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Fusion of hydrogen or helium normally requires at least the conditions found in the the cores of stars.
通常情况下，发生氢或氦的聚变至少需要恒星核心所具备的条件。
High temperatures and densities allow hydrogen and helium nuclei to get close enough to fuse together into bigger nuclei and release a TON of energy,
高温和密度使得氢和氦的原子核靠得足够近，聚变形成更大的原子核，释放出大量能量，
powering even more fusion while releasing enough extra to power the star,
促使更多的核聚变，同时释放出足够多的能量给恒星提供能量，
or if you set this situation up on earth, you might have a hydrogen bomb.
或者如果你在地球上制造了这种情况，你可能会造成一个氢弹。
But it’s actually possible for fusion to occur at temperatures much, much lower than the core of the sun - like, room temperature, for example.
但实际上核聚变是有可能在比太阳核心温度低得多的温度下发生的，比如室温。
Now, I’m not talking about the infamous “cold fusion” of the 1980s that hasn’t been shown to work or involve any, well, fusion - no,
现在，我不是在谈论1980年代臭名昭著的“冷聚变”，它没有被证明是有效的，也没有涉及任何聚变。
I’m talking about the room-temperature fusion of the 1950s that actually does work: fusion with the help of muons!
我说的是20世纪50年代的室温聚变，它确实行得通：在介子的帮助下的聚变！
Nuclear fusion, of course, happens when atomic nuclei, like hydrogen nuclei,
当然，核聚变发生在原子核，比如氢原子核，
come close enough together that their strong nuclear attraction can overcome their electric repulsion,
它们靠得足够近，强大的核引力可以克服它们的电斥力，
and they fuse together into a single, bigger nucleus - like helium.
它们聚变形成一个单一的、更大的原子核，就像氦一样。
This typically happens in a plasma, that is, a super hot soup of electrons and atomic nuclei,
这通常发生在等离子体中，也就是电子和原子核的超级热汤中，
where if it’s hot enough every once in a while two nuclei bump hard enough into each other to fuse.
如果温度足够高，每隔一段时间，两个原子核就会猛烈碰撞并融合。
But fusion can in principle happen in regular, non-plasma molecules, too - like the hydrogen molecule,
但原则上，聚变也可以在常规的非等离子体分子中发生，比如氢分子，
in which two hydrogen nuclei are kept relatively near to each other by sharing electrons.
两个氢原子核通过共用电子而保持在相对较近的位置。
The nuclei don’t stay separated a rigid distance apart, though - they vibrate and wiggle and every so often,
原子核之间不会保持刚性距离，但它们会振动和摆动，
they can, in principle, get close enough to fuse together.
原则上，它们可以靠得很近，可以融合在一起。
But with hydrogen - or nitrogen, or oxygen, or pretty much all other molecules - this happens exceedingly rarely
但是对于氢，氮，氧，或者几乎所有其他的分子，这种情况很少发生
(which is why our atmosphere, which has a fair amount of molecules, isn’t a giant fusion bomb).
（这就是为什么我们的大气中有相当多的分子，不是一个巨大的聚变炸弹）。
However, things are different if you replace the electrons with particles called muons,
但是，如果你把电子换成叫做介子的粒子，情况就不一样了，
which are basically exactly the same as electrons except 200 times heavier.
它们基本上和电子一模一样，除了重200倍。
Muons, being essentially heavy electrons, form atoms and molecules in almost the exact same way as electrons,
介子本质上是重电子，以几乎完全相同的方式形成原子和分子，
but since they’re heavier, their orbits are much closer to the nucleus than an electron with the same energy and angular momentum would be .
但由于它们更重，它们的轨道比具有相同能量和角动量的电子更接近原子核。
And this means that atoms and molecules held together with muons instead of electrons are about 200 times smaller,
这意味着原子和分子与介子结合在一起，而不是与电子结合在一起，原子和分子比电子小200倍，
and their nuclei are correspondingly about 200 times closer together.
相应地，它们的原子核之间的距离要近200倍。
And being closer together makes nuclei many many many times more likely to fuse together,
原子核之间的距离越近，原子核融合的可能性就会增加很多很多倍，
so much so that hydrogen molecules made with muons can fuse together at temperatures much lower than the core of the sun - even room temperature!!
以至于由介子构成的氢分子可以在远低于太阳核心温度的情况下聚变——甚至在室温下！！
Which was predicted in 1947 and experimentally achieved in 1956.
它在1947年被预测，1956年被实验实现。
Physicists have even managed to achieve muon-aided nuclear fusion at temperatures close to absolute zero.
物理学家甚至成功地在接近绝对温度的条件下实现了介子辅助的核聚变。
So at this point, you’re probably asking yourself: if room-temperature nuclear fusion exists, why aren’t we using it to power modern civilization?
