TPO19聽力 lecture 2 16. - 英檢

※ 引述《eltonsmile (eltonsmile)》之銘言：
: TPO19 lecture 2 16.
: 16. according to the prof., why do radio astronomers sometime
: have difficulty studying very distant objects
: 應選兩個選項
: 但這個選項
: Radio waves from space are rest very strong
: 聽力檔案裏面沒有提到耶?
: 以下附上聽力原文逐字稿
有提到
How come people have to turn off their cell phones and all
our electronic devices when an
airplane is about to take off?



其實這篇的結構很清楚
先講講光學望遠鏡會受光害的影響

改用電波望遠鏡就不受可見光的影響
但是仍然有缺點 因為會受到電磁波的影響

聽力的內容其實也有一定的結構
跟閱讀是一樣的

老師說話的模式就像是模版
例如定義 改進 還有同學的疑問 老師糾正同學的地方都會出題
: TPO 19 Lecture 2 Astronomy(Radio Astronomy & Optical Astronomy)
: Narrator
: Listen to part of a lecture in an astronomy class.
: Professor
: So how many of you have seen the Milky Way, the Milky Galaxy in the sky? You,
: you have?
: Student
: Yeah, I was camping, and there was no moon that night, it was super dark.
: Professor
: 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? Now,
: what’s the problem here?
注意第一個問題
: Student
: Light pollution, right? From street lights and stuff ...
光害
: Professor
: Yes, Especially unshielded street light, you know, ones that aren’t pointed
: downward. Now, here’s an irony, the buiding we are in now, the astronomy
: building not far from our observatory, has unshielded lights.
: Student
: So the problem is pretty widespread.
: Professor
: It is basically beyond control, as far as expecting to view the night sky
: anywhere near city, I mean. I have lived around here my whole life. And I
: have never seen the Milky Way within city limits, and I probably never will.
: There is a price for progress, eh? But let’s think beyond light pullution,
: that’s only one kind of a technological advance that has interfered with
: astronomical research.
: Can anyone think of another? No? 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 astronomy1 , which lets us study radio waves from the
: sky.
因為沒有人回答 所以老師自己說答案
新科技是 電波天文學
: Student
: How can you observe radio waves? I mean, tell anything about the stars from
: that.
教授解釋學生的問題
: Professor
: Well, in optical astronomy, using a telescope and observing the stars that
: way, we rely on visible light waves. What we are seeing from earth is
: actually electromagnetic radiation that’s coming from stars. And just one
: part of it is visible light. But there are problems with that. When
: photons2 and light waves hit objects in our atmosphere, water droplets,
: oxygen and nitrogen molecules, dust particles and so on. 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. And on top of that, when
: that visible radiation bounces off those molecules, it scatters in all
: directions. And well, light from stars, even nearby in our own galaxy, doesn’
: t stand a chance against that. Basically the light bouncing off all these
: objects close to earth is brighter than what’s coming from the stars.
: Now, radiowaves are electromagnetic radiation that we can’t see. Nearly all
: astronomical objects in space emit radio waves, whether nearby stars, objects
: in far away galaxies, they all give off radio waves. 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.
: Student
: Ok, then we might as well give up on optical astronomy and go with radio
: astronomy.
: Professor
: Well, the thing is, with the radio astronomy, you can’t just set up a
: telescope in you backyard and observe stars.
新科技還是有限制
1.訊號弱
: One problem is that radio waves from these far away objects, even though they
: can get through, are extremely
: faint. 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.
: Student
: That sounds cool. So, how do they do that?
: Professor
: Well, it is kind of like the same way a satellite dish3
: receives its signal, if you are familiar with that. But radio
: telescopes are sometimes grouped together, is the same effect as having one
: big telescope to increase radio
: wave gathering power. And they use electronics, quite sophisticated. Yeah, it
: is neat how they do it, but for now
: why don’t we just stick with what we can learn from it. 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. We
: have trouble discovering those sorts of bodies, much less studying them using
: just optical telescopes.
: Student
學生質問
: Well, If the radio waves are so good at getting throught the universe, what’
: s the problem?
: Professor
: 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?
: Student
: The phones interfere with the radio communication at the airport, right?
: Student
: Oh, so our radio waves here on earth interfere with the waves from space?
: Professor
: Yes, signal from radios, cell phones, TV stations, remote controls, you name
: it. All these things cause interference.
: We don’t think about that as often as we think about light pollution. But
: all those electrical gauges pollute the
: skies, just in a differen way.
最後一句顯示光害與電磁波污染 有些共同的地方

--