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Question 1 of 45
Listen to the following Lectures. Then answer the questions.
What is the lecture mainly about? Click on 2 answers
Narrator: Listen to part of a lecture in a music history class. The professor has been discussing Opera.
Professor: The word opera means work, actually it means works. It’s the plural of the word opus from the Latin. And in Italian, it refers in general to works of art. Opera Lyric or Lyric Opera refers to what we think of as opera, the musical drama. Opera was commonplace in Italy for almost a thousand years before it became commercial as a venture. And during those years, several things happened, primarilylinguistic or thematic and both involving secularization. Musical drama started in the churches. It was an educational tool. It was used primarily as a vehicle for teaching religion and was generally presented in the Latin, the language of the Christian Church which had considerable influence in Italy at that time. But the language of everyday life was evolving in Europe and at a certain point in the middle ages, it was really only aristocrats,merchants, and clergy who can deal with Latin. The vastmajority of the population used their own regional vernacular in all aspects of their lives. And so, in what is now Italy, operas quit being presented in Latin and started being presented in Italian. ]And once that happened, the themes of the opera presentations also started to change. And musical drama moved from the church to the plaza right outside the church. And the themes again, the themes changed. And opera was no longer about teaching religion as it was about satire and about expressing the ideas of society or government without committing yourself to writing and risking imprisonment or persecution, or what have you. Opera, as we think of it, is of course a resurrected form. It is the melodious drama of ancient Greek theater, the term ‘melodiousdrama’ being shortened eventually to ‘melodrama’ because operas frequently are melodramatic, not to say unrealistic. And the group that put the first operas together that we have today even, were, well…it was a group of men that included Galileo’s father Vincenzo, and they met in Florence. He and a group of friends of the Count of Bardi and they formed what is called the Camerata de Bardi. And they took classical theater and reproduced it in the Renaissance’s time. This…uh…this produced some of the operas that we have today. Now what happened in the following centuries is very simple. Opera originated in Italy but was not confined to Italy any more than the Italians were. And so as the Italians migrated across Europe, they carried theater with them and opera specifically because it was an Italian form. What happened is that the major divide in opera that endures today took place. The French said opera ought to reflect the rhythm and cadence of dramaticliterature, bearing in mind that we are talking about the golden age in French literature. And so the music was secondary, if you will, to the dramaticcadence of language, to the way the rhythm of language was used to express feeling and used to add drama and of course as a result, instead of arias or solos, which would come to dominated Italian opera. The French relied on what the Italians called recitativo or recitative in English. The lyrics were spoken, frequently to the accompaniment of a harpsichord. The French said you really cannot talk about real people who lived in opera and they relied on mythology to give them their characters and their plots, mythology, the past old traditions, the novels of chivalry or the epics of chivalry out of the middle Ages. The Italian said, “no, this is a great historical tool and what a better way to educate the public about Neo or Attalla or any number of people than to put them into a play they can see and listen to”. The English appropriated opera after the French. Opera came late to England because all theaters, public theaters were closed, of course, during their civil war. And it wasn’t until the restoration in 1660 that public theaters again opened and opera took off. The English made a majoradjustment to opera and exported what they had done to opera back to Italy. So that you have this circle of musical influences, the Italians invented opera, the French adapted it, the English adopted it, the Italians took it back. It came to America late and was considered too elitist for the general public. But Broadway musicals fulfilled a similarfunction for a great long while. John J. Chapman wrote about opera, quote “If an extraterrestrial being or two appear before us and say: What is your society like? What is this Earth thing all about? You could do worse than take that creature to an opera.” End quote. Because opera does, after all, begin with a man and a woman and an emotion.
Question 2 of 45
According to the professor, what happened after the Italian language replaced Latin in Italian opera?
Question 3 of 45
Why does the professor mention ancient Greek theater?
Question 4 of 45
What does the professor say about music in French opera?
Question 5 of 45
What does the professor say this:
Question 6 of 45
What does the professor imply when he says this:
Question 7 of 45
What is the lecture mainly about?
Narrator: Listen to part of a lecture in an environmental science class.
