自然科学
◆天文学
Passage 1
The bright star we call Sirius is really a binary star—a gigantic white star known as Sirius A and a far smaller dwarf called Sirius B. Sirius A is truly massive—about twice the size of our sun and around 25 times more luminous.
Seen with the naked eye, the two stars coalesce into a single bright object in the nighttime sky. Sirius’s existence was recorded by the ancient Egyptians, who used its initial date of visibility—the date at which the earth’s rotation moves it far enough from the glare of our sun to be clearly seen—as the basis for their calendar. Its extreme brightness frightened the ancient Greeks, who ascribed to it evil powers. It wasn’t until 1844 that astronomer Friedrich Bessel determined that Sirius must have an invisible companion star, and in 1862, American Alvan Graham Clark finally observed the tiny Sirius B.
1. Which statement could most logically follow the final sentence in the passage?
A. The Romans liked to celebrate the setting of Sirius with a canine sacrifice.
B. We see Sirius as extraordinarily bright due to its proximity to Earth.
C. The name of the star comes from the ancient Greek word for “glowing”.
D. More recently, orbital irregularities have suggested a third, even smaller companion.
E. Sirius is nicknamed the “Dog Star”, as it is part of the Canis Major constellation.
Consider each of the choices separately and select all that apply.
2. The passage suggests that Sirius A is unusual in which of the following qualities?
A. radiance
B. density
C. hue
「文章大意」
本文主要内容与天狼星（Sirius）相关，第一段指出天狼星实际上是双子星（binary star），由巨大的白星天狼星A和小得多的矮星天狼星B构成。第二段则着重则描述了古时候不同文化对于天狼星的不同认识，及天狼星被发现是双子星的过程。
答案详解
1. D 分析最后一句的主题和逻辑关系可知，它按照时间顺序讲述的是“the discovery of the invisible companion of Sirius”，因此最符合逻辑的选项因该是D项，接着前文的话题，继续讲述“a third companion”的发现。
2. A 文段第一段第二句提到了Sirius A的不同之处：“Sirius A is truly massive—about twice the size of our sun and around 25 times more luminous”，强调的是其大小和亮度，因此A项radiance（发亮度，光辉）符合题意，而B项density（密度）和C项hue（色彩）在文中均没有提及。
Passage 2
Is there intelligent life elsewhere in the Milky Way? The odds seem to favor a positive response, but scientists like numbers and proofs. For that reason, radio astronomer Frank Drake created a formula that has become fundamental for many in the field of SETI—the search for extraterrestrial intelligence.
The 1961 Drake equation begins with N = the number of intelligent civilizations, defined as those with whom we might communicate. It finds N by multiplying the rate of star formation in our galaxy, which Drake calculated as 10 per year, by the fraction of stars with planets, about one-hall. That in turn is multiplied by the number of planets per star that might be capable of sustaining life, which Drake figured as two, and by the fraction of those planets that will develop life, which he considered to be 100%. Finally, that is multiplied by the percentage of those life-bearing planets that might develop intelligent life, the percentage of that life that might be able to communicate, and the length of time during which such life might send communications into space. Drake’s figures, being 50 years old, have since been superseded by more accurate predictions.
1. Which of these premises did Drake NOT include in his calculations?
A. Not every life-form can communicate.
B. The time during which communication might occur is finite.
C. Not every planet is capable of sustaining life.
D. Not every planet is orbited by satellites.
E. Not every star is orbited by planets.
2. In the last sentence of the passage, the author probably mentions the age of Drake’s equation to
A. show how long a single hypothesis may prove valid and useful
B. indicate that some variables within the hypothesis have changed
C. suggest that intelligent life should have been found by now
D. provide a timeline to use when calculating the odds of intelligent life
E. surprise the reader with the unexpected age of a forward-looking model
3. NASA now calculates that the rate of star formation in our galaxy is closer to seven per year than to Drake’s original calculation. If that were the only change, how would it affect Drake’s equation?
A. The fraction of stars with planets would decline about 30 percent.
B. The number of planets per star capable of housing life would decline.
C. The number of intelligent civilizations would decline by 30 percent.
D. The number of planets per star capable of housing life would increase.
E. The number of intelligent civilizations would increase by 70 percent.
「文章大意」
本文主要介绍了Frank Drake用于计算外星人是否有可能存在的公式，文章最后指出该公式已存在了50年之久，从那之后就被更加精确的预测所取代。
答案详解
1. D Drake的计算中包括：“the percentage of that life that might be able to communicate”；“the length of time during which such life might send communications into space”；“the number of planets per star that might be capable of sustaining life”；“the fraction of stars with planets”，其中不包括D项，故本题选D。
2.B 最后一句话中，作者提到因为数据很陈旧了，所以需要重新计算，故B项是正确的。
3.C 最新统计，行星的形成要比Drake计算的少30%。Drake在计算中用10来计算行星的形成，所以现在要将其变为7，所以得到的总的结果要减少30%，故C项是正确的。
Passage 3
Human fascination with space began hundreds of years ago. That interest has not waned, and today, the Hubble Telescope orbits 375 miles above Earth, working non-stop to unlock the secrets of the universe. The Hubble uses state-of-the-art instruments to provide amazing views of the universe that cannot be matched by ground-based telescopes. The reason for this is that, from the ground, we look at stars and other objects in space through Earth’s atmosphere. Our atmosphere is full of clouds, dust, and pollution, which cause everything we see to shimmer and shake. This effect creates difficulty for scientists on the ground to make steady, accurate measurements of objects moving in space. With assistance from the Hubble Telescope, astronomers can pinpoint the location of faraway stars and galaxies, and measure the speeds and distances of astronomical objects with far greater precision. Astronomers may even one day tell us exactly when the universe began.
