評論
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Narrator:Listen to part of a lecture in an astronomy class.
獨白:聽下面一段的天文學課程。
So how many of you have seen the Milky Way, the Milky Way Galaxy in the sky? You, you have?
嗯，你們中有多少人注意過銀河系，觀測過它的天象？你，你看過？
Yeah, I was camping, and there was no moon that night, it was super dark.
是的，教授。我曾露營的時候觀測過，當時天上沒有月亮，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?
還有別的同學嗎？嗯，沒有多少同學看過。銀河系是我們地球安身的地方，但大多數(shù)同學們卻從來沒有注意過，這難道不奇怪嗎？
Now, what's the problem here?
嗯，既然如此，問題在哪兒呢？
Light pollution, right? From street lights and stuff ...
光污染，是嗎？比如街道上的路燈等…
Yes, Especially unshielded street light, you know, ones that aren't pointed downward.
是的，特別是沒有加燈罩的路燈，它們的光是漫射的。
Now, here's an irony, the building we are in now, the astronomy building not far from our observatory, has unshielded lights.
現(xiàn)在，我給大家講一件比較諷刺的事情。和觀測樓隔得不遠的、我們現(xiàn)在所在的這棟天文中心，就安裝了無罩燈。
So the problem is pretty widespread.
所以這個問題其實特別普遍。
It is basically beyond control, as far as expecting to view the night sky anywhere near city, I mean.
這個問題基本上超出了控制范圍，我的意思是，對于在城市中觀測天空來講。
I have lived around here my whole life.
我這一輩子都住在這個地方，
And I have never seen the Milky Way within city limits, and I probably never will.
并且在市區(qū)里我從來沒有看到過銀河系的模樣，而且可能我永遠也看不到。
There is a price for progress, eh?
所以，發(fā)展、進步是要付出代價的，對吧？
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，我們再想想，除了光污染這一種科技進步導致的天文觀測不便之外，有同學能想到別的嗎？沒有嗎？
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，我來給大家一些提示吧！過去 70 年里，我們不只是靠肉眼觀測天空來獲得天文信息，我們還用無線電技術(shù)，他使得我們可以研究天空中的各種波段。
How can you observe radio waves?
你怎么觀測波段呢？
I mean, tell anything about the stars from that.
我的意思是，怎樣利用波段來解讀行星相關(guān)的信息？
Well, in optical astronomy, using a telescope and observing the stars that way, we rely on visible light waves.
嗯，在光電天文學領(lǐng)域中，我們的觀測工具是望遠鏡，通過可見光波來研究星體。
What we are seeing from earth is actually electromagnetic radiation that's coming from stars.
我們在地球上接受到的圖像，實際上是來自其他星球的電磁波，
And just one part of it is visible light. But there are problems with that.
這只是可見光的部分。而且，這種方法有一些問題。
When photons and light waves hit objects in our atmosphere, water droplets, oxygen and nitrogen molecules, dust particles and so on.
當光子和光波擊打在我們大氣層的水滴、氧氣和氮氣分子上時，它們就被點亮了。
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.
而這些東西同時也可能會被我們的街燈、月光等不明光源點亮。
And on top of that, when that visible radiation bounces off those molecules, it scatters in all directions.
這樣的話，當可見光波從這些分子上反射出去的時候，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.
這樣一來，從其他星球發(fā)射出來的光—即使他們的距離和地球很近—根本不可能能夠經(jīng)受起這樣的能量消耗。
Basically the light bouncing off all these objects close to earth is brighter than what's coming from the stars.
基本上，其他星球的可見光在大氣中的消耗比起最終剩余的要強得多。
Now, radio waves are electromagnetic radiation that we can't see.
而無線電波則是我們看不到的電磁波。
Nearly all astronomical objects in space emit radio waves, whether nearby stars, objects in faraway galaxies, they all give off radio waves.
幾乎空間中的所有天體都會發(fā)射電磁波，無論是近星域還是遙遠星域的物體，它們隨時隨地都在發(fā)射電磁波。
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.
而且這些波與可見光不同之處在于，它們可以相對容易地穿透各種氣障和塵障，穿過我們的大氣層。
Ok, then we might as well give up on optical astronomy and go with radio astronomy.
這樣的話，我們會放棄光電望遠鏡而只使用無線電波嗎？
Well, the thing is, with the radio astronomy, you can't just set up a telescope in you backyard and observe stars.
嗯，情況是，我們當然不能只在后院立一個射電望遠鏡然后就依靠它觀察星空。
One problem is that radio waves from these far away objects, even though they can get through, are extremely faint.
這樣做的一個問題是，從遙遠星體上發(fā)射過來的電波，即便它們能夠穿透大氣層，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.
所以我們還需要建立射電望遠鏡；它們的原理是接收電波，并且通過電波信息建立電腦模擬圖像。
That sounds cool. So, how do they do that?
這聽上去很不錯！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.
如果你知道衛(wèi)星接收盤的接收信號的原理的話，射電望遠鏡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.
但射電望遠鏡的接收器常常建立在一起的，從而組成一個更大功率的信號接收盤。
And they use electronics, quite sophisticated.
并且它們使用大功率電源，而且工藝要求非常高。
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，射電望遠鏡的原理差不多是這樣的，但我們還是接著跟進我們課堂上的內(nèi)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.
這項創(chuàng)新使得我們獲得了許多重大的發(fā)現(xiàn)，特別是關(guān)于那些在太空中只發(fā)射無線電波而不發(fā)射光的物體的。
We have trouble discovering those sorts of bodies, much less studying them using just optical telescopes.
我們曾經(jīng)在研究這一類天體時很不順利，因為光學鏡不能進行太多有效的研究。
Well, If the radio waves are so good at getting through the universe, what's the problem?
嗯，如果無線電波真的能夠穿透宇宙空間的話，它有什么問題呢？
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?
它的答案與這個問題是一樣的:為什么人們在飛機降落的時候要關(guān)閉手機登電子設(shè)備呢？
The phones interfere with the radio communication at the airport, right?
因為電話干擾了飛機和機場的無線電通信，是嗎？
Oh, so our radio waves here on earth interfere with the waves from space?
這樣說來，地球上的無線電信號干擾了空間傳來的電波？
Yes, signal from radios, cell phones, TV stations, remote controls, you name it. All these things cause interference.
對的，電臺、手機、電視臺、無限遙控等你們所知的無線電設(shè)備都能干擾空間電波。
We don't think about that as often as we think about light pollution.
我們對此的考慮不如光污染多。
But all those electrical gauges pollute the skies, just in a different way.
但這些電子儀器同樣污染了天空，只是方式不一樣罷了。
