電影《星際穿越》中的科學
Our Universe in Brief宇宙簡史
Our universe is vast.Achinglybeautiful.Remarkablysimple in some ways,intricatelycomplex in others. From our universe』s great richness, we』ll need only a few basic facts that I』ll nowlay bare.宇宙極其廣闊、美麗，在某種情況下它是簡潔的，其他的情況下，卻是無比的複雜。考慮到宇宙的豐富多樣，我們需要闡述一些基本的物理事實。
The Big Bang大爆炸
Our universe was born in a gigantic explosion 13.7 billion years ago. The explosion was given theirreverentname 「the big bang」 by my friend Fred Hoyle, a cosmologist who at that time (the 1940s) thought it anoutrageous,fictionalidea.宇宙誕生於137億年前一場巨大的爆炸之中，我的朋友Fred Hoyle——一位宇宙學家，在20世紀40年代將這場爆炸調侃為「宇宙大爆炸」，但是他認為這是一個不文雅、虛構的觀點。
Fred was proved wrong. We』ve since seen radiation from the explosion, even in just the last week (as I write this)tentativeevidence for radiationemittedinthefirst trillionth of a trillionth of a trillionthof a second after the explosion began!2後來證明，Fred是錯的。至今我們都能觀察到這場爆炸殘留的輻射，就在寫這篇文章的上一周，實驗觀測到大爆炸開始後的第一萬億億億分之一秒後散發的的輻射證據。
We don』t know what triggered the big bang, nor what, if anything, existed before it. Butsomehowthe universeemergedas a vast sea of ultrahot gas, expanding fast in all directions like the fireball ignited by a nuclear bomb blast or by the explosion of a gas pipeline. Except that the big bang was not destructive (so far as we know). Instead, itcreatedeverything in our universe, or rather the seeds for everything.目前大爆炸的起源尚不得知，同樣，大爆炸之前的狀態也不清楚。宇宙中出現了極端熾熱的氣體海洋，快速向各個方向擴散，類似於核爆炸之後或輸氣管道爆炸之後的情形。不同於上述兩種情形，大爆炸的結果並不是毀滅一切（至少現在認為），而是創造了宇宙，形成了萬物的萌芽。
I would love to write a long chapter about the big bang, butwith great force of willI restrain myself. We don』t need it for the rest of this book.關於大爆炸，筆者本想擴展長文，出於自我約束決定放棄，對本書的其餘部分我們無需了解此類知識。
Galaxies星系
As our universe expanded, its hot gas cooled. In some regions the gas』s density was a bit higher than in others,randomly. When the gas got cold enough,gravity pulled each high-density region inward on itself,giving birth to a galaxy (a huge cluster of stars and their planets anddiffusegas between the stars); see Figure 2.1. The earliest galaxy was born when the universe was a few hundred million years old.隨著宇宙的不斷膨脹，炙熱也在下降。無規律地，在某些區域氣體密度比其他區域略高，當氣體溫度降到足夠低時，萬有引力將各個高密度區域向內拉，彼此集聚，星系便誕生了（巨量的恆星、行星以及星際中彌散的氣體），見圖2.1.最早的星系形成於宇宙產生數億年之後。
There are roughly a trillion galaxies in the visible universe. The largest galaxies contain a few trillion stars and are about a million light-years across;3the smallest, about 10 million stars and a thousand light-years across. At the center of most every large galaxy there is a huge black hole
(Chapter 5), one that weighs a million times the sun』s weight or more.4在可觀察宇宙之內有大約一萬億個星系，其中最大的星系包含數萬億個恆星，直徑約百萬光年記；最小的星系，包含100萬個恆星，直徑約1000光年。在每一個大型星系的中心都有一個巨大的黑洞（見第五章），其質量相當於太陽的一百萬倍甚至更多。
Fig. 2.1.
A rich cluster of galaxies named Abell 1689 and many other more distant
galaxies, as photographed by the Hubble Space Telescope.
圖2.1Abell 1689星系群以及其他遙遠星系，由哈勃太空望遠鏡攝得
The Earthresides ina galaxy called the Milky Way. Most of the Milky Way』s starsare in the bright band of light that stretches across Earth』s sky on a clear, dark night. And almost all thepinpricksof lightthat we see in the sky at night, not just those in the bright band, also lie in the Milky Way.
地球位於一個名叫銀河系的星系內，銀河系內大部分恆星呈現出一條光帶狀，橫亘在地球晴朗漆黑的夜空。除帶狀部分之外，在夜空中所有肉眼可見的光點，幾乎都位於銀河系內。
The nearest large galaxy to our own is called Andromeda (Figure 2.2). It is 2.5 million light-years from Earth. It contains about a trillion stars and is about 100,000 light-years across. The Milky Way is a sort of twin to Andromeda, about the same in size, shape, and number of stars. If Figure 2.2 were the Milky Way, then the Earth would be where I placed the yellowdiamond.距離銀河系最近的大型星系是仙女星系（圖2.2），距離地球大約2500光年，包含約一萬億顆恆星，直徑約10萬光年。銀河系是仙女星系的孿生星系：大小、形狀以及恆星數目都相同。如果圖2.2表示銀河系，那麼地球就是黃色方框所指。
Andromeda contains a gigantic black hole, 100 million times heavier than the Sun and as big across as the Earth』s orbit (the same weight and size asInterstellar』s Gargantua; Chapter 6). It resides in the middle of thecentral bright spherein Figure 2.2.仙女星系包含一個巨大的黑洞，質量超過太陽的一億倍，大小與地球軌道一樣（《星際穿越》中Gargantua黑洞的質量和尺寸與之一致），它位於圖2.2中的中央明亮球體的中間部位。
Fig. 2.2.
