时差N小时 你对潜水艇了解多少?(下)（在线收听）

A submarine works in much the same way, with one major exception: a sub can alter its buoyancy by manipulating overall density.

海底工作大致是相同的，但有一点例外：通过操控整体密度，潜水艇能够改变其浮力。

Submarines come equipped with tanks that can be filled with various levels of water and air.

潜艇都配备蓄水池，贮备着不同的水量和空气。

When a sub floats on the surface, its tanks are filled mostly with air, which makes the sub less dense than the surrounding water.

但潜水艇浮在水面的时候，它的蓄水池里大部分都是空气，这样可以使得潜水艇的密度小于水的密度。

When the crew wants to make the sub sink they open valves to allow just enough water to flood the tanks and make the sub sink to a specific depth.

若工作人员想要使潜艇下沉，他们可以打开阀门，让足够多的水流入蓄水池，然后使其下沉到一个特定的深度。

Of course the sub must be able to rise again after filling its tanks with water.

当然将蓄水池注满水，潜艇会再次上升。

To that end submarines carry tanks of compressed air that can be used to displace water from the tanks and increase buoyancy.

最后潜艇会携带带有压缩空气的蓄水池，用来替换蓄水池中的水，增加浮力。