We know about our universe’s past: the Big Bang theory predicts that all matter, time, and space began in an incredibly tiny, compact state about 14 billion years ago. And we know about the present: scientists’ observations of the movement of galaxies tell us that the universe is expanding at an accelerated rate. But what about the future? Do we know how our universe is going to end?
我們知道宇宙的過去: 根據大爆炸理論的預測, 所有的物質、時間、空間 都開始於一個極小、 極緊實的狀態, 時間是大約一百四十億年前。 我們也知道現在: 根據科學家對於銀河運動的觀察, 宇宙正在擴張,且速度越來越快。 但,未來呢? 我們是否知道宇宙會如何結束?
Cosmologists have three possible answers for this question, called the Big Freeze, the Big Rip and the Big Crunch.
宇宙學家針對這個問題 有三個可能的答案: 大凍結、 大撕裂,和大擠壓。
To understand these three scenarios, imagine two objects representing galaxies. A short, tight rubber band is holding them together— that’s the attractive force of gravity. Meanwhile, two hooks are pulling them apart— that’s the repulsive force expanding the universe. Copy this system over and over again, and you have something approximating the real universe. The outcome of the battle between these two opposing forces determines how the end of the universe will play out.
若要了解這三種情境, 先想像一下,用兩個物體 來代表兩個銀河。 有一條很短、很緊的橡膠帶 將它們連結在一起—— 那就是重力造成的引力。 同時,有兩個勾子 在將它們拉開—— 那就是讓宇宙擴張的排斥力。 將這個系統不斷複製, 得到的結果就會 很接近真實的宇宙。 這兩種相反力量之間的對抗 會決定宇宙最後的結局是什麼。
The Big Freeze scenario is what happens if the force pulling the objects apart is just strong enough to stretch the rubber band until it loses its elasticity. The expansion wouldn’t be able to accelerate anymore, but the universe would keep getting bigger. Clusters of galaxies would separate. The objects within the galaxies– suns, planets, and solar systems would move away from each other, until galaxies dissolved into lonely objects floating separately in the vast space. The light they emit would be redshifted to long wavelengths with very low, faint energies, and the gas emanating from them would be too thin to create new stars. The universe would become darker and colder, approaching a frozen state also known as the Big Chill, or the Heat Death of the Universe.
大凍結的情境是預期 將物體拉開的力量 強大到足以將橡膠帶延伸開來, 到失去彈性的程度。 此時擴張無法再加速了, 但宇宙會持續變得更大。 一群一群的銀河會分離開來。 在銀河中的物體—— 太陽、行星,和太陽系, 會彼此遠離, 直到銀河瓦解成單獨的物體, 在浩瀚的太空中各自漂浮。 它們發散的光會發生紅移, 成為長的波長, 能量則非常低、非常微弱, 它們散發出來的氣體 會太稀薄而無法創造出新星。 宇宙會變得更黑暗、更寒冷, 接近一種冰凍的狀態, 也就是所謂的大冰凍, 或是宇宙的「熱寂」。 但,如果排斥力很強,
But what if the repulsive force is so strong that it stretches the rubber band past its elastic limit, and actually tears it? If the expansion of the universe continues to accelerate, it will eventually overcome not only the gravitational force – tearing apart galaxies and solar systems– but also the electromagnetic, weak, and strong nuclear forces which hold atoms and nuclei together. As a result, the matter that makes up stars breaks into tiny pieces. Even atoms and subatomic particles will be destroyed. That’s the Big Rip.
強到讓橡膠帶的延伸 超出它的彈性極限, 真的將它撕裂了,會如何? 如果宇宙的擴張持續加速, 最後,它不僅會戰勝重力引力—— 將銀河和太陽系給扯開—— 同時也會戰勝電磁的、 弱的、強的核力, 也就是讓原子和核子 結合在一起的力量。 結果就是,形成天體的 物質會破成碎片。 就連原子和亞原子粒子 都會被摧毀。 那就是大撕裂。 那麼,第三個情境,
What about the third scenario, where the rubber band wins out? That corresponds to a possible future in which the force of gravity brings the universe’s expansion to a halt— and then reverses it. Galaxies would start rushing towards each other, and as they clumped together their gravitational pull would get even stronger. Stars too would hurtle together and collide. Temperatures would rise as space would get tighter and tighter. The size of the universe would plummet until everything compressed into such a small space that even atoms and subatomic particles would have to crunch together. The result would be an incredibly dense, hot, compact universe — a lot like the state that preceded the Big Bang. This is the Big Crunch.
也就是橡膠帶獲勝的情境呢? 在這個情境所對應的可能未來, 重力引力會讓宇宙的 擴張停下來—— 接著將它逆轉。 銀河會開始衝向彼此, 它們會結成一團, 它們的重力引力就會變得更強。 天體也會衝向彼此並相撞。 隨著空間變得越來越 緊密,溫度會上升。 宇宙的大小會極劇縮小, 直到一切都壓縮成 這麼一個小空間, 就連原子和亞原子粒子 也會擠在一起。 結果就會造成一個非常高密度、 高溫、緊密的宇宙—— 很像是大爆炸之前的狀態。 這就是大擠壓。 這個物質小圓點有沒有可能會爆炸, 發生另一次的大爆炸?
Could this tiny point of matter explode in another Big Bang? Could the universe expand and contract over and over again, repeating its entire history? The theory describing such a universe is known as the Big Bounce. In fact, there’s no way to tell how many bounces could’ve already happened— or how many might happen in the future. Each bounce would wipe away any record of the universe’s previous history.
宇宙有沒有可能會擴張又收縮, 一而再,再而三, 不斷重覆它的整段歷史? 描述這種宇宙的理論叫做大反彈。 事實上,無法知道目前 已經發生過多少次反彈—— 或是未來還會發生多少次。 每一次反彈都會將 宇宙的先前歷史紀錄給抹除。 這些情境中, 哪一個比較可能是真的?
Which one of those scenarios will be the real one? The answer depends on the exact shape of the universe, the amount of dark energy it holds, and changes in its expansion rate. As of now, our observations suggest that we’re heading for a Big Freeze. But the good news is that we’ve probably got about 10 to the 100th power years before the chill sets in — so don’t start stocking up on mittens just yet.
答案會依宇宙的形狀而定, 要看它所保有的暗能量有多少, 以及它擴張速度的改變。 目前為止,根據我們的觀察, 我們正在朝大冰凍前進。 但,好消息是,我們可能 還要等「十的一百次方」年, 才會開始感到寒冷—— 所以,還不用開始儲備長手套啦。