The Andromeda galaxy.
圖2.2仙女星系
Solar System太陽系
Stars are large, hot balls of gas, usually kept hot by burning nuclear fuel in their cores. The Sun is a fairly typical star. It is 1.4 million kilometers across, about a hundred times larger than the Earth.Its surface has flares and hot spots and cooler spots,and is fascinating to explore through atelescope(Figure 2.3).恆星是巨大熾熱的氣體星球，其內核通過燃燒核燃料維持高溫，太陽是一顆相當典型的恆星，直徑約1400萬公里，是地球的100倍大。它的表面有耀斑、亮斑和暗斑，通過望遠鏡觀察表面是非常有趣的（圖2.3）。
Eight planets, including the Earth, travel around the Sun in elliptical orbits, along with manydwarf planets(of which Pluto is the most famous) and manycomets, and smaller, rocky bodies called asteroids and meteoroids (Figure 2.4). Earth is the third planet from the Sun.Saturn, with
its gorgeous rings, is the sixth planet out and plays a role inInterstellar(Chapter 15).包含太陽在內的八大行星，在以太陽為中心的橢圓軌道上旋轉，其他的一些矮行星（很有名的冥王星）、彗星、由石塊組成的小行星和流星體同樣圍繞太陽旋轉（圖2.4）.地球是距離太陽的第三顆行星，土星和其壯麗的光環是距離太陽的第六顆行星，出現在了《星際穿越》中（第15章）。
Fig 2.3.
The Sun as photographed by NASA』s Solar Dynamics Observatory.
圖2.3NASA的太陽動力學天文台拍攝的太陽
Fig. 2.4.
The orbits of the Sun』s planets and Pluto, and a region containing many asteroids.
圖2.4太陽系內行星、冥王星、以及小行星的運行軌道
The solar system is a thousand times bigger than the Sun itself; light needs eleven hours to travel across it.太陽系是太陽本身的1000倍大，光需要11個小時才能穿越。
The distance to the nearest star other than the Sun, Proxima Centauri, is 4.24 light-years, 2500 times farther than the distance across the solar system! In Chapter 13, I discussthe awful implications for interstellar travel.距離太陽最近的恆星是比鄰星半人馬座，距離4.24光年，是光穿越太陽系所需時間的2500多倍！第13章將討論星際旅行的嚴格含義。
Stellar Death: White Dwarfs, Neutron Stars, and Black Holes
恆星死亡：白矮星，中子星和黑洞
The Sun and Earth are about 4.5 billion years old, about a third the age of the universe. After another 6.5 billion years or so, the Sun willexhaustthe nuclear fuel in its core, the fuel that keeps it hot.The Sun then will shift to burning fuel in a shell around its core, and its surface will expand to engulf and fry the Earth. With the shell』s fuel spent and the Earth fried, the Sun will shrink to become a white dwarf star, about the size of the Earth but with density a million times higher. The white dwarf will gradually cool, over tens of billions of years, to become a dense, darkcinder.太陽和地球的年齡是45億歲——宇宙年齡的三分之一，在距今65億年以後（或更長時間），太陽將會燃盡核心的核燃料，然後燃燒其核心周圍的燃料，表面會不斷膨脹、炙烤并吞噬掉地球；隨著核心周圍燃料的不斷消耗，地球被蒸干，太陽會縮小成白矮星——尺寸與地球相當，密度卻是地球的100萬倍之多。白矮星會逐漸冷卻，數百億年之後變為緻密黑暗的灰燼。
Stars much heavier than the Sun burn their fuel much more quickly, and then collapse to form a neutron star or a black hole.比太陽質量更大的恆星燃燒的更快，之後坍縮形成中子星或黑洞。
Neutron stars have masses about one to three times that of the Sun,circumferencesof 75 to 100 kilometers (about the size of Chicago), and densities the same asthe nucleus of an atom: a hundred trillion times more dense than rock and the Earth. Indeed, neutron stars are made of almost pure nuclear matter: atomic nuclei packed side by side.中子星的質量相當於1到3倍的太陽，圓周周長約為75到100公里（相當於芝加哥的周長），密度約等於原子核的密度：地球上岩石的一百萬億倍。嚴格地講，中子星的構成是純粹的核物質：原子核並排堆積形成。
Black holes (Chapter 5), by contrast, are made fully andsolelyfrom warped space and warped time (I』ll explain this weird claim in Chapter 4). They contain no matter whatsoever, butthey have surfaces, called 「event horizons,」 or just 「horizons,」 through which nothing can escape, not even light. That』s why they are black. A black hole』scircumferenceis proportional to its mass: the heavier it is, the bigger it is.黑洞（第5章介紹）完全、純粹、單一的由彎曲的時間和空間構成（第4章闡述這些怪異的概念）。它不包含任何物質，卻有表面，稱作「視界」，任何物質都無法逃出黑洞，甚至光都不可以。黑洞的周長與它的質量成比例：質量越大，周長越長。
A black hole with about the same mass as a typical neutron star or white dwarf (say 1.2 times as heavy as the Sun) has a circumference of about 22 kilometers: a fourth that of the neutron star and a thousandth that of the white dwarf. See Figure 2.5.質量與普通中子星或白矮星相同的黑洞（太陽質量的1.2倍）的周長約為22公里——中子星的四分之一，白矮星的千分之一。見圖2.5。
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