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托福TPO-19 Lecture 2

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Narrator:Listen to part of a lecture in an astronomy class.

独白:听下面一段的天文学课程。
So how many of you have seen the Milky Way, the Milky Way Galaxy in the sky? You, you have?
嗯,你们中有多少人注意过银河系,观测过它的天象?你,你看过?
Yeah, I was camping, and there was no moon that night, it was super dark.
是的,教授。我曾露营的时候观测过,当时天上没有月亮,四周很暗。
Anybody else? Not too many. Isn't that strange that the Milky Way is the galaxy that the planet earth is in, and most of us have never seen it?
还有别的同学吗?嗯,没有多少同学看过。银河系是我们地球安身的地方,但大多数同学们却从来没有注意过,这难道不奇怪吗?
Now, what's the problem here?
嗯,既然如此,问题在哪儿呢?
Light pollution, right? From street lights and stuff ...
光污染,是吗?比如街道上的路灯等…
Yes, Especially unshielded street light, you know, ones that aren't pointed downward.
是的,特别是没有加灯罩的路灯,它们的光是漫射的。
Now, here's an irony, the building we are in now, the astronomy building not far from our observatory, has unshielded lights.
现在,我给大家讲一件比较讽刺的事情。和观测楼隔得不远的、我们现在所在的这栋天文中心,就安装了无罩灯。
So the problem is pretty widespread.
所以这个问题其实特别普遍。
It is basically beyond control, as far as expecting to view the night sky anywhere near city, I mean.
这个问题基本上超出了控制范围,我的意思是,对于在城市中观测天空来讲。
I have lived around here my whole life.
我这一辈子都住在这个地方,
And I have never seen the Milky Way within city limits, and I probably never will.
并且在市区里我从来没有看到过银河系的模样,而且可能我永远也看不到。
There is a price for progress, eh?
所以,发展、进步是要付出代价的,对吧?
But let's think beyond light pollution, that's only one kind of a technological advance that has interfered with astronomical research. Can anyone think of another? No?
那么,我们再想想,除了光污染这一种科技进步导致的天文观测不便之外,有同学能想到别的吗?没有吗?
Ok, let's look at it this way, we don't only gain information by looking at the stars, for the past 70 years or so, we have also used radio astronomy, which lets us study radio waves from the sky.
好吧,我来给大家一些提示吧!过去 70 年里,我们不只是靠肉眼观测天空来获得天文信息,我们还用无线电技术,他使得我们可以研究天空中的各种波段。
How can you observe radio waves?
你怎么观测波段呢?
I mean, tell anything about the stars from that.
我的意思是,怎样利用波段来解读行星相关的信息?
Well, in optical astronomy, using a telescope and observing the stars that way, we rely on visible light waves.
嗯,在光电天文学领域中,我们的观测工具是望远镜,通过可见光波来研究星体。
What we are seeing from earth is actually electromagnetic radiation that's coming from stars.
我们在地球上接受到的图像,实际上是来自其他星球的电磁波,
And just one part of it is visible light. But there are problems with that.
这只是可见光的部分。而且,这种方法有一些问题。
When photons and light waves hit objects in our atmosphere, water droplets, oxygen and nitrogen molecules, dust particles and so on.
当光子和光波击打在我们大气层的水滴、氧气和氮气分子上时,它们就被点亮了。
These objects are illuminated, they are lit up, and those things are also being lit by all our street lights, by the moon, all these ambient light.
而这些东西同时也可能会被我们的街灯、月光等不明光源点亮。
And on top of that, when that visible radiation bounces off those molecules, it scatters in all directions.
这样的话,当可见光波从这些分子上反射出去的时候,它就向四周分散了。
And well, light from stars, even nearby in our own galaxy, doesn't stand a chance against that.
这样一来,从其他星球发射出来的光—即使他们的距离和地球很近—根本不可能能够经受起这样的能量消耗。
Basically the light bouncing off all these objects close to earth is brighter than what's coming from the stars.
基本上,其他星球的可见光在大气中的消耗比起最终剩余的要强得多。
Now, radio waves are electromagnetic radiation that we can't see.
而无线电波则是我们看不到的电磁波。
Nearly all astronomical objects in space emit radio waves, whether nearby stars, objects in faraway galaxies, they all give off radio waves.
几乎空间中的所有天体都会发射电磁波,无论是近星域还是遥远星域的物体,它们随时随地都在发射电磁波。
And unlike visible light waves, these radio waves can get through the various gases and dusts in space and through our own earth's atmosphere comparatively easily.
