超级思想录- 原子来自哪里？来自许多亿年前的宇宙烟火

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Don, you have asked a question that's related to what I think is my absolute favorite fact in the universe, and that is that we are made of dead stars. And that's literally true.

Don，你问的这个问题和我自认为最喜欢的宇宙事实具有一定的相关性，那就是，我们是由死恒星组成的。这是千真万确的。

The atoms in our bodies were actually created inside the cause of stars that then it exploded and died, or unraveled into space. And so your question about the periodic table is very interesting.

我们体内的原子实际上是在恒星内部产生的，然后恒星爆炸、死亡，或者解体进入太空。所以你提出的关于元素周期表的问题非常有趣。

Well, what's the periodic table like at the beginning of the universe, the moment of Big Bang? Well one thing I can say, it was a lot simpler.

那宇宙初开，也就是宇宙大爆炸的那一刻，元素周期表是什么样的呢？我可以说，它要简单得多。

Eh, The Big Bang, when it went off, produced basically three elements. Almost everything was hydrogen.

宇宙大爆炸发生的时候，总的来说就产生了三种元素。主要是氢。

There was a little bit of helium, and a tiny tiny little smattering of lithium as well. So those three elements were around just a couple of minutes after the formation of the universe, but nothing else.

有少量的氦，还有极少量的锂。所以，这三种元素是在宇宙形成后几分钟就产生了，但除此之外，别无他物。

And, and that's actually not a theory. That's actually something we can observe.

而且，这并不是一个理论。而是我们可以真真切切观察到的。

One of the wonderful things about being an astronomer is, as you look out into space farther and farther away, the light has taken longer to get to you. And the farthest we can see is actually back to a time only about 400,000 years after the Big Bang.

成为天文学家的其中一个美妙之处就在于，当你观望的宇宙空间越来越遥远，光来到你身边的旅途就越来越漫长。目之所及，最遥远的实际上就要回到宇宙大爆炸后的40万年左右。

And really, at that time, there was nothing but very hot hydrogen gas, and a little bit of helium and lithium as well. So everything larger than that, every atom more complex, had to be formed inside a star.

说真的，那个时候，宇宙除了滚烫的氢气，还有一点点的氦和锂，其它什么都没有。所以，所有比这些更大、更复杂的原子，都必须要在恒星内部形成。

Over time, our stars, like the sun, are pretty good over the life circle of producing things like carbon and oxygen. They don't really get much more far off the periodic table than that.

随着时间的推移，恒星，比如说太阳，在生命演化过程中很容易产生碳氧之类的物质。它们在元素周期表中确实没有处于太靠后的位置。

If you want to go any farther than the element iron, you actually need a very violent explosion, a supernova explosion. The cores of very massive stars - by that I mean stars that are 10,20 maybe as much as 50 times the mass of the sun,

如果你想得到铁之后的元素，那就需要非常剧烈的爆炸，超新星爆炸。大质量恒星的核心——大质量的意思是说，这些恒星的质量是太阳质量的10倍、20倍亦或50倍。

Their cores are much hotter, because the gravity crushes things down, and temperature goes up many many millions of degrees hotter than inside the sun. So these stars can actually form bigger and bigger atoms.

而它们的核心温度更高，因为引力的坍缩作用，它们的核心温度要高于太阳内部温度几百万度。所以，事实上它们是能够形成越来越大的原子。

The hotter the temperature, the denser the core, the more you can ram things together and actually form bigger and bigger atoms over time. But there's a very special thing that happens when you get to the atom iron.

温度越高，核密度越大，就有越多的物质发生撞击，随着时间的推移，就会形成越来越大的原子。但是，当铁原子形成时，就会些有特殊的事情发生。

And it's something you've actually heard about but you may never have thought of. And that when people think about getting energy out of a nuclear reaction, you've heard about fusion reactions.

这些事你已经听说，但可能从未想过。而当人类想从核反应中获取能量时，你们听说过核聚变反应。

So like a fusion bomb, actually takes hydrogen, fuses it together to make helium, and that creates energy. And that's a nuclear bomb.

像氢弹一样，将氢聚变生成氦，并释放大量能量。这就是核弹。

The sun also runs on that particular reaction, fusing hydrogen together. But then you also heard that there's something called fission.

太阳也发生着氢聚变这种特殊的反应。但你们可能也听说过，还有一些所谓的核裂变。

And this is how, say, a uranium bomb would work. A uranium nucleus has many, many particles inside it.

