Faint Young Sun Paradox托福聽力原文翻譯及問題答案

Faint Young Sun Paradox托福聽力原文翻譯及問題答案

一、Faint Young Sun Paradox托福聽力原文：

NARRATOR:Listen to part of a lecture in an astronomy class.

MALE PROFESSOR:Today I want to talk about a paradox that ties in with the topic we discussed last time. We were discussing the geological evidence of water—liquid water—on Earth and Mars three to four billion years ago.So what evidence of a liquid water environment did we find in rock samples taken from the oldest rocks on Earth?

MALE STUDENT:Uh,like pebbles?fossilized algae?MALE PROFESSOR:Right.And on Mars?FEMALE STUDENT:Dry channels?MALE PROFESSOR:Good...all evidence of water in liquid form—large quantities of it.Now remember when we talked about star formation,we said that as a star ages,it becomes brighter.Right? Hydrogen turns into helium,which releases energy.So our standard model of star formation suggests that the Sun wasn't nearly as bright three to four billion years ago as it is today,which means that temperatures on Earth and Mars would have been lower...which,in turn,suggests??

MALE STUDENT:There would have been ice on Earth or Mars...?

MALE PROFESSOR:Correct...if the young Sun was much fainter and cooler than the Sun today,liquid water couldn't have existed on either planet.Now,this apparent contradiction between geologic evidence and the stellar evolution model became known as"the faint young Sun paradox."Now,there have been several attempts to solve this paradox.

First there was the greenhouse-gas solution. Well,you're probably familiar with the greenhouse gas effect,so I won't go into details now. The idea was that trapped greenhouse gases in the atmospheres of Earth and Mars might have caused temperatures to rise enough to compensate for the low heat the young Sun provided.And so it would have been warm enough on these planets for liquid water to exist.So what gas do you think was the first suspect in causing the greenhouse effect?

FEMALE STUDENT:Um,carbon dioxide,I guess...like today?MALE PROFESSOR:In fact,studies indicate that four billion years ago,carbon dioxide levels in the atmosphere were much higher than today's levels.But the studies also indicate that they weren't high enough to do the job—take up for a faint Sun.Well,

then,some astronomers came up with the idea that atmospheric ammonia may have acted as a greenhouse gas, but ammonia would have been destroyed by the ultraviolet light coming from the Sun,and it had to be ruled out,too.

Another solution,mm,which was proposed much later,was that perhaps the young Sun wasn't faint at all.Perhaps it was bright. So it's called the"bright young Sun"solution,according to which the Sun would have provided enough heat for the water on Earth and Mars to be liquid..But how could the early Sun be brighter and hotter than predicted by the standard model? Well,he answer is"mass."

MALE STUDENT:You mean the Sun had more mass when it was young?MALE PROFESSOR:Well,if the young Sun was more massive than today's,it would have been hotter and brighter than the model predicts. But this would mean that it has lost mass over the course of four billion years.

FEMALE STUDENT:Is that possible?MALE 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.MALE STUDENT:Maybe the solar wind was stronger then?MALE 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 planets.They also took into account that with a more massive young Sun,the planets would be closer to the Sun than they are today.And they found that about seven percent more mass would be required.

FEMALE STUDENT:So the young Sun had seven percent more mass than our Sun?MALE 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"bright young Sun"solution is appealing.We simply need more data to determine the mass-loss rate of stars.So there's reason to believe that we'll get an answer to that piece of the puzzle one day.

二、Faint Young Sun Paradox托福聽力中文翻譯：

旁白：在天文學(xué)課上聽一節(jié)課的一部分。

男教授：今天我想談?wù)勔粋€(gè)與我們上次討論的話題相關(guān)的悖論；我們討論了三四十億年前地球和火星上存在水-液態(tài)水的地質(zhì)證據(jù)。那么，我們從地球上最古老的巖石樣本中發(fā)現(xiàn)了什么液態(tài)水環(huán)境的證據(jù)呢？

男學(xué)生：呃，像鵝卵石？藻類化石？男教授：對(duì)。在火星上呢？女生：干渠？男教授：好。。。所有液態(tài)水的跡象都會(huì)形成大量的液態(tài)水?，F(xiàn)在請(qǐng)記住，當(dāng)我們談到恒星形成時(shí)，我們說過，隨著恒星年齡的增長(zhǎng)，它會(huì)變得更亮。對(duì)吧；氫變成氦，釋放能量。因此，我們的恒星形成的標(biāo)準(zhǔn)模型表明，太陽在三十億到四十億年前還沒有今天那么明亮，這意味著地球和火星的溫度會(huì)更低。。。這反過來又表明？？

男學(xué)生：地球或火星上會(huì)有冰。。。？

男教授：對(duì)。。。如果年輕的太陽比今天的太陽暗得多、冷得多，那么這兩顆行星上都不可能存在液態(tài)水?，F(xiàn)在，地質(zhì)證據(jù)和恒星演化模型之間的這種明顯矛盾被稱為“微弱的年輕太陽悖論”現(xiàn)在，有人試圖解決這一矛盾。

首先是溫室氣體解決方案&nbsp；嗯，你可能對(duì)溫室氣體效應(yīng)很熟悉，所以我現(xiàn)在就不詳細(xì)介紹了；當(dāng)時(shí)的想法是，地球和火星大氣層中的溫室氣體可能導(dǎo)致溫度上升，足以補(bǔ)償年輕太陽提供的低熱。因此，這些行星上的溫度足以讓液態(tài)水存在。那么你認(rèn)為引起溫室效應(yīng)的第一個(gè)嫌疑是什么氣體呢？

