚待填補，但它的基本內容是很清晰並被廣泛接受的，即從簡單的初始狀態按照簡單的定律演化出豐富的複雜性，需要漫長的時間和大量的物質（也許不需要其他任何條件）。謝天謝地，我們的宇宙在這兩方面都很豐富。
This is a very broad-brush account of how the complex universe that we inhabit today could have emerged. Though many crucial details need filling in, the outlines are straightforward and widely accepted: The emergence of abundant complexity from simple beginnings and simple laws takes a long time and requires lots of matter (but maybe nothing else). Thankfully, our universe is blessed with plentiful supplies of both.
作者簡介
Frank Wilczek：弗蘭克·維爾切克是麻省理工學院物理學教授、量子色動力學的奠基人之一。因在夸克粒子理論（強作用）方面所取得的成就，他在2004年獲得了諾貝爾物理學獎。
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