Professor: All right, folks, let’s continue our discussion of alternative energy sources and move on to what’s probably the most well-known alternative energy source, uh, solar energy. The Sun basically provides Earth with a virtually unlimited source of energy everyday but the problem has always been how do we tap this source of energy? Can anyone think of why it’s so difficult to make use of solar energy? Student A: Because it is hard to gather it? Professor: That’s exactly it! Solar energy is everywhere but it’s also quite diffused. And the thing is the dream of solar energy is not a new one, humanities have been trying to use the Sun’s light as a reliablesource of energy for centuries. And, uh, around the beginning of the twentieth century, there were actually some primitivesolar water heaters on the consumer market, but they didn’t sell very well. Any of you want to guess why? StudentA: Well, there were other energy choices like oil and natural gas, right? Professor: Yeah! And for better or for worse, we chose to go down that path as a society. When you considereconomic factors, it’s easy to see why. But then in the 1970s, there was an interest in solar energy again. Why do you think that happened? Student B: Because oil and natural gas were…err…became scarce? Professor: Well, not exactly. The amount of oil and natural gas in the Earth was still plentiful, but there were other reasons. Uh, it’s a political thing really and I’m not gonna get into that now. So what happened in the 1970s was: oil and natural gas became very expensive very quickly. And that spurred people to start looking into alternative forms of energy, solar energy probably being the most popular. But then in the 80s, this trend reversed itself when price of oil and natural gas went down. All right, let’s shift our focus now to some of the technologies that have been invented to overcome the problem of gathering diffused solar energy. The most basicsolution is simply to carefully place windows in a building so that the Sun shines into the building and then it’s absorbed and converted into heat. Can anyone think of where this is most commonly used? Student A: Greenhouses. Professor: Yep, greenhouses where plants are kept warm and provided with sunlight because the walls of the building are made entirely of glass. But we do also have more complex systems that are used for space heating and they fall into two categories, passive and active heating systems. Passive systems take advantage of the location or design of a house. For example, solar energy is gathered through large glass panels facing the Sun. The heat is then stored in water-filled tanks or concrete. No mechanical devices are used in passive heating systems. They operate with little or no mechanicalassistance. With active systems, on the other hand, you collect the solar energy at one location and then you use pumps and fans to move heat from the collectors through a plumbing system to a tank, where it can be used to heat a home or to just provide hot water. Student B: Excuse me, professor, but I’ve got to ask, “how can solar energy work at night or on cloudy days?” Professor: That’s, well, that is a really good question. As a matter of fact, science is still working on it, uh, trying to find ways in enhancing energy storage techniques, so that the coming of night or cloudy days really wouldn’t matter. That is the biggest drawback of solar energy, the problem of what do you do in cases where the sun’s light is weak or virtually non-present. So, the storage of solar energy, lots of solar energy is really an important aspect. Student A: Does that mean that solar energy can only be used on a small scale, like heating a home? Professor: Well, actually, there have been some attempts to build solar energy power plants. The world’s largest solar power plant is located in Kramer Junction, California. It can generate 194 megawatts of electric power, but that’s just a drop in the bucket. Right now the utility companies are interested in increasing the capacity of their Kramer Junction plant, but only time will tell if it will ever develop into a majorsource of power for that region, considering the economic and political factors involved.
Question 8 of 45
What are the two main problems solar power presents as an energy source? Click on two answers
Question 9 of 45
According to the professor, what led to the popularity of solar energy in the 1970’s?
Question 10 of 45
What is the difference between passive and active heating systems?
Question 11 of 45
What is the professor’s opinion about the future of Kramer Junction power plant?
Question 12 of 45
What does the professor mean when he says that:
Question 13 of 45
1.Why does the student go to see the professor?
Narrator: Listen to a conversation between a student and his psychology professor.
