6．
阅读理解
Scientists think that there has been life on
earth for millions of years. However, we haven't found life on other planets
yet. The earth is a planet and it goes around the sun. And there are seven
other planets that also go around the sun. The sun and its planets are called
the solar system. The solar system is a small part of the universe.
Scientists have launched many spaceships to
explore other planets in the solar system. Some spaceships have gone beyond the
solar system. However, no one has discovered any life in space yet.
Why has no one from other planets sent us a
message? Have they tried to send information to us? With so many stars in
space, are we alone, or is there life on other planets in space?
