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Thanks to Brilliant for supporting this episode of SciShow. Go to Brilliant.org/SciShow to learn more.
感谢Brilliant对本期视频的支持。登录Brilliant.org/SciShow了解更多。
During long, cold winters in medieval Europe, there was something weird going on with church organs.
在中世纪欧洲漫长寒冷的冬天，教堂风琴会发生一些奇怪的事情。
Across the continent, some of these instruments were getting what people at the time called "tin leprosy" or "tin pest."
整个大陆中，一些乐器会患上人们当时所说的“锡病”或“锡害虫病”。
The organs grew gray, sickly-looking circles that spread over time and made the pipes hard and brittle.
随着时间的推移，这些风琴长出灰色的、病状状的圆圈，使得这些管子变得又硬又脆。
Eventually, many of them fell apart.
最终很多乐器都断裂。
But tin pest isn't actually a sickness — or, as people once thought — the work of the devil.
但是锡害虫其实并不是一种疾病——或者像人们曾经认为的那样——是魔鬼的杰作。
It's actually just some pretty simple chemistry.
这其实只是一些很简单的化学反应。
It all comes down to the fact that a lot of organ pipes, even now, are made with tin, since it can produce bright, resonant tones.
这一切都归结于一个事实，许多管风琴，即使是在现在，都是用锡做的，因为它可以发出明亮共振的音调。
And it's pretty and shiny. At least, sometimes.
而且它又漂亮又闪亮。至少，有时如此。
The thing is, tin exists in two different forms, or phases, depending on the temperature.
问题是，根据温度的不同，锡有两种不同的形式或状态。
It's a lot like how water can be liquid at room temperature and solid when it gets cold.
就像是水在室温中是液体，在变冷时是固体。
Except, instead of going from liquid to solid, tin goes from one type of solid to another.
不同的是，锡不是从液体变成固体，而是从一种固体变成另一种固体。
Above 13.2 degrees Celsius, tin is a white, shiny, strong metal. That's the form of tin that people use to make organ pipes.
在13.2摄氏度以上，锡是一种白色、有光泽的坚固金属。人们就是使用这种形态的锡来制作管风琴。
But below that temperature, tin becomes dull, gray, and easy to break.
但低于这个温度，锡就会变暗、变灰且很容易断裂。
That's the form those pipes were transforming into during those long, cold winters.
在漫长寒冷的冬季里，那些风琴会变成这种形式。
The reason these two forms are so different, even though they're both tin,
虽然都是锡，但两种形态如此不同的原因是
is because of the way the atoms arrange themselves in each phase.
由于原子在每一相中的排列方式。
In white tin, atoms are arranged in what's called a tetragonal, or rectangular, structure.
在白色锡中，原子排列成所谓的四角形或长方形结构。
But in gray tin, atoms are farther apart, arranged in more of a cube shape that's less sturdy.
但在灰色的锡中，原子间的距离更远，排列成一个不那么坚固的立方体。
These two forms are called allotropes. And you might be more familiar with this phenomenon than you think.
这两种形式被称为同素异形体。你可能比你想象的更熟悉这个现象。
A similar thing happens with carbon, which can either take the form of graphite, like in your pencil,
类似的事情也发生在碳上，它可以是石墨的形式，就像你的铅笔，
or a crystal-clear diamond, all depending on how its atoms are arranged.
也可以是水晶般透明的钻石，这都取决于它的原子是如何排列的。
When it comes to tin, though, the process of turning from white to gray doesn't happen overnight.
不过，说到锡，从白变灰的过程不是一蹴而就的。
In fact, it can take months or years of cold temperatures for it to noticeably transform.
事实上，它可能需要数月或数年的低温才能显著转变。
This is because it doesn't happen as soon as temperatures drop to 13 degrees Celsius.
因为它不会在低温一降到13度时就发生。
Just below the transition temperature, there's not enough difference between
就在转变温度之下，白锡的能量和灰锡的能量之间
the energy of white tin and the energy of gray tin to motivate a transformation — unless something acts as a catalyst.
没有足够的差异来激发转变——除非有什么东西作为催化剂。
But that energy difference increases as temperature drops.