Professor: Good afternoon, Alex. Can I help you with something? Man: Well, I wanted to talk with you about the research project you assigned today. I, um, hope you could clarify a few things for me. Professor: I’ll certainly try. Man: OK, all we have to do is do two observations and take notes on them, right? Professor: Oh, that’s a start, but you’ll need to do some research, too. Then you’ll write a paper that’s not so much about the observations but a synthesis of what you observed and read. Man: OK, and what about the children I am supposed to observe? Professor: Not children, a single child observed twice. Man: Oh, OK! So I should choose a child, with the permission of the child’s parents, of course, and then observe that child a couple of times and take good notes, then? Professor: Actually, after your first observation, you’ll go back and look through your textbook or go to the library and find a few sources concerning the stage of development this particular child is in. And then, with that knowledge, you’ll make a second observation of the same child to see if the expected developmental behaviors are exhibited. Man: Can you give me an example? Professor: Well, uh, if you observe a four-year-old child, uh, for example, my daughter’s four years old, you might read up on Piaget’s Stages of CognitiveDevelopment. We covered those in class. Man: Uh huh. Professor: Most likely, what stage would a child of that age be in? Man: Um, the pre-operational stage? Professor: Exactly! If that’s the case, her language use would be maturing and her memory and imagination would be developed. Man: So she might play pretend, like she can pretend when driving her toy car across the couch that the couch is actually a bridge or something. Professor: That’s right! In addition, her thinking would be primarily egocentric. Man: So she’d be thinking mostly about herself and her own needs and might not be able to see things from anyone else’s perspective? Professor: Um hmm. Man: But, what if she doesn’t? I mean, what if she doesn’t demonstrate those behaviors? Professor: That’s fine. You’ll note that in your paper. See, your paper should compare what is expected of children at certain stage of development with what you actually observe. Man: OK. I have one more question, though. Professor: And what’s that? Man: Where can I find a child to observe? Professor: Um, I’d suggest you contact the Education Departmentsecretary. She has a list of contacts of various schools and with certain families who are somehow connected to the University. Sometimes they are willing to help out students with projects like yours. Man: OK, I’ll stop by the Education Department Office this afternoon. Professor: And if you have any trouble or any more questions, feel free to come by during my office hours.
Question 14 of 45
2.According to the professor,what should the student do after completing the first observation?
Question 15 of 45
3.Why does the student mention a child playing with a toy car?
Question 16 of 45
4.Why should the student contact the education department secretary?
Question 17 of 45
5.What does the professor mean when she says this?
Question 18 of 45
What is the main topic of the lecture?
Question 19 of 45
According to the professor, what is the basic reason for building pedestrian malls in the city center?
Narrator: Listen to part of a lecture in a city planning class. Female Professor: In the last fifty years or so, many American cities have had difficulty in maintaining a successful retail environment. Business owners in the city centers or, uh, the downtown areas have experienced some financial losses because of a steady movement of people out of the cities and into the suburbs. In general, downtown areas just don’t have that many residential areas, uh, not that many people live there. So, what if city planners decided to do about it? Well, one way they’ve come up with some ways to attract more people to shop downtown was by creating pedestrian malls. Now what is a pedestrian mall? It’s a pretty simple concept really. It’s essentially, um, an outdoor shopping area, designed just for people on foot, and, uh, well, unlike many other shopping malls that are built on the suburbs nowadays, these pedestrian malls are typically located in the downtown area of the city. And there are features like wide sidewalks, comfortable outdoor seating and, uh, maybe even fountains and, you know, art. Uh, there are variations on this model, of course. But the common denominator is always the idea of creating a shopping space that would get people to shop in the city without needing their cars. So I’m sure you can see how having an area that’s off limits to automobile traffic would be ideal for a heavily populated city, where, well, the streets would otherwise be bustling with noisy unpleasant traffic congestion. Now, the concept, which originated in Europe, was adopted by American city planners in the late 1950s. And since then, a number of United States cities have created pedestrian malls and many of them have been highly successful. So, what have city planners learned about making these malls succeed? Well, there are two critical factors to consider when creating a pedestrian mall: location and design, both of which are equally important. Now let’s start with the location. In choosing a specific location for a pedestrian mall, there are, in fact, two considerations: proximity to potential customers (um, that’s what we would call customer base) and accessibility to public transportation, which we’ll get to it in just moment. Now, for a customer base, uh, the most obvious example would be a large office building, since the employees could theoretically go shopping after work or during their lunch hour, right? Uh, another really good example is a convention center, which typically has a hotel and large meeting spaces to draw visitors to the city for major business conferences and events. Um, but ideally, the pedestrian mall would be used by local residents, not just people work in the city or visiting the area, so that’s where access to public transportation comes in. Either the designers plan to locate the mall near a central transportation hub, like a bus terminal or a major train or subway station, or they work with city officials to create sufficientparking areas not too far from the mall, which make sense because if people can’t drive into the mall area, well, then they need to have easy access to it. OK, so that’s location. But what about