As we all know, the universe includes the Sun and Earth, the planets and moons, the galaxies, stars and other forms of matter and energy. .
Within the universe are billions of galaxies. A galaxy such as our own Milky Way contains billions of stars. Like many stars, the Sun is orbited by planet, comets, and billions of stars and asteroids. Together they form a solar system, around which the Earth moves.
Scientists think that before the universe existed, all matter and energy were gathered in a tiny point. Then the point exploded. This explosion is called the Big Bang. After the Big Bang, the universe expanded at an amazing rate. It took about 400 million years for the stars and galaxies to form. Earth and the rest of the solar system came into being about 9 billion years after the Big Bang.
We still have much to learn about the universe. One important question remains unanswered: Does life exist beyond Earth? Scientists do not have the answer. They hold different ideas about it. . Others believe that there are thousands of worlds with people or animals living there yet to be discovered. But no one can say for sure.
Some think that the universe may continue to expand forever. Others feel that the galaxies, solar systems and planets might someday be torn a part. Whatever happens to the universe, don't worry--it's not going to happen for billions of years!
A. One of those is the Sun.
B. The Sun and the Earth are also in the solar system.
C. Some people believe that people have a good life on Earth.
D. The expansion then slowed and, over time, the universe cooled
E. In other words, the universe includes space and everything in it.
F. Scientists are also trying to determine what the universe will be like.
G. Some think that Earth is the only planet in the universe with intelligent life.
