I is much harder for us to understand the universe ___1___
we know it today, than it was for ancient people to grasp ___2___
idea of the universe. They had a very simple picture ___3___
the universe. They thought that the sun, moon, star, and planets
were small objects ___4___
around the earth. Today, we know that our planet is part of a
solar system, ___5___ is
simply the sun and all the bodies circling around it. Our solar
system ___6___ to the galaxy
called the Milky Way. The Milky Way Galaxy is a collection ___7___
around 200,000 million stars. Our sun is just one ordinary star
in this galaxy.
There are millions of galaxies in the universe. The most ___8___
ones are 10,000 million light years away; one light year ___9___
about 10 million million kilometer. This is only that part of
the universe that we ___10___
about. There may be more distant galaxies that we have not
detected yet. It is just simply impossible for human imagination
to comprehend the huge distances involved.
Since our solar system is only a tiny part of the universe,
people often wonder ___11___
there are other worlds where life ___12___
exist. |