Asteroids and comets that repeatedly smashed into the early Earth covered the planet ’s surfacewith molten rock during its earliest days, but still may have left oases of water that could havesupported the evolution of life, scientists say. The new study reveals that during the planet ’sinfancy, the surface of the Earth was a hellish environment, but perhaps not as hellish as oftenthought, scientists added. 

Earth formed about 4.5 billion years ago. The first 500 million years of its life are known as theHadean Eon. Although this time amounts to more than 10 percent of Earth’s history, little isknown about it, since few rocks are known that are older than 3.8 billion years old. 

For much of the Hadean, Earth and its sister worlds in the inner solar system were pummeled withan extraordinary number of cosmic impacts. “It was thought that because of these asteroids andcomets flying around colliding with Earth, conditions on early Earth may have been hellish, ” saidlead study author Simone Marchi, a planetary scientist at the Southwest Research Institute inBoulder, Colorado. This imagined hellishness gave the eon its name —Hadean comes fromHades, the lord of the underworld in Greek mythology. 

However, in the past dozen years or so, a radically different picture of the Hadean began toemerge. Analysis of minerals trapped within microscopiczircon crystals dating from this econ“suggested that there was liquid water on the surface of the Earth back then, clashing with theprevious picture that the Hadean was hellish,” Marchi said. This could explain why the evidenceof the earliest life on Earth appears during the Hadean —maybe the planet was less inhospitableduring that eon than previously thought. 

The exact timing and magnitude of the impacts that smashed Earth during the Hadean areunknown. To get an idea of the effects of this bombardment, Machi and his colleagues looked atthe moon, whose heavily cratered surface helped model the battering that its close neighbor Earthmust have experienced back then. 

“We also looked at highly siderophile elements (elements that bind tightly to iron), such as gold,delivered to Earth as a result of these early collisions, and the amounts of these elements tells usthe total mass accreted by Earth as the results of these collisions,”Marchi said. Prior researchsuggests these impacts probably contributed less than 0.5 percent of the Earth’s present-day mass.The researchers discovered that “the surface of the Earth during the Hadean was heavily affectedby very large collisions, by impactors [ ?m'p?kt?] larger than 100 kilometers (60 miles) or so —really, really big impactors, ’ Marci said. “When Earth has a collision with an object that big, thatmelts a large volume of the Earth’s crust and mantle, covering a large fraction of the surface,”Marchi added. These findings suggest that Earth ’s surface was buried over and over again by largevolumes of molten rock —enough to cover the surface of the Earth several times. This helpsexplain why so few rock survive from the Hadean, the researchers said. 

Why is little known about the Earth ’s first 500 million years?

Write a composition in no less than 150 words on the topic: What Do You Think of Advanced Artificial Intelligence. Read the following words in English. You should write according to the outline given below. Write your composition on the ANSWER SHEET.

1. Google’s DeepMind Alpha Go program has beaten all the world champions of the game Go in a series of battles between man and artificial intelligence.

2. Some people fear advanced artificial intelligence because?

3. Your attitude towards advanced artificial intelligence.

为了找到实验室试验的替代实验，经济学家会密切关注由历史提供的自然实验。例如，当中东的一次战争中断了原油供应时， 油价在全球范围内狂涨。对于石油及石油产品的消费者来说，这样的一次事件会降低生活水平。对于经济决策者来说，它给他们出了一道难题，即如何做出最佳应对。但对于经济学家来说，它为研究重要自然资源对世界经济的影响提供了一次机会，且这种机会在战时的油价飞涨结束很久依然存在。因此，整本书中，我们会分析很多历史事件。这些历史事件值得研究，因为，它们让我们对旧时的经济有所了解，更重要的是，因为它们使我们能够说明和评价当今的经济理论。

(4)__________________________________

(2)__________________________________

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What does the author mean by “while the tinsel is hot (Line 2, Para. 6)?

Economics is no different. Supply, demand, elasticity, comparative advantage, consumer surplus,deadweight loss--these terms are part of the economist ’s language. In the coming chapters, youwill encounter many new terms and some familiar words that economists use in specialized ways.(1)At first, this new language may seem needlessly arcane. But, as you will see, its value lies in itsability to provide you a new and useful way of thinking about the world in which you live. 

Economists try to address their subject with a scientist ’s objectivity. They approach the studyof the economy in much the same way as a physicist approaches the study of matter and abiologist approaches the study of life: (2)They devise theories, collect data, and then analyze thesedata in an attempt to verify or refute their theories. 

To beginners, it can seem odd to claim that economics is a science. After all, economists donot work with test tubes or telescopes. (3)The essence of science, however, is the scientificmethods--the dispassionate development and testing of theories about how the world works. 

This method of inquiry is as applicable to studying a nation ’s economy as it is to studying thearth’s gravity or a species ’ evolution. (4)As Albert Einstein once put it, “The whole ofnothing more than the refinement of everyday thinking. ” (225words) 

(1)__________________________________

In a thank-you note, “The book will be my good companion when I am alone”serves as________.

According to Ms. Demeanor, showing appreciation has the benefit of ________.

Of all the people on my holiday shopping list, there was one little boy for whom buying a gift hadbecome increasingly difficult. He ’s a wonderful child, adorable and loving, and he ’s not firritable or spoiled. Though he lives across the country from me, I receive regular updates andphotos, and he likes all the things that the boys his age want to play with. Shopping for him shouldbe easy, but I find it hard to summon up any enthusiasm, because in all the years I ’ve givpresents, he never once sent me a thank-you note. 

“Sending thank-you notes is becoming a lost art, ” mourns Mary Mitchell, a syndicated columnistknown as “Ms. Demeanor”and author of six etiquette books. In her view, each generation,compared with the one before, is losing a sense of consideration for other people. “Withoutrespect, ” she says, “you have conflict. ” 

Ms. Demeanor would be proud of me: I have figured out a way to ensure that my children alwayssend thank-you notes. And such a gesture is important, says Ms. Demeanor, because “a gratefulattitude is a tremendous life skill, an efficient and inexpensive way to set ourselves apart in thework force and in our adult lives. Teach your children that the habit of manners comes frominside ― it ’s an attitude based on respecting other people. ”