Black holes are among the most destructive objects in the universe. Anything that gets too close to the central singularity of a black hole, be it an asteroid, planet, or star, risks being torn apart by its extreme gravitational field. And if the approaching object happens to cross the black hole’s event horizon, it’ll disappear and never re-emerge, adding to the black hole’s mass and expanding its radius in the process. There is nothing we could throw at a black hole that would do the least bit of damage to it. Even another black hole won’t destroy it– the two will simply merge into a larger black hole, releasing a bit of energy as gravitational waves in the process. By some accounts, it’s possible that the universe may eventually consist entirely of black holes in a very distant future. And yet, there may be a way to destroy, or “evaporate,” these objects after all. If the theory is true, all we need to do is to wait.
黑洞是宇宙最具破坏性的物体之一, 任何太靠近黑洞中心奇点的物体, 无论是小行星,行星还是恒星, 都有被其巨大引力场摧毁的危险。 如果接近黑洞的物体 恰好穿过黑洞的事件视界, 它将会消失,永不再出现, 此过程中,黑洞质量增加, 而且黑洞半径扩大。 没有任何扔向黑洞的东西 会对它造成一点损害 即使另一个黑洞也无法摧毁它—— 这两个黑洞只会合成一个更大的黑洞, 此过程中释放出一点引力波能量。 理论证明, 在遥远的将来, 黑洞会组成整个宇宙。 然而有一种方法 可能可以摧毁或“蒸发”这些黑洞。 如果那个理论可靠, 我们只需要等待。
In 1974, Stephen Hawking theorized a process that could lead a black hole to gradually lose mass. Hawking radiation, as it came to be known, is based on a well-established phenomenon called quantum fluctuations of the vacuum. According to quantum mechanics, a given point in spacetime fluctuates between multiple possible energy states. These fluctuations are driven by the continuous creation and destruction of virtual particle pairs, which consist of a particle and its oppositely charged antiparticle.
1974年, 斯蒂芬·霍金提出 一个可能导致黑洞 逐渐失去质量的过程: 霍金辐射学说。 这个理论基于一种 真空量子波动的已知现象。 根据量子力学, 时空中的一个点在多个 可能的能量状态之间波动。 这些波动是由虚粒子对的 不断产生和湮灭所造成的, 虚粒子对由粒子 和带相反电荷的反粒子组成。
Normally, the two collide and annihilate each other shortly after appearing, preserving the total energy. But what happens when they appear just at the edge of a black hole’s event horizon? If they’re positioned just right, one of the particles could escape the black hole’s pull while its counterpart falls in. It would then annihilate another oppositely charged particle within the event horizon of the black hole, reducing the black hole’s mass. Meanwhile, to an outside observer, it would look like the black hole had emitted the escaped particle.
通常两者出现后不久 就会相互碰撞和湮灭, 总能量不变。 但它们出现在黑洞 事件视界时会发生什么呢? 如果它们恰好位于视界边缘, 一个粒子可能会逃脱黑洞引力, 而另一个坠入黑洞。 黑洞视界边缘内的粒子 会中和另一个带相反电荷的粒子, 从而减少黑洞的质量。 对外部观察者来说, 就好像黑洞发射了逃逸粒子。
Thus, unless a black hole continues to absorb additional matter and energy, it’ll evaporate particle by particle, at an excruciatingly slow rate. How slow? A branch of physics, called black hole thermodynamics, gives us an answer.
因此,除非黑洞继续 吸收外部物质和能量, 它将以极其缓慢的速度蒸发粒子。 有多慢呢? 黑洞热力学给出了答案。
When everyday objects or celestial bodies release energy to their environment, we perceive that as heat, and can use their energy emission to measure their temperature. Black hole thermodynamics suggests that we can similarly define the “temperature” of a black hole. It theorizes that the more massive the black hole, the lower its temperature. The universe’s largest black holes would give off temperatures of the order of 10 to the -17th power Kelvin, very close to absolute zero. Meanwhile, one with the mass of the asteroid Vesta would have a temperature close to 200 degrees Celsius, thus releasing a lot of energy in the form of Hawking Radiation to the cold outside environment. The smaller the black hole, the hotter it seems to be burning– and the sooner it’ll burn out completely.
日常物体或天体 向周围环境释放能量, 我们把其感受为热量, 并且根据释放的能量 来测量它们的温度。 黑洞热力学认为, 我们也可以类似地 定义黑洞的“温度”。 该理论认为,黑洞质量越大, 其温度越低。 宇宙最大的黑洞, 其温度为10的负17次方开尔文, 非常接近绝对零度。 而一个与灶神星 同质量的黑洞的温度, 则接近200摄氏度, 它以霍金辐射的形式, 向寒冷的外部环境释放大量能量。 黑洞越小, 其燃烧得更加炽热—— 而且很快就会烧光。
Just how soon? Well, don’t hold your breath. First of all, most black holes accrete, or absorb matter and energy, more quickly than they emit Hawking radiation. But even if a black hole with the mass of our Sun stopped accreting, it would take 10 to the 67th power years– many many magnitudes longer than the current age of the Universe— to fully evaporate. When a black hole reaches about 230 metric tons, it’ll have only one more second to live. In that final second, its event horizon becomes increasingly tiny, until finally releasing all of its energy back into the universe. And while Hawking radiation has never been directly observed, some scientists believe that certain gamma ray flashes detected in the sky are actually traces of the last moments of small, primordial black holes formed at the dawn of time.
到底多快呢? 好吧,别期望太高。 首先,多数黑洞聚集 或吸收物质和能量的速度 远远大于发出霍金辐射的速度, 即使一个与太阳质量 相同的黑洞停止了聚集物质能量, 它也需要10的67次方年—— 也就是比现在宇宙的年龄更长的时间—— 才能完全消失。 当黑洞达到230公吨左右时, 它只会再生存一秒。 在最后一秒, 它的事件视界变得越来越小, 直到最终将所有能量释放回宇宙。 虽然人们从未直接观察到霍金辐射, 但一些科学家认为,天空中 探测到的某些伽马射线闪光 就是是远古时期形成的、 小的原始黑洞最后一刻的痕迹。
Eventually, in an almost inconceivably distant future, the universe may be left as a cold and dark place. But if Stephen Hawking was right, before that happens, the normally terrifying and otherwise impervious black holes will end their existence in a final blaze of glory.
最终,在未知的遥远未来, 宇宙会成为冰冷、黑暗之所。 但如果霍金辐射的理论是正确的, 在那发生之前, 可怕而神秘莫测的黑洞, 将在最后的荣耀之火中湮灭。