时差N小时 潜水艇

Some of the best moments in World War II movies occur when, during a battle at sea, a periscope¹ pokes³ up from the water, surveying the ocean terrain⁴.

二战题材的电影中一些可赞的片段是，海上作战的时候，一个潜望镜从水中穿出，用以测量海洋地形。

Cut to a submarine gliding⁵ through the depths. Torpedoes⁶ away, and the enemy battleship is doomed⁷. How do these amazing vessels⁸ rise and sink so quickly to specific depths?

镜头切换到潜水艇潜到水下。然后发射鱼雷，敌军战队注定会失败。这些神奇的军舰是如何实现快速上升下沉到特定的深度？

Although submarines are sophisticated machines, their ability to rise and sink is based on the elementary principle of buoyant force.

尽管潜艇是很复杂的机器，但它们上升下沉所依据的却是浮力的基本原理。

Say you fill your bathtub with water and put a rubber gym ball on the surface of the water.

将浴缸填满水然后在水面上放一个橡胶健身球。

It floats because the air-filled ball is less dense⁹ than the surrounding water.

它会在水面上漂着因为充气球的密度小于水的密度。

But poke² a hole in the ball and as water displaces the air, the overall density¹⁰ increases until the ball is heavy enough to sink to the bottom.

但在球上戳一个洞，用水代替健身球中的空气，其整体密度会变大，一直到该球重的足以落到水的底部。

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 air.

当然将蓄水池充入空气，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。

1 periscope   

n. 潜望镜

参考例句：

• The captain aligned the periscope on the bearing.船长使潜望镜对准方位。
• Now,peering through the periscope he remarked in businesslike tones.现在，他一面从潜望镜里观察，一面用精干踏实的口吻说话。

2 poke   

n.刺，戳，袋；vt.拨开，刺，戳；vi.戳，刺，捅，搜索，伸出，行动散慢

参考例句：

• We never thought she would poke her nose into this.想不到她会插上一手。
• Don't poke fun at me.别拿我凑趣儿。

3 pokes   

v.伸出( poke的第三人称单数 )；戳出；拨弄；与（某人）性交

参考例句：

• He pokes his nose into everything. 他这人好管闲事。 来自《现代汉英综合大词典》
• Only the tip of an iceberg pokes up above water. 只有冰山的尖端突出于水面。 来自辞典例句

4 terrain   

n.地面，地形，地图

参考例句：

• He had made a detailed study of the terrain.他对地形作了缜密的研究。
• He knows the terrain of this locality like the back of his hand.他对这一带的地形了如指掌。

5 gliding   

v. 滑翔 adj. 滑动的

参考例句：

• Swans went gliding past. 天鹅滑行而过。
• The weather forecast has put a question mark against the chance of doing any gliding tomorrow. 天气预报对明天是否能举行滑翔表示怀疑。

6 torpedoes   

鱼雷( torpedo的名词复数 )； 油井爆破筒； 刺客； 掼炮

参考例句：

• We top off, take on provisions and torpedoes, and go. 我们维修完，装上给养和鱼雷就出发。
• The torpedoes hit amidship, and there followed a series of crashing explosions. 鱼雷击中了船腹，引起了一阵隆隆的爆炸声。

7 doomed   

命定的

参考例句：

• The court doomed the accused to a long term of imprisonment. 法庭判处被告长期监禁。
• A country ruled by an iron hand is doomed to suffer. 被铁腕人物统治的国家定会遭受不幸的。

8 vessels   

n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人

参考例句：

• The river is navigable by vessels of up to 90 tons. 90 吨以下的船只可以从这条河通过。 来自《简明英汉词典》
• All modern vessels of any size are fitted with radar installations. 所有现代化船只都有雷达装置。 来自《现代汉英综合大词典》

9 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

10 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。