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?
Student
Light pollution, right? From street lights and stuff ...
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 withastronomical 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.
Student
How can you observe radio waves? I mean, tell anything about the stars from that.
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 comingfrom 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. Basicallythe 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 offradio 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.
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 dish3receives 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
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.
TPO 19 Conversation 2
Narrator
Listen to a conversation between a student and the director of the student cafeteria.
Student
Hi, I... I am sorry to interrupt, could I ask you a few questions?
Director
Sure, but if it is about you meal plan, you'll need to go to Room 45, just down the hall.
Student
Eh, no, I am OK with my meal plan. I am actually here about the food in the student cafeteria.
Director
Oh, we do feed a lot of students, so we can't always honor individual requests. I am sure you understand.
Student
Of course. It is just that I am a little concerned, I mean, a lot of us are, that a lot of the food you serve isn't really that healthy. Like there are so many deep-fried foods.
Director
As a matter of fact, we recently changed the type of oil we use in our fryer . It is the healthiest available. And would you believe that at least ten students have already complaint that their french fries and fried chicken don't taste as good since we switched?
Student
Oh, I try not to eat too many fried foods anyway. I am just aware that, eh...You see, I used to work in a natural food store. They had all these literature4 advising people to eat fresh organic growing food. Working there really open my eyes.
Director
Did you come to the organic food festival we had to celebrate Earth Day?
Student
Oh, sorry, I must have missed that.
Director
We served only certified organic food, most of which was from local farms. It is not something we can afford to do on a daily basis, and there aren't too many organic farms around here. But sometime the produce we offer is organically grown. It depends on the season and the prices of course.
Student
That's good to know. I like the fact that organic farms don't use chemical pesticides or anything that can pollute the soil or the water.
Director
I do too. But let me ask you this. Is it better to buy locally grown produce that is not certified as organic or is it better to get organically grown fruits and vegetables that must be trucked in from California, three thousand mile away. What about fossile fuels burned by the trucks' engine. Plus the expense of shipping food across long distances. And nutritionally speaking, an apple is an apple however it is grown.
Student
I see your point. It is not so clear-cut.
Director
Why don't you visit our cafeteria's website? We list all our food suppliers. You know, where we buy the food that we serve. And the site also suggests ways to make your overall diet a healthy one. You can also find some charts listing fat and calorie content for different types of seafood, meat and the other major food groups.
Student
I didn't realize you thought about all these things so carefully, I just noticed the high-calorie food in the cafeteria.
Director
Well, we have to give choices so everyone is satisfied. But if you wish to pursue this further, I suggest that you talk to my boss.
Student
That's OK, seems like you are doing what you can.