所以在这一点上，你可能会问自己:如果室温核聚变存在，为什么我们不用它来为现代文明提供动力?
Well, while muon-facilitated fusion is indeed fully legit nuclear fusion at non-crazy temperatures,
虽然介子促成的聚变在非疯狂温度下确实是完全合法的核聚变，
there are some major problems which prevent it from being used as a power source.
有一些主要的问题会阻止它被用作能源。
First, muons don’t live very long .
首先，介子寿命不长。
Unlike electrons which have an in principle infinite lifespan, after about 2 microseconds muons spontaneously decay into an electron and some neutrinos,
不同于理论上具有无限寿命的电子，介子在大约2微秒后自发地衰变为一个电子和一些中微子，
so if you’re going to do anything with muons, you have to do it real quick!
所以如果你要用介子做任何事情，你必须得非常快！
This turns out not to matter much for the purposes of facilitating fusion, but because of their short lifespan,
这对于促进核聚变来说并没有太大影响，但由于它们的寿命很短，
there aren’t a ton of muons around - so if you want a reliable supply of muons,
没有大量的介子可以使用，所以如果你想要一个可靠的介子供应，
you pretty much have to make them with a high energy particle accelerator,
你得用高能粒子加速器来制造它们，
which takes a lot of energy per muon - at best about 5 giga electron volts , or about 50 times the E=mc^2 mass-energy of a muon itself.
每一个介子需要大量的能量——最多大约5千兆电子伏特，或者大约是一个介子本身能量的50倍。
Now, luckily you don’t need a muon for every single pair of hydrogen nuclei you want to fuse,
现在，幸运的是，你不需要每一对想要聚变的氢原子核都有一个介子，
because after a pair of nuclei fuses into helium the muon can go off and help more nuclei fuse …and then help more… and more… and more….
因为在一对原子核聚变形成氦之后介子就会爆炸帮助更多的原子核聚变，然后帮助更多的，更多的，更多的原子核聚变。
EXCEPT, every so often , the muon doesn’t - it’ll get stuck as part of the newly fused helium atom , and can’t facilitate any additional fusing.
不过，介子偶尔不会——它会作为新聚变氦原子的一部分被卡住，无法促进任何额外的聚变。
This means that each muon only helps an average of 150- fusions of nuclei before it gets stuck.
这意味着每一个介子在被卡住之前平均只能帮助150次原子核聚变。
And since each fusion of nuclei releases about 18 mega electron volts of energy,
由于原子核的每次聚变释放大约18兆电子伏的能量，
this means that, after 150 fusions, each muon facilitates an average of 2700 mega electron volts, or 2.7 giga electron volts, of energy generation.
这意味着，在150次聚变之后，每一个介子都能产生平均2700兆电子伏，或2.7千兆电子伏的能量。
Which means that, unfortunately, the numbers don’t add up - Remember it currently takes around 5 GeV of energy to produce a muon,
不幸的是，这意味着这些数字加起来并不合适——记住，目前产生一个介子大约需要五十亿电子伏特的能量，
but each muon only generates about two and a half GeV of energy before getting stuck to a nucleus.
但是每个介子在粘附到原子核之前只能产生大约25亿电子伏特的能量。
That is, muon-facilitated fusion is a net consumer of energy (rather than being a source of energy).
也就是说，介子促进的核聚变是能源的净消耗者（而不是能源的来源）。
This is the best case possible with current technology, and the numbers are still off by a factor of 2
这是在现有技术条件下可能出现的最好情况，
before even reaching any sort of break-even where muon-facilitated fusion could generate as much energy as it consumes.
在达到介子促成的聚变能产生与其消耗的能量相等的盈亏平衡点之前，这些数据仍相差两倍。
And we’d need to be much better than just breaking even, energy-wise, to make a viable commercial power plant.
在能源方面，我们需要做得比盈亏平衡更好，才能建造一个可行的商业发电厂。
Pretty much the only hope for muon-facilitated-fusion is to figure out how to make muons for less energy,
对于介子促进聚变来说，唯一的希望就是弄清楚如何以更少的能量制造介子，
or figure out how to have less of them stick to the helium nuclei,
或者想办法让更少的原子附着在氦原子核上，
or how to unstick them once they’re stuck - which are all hard problems limited by the unchangeable physical properties of muons and nuclei,
或者一旦它们卡住了，如何释放它们——在介子和原子核不可改变的物理特性的限制下，这些都是困难的问。
and so we’ve made quite slow progress in over 70 years of research.
所以在70多年的研究中，我们取得了相当缓慢的进展。
The summary is that muon-induced fusion exists, it’s fascinating science, but it’s not going to be powering the world any time soon.
总之，介子引发的核聚变是存在的，这是一项令人着迷的科学，但它不会在短期内为世界提供动力。
