『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 29 Lec 4听力练习：What is the main purpose of the lecture?原文题目答案解析，TPO/Official 29 Lec 4听力原文范文音频翻译。

托福TPO/Official 29 Lec 4听力原文What is the main purpose of the lecture?-新东方托福官方网校手机版

旁白：听一段建筑工程学的演讲。

Narrator: Listen to part of a lecture in a structural engineering class.

教授：今天，让我们开始看一下太空时代的建筑工程学。

Professor: Today let’s begin to look at structural engineering in the Space Age.

新的问题、新的可能性也就意味着我们可以用新的方式去思考，发现完全不同的方法。

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

所以让我们想想，你认为当今将建筑物、仪器等东西放到天空中最大的障碍是什么？

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?

教授：正是如此。我的意思是，仅仅将航天飞机升降一次就已经是很贵了。那么，为什么呢？

Professor: Exactly. I mean, just taking the space shuttle up and back one time is hugely expensive. Uh, why?

学生：我猜很大一部分是用到燃料上了，对吗？

Student: I guess a lot of it is for fuel, right?

To…to get the rocket going fast enough.

教授：很好。所以我们燃烧大量的燃料，为的就是让火箭摆脱所谓的逃逸速度。

Professor: 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.

现在，逃逸速度大约是11千米/秒，很快。

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

学生：是的。我的意思是你还能怎么逃脱？

Student: Well, yeah. I mean, how else can you, um…escape?

我指的是，这是逃逸速度的要点，不是吗？

I mean, that’s the whole point of escape velocity, right?

不然重力会将你拉下来回到地球。

Otherwise gravity will pull you back down to the Earth.

教授：事实上，这是一个常见的误解。

Professor: Actually, that’s a common misconception.

逃逸速度仅仅是物体的速度，额…比如说，将一个大炮射出用最小的起始速度，这个物体随后可以凭它自己摆脱地球引力。

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.

但是那只是在没有别的外力施加的情况下。

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

如果你持续给这个物体施加外力，将它持续向上推。

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

它就可以以任何速度摆脱地球引力。

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

所以你说的是，像是，如果你有一个足够高的阶梯，你就可以爬到太空里去了？

So you’re saying …like, if you had a ladder tall enough, you could just climb into space?

Professor: Yeah! Uh, well, theoretically.

我的意思是，阶梯这个例子是有很多实际问题的。

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

像是在起初的几千米过后，你可能会觉得有十分疲劳，尤其是你必须要带着氧气瓶向上爬。

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.

所以不是，我说的更接近一个升降电梯。

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

这对于我们大多数人来说都是非常新的概念，但是事实上它已经存在超过一个世纪了。

That’s a new idea to most of us, but in fact it’s been around for over a century.

如果我们可以给这样一个电梯提供太阳能，我们就可以简单进入太空，成本是使用火箭或者航天飞机的零头。

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.

学生：等等，直升电梯不仅仅是上升。

Student: But wait, elevators don’t just rise up.

它必须悬挂在某种电线或者轨道之类的东西。

It have (sic) to hang on some kind of wire or track or something.

教授：是的。在过去几十年中，这防止人们认为这个可行或者认真看待这件事。

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

我们到哪里去找又坚固但又轻便的材料去充当缆绳或者轨道呢？

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

我的意思是，我们谈论的是36,000公里。

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

缆绳上的压力可能超出是大多数材料所能承受的。

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

但是，有一个新开发的材料有着比钻石更大的抗拉强度，但是却更加柔韧。

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

学生：我听说过碳纳米管的一些事情。

Student: OK. I’ve read something about carbon nanotubes.

它们很坚固，但是他们不是非常短小的圆柱体吗？

They are strong, alright, but aren’t they just very short little cylinders in shape?

教授：是的。但是这些圆柱体在分子水平上黏在一起。

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

你拔出一个或者一排纳米管，它或者他们的相邻的纳米管会一起出来。

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

所以，事实上你可以拉长出一个比钢铁坚固，36,000公里长的纳米管线或纳米管带，但可能只有人类发丝的千分之一那么细。

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.

学生：好吧。怎么讲这样一个带升高，使它可以支撑一个升价吊笼呢？

Student: OK. Fine. But what’s going to hold this ribbon up and keep it reach enough to support an elevator car?

教授：我们当然必须将它两段固定。

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

就在赤道上，我们在地面上需要一个很高的塔，并且在地球同步轨道上要有一个同步卫星。

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.

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

那是一个物体为了保持在旋转地球的同一点的上方，在赤道上方轨道运转所必须要达到的高度。

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.

所以你一旦进入了这个塔上方的同步轨道，只要从卫星降上放下你的碳纳米管缆绳，将它系到地球上的塔上。

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.

学生：所以，你真的认为这是一种可能性？

Student: So you really think this is a possibility?

教授：在20世纪70年代科幻小说家C.Clarke曾经谈及过在宇宙建立升降机。

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

当有人问他，认为何时他的说法会变成现实，他的回答说，“可能当人们停止取笑这个说法的50年后吧。”

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.”

Why does the student mention climbing a ladder?

What does the professor imply about using carbon nanotubes in the development of space elevators?

According to the professor, what is the significance of having a satellite in orbit about 36,000 kilometers above Earth’s surface?

Why does the professor mention the writer Arthur C.Clarke?

What can be inferred about the professor when he says this?