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So, when was the last time you guys actually knew how something worked?
你们最后一次了解某个东西的工作原理是在什么时候？
And no, I do not mean Googling it. I mean really learned how something worked?
不，我不是说用谷歌搜索。我是说真正学会了某个东西的工作原理？
One thing I've always been wondering about is how submarines work.
我一直想知道的一件事是潜艇的工作原理。
How do these ginormous machines go under water and above the water in the ocean? And how do you even start to build one?
在海洋中，这些巨大的机器是如何在水下和水面上运行的？又是该如何开始建造一个潜艇呢？
Well, fortunately, National Geographic Kids has sent me my own expert to help me figure out these questions. This one got mailed straight to my loft. Whoa!
幸运的是，《National Geographic Kids》给我派了一名专家来帮我解决这些问题。直接寄到我的公寓了。哇!
Thanks Kamri! Good to see daylight again. I'm David Gruber, Marine Biologist.
谢谢卡姆里！很高兴又见到了阳光。我是大卫·格鲁伯，海洋生物学家。
So David, how do submarines go underwater?
所以大卫，潜艇是怎么潜入水下的？
Typical submarines are built with two hulls, think of it like two layers of skin with a space in between them.
传统的潜艇有两个船壳，可以把它想象成两层皮肤，中间有一个空间。
The space between the hulls contains what we call the "ballast tanks."
船壳之间的空间就包含我们所说的“压载水舱”。
Got it.
明白了。
When the crew of a submarine wants to dive, they fill the ballast tanks with water, increasing the density of the sub.
当潜艇的船员想要下潜时，他们要将压载水舱注满水，增加潜艇的密度。
So, denser objects sink?
所以密度大的物体会下沉？
Exactly. And when the crew wants to rise...
完全正确。当船员想要上浮时...
They force air into the tank to displace the water, making it lighter.
他们要压缩空气进入水舱以排出水，使其更轻。
You got it. Air is much lighter than water, so a submarine filled with air naturally becomes more buoyant. Buoyancy describes an object's floatability.
你说对了。空气比水轻得多，所以充满空气的潜艇自然会变得浮力更大。浮力指的就是物体的可浮性。
So, if I take a giant deep breath, I become more buoyant?
所以，如果我深吸一口气，我就会变得更轻松？
Correct.
没错。
Okay, so once a submarine is actually underwater, how does anyone know where they're going?
好吧，那么当潜艇在水下的时候，要怎么知道它们会去哪里呢？
Submarines rely on a system called SONAR to navigate. SONAR stands for...
潜艇依靠一种叫做声纳的系统来导航。声纳指的是...
Acronym pose!
是缩略词哦!
Sound, Navigation, and Ranging.
声音、导航和测距。
Okay, I've heard of that before. They send sound waves through the ocean, right?
好吧，我以前听说过。声波可以穿过海洋，对吧？
Exactly, the key is receiving the reflected echo of the sound.
没错，关键是接收到声音的反射回声。
Sound waves bounce off objects, so a submarine crew gauges what's around them by determining how long it takes to echo back to them.
声波在物体上反弹，所以潜艇艇员通过测量声波反射回物体所需的时间来测量周围的物体。
So, the shorter the time, the closer the object.
所以，时间越短，距离物体越近。
That's it!
就是这样！
Okay, so a submarine is like a giant half-whale half-bat with two hulls.
好的，潜艇就像一只巨大的鲸鱼和蝙蝠的混合体，有两个外壳。
Air and water fill the ballast tanks between the hulls to bring it up and down.
空气和水充满了船体之间的压载水舱，使其上下浮动。
It sends sound waves throughout the ocean to know where other objects are.
它向整个海洋发送声波，以了解其他物体的位置。
I can't believe I went through, like, many years of graduate school to learn that.
真不敢相信我在研究生院读了这么多年才明白这个原理。
Well, thanks for coming by!
感谢你的到来！
My pleasure.
我的荣幸。
