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Have you ever looked outside, only to see that the air was thick and gray, and you could barely see?
你有没有看外面只能看到灰沉沉的空气，几乎看不见东西的经历？
Squeaks and I looked out of the Fort window this morning, and that's exactly what we found.
今天早上，我和吱吱从沃斯堡的窗户往外看时，看到的就是这些。
It was such a strange and different thing to see!
它看起来如此奇怪又不同！
Normally, we can see a few trees outside, and even a road,
正常情况下，我们能看到外面的几棵树，甚至还有一条路，
but today, we could barely see the closest tree.
但今天我们几乎看不到最近的一棵树。
It was a little bit spooky, and the news put out a warning to be careful when driving on the roads.
这有点儿吓人，新闻警告人们在路上开车时要小心。
All of this was because of the gray mist covering everything, and it's called fog.
这一切都是因为笼罩万物的灰色雾气，它叫做雾。
Fog can make it hard to see outside, and walking through it can make you feel a bit damp or cold.
雾让人很难看到外面，走在雾中会让你感觉有点儿潮湿或寒冷。
When I walk through fog, I always imagine that I'm walking through a big raincloud.
当我在雾中行走时，总是想象自己正在穿过一块巨大的雨云。
That's right, Squeaks, it seems that way because fog does look a lot like clouds, except really close to the ground!
吱吱，你说得对，似乎是这样，因为雾看起来很像云，除了它离地面很近之外！
In fact, clouds and fog are made of the same thing: tiny droplets of water.
事实上，雾和云都是由同种物质构成的：微小的水滴。
From far away, clouds might sometimes look like thick fluffy pillows, or even cotton candy.
从远处看，云有时看起来像厚厚的蓬松枕头，甚至是棉花糖。
But really, walking through a cloud wouldn't feel fluffy or comfortable at all!
但是，真的，在云中行走一点儿也感觉不到蓬松或者舒服！
You'd get very wet. There's always some water in the air, except it's not a liquid.
你会被打湿。空气中总有一些水分，只是它不是液体。
It's usually a gas, the same type of thing as the air itself, which is why we can't see it.
它通常是气体，和空气是一样的，这就是我们看不到它的原因。
We call that type of water, water vapor.
我们称这种水为水蒸气。
But when there's too much water in the air, it condenses, or pulls together really close,
但空气中的水太多时，它就会凝结，或者相互拉近距离，
to become a bunch of super tiny droplets of liquid.
变成一堆极小的液滴。
When this happens high up in the sky, all those little droplets form what we call a cloud.
当这种情况发生在高空时，所有这些小水滴形成了我们所说的云。
This can happen much closer to the ground, too, which is when we call it fog.
这种情况也可能发生在离地面更近的地方，我们称之为雾。
It just doesn't happen as often.
它不经常发生。
For fog to form, there needs to be a lot of water that's just reached the ground.
要想形成雾，需要大量刚刚到达地面的水分。
That's right. Just after a rainstorm is the perfect time for fog to happen.
没错。一场暴风雨过后是雾形成的最佳时间。
There's all that water on the ground, plus there's a lot of water vapor that's still in the air.
因为地面上有那么多水，加上空气中还有很多的水蒸气。
Next, the water vapor has to get pretty cold, very quickly.
接下来，水蒸汽必须变得快速变冷。
If the temperature drops, the water vapor in the air starts to collect into those little liquid droplets.
如果温度下降，空气中的水蒸气就会开始凝结成小液滴。
You can see this happen in real life if you have some cold water in a glass!
在现实生活中，如果你在玻璃杯里放一些冷水，就会看到这种情况。
Pretty soon the outside of the glass will be wet,
玻璃外壁很快就会变湿，
but that water doesn't come from inside the glass …it comes from the air.
但水不是来自玻璃杯里面，而是来自空气。
The cold glass makes water vapor in the air collect into liquid drops.
寒冷的玻璃杯让空气中的水蒸气凝结成小液滴。
When this happens in the air outside,
当这发生在外面的空气时，
the little droplets are so small that they can float through the air, and we can see them all spread out.
这些小水滴非常小，以至于它们漂浮在空气中，我们可以看到它们都散开了。
And that's fog! It really is just like a cloud on the ground.
这就是雾！它真的很像地上的一朵云。
There are lots of different types of fog,
雾有很多不同的类型，
and each happens in different places, with different amounts of cold air.
每种类型根据不同冷空气的量发生在不同的地区。
The most common kind is called radiation fog.
最常见的类型叫做辐射雾。
This is the kind of fog that sets in overnight, when air with a lot of water vapor in it cools down.
这种雾会在夜间形成，此时含有大量水蒸气的空气冷却下来。
In the morning, when the sunlight warms the air again, the radiation fog disappears.
早上，阳光再次温暖空气时，辐射雾消失了。
Good question, Squeaks. Where does the water go when the fog disappears?
吱吱，问得好。当雾消失时，水分去了哪里？
When the water in the fog starts to heat up,
当雾中的水分开始加热时，
it begins to evaporate, or to turn back into water vapor and spread out.
它开始蒸发或者回到水蒸气状态扩散开了。
When the water vapor is spread out again in the air, we can't see it.
当水蒸气再次在空气里散开时，我们是看不到它的。
It's too small for our eyes. But just you wait, Squeaks.
它太小了，我们的眼睛看不到。但吱吱，等一下。
I hear it's supposed to get pretty cold tonight, and I bet we'll get some more fog!
我听说今晚天气会很冷，我打赌雾会更多！
I have a great idea. Let's bring our weather journals outside so we can observe what we find.
我有个好主意。我们把天气日记带出去，这样我们就能观察我们的发现了。
Is there fog where you live?
你住的地方有雾吗？
Have you ever walked through fog and not been able to see well?
你是否曾在雾中行走却看不清楚？
Do you have any other questions about the weather?
你对天气还有其他问题吗？
Have a grown-up help you leave a comment below,
找个大人帮忙在下方留言
or send us an email tokids@scishow.com.
或发邮件至kids@scishow.com.
And don't forget to hit the subscribe button!
不要忘了点击订阅键哦！
We'll see you next time, here at the Fort!
我们下期见，沃斯堡等你哦！
