This is our planet's final frontier.
这里是地球上最后的边缘地带
An inner world where only the most adventurousdare to go.
一个只有最勇敢者才敢涉足的地底世界
Beneath our feet are countless miles of cave shaftsand passages.
我们脚下有着绵延不绝的洞窟和隧道
The Cave of Swallows in Mexico, 400 metres to the bottom, deep enough to engulf the EmpireState Building.
墨西哥境内的燕子洞深达400多米，足以吞没整座帝国大厦
This is the biggest cave shaft in the world,
这是世界上最大的深洞
yet these depths were first explored only two years before men landed on the moon.
然而人类直到登月前两年才第一次进入这个深渊
Today, caves remain the least explored places on Earth.
A silken strand is lowered from the ceiling alongside hundreds of others.
一根坚韧的丝从天顶上垂下，边上还有好几百根。
Beautiful though these threads are, they have a sinister purpose.
虽然这些丝看起来很漂亮，它们却是阴险的陷阱。
This is a cave glow-worm.
这是一种洞穴萤火虫
To trap its prey, it goes fishing with a line of silk.
它利用一根根的丝来诱捕猎物
The silk comes from glands in the glow-worm's mouth and is loaded with droplets of mucus.
丝产生自萤火虫口中的腺体，上面缀着一串粘液滴。
Each glow-worm produces dozens of these threads.
每条萤火虫都会吐很多根这样的丝
0nce its lines are set, the glow-worm hangs from a mucous hammock and waits like a patient angler.
当一排丝架设完毕后，萤火虫便用粘液将自己悬吊起来，然后像一位耐心的钓鱼者似的等待猎物上钩
But the glow-worm doesn't leave everything to chance.
不过，萤火虫并不会听天由命
That ghostly blue light is the result of a chemical reaction
这些诡异的蓝光是一种化学反应的结果
taking place inside a special capsule in its tail.
由尾部的一个特殊腔囊产生
The light literally shines out of its backside. It's a lure for attracting prey.
这些从尾部发散出来的荧光正是用来吸引猎物的诱饵。
1.be loaded with...
Stay extra safe: You'd never put raw meat, which can be loaded with bacteria, directly on the counter.
更安全的做法： 不要把生肉直接放在灶台上，因为生肉表面满载细菌，其它未经过清洗的原料也一样。
2.hang from 从…悬挂
Inside a warehouse, giant slabs of meat hang from the ceiling and butchers stand about, chopping beef.
在一座仓库里，天花板下悬挂着一些大块的肉片，站着的屠夫们在忙着砍、切牛肉。
3.leave everything to chance 听天由命
I say this because many people leave everything to chanceto achieve their dreams and are too timid to transform.
我这样说是因为很多人在实现他们梦想的时候只是听天由命，而且他们过于胆小而不能完成转变的过程。
Insects seem irresistibly drawn towards the sourceand then get trapped by the sticky lines.
昆虫总是禁不住光源的诱惑，结果就被这些粘乎乎的丝拿住了
Once stuck, there is no escape.
一旦被粘住，根本没有脱逃的机会。
Now it's just a matter of reeling in the line and slowlyconsuming the catch alive.
现在，它只需收起丝线，然后慢慢吃掉尚且活着的猎物。
By ensnaring the insects that hatch in this cave,
通过诱捕洞穴内羽化的昆虫
these glow-worms have solved the biggest challenge
这些萤火虫成功地解决了终生穴居动物面临的最大难题
that permanent cave-dwellers face, finding a regular and reliable source of food.
即找到长期而可靠的食物资源
One kind of rock makes this whole underground world possible, limestone.
这些地底世界之所以会存在，都是因为一种岩石，石灰岩。
Most of the world's caves are found within it and it covers nearly 10% of the Earth's surface.
世界上大部分洞穴内都存在石灰岩，它覆盖了地球表面将近10%的面积。
Limestone is composed of minerals derived from marine shells and corals.
石灰岩由海螺和珊瑚中的矿物沉积后形成
So although this rocky escarpment in the United States
所以，尽管美国境内的这座石壁，
is now hundreds of metres above sea level, it was actually formed underwater.
如今矗立在海平面以上几百米高的地方，它实际上却是在水下形成的。
1.be composed of 由……组成
Regardless of the type of business you own, your work will be composed of those three items.
无论你从事什么类型的行业，你所有的工作都由这三项组成。
2.derive from 来自
Thousands of English words are derived from Latin.
数以千计的英语词汇源自拉丁语。
The limestone towers of Vietnam's Halong Bay are areminder of this link with the sea.
越南下龙湾的石林能说明石灰岩与海洋的关系
Originally this whole area would have been one solidblock of limestone, the base of a coral reef.
起初，这整个地方都是一整块坚固的石灰岩床，珊瑚礁的基座
In Borneo, rain has sculpted the limestone into extremely sharp-sided pinnacles.
在婆罗洲，雨水已将石灰岩雕凿成无比尖削的石塔
But the dissolving power of rainwater has other, much more dramatic, effects underground.
不过在地下，雨水的溶解作用还能产生其它更壮观的效果
Rivers that flow over limestone often seem to completely disappear.
流经石灰岩的河川到最后似乎总是无影无踪
When the water reaches a more resistant bed of limestone, its course is altered.
当水流遇到更坚硬的石灰岩床时，就会改变路线。
Once underground, the water takes on a new, more erosive power.
一旦进入地下，水便有了一股新的、更强的侵蚀力。
During its journey from the surface, the water absorbed carbon dioxide from the soil, making itmildly acidic.
在地面上流淌时，水从土壤中吸收了二氧化碳，成为弱酸性。
And over millions of years, this acid eats away the limestone,
石灰岩经过几百万年的酸蚀作用
creating a maze of caverns and passages that sometimes go on for miles.
形成了迷宫般的溶洞和通道，有的甚至深达数英里。
1.link with 与……有关
Currently, these programmes do not educate people on the link with prevention of infertility.
目前，这些规划未向人们阐明其与预防不孕症之间的关系。
2.sculpt...into... 将...雕刻成...
We can sculpt our existence into something beautiful, or debase it into ugliness.
我们可以把我们的生命雕刻成美的，也可将它贬为丑。
3.take on 具有
The old term has taken on a new meaning.
这个旧词有了新的含义。
洞穴是不受阳光控制的生物栖息地之一，但这并不意味着那里就不存在野生生物。本集节目将深入洞穴内神秘而永恒的黑暗，探索山洞、洞穴和隧洞中未知的地下世界。
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