但是这种能量差随着温度的下降而增加。
Around -30 degrees Celsius, that energy difference becomes significant, and transformation can happen much more easily.
零下30摄氏度时，这种能量差变得显著，并且转化就会容易得多。
But! If it gets much colder than that, another factor comes into play that makes a transformation less likely.
但是！如果温度比这低得多，另一个因素就会起作用，使转化的可能性降低。
See, white tin has to expand by about a quarter to transition to the gray form, and it takes a lot of energy to get the process started.
白色的锡要膨胀四分之一左右才能变成灰色，这个过程需要很多能量。
Except, as the temperature drops, the molecules in tin vibrate slower,
只是当温度下降时，锡中的分子振动变慢，
so they don't have the energy to overcome the barrier that it takes to start the phase change.
所以它们没有足够的能量来克服引起相变的势垒。
That means that right around -30 degrees, there's sort of a sweet spot where the transition is most likely to happen.
这意味着在零下30度左右，有一个最佳温度点，最可能发生转变。
But even at an ideal temperature, tin takes a long time to transform.
但即使在理想的温度下，锡也需要很长时间才能转变。
It's not like water, which quickly turns into ice as soon as it's cold enough.
它不像水，水一遇冷就会很快变成冰。
That's because both phases of tin are solid, so its atoms are locked up in tight lattices,
这是因为锡的两个阶段都是固体，所以其原子被锁在紧密的晶格中，
and it takes a long time for them to rearrange themselves. That's why old tin organs weren't just collapsing constantly.
需要很长时间来重新排列。这就是为什么旧的风琴不会马上断裂。
It took a long cold winter for those tin pipes to start transforming.
经过一个漫长寒冷的冬天，那些锡管才开始变形。
But once gray tin appears, it can spread really quickly, like a rash.
但是一旦灰色的锡出现，它就会迅速扩散，就像皮疹一样。
The expansion of the tin makes little cracks in the metal, and that creates more exposed edges,
锡的膨胀会在金属上产生小的裂纹，从而产生更多暴露的边缘，
where atoms are free to move around and rearrange themselves.
原子可以在这里自由移动和重新排列。
And before long, the atoms of the white tin reorganize into the structure of gray tin.
不久，白色锡的原子重组成灰色锡的结构。
Luckily, now that we know what causes it, the tin pest is easy to prevent.
幸运的是，现在我们知道了它的原因，锡害虫很容易预防。
Just adding small amounts of other metals, like lead, can keep tin atoms from moving around and changing form.
只要添加少量的其他金属，比如铅，就可以阻止锡原子移动和改变形态。
And since a lot of organ pipes are made of metal blends, many have been able to withstand the test of time.
由于许多管风琴是由金属混合物制成的，因此许多管风琴能够经受住时间的考验。
It turns out a lot of mysteries aren't so mysterious once you've figured out a little bit of the science behind them.
一旦你了解了其中的科学原理，你就会发现很多奥秘其实并没有那么神秘。
And you can build your science skills with the courses on Brilliant.org.
你可以通过Brilliant.org上的课程来提高你的科学技能。
Brilliant's course on everyday physics is all about the unexpected ways you interact with physics in your day-to-day life.
Brilliant日常物理课程都是关于你在日常生活中与物理互动的各种意想不到的方式。
By the end, you'll learn how traffic jams, bridges, and even axe-throwing are founded in physics.
最后，你将学到交通堵塞、桥梁，甚至是扔斧头是如何在物理学中形成的。
And there are dozens of courses to choose from in science, engineering, and math —
在科学、工程和数学方面有几十门课程可供选择，
all designed by educators at leading universities, like MIT, Caltech, and Duke.
这些课程都是由MIT、加州理工学院和杜克大学等顶尖大学的教育工作者设计的。
The courses are hands-on, with interactive quizzes and guided problems with explanations,
这些课程是实践性的，有互动式的小测验和讲解性的问题，
and they'll help you hone your scientific thinking.
它们将帮助你磨练你的科学思维。
If you're one of the first 200 people to sign up at Brilliant.org/SciShow,
如果你是前200名注册的人，
you'll save 20% on an annual premium subscription. And as always, thanks for watching SciShow.
可获得年度会员八折优惠。一如既往，感谢收看。