design? Well, design doesn’t necessarily include things like sculptures or decorative walkways or even eye-catching window displays, you know, art, although I’d be the first to admit those things are aesthetically appealing. However, visually pleasing sights, well, they are not a part of the pedestrian mall design that matter the most. The key consideration is a compact and convenientlayout, um, one which allows pedestrians to walk from one end of the mall to the other in just a few minutes, so they can get to the major stores, restaurants and other central places without having to take more than one or two turns. Now this takes careful and creative planning. But, now, what if one ingredient to this planning recipe is missing? There could quite possibly be long-lasting effects. And, uh, I think a good example is the pedestrian mall in Louisville, Kentucky, for instance. Now when the Louisville mall was built, it had lots of visualappeal. It was attractively designed, right in a small part of downtown, and it pretty much possessed all of the other design elements for success. But, uh, now here is my point about location comes into play. There wasn’t a convention center around to help drawing visitors and, uh, the only nearby hotel eventually closed down for that same reason. Well, you can imagine how this must affected local pedestrian mall business owners, sort of what we called a “chainreaction”. It wasn’t until a convention center and a parking garage were built about a decade later that the mall started to be successful.
Question 20 of 45
What are two aspects of location that need to be considered when planning a pedestrian mall? Click on 2 answers
Question 21 of 45
Why does the professor explain the design of a pedestrian mall?
Question 22 of 45
Why does the professor mention the Louisville, Kentucky pedestrian mall?
Question 23 of 45
What does the professor mean when she says this? …
Question 24 of 45
What is the class mainly discussing?
Narrator: Listen to part of a lecture in an ecology class. Female Professor: So, um, continuing our discussion of ecological systems, whole systems, the main thing to keep in mind here is the inter-relationships. The species in the system, um, and even the landscape itself, they are inter-dependent. Let’s take what you’ve read for this week and see if we can apply this inter-dependence idea. Mike? Male student: Well, um, how about beavers? Ecosystems with beavers in waterways. Professor: Good! Good, go on. Male student: Like, well, you can see how it’s so important because if you go back before Europeans settled the North America, like, before the 1600s back when Native Americans were the only people living here. Well, back then there were a lot of beavers. But later on, after Europeans… Professor: OK, wait. I see where you’re heading with this, but before we go into how European settlement affected the ecosystem, tell me this, what kind of environment do beavers live in? Think about what it was like before the European settlers came. We will come back where you’re headed. Female student: OK. Well, beavers live near streams and rivers and they block up the streams and rivers with, like, logs and sticks and mud. You know, they build dams that really slow down the flow of the stream, so then the water backs up and creates like a pond that floods the nearby land. Professor: And that creates wetlands. OK. Tell me more. Female student: Well, with wetlands, it’s like there’s more standing water, more still water around. And that waters are a lot cleaner than swiftly flowing water because the dirt and sediment and stuff has a chance to sink to the bottom. Professor: More important for our discussion, wetland areas support a lot more varieties of life than swiftly flowing water. For example, there are more varieties of fish, of insects, lots of frog species. And species that rely on those species start to live near the wetlands, too. Female student: Yes, like birds and mammals that eat the fish and insects. And you get trees and plants that begin to grow near standing water that can’t grow in running water. Oh, and there’s something about wetlands and groundwater, too. Professor: OK. Good! Wetlands have a big effect on groundwater, the amount of water below the surface of the land. Think of wetlands as, um, like a giantsponge. The earth soaks up a lot of this water that’s continually flooding the surface, which increases the amount of water below. So where there are wetlands, you get a lot of groundwater. And groundwater happens to be a big source of our own drinking water today. All right, so back to the beavers. What if the beavers weren’t there? Male student: You just have a regular running stream ‘cause there was no dam. So the ecosystem would be completely different. There’d be fewer wetlands. Professor: Exactly! So now let’s go back to where you were headed before, Mike. You mentioned a change that occurred after Europeans came to North America. Male student: Yeah, well, there used to be beavers all over the place, um, something like two hundred million beavers just in the continental United States. But when Europeans came, they started hunting the beavers for their fur, because beaver furs were really warm and it was really popular for making hats in Europe, so the beavers were hunted a lot, over hunted; they were almost extinct by the 1800s. So that meant fewer wetlands, less standing water. Professor: And what does that mean for the ecosystem? Kate? Female student: Well if there’s less standing water then the ecosystem can’t support as many species, because a lot of the insects and fish and frogs can’t live in running water and then the birds and animals that eat them lose their food supply. Professor: Precisely! So the beaver in this ecosystem is what we called a keystone species. The term keystone kind of explains itself. In architecture, a keystone in an archway or doorway is the stone that holds the whole thing together and keeps it from collapsing. Well, that’s what a keystone species does in an ecosystem. It’s the crucialspecies that keeps the system going. Now, beaver populations are on the rise again, but there’s something to think about. Consider humans as part of these ecosystems. You’ve probably heard about water shortages or restrictions on how much water you can use, especially in the summer time in recent years. And remember what I said about groundwater, imagine if we still had all those beavers around, all those wetlands, what would our water supply be like then?
