Module 3 Journey to space 知识点题库

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    We know the earth is a planet．There are seven other planets，and they go  1 the sun together．The eight planets and the sun are2 the solar system．The first planet，3   the sun，is Mercury(水星)．It is 58 miIlion  4  from the sun．Venus(金星)is the second planetfrom the sun，and  5 planet，the earth，is the third．It is from the sun,and 55  planet,the earth,is the third.It is 2,650 million kilometres from the sun．

    Jupiter(木星)，Saturn(土星)，Neptune(海王星)and Uranus(天王星)are all 6 than the earth，7 Venus，Mars and Mercury are smaller than the earth．

    Animals，trees and humans can only 8  on the earth，because the other planets in our solar system don't  9  air or water．Do any  10planets in   solar systems have life?We don't know about it．

—Well, we__________ yet.

    Is there intelligent（有智力的）life on other planets? For years, scientists said "no." or "we don't know." But today this is changing. Seth Shostak and Alexandra Barnett are astronomers（天文学家）. They believe intelligent life exists（存在）somewhere in the universe. They also think we will soon contact them.

    Why do Shostak and Barnett think intelligent life exists on other planets? The first reason is time. Scientists believe the universe is about 12 billion years old. "This is long enough for other planets to have intelligent life, "say Shostak and Barnett. The second reason is size the universe is huge. "Tools like the Hubble Telescope（哈勃望远镜）have shown that there are at least 100 billion galaxies, "says Shostak. "And our galaxy, the Milky Way, has at least 100 billion stars. Some planets going around these stars might be similar to the earth. "

    In the past, it was hard to look for signs of intelligent life in the universe. But now, powerful telescopes（高倍望远镜）allow scientists to discover smaller planets-the size of Mars or the earth-in other solar systems, these planets might have intelligent life.

    Have beings from space already visited the earth? "Probably not, "says Shostak. "It's a long way away. However, intelligent beings may contact us in other way, such as radio signals（信号）. In fact, they may be trying to communicate with us now, but we don't have the right tools to receive their messages. However, this is changing. By 2025, we could make contact with other life forms in our universe and we might help each other. "

she ?

—She ______the supermarket.

—The same as you said, eight hundred dollars each.