Can a black hole be destroyed? - Fabio Pacucci

1,771,240 views ・ 2019-05-16

TED-Ed


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翻译人员: Carol Wang 校对人员: Ziyao Wang
00:06
Black holes are among the most destructive objects in the universe.
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黑洞是宇宙最具破坏性的物体之一,
00:11
Anything that gets too close to the central singularity of a black hole,
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任何太靠近黑洞中心奇点的物体,
00:16
be it an asteroid, planet, or star,
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无论是小行星,行星还是恒星,
00:19
risks being torn apart by its extreme gravitational field.
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都有被其巨大引力场摧毁的危险。
00:23
And if the approaching object happens to cross the black hole’s event horizon,
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如果接近黑洞的物体 恰好穿过黑洞的事件视界,
00:28
it’ll disappear and never re-emerge,
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它将会消失,永不再出现,
00:31
adding to the black hole’s mass and expanding its radius in the process.
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此过程中,黑洞质量增加, 而且黑洞半径扩大。
00:36
There is nothing we could throw at a black hole
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没有任何扔向黑洞的东西
00:38
that would do the least bit of damage to it.
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会对它造成一点损害
00:41
Even another black hole won’t destroy it–
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即使另一个黑洞也无法摧毁它——
00:43
the two will simply merge into a larger black hole,
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这两个黑洞只会合成一个更大的黑洞,
00:47
releasing a bit of energy as gravitational waves in the process.
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此过程中释放出一点引力波能量。
00:52
By some accounts,
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理论证明,
00:53
it’s possible that the universe may eventually consist entirely of black holes
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在遥远的将来,
黑洞会组成整个宇宙。
00:57
in a very distant future.
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00:59
And yet, there may be a way to destroy, or “evaporate,” these objects after all.
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然而有一种方法 可能可以摧毁或“蒸发”这些黑洞。
01:05
If the theory is true,
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如果那个理论可靠,
01:07
all we need to do is to wait.
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我们只需要等待。
01:10
In 1974,
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1974年,
01:11
Stephen Hawking theorized a process
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斯蒂芬·霍金提出
01:13
that could lead a black hole to gradually lose mass.
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一个可能导致黑洞 逐渐失去质量的过程:
01:16
Hawking radiation, as it came to be known,
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霍金辐射学说。
01:19
is based on a well-established phenomenon called quantum fluctuations of the vacuum.
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这个理论基于一种 真空量子波动的已知现象。
01:25
According to quantum mechanics,
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根据量子力学,
01:27
a given point in spacetime fluctuates between multiple possible energy states.
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时空中的一个点在多个 可能的能量状态之间波动。
01:32
These fluctuations are driven by the continuous creation and destruction
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这些波动是由虚粒子对的
01:37
of virtual particle pairs,
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不断产生和湮灭所造成的,
01:39
which consist of a particle and its oppositely charged antiparticle.
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虚粒子对由粒子 和带相反电荷的反粒子组成。
01:44
Normally, the two collide and annihilate each other shortly after appearing,
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通常两者出现后不久 就会相互碰撞和湮灭,
01:48
preserving the total energy.
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总能量不变。
01:50
But what happens when they appear just at the edge of a black hole’s event horizon?
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但它们出现在黑洞 事件视界时会发生什么呢?
01:56
If they’re positioned just right,
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如果它们恰好位于视界边缘,
01:58
one of the particles could escape the black hole’s pull
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一个粒子可能会逃脱黑洞引力,
02:01
while its counterpart falls in.
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而另一个坠入黑洞。
02:04
It would then annihilate another oppositely charged particle
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黑洞视界边缘内的粒子
会中和另一个带相反电荷的粒子,
02:08
within the event horizon of the black hole,
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02:10
reducing the black hole’s mass.
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从而减少黑洞的质量。
02:12
Meanwhile, to an outside observer,
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对外部观察者来说,
02:14
it would look like the black hole had emitted the escaped particle.
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就好像黑洞发射了逃逸粒子。
02:19
Thus, unless a black hole continues to absorb additional matter and energy,
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因此,除非黑洞继续 吸收外部物质和能量,
02:24