Question 25 of 45
Why does the professor interrupt the student when he first mentions European settlement in North America?
Question 26 of 45
What does the professor say about still water and swiftly flowing water?
Question 27 of 45
According to the professor, what was the impact of the extensive hunting of beavers in North America?
Question 28 of 45
Why does the professor say this: …
Question 29 of 45
What does the professor imply when she says this: …
Question 30 of 45
1. What are the speakers mainly discussing?
Narrator: Listen to a conversation between a student and the language lab manager. Student: Hi, I’m not sure, but, um, is this the Carter language lab? Language Lab Manager: Yes, it is. How can I help you? Student: I’m taking first year Spanish this semester. Our professor says we need to come here to view a series of videos. I think it’s called “Spanish Working On Your Accent”? Language Lab Manager: Yes, we have that. Um, they are on the wall behind you. Student: OK, so I can just take, can I take the whole series home? I think there are three of them. Language Lab Manager: I guess you haven’t been here before. Student: No, no, I haven’t. Language Lab Manager: OK, well, you have to watch the videos here. You need to sign in to reserve an open room, and sign out the video you need. Just start with the first one in the series. Each video is half-an-hour long. Student: So it’s a video library, basically? Language Lab Manager: Yes, but unlike the library, you can’t take any videos out of the lab. Student: OK, so how long can I use a video room for? Language Lab Manager: You can sign out for two hours at a time. Student: Oh, good. So I can watch more than one video when I come up here. Is the lab pretty busy all the time? Language Lab Manager: Well, rooms are usually full right after dinner time. Um, but you can sign up the day before to reserve a room if you want. Student: The day before, but I can just stop in, too, to see if there’s any room open, right? Language Lab Manager: Sure, stop in anytime. Student: Umm, what about copies of the videos? Is there just one copy of each in the series? I don’t want to miss out if everyone comes in at once. Language Lab Manager: Oh, no. We have several copies of each tape in the Spanish accentseries. We usually have multiple copies of everything for each video collection. Student: Super! So how many rooms are there total in the lab? Language Lab Manager: Twenty. They are pretty small, so we normally get one person or no more than a small group of people in there watching a video together. Actually, someone else from your class just came in and took the first Spanish video in to watch. You could probably run in there and watch it with him. Of course, you’re welcome to have you own room, but sometimes students like to watch with their classmates so they can review the material with each other afterwards. For example, if there was some content they didn’t really understand. Student: I guess I prefer my own room. I concentrate better by myself. And I don’t want to miss anything, and he’s probably already started watching it. Language Lab Manager: No problem. We’ve got a lot of rooms open right now. When you come in, you sign your name on the list and assigned a room number. Or if you call in advance, the attendant will tell you your room number. If you forget, just come in and take a look at the list. The videos are over there. Student: Great! Thanks.
Question 31 of 45
How is the language lab different form the library?
Question 32 of 45
When can students reserve a room in the language lab? Click on 2 answers.
Question 33 of 45
What will the student probably do next?
Question 34 of 45
Listen again to part of the conversation. Then answer the question. What does the woman imply?
Question 35 of 45
What is the main purpose of the lecture?
