Scientists think that there has been life on Earth for millions of years.However,we haven't found life on other planets yet.Why not?
The Earth is a planet and it goes around the Sun.Eight other planets also go around the Sun.None of them has an environment with air,so people and things cannot grow.The Sun and its planets are called the solar systemThe solar system is a small par of our galaxy.
But scientists have discovered many other galaxies in the universe.They are a long way away and their light has travelled for many years to reach us.It is hard to understand how large the universe is.
Scientists have sent lote of spacecraft to look at other planets in our solar system,and some spacraft have gone beyond the solar system.However,mo ome has discovered any life in space yet.
But why has no one from other planets sent us a message?Have they tried to send information to us?With so many stars in the universe,are we alone,or is there life out there in space?We don't know...yet.
參考答案:科学家认为在好几百万年前地球上就已经有生命.尽管这样,我们还没有在其他行星上找到生命的 痕迹,为什么呢?
地球是一个行星,他绕着太阳转,其他8个行星也围着太阳,他们中没有一个是有空气的,所以人和生物不能在那里生存.太阳和行星叫做太阳系,太阳系是银河系的一部分.
但是科学家在宇宙中也找到了其他银河系,他们离我们有很多光年,很难理解宇宙到底有多大.
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