Scientists think that there has been life on the 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 planet that also go around the sun.
科学家认为生命已经在地球上存在了数百万年。但是，人类还没有在其他星球上发现生命。地球是行星，围绕太阳运行。还有另外七个行星也绕着太阳运行。
The sun and its planets are called the solar system. The solar system is a small part of the universe.
太阳以及围绕它运行的行星被称为太阳系。太阳系只是宇宙的一小部分。
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.
科学家们发射了很多宇宙飞船，去探索太阳系中的其他星球。有些宇宙飞船已经飞出了太阳系。但是，还没有人在太空中发现任何生命。
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?
为什么其他星球上没有任何人给我们发信息呢？他们有试过给我们发信息吗？太空中有这么多行星，我们是唯一的生命吗？还是其他星球上也有生命？
