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?
我们了解宇宙的过往: 大爆炸原理预测了 所有的物质、时间和空间 都始于140亿年前的极小极紧密的状态。 我们了解宇宙的当下, 科学家们对于银河运动的观察 告诉我们宇宙正在加速扩张。 但是未来呢? 我们知道我们的宇宙将会如何终结吗?
Cosmologists have three possible answers for this question, called the Big Freeze, the Big Rip and the Big Crunch.
宇宙学家们关于这个问题有三种可能的回答: 大冻结、 大撕裂和大挤压。
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.
为了理解这三种设想, 请想象一下两个物体代表银河。 一根橡皮筋将它们定在一起—— 这就是引力。 同时,两个钩子将它们分开—— 这就是扩展宇宙的斥力。 如果这个系统复制下去, 你就会得到一个近似宇宙的模型。 这一对相反作用力的结果 决定了宇宙的尽头在哪里。
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.
大冻结学说指的是 这个拉力刚好大到让皮筋失去弹力。 这样,宇宙的扩张就不会再加速, 但宇宙还是会继续变大。 银河系会散开。 银河系中的物体—— 恒星、行星和星系 会远离彼此, 直到银河系彻底分解, 漂浮在广阔的宇宙中。 它们发出的光会被红移成长波, 所含的能量很少,很模糊。 它们放出的气体太薄, 无法让人看见星星。 宇宙会变得黑暗寒冷, 趋近于冰冻的状态, 这也叫做宇宙大寒, 或者热寂。
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.
但如果这对斥力非常强大呢? 大到使皮筋超出弹力极限, 然后拉断。 如果宇宙的扩张继续加速, 这个拉力最终不仅会克服重力影响—— 导致银河系和太阳系分离—— 还会克服强核力和弱核力, 这两种力是保持原子和核子的。 其结果是, 形成星球的物质会变成细小的碎片。 甚至于原子和亚原子颗粒都会被摧毁。 这就是大撕裂。
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.
那第三种情况呢? 如果是皮筋比较有力量会怎么样? 这就对应了一个未来 可能会出现的情况—— 重力让宇宙的扩张停止, 然后往回收。 星系会开始互相靠拢。 在它们凝结在一起的同时, 它们的重力会变得更加强大。 星球也会互相猛烈碰撞。 温度会随着宇宙变小而升高。 宇宙会骤然变小, 直到所有东西都压缩成一个小空间。 甚至原子和亚原子都会被压碎。 宇宙最终会变得稠密,异常得热和紧密, 这与大爆炸之前的状态很相似。 这就是大挤压。
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.
这个点上的物质会不会又一次大爆炸? 宇宙会不会重复地扩张和收缩, 重演整段历史呢? 描述上述现象的原理叫作大反弹。 事实上,我们不知道宇宙 已经经过了几次反弹, 或者将来会发生几次。 每一次反弹都会清除宇宙之前的所有历史。
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.
这些情况中哪一个是真实的? 答案取决于宇宙的准确形状, 它含有的暗物质的数量, 和它扩张率的变化。 到现在为止,我们的观察显示 我们正往大冻结的方向前进。 但好消息是还要过十的一百次方年, 寒冷才会降临。 所以,先别急着囤手套。