女生：嗯，二氧化碳，我想。。。比如今天？男教授：事實(shí)上，研究表明，40億年前，大氣中的二氧化碳含量遠(yuǎn)遠(yuǎn)高于今天的水平。但研究還表明，它們的高度不足以在昏暗的太陽下完成這項(xiàng)工作。好

然后，一些天文學(xué)家提出了大氣氨可能是溫室氣體的想法；但是氨會(huì)被太陽發(fā)出的紫外線所破壞，因此也必須排除這種可能性。

另一個(gè)解決方案，mm，是在很久以后提出的，可能是年輕的太陽一點(diǎn)也不暗淡。也許它是明亮的&nbsp；因此，它被稱為“明亮的年輕太陽”解決方案，根據(jù)該解決方案，太陽將為地球和火星上的水提供足夠的熱量，使其成為液體。。但是，早期的太陽怎么可能比標(biāo)準(zhǔn)模型預(yù)測(cè)的更明亮、更熱呢；嗯，他的答案是“質(zhì)量”

男學(xué)生：你是說太陽年輕時(shí)質(zhì)量更大？男教授：嗯，如果年輕的太陽比今天的質(zhì)量更大，它會(huì)比模型預(yù)測(cè)的更熱、更亮；但這意味著它在40億年的時(shí)間里失去了質(zhì)量。

女生：可能嗎？男教授：事實(shí)上，太陽通過太陽風(fēng)不斷失去質(zhì)量？一股帶電粒子流不斷地從太陽上吹走。我們知道太陽目前的質(zhì)量損失率嗎？但是，如果我們假設(shè)這一速度在過去40億年中保持穩(wěn)定，那么年輕的太陽就不會(huì)有足夠的質(zhì)量來加熱地球，更不用說火星了，也不足以產(chǎn)生液態(tài)水。男學(xué)生：也許當(dāng)時(shí)太陽風(fēng)更強(qiáng)？男教授：有證據(jù)表明，過去太陽風(fēng)更強(qiáng)烈；但我們不確定太陽在過去40億年中損失了多少質(zhì)量。天文學(xué)家試圖估計(jì)太陽質(zhì)量能產(chǎn)生所需的光度來解釋這些行星上的液態(tài)水。他們還考慮到，如果年輕的太陽質(zhì)量更大，那么這些行星將比現(xiàn)在離太陽更近。他們發(fā)現(xiàn)需要增加大約7%的質(zhì)量。

女學(xué)生：那么年輕的太陽的質(zhì)量比我們的太陽多7%？男教授：嗯，我們不知道；根據(jù)對(duì)年輕的類太陽恒星的觀察，我們的太陽可能已經(jīng)失去了其初始質(zhì)量的6%，但這并不能使其完全恢復(fù)；另一方面，這一估計(jì)是基于一個(gè)小樣本，而“年輕明亮的太陽”解決方案很有吸引力。我們只需要更多的數(shù)據(jù)來確定恒星的質(zhì)量損失率。所以我們有理由相信，總有一天我們會(huì)找到這個(gè)謎題的答案。

三、Faint Young Sun Paradox托福聽力問題：

Q1:1.What is the main propose of the lecture?

A.To compare solutions to the greenhouse-gas problem

B.To examine methods used to study star formation in other solar systems

C.To discuss evidence for liquid water on young Earth and Mars

D.To discuss attempts to solve a puzzle related to the Sun

Q2:2.Why is geological evidence of liquid water on Earth and Mars three to four billion years ago problematic?

A.It suggests that the solar system is younger than it could possibly be.

B.It suggests that the young Sun was less bright than it is today.

C.It challenges the prevailing model of star formation.

D.It contradicts theories about the beginning of the universe.

Q3:3.Why did the greenhouse-gas solution fail to explain the early presence of liquid water on Earth and Mars?[Click on 2 answers.]

A.The types of gases that were present in their atmospheres could not have caused temperatures to rise.

B.There was insufficient carbon dioxide in their atmospheres to produce a greenhouse effect.

C.Solar radiation would have destroyed the ammonia in their atmospheres.

D.Clouds of ammonia would have lowered temperatures by blocking out sunlight.

Q4:4.Why does the professor mention the solar wind?

A.To explain a way the Sun is losing mass

B.To point out that it was less intense billions of years ago

C.To suggest a reason for early climate differences between Earth and Mars

D.To explain the importance of solving the faint-young-Sun paradox

Q5:5.What factor did astronomers consider when calculating the required solar mass for liquid water to exist on Earth and Mars?

A.The young Sun lost mass at a slower rate than it currently does.

B.The young Sun was closer to the planets than it currently is.

C.The young Sun had less solar wind activity than it currently does.

D.The young Sun comprised greater amounts of helium than it currently does.

Q6:6.What is the professor's attitude about the bright-young-Sun solution?

A.He is surprised that it is not more widely accepted.

B.He feels that it raises too many unanswerable questions.

C.He is confident that future research will determine whether it is true.

D.He expects that other possible solutions to the paradox will be proposed.

四、Faint Young Sun Paradox托福聽力答案：

A1:正確答案：D

A2:正確答案：C

A3:正確答案：BC

A4:正確答案：A

A5:正確答案：B

A6:正確答案：C

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