而且这些波与可见光不同之处在于,它们可以相对容易地穿透各种气障和尘障,穿过我们的大气层。
Ok, then we might as well give up on optical astronomy and go with radio astronomy.
这样的话,我们会放弃光电望远镜而只使用无线电波吗?
Well, the thing is, with the radio astronomy, you can't just set up a telescope in you backyard and observe stars.
嗯,情况是,我们当然不能只在后院立一个射电望远镜然后就依靠它观察星空。
One problem is that radio waves from these far away objects, even though they can get through, are extremely faint.
这样做的一个问题是,从遥远星体上发射过来的电波,即便它们能够穿透大气层,依然非常的微弱。
So we need to use radio telescopes, specially designed to receive these waves and then, well, we can use computers to create pictures based on the information we receive.
所以我们还需要建立射电望远镜;它们的原理是接收电波,并且通过电波信息建立电脑模拟图像。
That sounds cool. So, how do they do that?
这听上去很不错!但到底是怎么做到的呢?
Well, it is kind of like the same way a satellite dish receives its signal, if you are familiar with that.
如果你知道卫星接收盘的接收信号的原理的话,射电望远镜的工作原理和它差不多。
But radio telescopes are sometimes grouped together, is the same effect as having one big telescope to increase radio wave gathering power.
但射电望远镜的接收器常常建立在一起的,从而组成一个更大功率的信号接收盘。
And they use electronics, quite sophisticated.
并且它们使用大功率电源,而且工艺要求非常高。
Yeah, it is neat how they do it, but for now why don't we just stick with what we can learn from it.
嗯,射电望远镜的原理差不多是这样的,但我们还是接着跟进我们课堂上的内容吧!
Some very important discoveries have been made by this technology, especially you consider that some objects in space give off radio waves but don't emit any light.
这项创新使得我们获得了许多重大的发现,特别是关于那些在太空中只发射无线电波而不发射光的物体的。
We have trouble discovering those sorts of bodies, much less studying them using just optical telescopes.
我们曾经在研究这一类天体时很不顺利,因为光学镜不能进行太多有效的研究。
Well, If the radio waves are so good at getting through the universe, what's the problem?
嗯,如果无线电波真的能够穿透宇宙空间的话,它有什么问题呢?
Well, answer this. How come people have to turn off their cell phones and all our electronic devices when an airplane is about to take off?
它的答案与这个问题是一样的:为什么人们在飞机降落的时候要关闭手机登电子设备呢?
The phones interfere with the radio communication at the airport, right?
因为电话干扰了飞机和机场的无线电通信,是吗?
Oh, so our radio waves here on earth interfere with the waves from space?
这样说来,地球上的无线电信号干扰了空间传来的电波?
Yes, signal from radios, cell phones, TV stations, remote controls, you name it. All these things cause interference.
对的,电台、手机、电视台、无限遥控等你们所知的无线电设备都能干扰空间电波。
We don't think about that as often as we think about light pollution.
我们对此的考虑不如光污染多。
But all those electrical gauges pollute the skies, just in a different way.
但这些电子仪器同样污染了天空,只是方式不一样罢了。

重点单词   查看全部解释    
control [kən'trəul]

想一想再看

n. 克制,控制,管制,操作装置
vt. 控制

 
widespread ['waidspred]

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adj. 分布(或散布)广的,普遍的

 
universe ['ju:nivə:s]

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n. 宇宙,万物,世界

联想记忆
galaxy ['gæləksi]

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n. 银河,一群显赫之人

联想记忆
interference [.intə'fiərəns]

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n. 妨碍,干扰
[计算机] 干涉

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comparatively [kəm'pærətivli]

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adv. 比较地,相对地

 
stick [stik]

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n. 枝,杆,手杖
vt. 插于,刺入,竖起<

 
remote [ri'məut]

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adj. 偏僻的,遥远的,远程的,(感情等)距离很大

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observe [əb'zə:v]

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v. 观察,遵守,注意到
v. 评论,庆

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astronomy [əst'rɔnəmi]

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n. 天文学

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