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为何喷气飞机会留下白色的云带 – 译学馆
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为何喷气飞机会留下白色的云带

Why do Planes Leave White Streaks in the Sky?

[简介]
[INTRO]
几天前 我和吱吱在户外观察云的形状
Squeaks and I were outside the other day looking for shapes in the clouds.
我们发现有些云
We found some clouds that looked
特别像我们的朋友松鼠瑞菲斯
like our friend Ruffles the Squirrel,
另一朵像一只火鸡
and one that looked like a turkey,
甚至还有一朵看上去像城堡!
and even one that looked like the Fort!
我们在天空中看到的还不止这些
And that’s not all we saw in the sky…
还有一架喷气式飞机从我们头顶飞过
We got to watch a jet plane fly overhead!
吱吱观察到一些非常有趣的事
Squeaks noticed something interesting about it:
飞机后面拖出一条白色轨迹
there was a white trail that came out from the back of the airplane.
就好像飞机在飞过天空时画出了一条线
It looked like the plane was leaving a line behind it across the sky!
你可能也看到过
Maybe you’ve seen this too —
或者你没看到飞机
or maybe you didn’t even see the plane,
只看到了它留下的轨迹
and only saw the trail it left behind.
飞机飞过后你还可以看见轨迹留在那里很久
Sometimes you can see them for a long time after the jet is gone.
这些轨迹不是云 虽说它们真的很像
These trails aren’t really clouds, eventhough they look like it.
但组成轨迹和云的大部分物质是相同的
But jet trails and clouds are made mostly of the same stuff.
你知道云由什么组成吗?
Do you know what clouds are made of?
[吱吱回答]对的
[ Squeaks squeaks] Right,
吱吱!
Squeaks!
云大部分都是由水组成
Clouds are mostly made out of water,
这些白色的轨迹也是从飞机里喷出
and so are the trails that come from airplanes.
但是这些轨迹里的水从哪来?
But where does the water in the trails comefrom? Well,
你可能了解
you might know
喷气式飞机能够飞得又高又快
that jets can fly really high and super fast
是因为有给力的发动机
because of their powerful engines.
就像大部分汽车发动机需要汽油
And just like most car engines need gas,
喷气式的发动机也需要燃料才能运行
jet engines need fuel to make them run.
发动机里的燃料燃烧的同时 排放多余物质
When engines burn fuel, they let out waste
这个叫废气
which we call exhaust.
废气里有各种各样的物质
Jet exhaust is made of lots of things
比如 少量的
all mixed together like little pieces of
灰尘 热量 和水
dirt ,heat and a type of water
但我们却看不见它们
that we can’ t see because
因为它们被高速喷出 这就是水蒸气
it’s so spread out in the air called water vapor.
你知道吗 你也可以制造废气
You know, you make a kind of exhaust too
当你呼气的时候!
everytime you breathe out!
和喷气式飞机的废气不同
It’s not the same as jet exhaust,
但它们又含有相同的物质
but it has does have some of the same things
像热量和水蒸气
in it, like heat and vapor.
如果你把手靠近你的嘴巴
If you put your hand close to your mouth…
然后 轻轻的呼气
…and breathe out on it gently…
感觉怎么样?
how does it feel?
暖暖的 是不是?
Warm right?
呼气时就你能感受到热量
You can feel /heat/ when you breathe out.
那蒸气呢?
But what about vapor?
它一种十分狡猾的物质 因为非常难看见
That’s a little trickier because it’shard to see.
但是如果你对着镜子或窗户
But if you breathe out the same way, gently,
轻轻哈气
on a mirror or window,
你就可以看见一层薄雾
you’ll see that it gets foggy.
然后你就知道在你的呼吸里有水蒸气啦
And that’s how you know there’s watervapor in your breath.
当你哈气时 水蒸气
When the water vapor in your warm breath
碰到冷的窗户或镜面时
touches the cooler window or mirror,
就会凝结成极小的小水珠
it changes into teeny tiny droplets of water.
小水珠聚集在一起
Together,all those little tiny droplets
就成了在窗面或镜面上的雾
make the fog you see on the window or mirror.
就像你通常不能看见
Now you can’t usually see
你呼气时呼出的水蒸气一样
the vapor that’s in jet exhaust, either
你通常也看不见喷气式飞机排出的水蒸气
just like you usually can’t see your breath when you breathe out.
但天冷的时候 你就可以看见啦
But you can see your breath sometimes, whenit’s cold!
[吱吱回答]对的 吱吱!
[Squeaks squeaks] Right Squeaks!
在冷天呼吸时
When you breathe out on a cold day,
呼出气体中的水蒸气会凝成小水珠
the vapor in your breath changes into droplets of water,
在你呼气的地方
which is how you can see where you
就可以看见它们
breathed out in the air.
飞机上的水蒸气也是同一个道理
The same kind of thing happens to the vapor coming from the plane. See,
你看 越高的天空
the higher you get up in the sky,
就会变得越冷
the colder it gets.
喷气式飞机飞得真的非常非常高
And jet planes fly really, really high up,
那里特别冷
where it’s super duper cold. So,
冷到废气一出来
the cold air cools down the vapor
里面的水蒸气就冷却成了水滴
in the jet exhaust, turning it into drops,
有的甚至凝成了冰花
or even tiny pieces of ice.
大量的小水滴和冰花就组成了
Tons of these little drops
我们在蓝天上看到的白色轨迹!
of water and ice make the trail that we see in the sky!
你可能还观察到有的飞机轨迹宽 有的窄
You might notice that some plane trails are wide and some are thin.
一些持续时间长
Some last a long time
一些却转瞬即逝
and some disappear pretty quickly.
这些大部分取决于
All of these things depend mostly
喷气式飞机废气里的水蒸气量
on how much vapor there is in the jet’s exhaust, and
和飞机飞得有多高
how high the jet is flying.
[吱吱提问]
[Squeaks squeaks]
问得好 吱吱!
Good question, Squeaks!
是真的
It’s true
飞机后面不是总会有轨迹的
that you won’t always see a trail behind a plane.
如果你看到一架没有轨迹的飞机
If you see a plane without a trail,
那可能是环境还没有冷到足以使水蒸气
it might not be cold enough for the vapor to turn into
转变为水珠或冰晶
water droplets or ice.
有时 也取决于飞机用的发动机
And sometimes it just depends on the kind of engine that the plane has.
但现在如果你看到没有轨迹的飞机
But if you do see one…
现在的你就知道是怎么回事啦
now you know why!
吱吱 来!我们去找更多形状的云!
Come on, Squeaks, let’s go look for morecloud shapes.
现在 我们可以认出任何一架飞机啦
We can see if we can spot any more planes, too!
感谢参与!
Thanks for joining us!
如果你想继续学下去
If you want to keep learning
同我和吱吱一起玩
and having fun with Squeaks and me,
订阅我们
hit the subscribe button,
别忘了在Yutube上的儿童APP上点赞哟
and don’t forget to check us out on the YouTube Kids app.
这里是福特 下次再见啦
We’ll see you next time, here at the Fort!
[片尾]
[ OUTRO ]

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奇妙的水蒸气!

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视频来源

https://www.youtube.com/watch?v=UfGUk3bVr5s

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