it’ll evaporate particle by particle, at an excruciatingly slow rate.
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它将以极其缓慢的速度蒸发粒子。
02:30
How slow?
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有多慢呢?
02:31
A branch of physics, called black hole thermodynamics, gives us an answer.
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黑洞热力学给出了答案。
02:36
When everyday objects or celestial bodies release energy to their environment,
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日常物体或天体 向周围环境释放能量,
02:41
we perceive that as heat,
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我们把其感受为热量,
02:43
and can use their energy emission to measure their temperature.
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并且根据释放的能量 来测量它们的温度。
02:47
Black hole thermodynamics
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黑洞热力学认为,
02:48
suggests that we can similarly define the “temperature” of a black hole.
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我们也可以类似地 定义黑洞的“温度”。
02:53
It theorizes that the more massive the black hole,
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该理论认为,黑洞质量越大,
02:56
the lower its temperature.
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其温度越低。
02:58
The universe’s largest black holes
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宇宙最大的黑洞,
03:00
would give off temperatures of the order of 10 to the -17th power Kelvin,
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其温度为10的负17次方开尔文,
03:06
very close to absolute zero.
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非常接近绝对零度。
03:08
Meanwhile, one with the mass of the asteroid Vesta
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而一个与灶神星 同质量的黑洞的温度,
03:12
would have a temperature close to 200 degrees Celsius,
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则接近200摄氏度,
03:16
thus releasing a lot of energy in the form of Hawking Radiation
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它以霍金辐射的形式,
向寒冷的外部环境释放大量能量。
03:20
to the cold outside environment.
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03:23
The smaller the black hole,
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黑洞越小,
03:24
the hotter it seems to be burning–
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其燃烧得更加炽热——
03:26
and the sooner it’ll burn out completely.
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而且很快就会烧光。
03:29
Just how soon?
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到底多快呢?
03:30
Well, don’t hold your breath.
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好吧,别期望太高。
03:32
First of all, most black holes accrete, or absorb matter and energy,
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首先,多数黑洞聚集 或吸收物质和能量的速度
03:37
more quickly than they emit Hawking radiation.
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远远大于发出霍金辐射的速度,
03:40
But even if a black hole with the mass of our Sun stopped accreting,
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即使一个与太阳质量 相同的黑洞停止了聚集物质能量,
03:45
it would take 10 to the 67th power years–
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它也需要10的67次方年——
03:48
many many magnitudes longer than the current age of the Universe—
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也就是比现在宇宙的年龄更长的时间——
03:53
to fully evaporate.
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才能完全消失。
03:54
When a black hole reaches about 230 metric tons,
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当黑洞达到230公吨左右时,
03:58
it’ll have only one more second to live.
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它只会再生存一秒。
04:02
In that final second,
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在最后一秒,
04:03
its event horizon becomes increasingly tiny,
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它的事件视界变得越来越小,
04:06
until finally releasing all of its energy back into the universe.
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直到最终将所有能量释放回宇宙。
04:11
And while Hawking radiation has never been directly observed,
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虽然人们从未直接观察到霍金辐射,
04:14
some scientists believe that certain gamma ray flashes detected in the sky
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但一些科学家认为,天空中 探测到的某些伽马射线闪光
04:19
are actually traces of the last moments
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就是是远古时期形成的、
04:22
of small, primordial black holes formed at the dawn of time.
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小的原始黑洞最后一刻的痕迹。
最终,在未知的遥远未来,
04:28
Eventually, in an almost inconceivably distant future,
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04:32
the universe may be left as a cold and dark place.
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宇宙会成为冰冷、黑暗之所。
04:36
But if Stephen Hawking was right,
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但如果霍金辐射的理论是正确的,
04:37
before that happens,
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在那发生之前,
04:39
the normally terrifying and otherwise impervious black holes
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可怕而神秘莫测的黑洞,
04:43
will end their existence in a final blaze of glory.
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将在最后的荣耀之火中湮灭。
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