Narrator: Listen to part of a lecture in a poetry class. The professor is discussing medievalpoetry. professor: OK. So the two poems we are looking at today fall into the category of medieval times, which was how long ago? Female student: Almost a thousand years ago, right? Professor: Yes, that’s right. Female student: But, professor, are you sure these were poems? I mean, I thought poems were shorter. These were more like long stories. I mean, one of them was all about love but the other one that chan… whatever it’s called, the other one, it was all about fighting and battles. I mean, can both of them be considered poems? Professor: Well, think back to the very beginning of this course. Female student: Uh huh? Professor: Remember how we, uh, we definepoetry? In the very broadest sense, um, we said, it’s written to evoke, uh, that to make you, the audience, have some kind of emotional experience through the use of imagery. Uh, some kind of predictable rhythm and usually but not always there’s more than one meaning implied with the words that are used. Let’s start with the chanson poetry first. That’s chanson. Chanson poems became popular in Europe, particularly in France. And the term is actually short for a longer French phrase that translates to, uh, songs of deeds. And now they were called songs of deeds because, strangely enough, they were written to describe the heroic deeds or actions of warriors, the knights during conflicts. We don’t know a lot about the authors. Um, it’s still contested somewhat, but we’re pretty sure about who the chanson poems were written for. Um, that is, they were written for knights and the lords, uh, the nobilities that they served. The poems were sung, uh, performed by a minstrel, a singer who traveled from castle to castle, uh, singing to the local lord and his knights. Um, well, uh, would someone summarize the main features of the chanson poem you read? Male student: Well, there’s a hero, a knight, who goes to battle and he’s admired by his courage, bravery and loyalty, loyalty to the lord he serves, his country and his fellow warriors. In the field, he’s, uh, he has, uh, he’s a skilled fighter warring the most extreme danger; um, sacrificial, willing to sacrifice anything and everything to protect his king and country. Professor: OK, now, given that the intended audience for these poems were knights and lords, what can we say about the purpose of chanson poetry? What kinds of feelings was it meant to provoke? Female student: I guess they must have been really appealing to those knights and lords who were listening to them, hearing the songs probably made them feel more patriotic, made them feel it was like a good and noble thing to serve their countries in whatever way they could. Professor: Good! Uh, we’ve got a pretty good picture of what the chanson hero was like. Now, let’s compare that to the hero in the other poem. The other poem is an example of what’s called romance poetry. And the hero in the romance poem was also a knight. But what made the knight in romance poetry different from the knight in chanson poetry? Well, first, the purpose of the hero’s action was different. Uh, the hero in romance poetry is independent, purely solitary in a way, not like the chanson poet who was always surrounded by his fighting companions. Um, he doesn’t engage in conflict to protect his lord or country. He does it for the sake of adventure, to improve himself, to show he’s worthy of respect and love from his lady. He’s very conscious of the particular rules of social behaviors he has to live up to somehow. And all of his actions are for the purpose of proving that he is, uh, an upright, moral, well-mannered, well-behaved individual. You may have noticed that in chanson poetry, there isn’t much about the hero’s feelings. Uh, the focus is on the actions, the deeds. Uh, but the romance poetry describes a lot of the inner feelings, the, uh, motivations, psychology, you could say, of a knight trying to improve himself, to better himself so that he’s worthy of the love of a woman. What explains this difference? Well, digging into the historical context tells us a lot. Um, romance poetry emerged a few generations after chanson. And its roots were in geographic regions of France that were calmer, where conflict wasn’t central to people’s lives. Uh, more peaceful times meant there was more time for education, uh, travel, more time for reflection. Another name for romance poetry that’s often synonymous with it is troubadour poetry. Troubadours were the authors of these new romance poems. And we know a lot more about the troubadours than we do about the chanson authors because they often had small biographical sketches added to their poems. That gave prettyspecific information about their social status, uh, geographical location and a small outline of their career. This information wasn’t particularly reliable because they were sometimes based on fictitious stories of great adventure or scrapped together from parts of different poems, but there is enough there to squeeze, or, uh, infer some facts about their social class. The politicalclimate had settled down enough so that, um, troubadours had the luxury of being able to spend most, if not all of their time, creating, uh, crafting, or composing their love songs for their audiences. And, yes, these poems were also sung, many troubadours were able to make a living being full-time poets, which should tell you something about the value of that profession during medieval times.
