【文章內(nèi)容簡介】 el predicts. But this would mean that it had lost mass over the course of four billion years. Student Is that possible? Professor Actually, the Sun is constantly losing mass through the solar wind, a stream of charged particles constantly blowing off the Sun. we know the Sun’s current rate of mass loss, but if we assume that this rate has been steady over the last four billion years, the young Sun wouldn’t have been massive enough to have warmed Earth, let alone Mars, not enough to have caused liquid water. Student Maybe the solar wind was stronger then? Professor There is evidence that the solar wind was more intense in the past. But we don’t know for sure how much mass our Sun’s lost over the last four billion years. Astronomers tried to estimate what solar mass could produce the required luminosity to explain liquid water on these plas. They also took into account that 《新托福突破口 TPO22 聽力原文》 無老師網(wǎng)站 無老師微博 ： 6 with a more massive young Sun, the plas would be closer to the Sun than they are today. And they found that about seven percent more mass would be required. Student So the young Sun had seven percent more mass than our Sun? Professor Well, we don’t know. According to observations of young Sun like stars, our Sun may have lost as much as six percent of its initial mass, which doesn’t quite make it. On the other hand, this estimate is based on a small sample. And the brightyoungSun solution is appealing. We simply need more data to determine the mass loss rate of stars. So there’s reason to believe that we will get an answer to that piece of the puzzle one day. Conversation 2 (Professor) Narrator Listen to part of a conversation between a student and his music history professor. Student So, I was wondering what I could do to improve my paper before the final draft is due. Professor Well, Michael, I have no problem with your writing style. It’s graceful and clear. Eh, and it’s interesting that you are writing about your grandmother’s piano concert. Student Yeah, when you said we had to attend a concert and write about it, I immediately thought of her. I have been to lots of her concerts. So I am really familiar with her music. Professor That’s not necessarily an advantage. Familiarity sometimes makes it hard to see things objectively. Student So I shouldn’t write about my grandmother? Professor No, no, no. I am just talking in general. But as I mentioned in my ments, I’d like you to place your grandmother’s concert in… in a broader context. Student Yeah, I saw that, but I wasn’t sure what you meant. I mean, I mentioned my grandmother’s childhood, how much her parents love music, how she played the piano at all our family gatherings. Professor 《新托福突破口 TPO22 聽力原文》 無老師網(wǎng)站 無老師微博 ： 7 Ok. I see what happened now. By broader context, I mean how the concert relates to some period in music history. Student I see. Ok. Um… I have an idea. Professor Ok. Student Well, as you read in my paper, my grandmother performs classical music. Professor Yes. Student That’s her true love. But for most of her career, she performed jazz. She originally studied to be a classical pianist. But jazz was in its heyday back then, and when she got out of the conservatory, she was invited to join a jazz orchestra. And the opportunity was just too good to turn down. Professor Really. Well, that’s fascinating. Because she probably had to reinvent her whole musical style. Student She did. But jazz was where the money was at that time, at least for her. Professor But she eventually went back to classical? Student Right. But only recently. Professor Ok. Student So if I can show how her choices relate to what was happening in the world of music at the time…? Professor I think that might work very nicely. Student And if I do that, I guess I’ll have to like, interview her. Professor 《新托福突破口 TPO22 聽力原文》 無老師網(wǎng)站 無老師微博 ： 8 Right. Student And I guess that would mean… Professor You’ll have to rewrite most of your paper. Student Ouch! Professor Yeah. Would an extra week ease the pain? Student Definitely. Professor Ok. So are there other musicians in your family? Student Yeah. My mother plays piano, too. Not as well as my grandmother, but… Professor And you? Student I don’t play any instruments, but I sing in the university choir. In fact, we are performing next week, and I have a solo. Professor That’s great! Could I tell the class about your concert? Student Um…sure. But…about my paper… what question should I be asking my grandmother? Professor