The author suggests that “steady, accurate measurements” can be difficult to attain because
A. scientists frequently introduce unnecessary complications to simple situations
B. Earth-based telescopes are insufficiently precise due to atmospheric dust and pollution
C. due to Earth’s constant rotation, it is nearly impossible to pinpoint exact distances in outer space
D. most telescopes require regular repair missions when their cameras aren’t functioning properly
E. astronomers are not yet able to tell us exactly when the universe began
「文章大意」
本文主要讲述到人们对于太空的兴趣几百年来从未消减，而围绕地球运行的Hubble Telescope使得人们可以清晰地看到太空中的景象，并且利用该望远镜宇航员也可对遥远星体和星系进行准确定位，以及更加精确地测量太空物体的速度和距离。
答案详解
B 根据文段倒数三四句，“Our atmosphere is full of clouds, dust, and pollution…This effect creates difficulty for scientists to make steady, accurate measurements of objects moving in space”可知，B项最符合题意。
Passage 4
Sending a robot into space to gather information is a viable option, but should only be regarded as that—an option. Even the most technologically advanced robots cannot and should not replace manned missions to outer space. Certainly it is cheaper and less dangerous to launch a computer probe that can gather reams of data, but often the information obtained by a machine only serves to produce more questions than it answers. Therefore, the space program should allow manned missions to follow up on those initial information-gathering robotic ventures.
While manned missions are more costly than are unmanned missions, they are also more successful. Robots and astronauts use much of the same equipment in space, but a human is more capable of calibrating those instruments correctly and placing them in appropriate and useful positions. A computer is often neither as sensitive nor as accurate as a human in managing the same terrain or environ-mental circumstances. Robots are also not as equipped as humans to solve problems as they arise, and robots often collect data that is not helpful or even desired. A human, on the other hand, can make instant decisions about what to explore further and what to ignore.
1. The passage supplies information to answer which of the following questions?
A. What is the cost of launching a computer probe into space?
B. What type of information can safely be ignored when exploring outer space?
C. How much information can a computer probe gather in outer space?
D. What is the next level in space exploration?
E. Are unmanned space missions more economical than manned space missions?
2. Select the sentence that offers potential advantages to using robots as information gatherers in space.
3. According to the passage all of the following are advantages of humans over robots EXCEPT
A. humans can more accurately manage the data collected
B. humans can apply critical thinking skills to new situations
C. humans can only calibrate instruments designed by robots
D. humans are more sensitive to environmental changes
E. humans are better at preparing instrumentation for use in space
「文章大意」
本文指出送机器人到太空中收集信息只可被作为一种备选方案，即使最先进的机器人也无法取代载人航天任务。虽然前者花费较低而且危险性相对较小，但收集到的信息只会让人们产生更多疑问，因此载人航天任务仍十分必要。接着第二段将两者进行了对比，突出载人航天任务的优势。
答案详解
1. E 根据文章第二段第一句话中“While manned missions are more costly than are unmanned missions”可知，有人操控的太空任务比无人操控的太空任务耗资更大，也就是说，无人操控的太空任务比有人操控的太空任务要节俭，经济得多，与选项E相对应。而A、B、C、D选项在文中都找不到明确答案，因此选择E。
2. Certainly it is cheaper and less dangerous to…than it answers.
题干中的关键词是“advantages”，文章中第一段第三句肯定了由机器操控收集数据的好处：“cheaper”，“less dangerous”，符合题干的要求。
3. C 此题为排除题。通读第二段不难发现，选项A、B、D、E都是人类相比机器的优势，可以在原文中找到对应，而选项C却与文章不符，文章中只提到人类比机器更“capable of calibrating those instruments correctly”，没有提及仪器是由谁设计的，因此选择C项。
Passage 5
Scientists believe that by raising atmospheric pressure and surface temperature, it is possible to transform the climate of Mars to the point where humans would be able to live there. The process by which a hostile or unsuitable environment is transformed into one that can sustain human life is called terraforming. In addition to potentially providing an alternate home for the people of Earth in the future, this undertaking may also allow scientists to test hypotheses about the process of global warming, which is a highly pertinent issue affecting our planet today.
For Question 1, consider each of the choices separately and select all that apply.
1. Which of the following can be inferred from the passage regarding the Martian atmosphere?
A. It has a lower pressure than Earth’s atmosphere.
B. It has a higher surface temperature than Earth.
C. It can most certainly be transformed to be more like Earth’s atmosphere.
For Question 2, select one answer choice.
2. The passage addresses which of the following consequences of terraforming?
A. The creation of a more hospitable planet.
B. The risk of overpopulation.
C. The elimination of suitable environments.
D. The depletion of the atmosphere.
E. The production of greenhouse gases.
「文章大意」
本文指出科学家认为通过改变大气压力和表面温度并无法使火星变得适合人类生存。改变恶劣或不稳定的环境使其适合人类生存的过程被称为terraforming，而这一过程对于人类未来和全球变暖问题的解决都会起到积极作用。
答案详解
1. A 这是一道推断题，题干中的关键词是“Martian atmosphere”。从段落中的信息可知，科学家们发现通过“raising atmospheric pressure and surface temperature”，可以改变火星上的气候环境，使其更适合人类居住。由此可知，选项A是正确的，而选项B是错误的，火星上的地表温度比地球上要低；科学家们只是表明改变火星的大气环境是可能的，并没有对此持绝对肯定态度。因此选择A项。
2. A 文中最后一句谈到了“terraforming”的结果：“providing an alternate home for the people of Earth”以及“allow scientists to test hypotheses about the process of global warming”。选项中只有A 项符合题意。