这就涉及到铀弹的工作原理。铀核内有很多很多的粒子。

You actually get energy out of breaking it up, and forming two smaller nuclei that are actually a bit denser and they hold together better. And so you get energy out of breaking them apart.

要获取能量，就要裂变铀核形成两个更小的核，这两个核的密度更大一点，也更容易结合。那么就可以通过分裂它们来获取能量。

And the element iron is exactly halfway between those two processes. So you've been getting energy by fusing things together until you get to iron.

而铁元素刚好处于这两个过程的中间环节。所以在聚变反应到达铁之前，你都可以通过聚变来获取能量。

And iron is the first nucleus where you don't get any energy out of fusing it. From anything bigger now, you get energy out of ripping apart fission.

而铁是第一个不能从聚变中获取能量的原子核。目前，从任何更大的原子那里，你都可以通过裂变获取能量。

So iron is what sets off a supernova explosion. When a star tries to fuse iron together, it absorbs energy.

因此，铁就是引发超新星爆炸的物质。当恒星要聚合铁，就要吸收能量。

And that's not great for the star. The core collapses. And that huge collapse creates this giant wave of heat and the formation of many, many new elements after that.

而恒星能量供给不足，其核心就会坍塌。而且这种巨大的坍塌会产生巨大的热浪，之后会形成许许多多的新元素。

So anything heavier than iron has to be created in a supernova explosion. Now there are some elements heavier still that even supernova energies don't really get up to quite high enough to make.

因此，所有比铁重的元素都是在超新星爆炸中产生的。目前，还有一些更重的元素，即使是超新星的能量都无法达到那么高，使其形成。

And this is something we only found out recently in the last couple of years. Elements like gold.

这是最近几年我们才发现的。比如说，金元素。

Gold is actually a really interesting one. Platinum are interesting enough. Bismuth, and all the big things like uraniumand, all of the really large atoms, they have to be formed by something that seems almost preposterous, but we have observed this happening two neutron stars colliding.

金是一种很有趣的元素。铂也很有趣。铋和所有铀之类的大元素，所有的大原子，它们必须是由某种看似荒谬的东西形成，而我们观测到这发生于两颗中子星相撞。

So neutron stars are the cores of dead stars. They're super-compressed.

所以中子星是死恒星的核心。它们超压缩。

The density of a neutron star is about a Mount Everest worth of mass in every square centimeter. So think about crushing Mount Everest into a little cube like that.

至于中子星的密度，它每平方厘米的质量就相当于一座珠穆朗玛峰。来想象一下，把珠穆朗玛峰压成这么小的一个立方体。

The entire star, which is only about 10 miles across, is actually that density. And that means you have a tremendous amount of nuclear components - neutrons, protons really close together.

而整个恒星的直径又只有10英里左右，事实上，中子星的密度就是这样。这也就意味着有大量的核成分——中子、质子非常靠近。

And two neutron stars collide, and when that happens, you make all of these very heavy elements up like gold, and platinum, and uranium, and all the big stuff. And again, this is not something that we just know theoretically.

当两个中子星相撞之时，所有这些超重元素就被组建起来了，比如金、铂、铀以及所有大元素。再次强调，这些并不仅仅只是我们所了解的理论。

We actually have observed this happening. Recently, we observed two neutron stars colliding.

而是我们确实见证过这种情况。最近，我们观测到两颗中子星相撞。

And in that single explosion, 10,000 times the mass of the Earth in gold came out of that explosion. It was tremendous. So we definitely know where those atoms come from now, we observed that happening.

而且在那一次爆炸中，释放出了10000倍地球质量的金元素。太惊人了。所以，现在我们清楚地知道原子从何而来，我们也见证过。

So to recap, at the beginning of the universe, you had three elements, mostly hydrogen, a little bit of helium, tiny little bit of lithium. Now we have the entire periodic table.

那么，来回顾一下，宇宙初开，就存在着三种元素，主要是氢，还有少量的氦和极少量的锂。现在我们有了整个元素周期表。

And a lot of those are formed in stars like the sun. Anything past iron has to be formed much more violently in a supernova explosion or in the case of very large atoms, two colliding neutron stars.

其中很多都是在像太阳之类的恒星中形成的。铁之后的元素都必须在更激烈的超新星爆炸中形成，或是在两个原子都非常大的情况下，由两颗中子星相撞形成。

And over billions of years, we've filled out the periodic table that way.

数十亿年来，我们就是这样填写元素周期表的。