考满分 toefl

1 .Listen to part of a lecture in a structural engineering class.

听一段结构工程课程上的演讲

1 .Today let's begin to look at structural engineering in the Space Age.

今天我们来看看太空时代的结构工程学。

2 .Uh, new problems... new possibilities mean we can think in new ways, find radically different approaches.

。新的问题，新的可能性意味着我们能够用新的方式思考，找到全新的方法。

3 .So let's consider... uh, well, what would you say is the biggest obstacle today to putting structures, equipment, people... uh, anything really, into space?

我们来考虑一下，你觉得现当今把构造，设备，人类运送到太空中面临的最大困难是什么？

1 .Well, the cost, right?

嗯，费用，对吧？

1 .Exactly. I mean, just taking the space shuttle up and back one time is hugely expensive.

没错。仅仅发射太空器到太空再把它们召回一次的费用就很高。

2 .Uh, why?

为什么？

1 .I guess a lot of it is for fuel, right?

我想有很大部分都用在了燃料上，对吧？

2 .To... to get the rocket going fast enough.

为了让火箭速度够快。

1 .OK. Fast enough to...

足够快干什么？

1 .To escape Earth's gravity.

快到能摆脱地球引力。

1 .Good. So we are burning up an enormous amount of fuel at every launch just to get the rocket up to what's known as escape velocity.

没错。每一次发射我们都会燃烧大量燃料以使火箭到达宇宙速度。

2 .Now, escape velocity is around 11 kilometers a second, pretty fast.

宇宙速度大约是11千米每秒，非常快。

3 .But do we really have to go this fast?

但是我们真的需要达到这么快的速度么？

1 .Well, yeah. I mean, how else can you, um... escape?

是的。还有什么其他办法能摆脱地球引力呢？

2 .I mean, that's the whole point of escape velocity, right?

我的意思是，宇宙速度就是这个意思不是么？

3 .Otherwise gravity will pull you back down to the Earth.

如果不到达宇宙速度的话引力会把火箭拉回地球的。

1 .Actually, that's a common misconception.

事实上，这是个非常普遍的误解。

2 .Escape velocity is simply the speed of an object that's... uh, let's say, shot out of a cannon the minimum initial speed, so that the object could later escape Earth's gravity on its own.

宇宙速度只是一个物体，比如一个从加农炮里射出的物体，要有的最小的能使它之后能靠自己摆脱地球引力的速度，

3 .But that's just if there's no additional force being applied.

但是这是仅指没有其他外力作用于这个物体的情况。

4 .If you keep on supplying force to the object, keep on pushing it upward.

如果你在发射过程中不断的对这个物体施加外力，不断的把它向前推，

5 .It could pull away from Earth's gravity at any speed.

那不管它最初速度多大，最终它都有可能摆脱地球引力

1 .Even really slow?

就算初速度非常低也可以？

2 .So you're saying... like, if you had a ladder tall enough, you could just climb into space?

这就好比如，如果你有个足够高的梯子，你就能沿着梯子爬到太空中？

1 .Yeah! Uh, well, theoretically.

没错！理论上讲是这样。

2 .I mean, I can see some practical problems with the ladder example.

但是你的梯子例子面临着一些实际操作上的问题。

3 .Uh, like you might get just a little bit tired out after the first few thousand kilometers or so, uh, especially with all the oxygen tanks you'll have to be hauling up with you.

比如你在爬了几千米之后会很累，尤其是当你还拖着一堆氧气瓶的时候。

1 .No. I was thinking more along the lines of an elevator.

我觉得电梯更适合。

1 .Wait! You are serious?

等等！你是认真的么？

1 .Sure. An elevator. That's a new idea to most of us, but in fact it's been around for over a century.

没错，电梯！对我们所有人来说这个想法可能很新鲜，但是其实一个世纪前就有人这么构想过了。

2 .If we could power such an elevator with solar energy, we could simply rise up into space for a fraction of the cost of a trip by rocket or shuttle.

如果我们能用太阳能对这样一个电梯供能，我们就能以用火箭或者飞行器的费用的几分之一的费用进入太空。

1 .But wait, elevators don't just rise up.

但是，电梯不能仅靠自己上升。

2 .They have to hang on some kind of wire or track or something.

它需要在一个轨道上运作。

1 .Uh, true. And for decades that's exactly what's prevented the idea from being feasible or even just taken seriously.

没错。几十年来就是这个想法阻碍了电梯的发展，也阻碍了人们严肃的考虑它的可行性

2 .Where do we find the material strong enough yet lightweight enough to act as a cable or track.

我们到哪里去找这样一个能承重并且超轻的材料做电梯的轨道或者绳索呢？

3 .I mean, we are talking 36,000 kilometers here.

绳索足足有36000千米。

4 .And the strain on the cable would be more than most materials could bear.

这个绳索将承受极大的压力，大到大多数材料都不能承受。

1 .But a new material developed recently has a tensile strength higher than diamond, yet it's much more flexible.

但是一种新开发的材料有比钻石还强的延展能力，而且很有柔韧性

2 .I am talking about carbon nanotubes.

。它，就是碳纳米管。

1 .OK. I've read something about carbon nanotubes. They are strong, alright, but aren't they just very short little cylinders in shape?

我读到过碳纳米管。它们承重能力很强是没错，但从形状上来说，它们不就是非常短小的圆柱么？

1 .Ah, yes. But these cylinders cling together at a molecular level.

是的。但是这些圆柱在分子层面上可以聚合在一起。

2 .You pull out one nanotube or a row of nanotubes, and its neighbor's come with it, and their neighbors, and so on.

从一个或者一排纳米管开始，临近的纳米管会聚合，然后再临近再聚合

3 .So you could actually draw out a 36,000-kilometer strand or ribbon of nanotubes stronger than steel, but maybe a thousandth the thickness of a human hair.

所以实际上你可以做一个比钢铁承重能力强但是只有头发千分之一细的36000千米的纳米管。

1 .OK. Fine. But what's going to hold this ribbon up and keep it rigid enough to support an elevator car?

的。 那如何才能保持这个管子不断向上并且达到电梯要达到的高度呢？

1 .Well, we definitely have to anchor it at both ends.

我们必须在两端固定这个管子。

2 .So what we need is a really tall tower here on the ground right at the equator and a satellite in geostationary orbit around the Earth.

所以我们需要在赤道上建一个很高的塔，然后还需要一个和地球旋转周期同步的卫星。

3 .There's a reason I mentioned that figure of 36,000 kilometers.

我先前提到过36000千米，

4 .That's about how high an object would have to be orbiting straight up from the equator to constantly remain directly above the exact same spot on the rotating planet Earth.

因为36000千米是赤道上空环绕物体要保持与地球相对静止的运动的轨道高度。

5 .So once you are in this geostationary orbit right over the tower, just lower your carbon nanotube cable down from the satellite, tether it to the tower here on Earth and there you have it!

你把卫星发射到赤道塔上空的地球旋转同步轨道后，你可以从卫星上垂下碳纳米管，然后把这一端固定在地球上。然后就成功了！

1 .So you really think this is a possibility? Like, how soon could it happen?

所以你觉得有这可能性？还要多久才能实现？

1 .Well, the science fiction writer Arthur C. Clarke talked about building a space elevator back in the 1970s.

科幻小说家Authur C. Clarke早在1970年代就提出过建造一个太空电梯的想法。

2 .And when someone asked him when he thought this idea might become a reality, his reply was, "Probably about fifty years after everybody quits laughing".

当有人问他觉得什么时候这个想法能变成现实时，他回答说，也许在人们停止嘲笑这个想法的50年之后就能实现。