【正文】 , a cloud either contributes to the cooling of Earth39。s climate system is constantly trying to strike a balance between the cooling and warming effects iBTTPO 之家 of clouds. It39。s absorbed by Earth, and the amount that39。s radiation budget. And one way we keep track of the radiation budget is by looking at the albedo of the different surfaces on the pla. A surface39。s reflected off that surface back into space. Oceans have a low albedo, because they reflect very little energy. Most of the solar energy that reaches the ocean gets absorbed and heats the water. Um... rainforests also have low albedos. Well, by contrast, deserts and areas covered by ice and snow, these places have high albedos. And clouds, in general, cloud also have high albedos. That means that a large percentage of the solar energy clouds receive is reflected into space. OK. Now, when we say that clouds have a high albedo. We are talking about the effect of all the clouds on earth averaged together. But different types of clouds have different reflective properties, they have different albedos. Student: So which type of clouds cools Earth? And which type heat it? Professor: Well, high thin clouds contribute to heating while low thick clouds cool Earth. High thin clouds are very transparent to solar radiation, like, uh, clear air. So they mostly transmit ining solar energy down to Earth. There39。s heat. Because of the trapped heat, these clouds have an overall heating effect. Student: Oh. OK. Since low thick clouds are not transparent to radiation... Professor: Exactly. They block most of the solar energy so it never reaches Earth39。s how they contribute to cooling? Professor: Yep. And as I said earlier, this cooling effect predominates. Now, what if there was a process that could control the type of clouds that form? Student: Are you talking about controlling the weather? Professor: Well, I am not sure I would go that far. But we recently noticed an increase in cloud cover over an area of the ocean waters around Antarctica. An increased area of low thick clouds, the type that reflects a lare portion of solar energy back to space and cools the Earth. Well, the reason for this increased cloud cover, it turns out, is the exceptionally large amount of microscopic marine plants. Well, the current hypothesis is that these microanisms produce a chemical, dimetho sulfide that interacts with the oxygen in the air, creating conditions that lead to the formation of the low thick clouds we observed. Well, that39。s great. Araby, that short story by James Joyce we read last week, it was awesome. Professor: I39。s work is very plex. A lot of students say that he is hard to understand. Normally, you wouldn39。d like to give my first year students a taste of his style, his psychological approach to literature, because ? mainly because it influenced other writers. I only wish we had more class time to discuss it. Bob: Me too. So why did you pick Araby instead of some other story? Professor: Well, um, first you should know that Araby is one of fifteen short stories by Joyce in a book called Dubliners. Uh, all the stories are related to one another, and they are set in the same time period. But Araby is the easiest one to follow. Though all the stories in the collection are written in stream of consciousness, which as you know, means they are told through the narrator39。s linear, the story unfold chronologically. Bob: Still, I wish we could read whole novels by Joyce and discussed them in class. Professor: That39。s such a privilege, spending an entire term diving into a single body of work. And my students, they bring so much insight to the table that it39。ve got room for one more course, and I39。m sorry. I should have mentioned. Uh, Master Writer is an advanced seminar. So students need to get a strong foundation in literary theory and criticism before I let them in the room. Bob: But I have gotten really good grades on all my paper so far, I39。t you make an exception? Professor: Your grades are excellent. But in our intro class, you are reviewing the basics, like plots, setting and character and getting your first real exposure to different literary styles. Bob: But why do I have to study different styles to understand Joyce39。s doctor Clain39。s more focused than the class you39。m sure you39。s not as easy as it might seem. You see, the denser the medium, the faster sound travels. So sound travels faster through water than it does through air. So what happens when a so