Question 36 of 45
According to the professor, who was the intended audience for chanson poetry? Click on 2 answers.
Question 37 of 45
Why does the professor mention that romance poems often included biographical sketches?
Question 38 of 45
What does the professor say about the political climate during the time troubadours were writing poetry?
Question 39 of 45
Why does the professor say this: …
Question 40 of 45
What is the main topic of the lecture?
Narrator: Listen to part of a lecture in an Astronomy class.
professor: OK. I want to go over the different types of meteorites and what we’ve learned about them from the formation of earth and the solar system. Uh, the thing is, what’s especially interesting about meteorites is that they come from interplanetary space, but they consist of the same chemical elements that are in matter originating on earth, just in different proportions. But that makes it easier to identify something as a meteorite as opposed to just a terrestrial rock. So to talk about where meteorites come from, we need to talk about comets and asteroids, which basically, they are basically made up of debris left over from the origin of the solar system 4.6 billion years ago. Now I’m going a little out of order here, um. I’m not going to go into any depth on comets and asteroids now, but we will come back later and do that. For now, I’ll just cover some basic info about them. OK, comets and asteroids, it might help if you think of, remember we talked about the two classes of planets in our solar system? And how they differ in composition? The terrestrial planets like Mars and Earth, composed largely of rocks and metals? And the large gas giants like Jupiter? Well, the solar system also has two analogous classes of objects smaller than planets, namely asteroids and comets, relatively near the Sun, in the innersolar system between Jupiter and Mars to be precise. We’ve got the asteroidbelt, which contains about 90 percent of all asteroids orbiting the Sun.These asteroids are, uh, like the terrestrial planets in that they are composed mostly of rockymaterial and metals. Far from the Sun, in the outer solar system, beyond Jupiter’s orbit, temperatures are low enough to permit ices to form out of water and, and out of gases like, uh, methane and carbondioxide. Loose collections of these ices and small rocky particles form into comets. So comets are similar in composition to the gas giants. Both comets and asteroids are, typically are smaller than planets. And even smaller type of interplanetarydebris is the meteoroid. And it’s from the meteoroids that we get meteors and meteorites. Roids are, for the most part anyway, they’re just smaller bits of asteroids and comets. When these bits enter earth’s atmosphere, well, that makes them so special that they get a special name: they’re called meteors. Most of them are very small and they burn up soon after entering earth’s atmosphere. The larger ones that make it through the atmosphere and hit the ground are called meteorites. So meteorites are the ones that actually make it through. Now, we’ve been finding meteorites on earth for thousands of years. And we’ve analyzed enough of them to learn a lot about their composition, most come from asteroids, though a few may have come from comets. So, essentially, they are rocks. And like rocks, they are mixtures of minerals. They are generally classified into three broad categories: stones, stony irons and irons. Stone meteorites, which we refer to simply as, uh, stones, are almost entirely rock material. They actually account for almost all of the meteoritematerial that falls to earth. But even so, it’s rare to ever find one. I mean, it’s easier to find an iron meteorite or stony iron. Any one guess why? Look at their names. What do you think iron meteorites consist of? Female student: Mostly iron? Professor: Yeah! Iron and some nickel, both of which are metals. And if you’re trying to find metal? Student: Oh, metal detectors! Professor: Right! Thank you! At least that’s part of it. Stone meteorites, if they lie around exposed to the weather for a few years, well, they’re made of rock, so they end up looking almost indistinguishable from commonterrestrial rocks, ones that originated on earth. So it’s hard to spot them by eye. But we can use metal detectors to help us find the others. And they are easier to spot by eye. So most of the meteorites in collections, uh, in museums, they’ll be, they are iron meteorites, or the stony iron kind, even though they only make up about 5 percent of the meteoritematerial on the ground.
Question 41 of 45
What comparison does the professor make to help describe the composition of asteroids and comets?
Question 42 of 45
What does the professor say about the origin of meteors and meteorites?
Question 43 of 45
According to the professor, what feature of a meteoroid generally determines whether the meteoroid becomes a meteorite?
Question 44 of 45
What are two points the professor makes about stone meteorites? Click on 2 answers.