Astronomers believe that the expanding universe is the result of an enormous and powerful explosion called the Big Bang. The Big Bang theory may explain how the universe formed. The Big Bang theory states that the universe began to expand with the explosion of concentrated matter and energy and has been expanding ever since. According to the theory, all the matter and energy in the universe was once concentrated into a single place. This place, of course, Was extemely hot and dense. Then some 15 to 20 billion years ago, all explosion-the Big Bang-shot the concentratedmatter and energy in all directions. The fastest moving matter traveled farthest away.Energy, too, began moving away from the area of the Big Bang.
If the Big Bang theory is correct, the energy left from the Big Bang will be evenly spread out throughout the universe. This energy is known as background radiation.And indeed, universe. The constant background radiation is one observation that supports the Big Bang theory. After the initial B ig Bang, the force of gravity began to affect the matter racing outward in every direction. Gravity is a force of attraction between objects. All objects have a gravitational attraction. This force of gravity began to pull matter into clumps.
At some time, the clumps formed huge clusters of matter. These clumps became the galaxies of the universe. But even as the galaxies were forming, the matter inside the galaxies continued to race away from the area where the Big Bang had occurred. And this is just what astronomers have discovered. All of the galaxies are speeding away from the center of the universe.
1.What is the passage mainly concerned?
A) Center of the universe.
B) Open or closed universe.
C) The Big Bang theory.
D) Gravitational attraction.
2.According to the passage, the Big Bang theory is important because it sheds light on the ___.
A) formation of the galaxies
B) formation of the universe
C) formation of the stars
D) future of the universe
3.What can we know about the Big Bang, according to the passage?
A) The Big Bang is the explosion of background radiation.
B) Whether its theory is correct still needs to be proved.
C) The Big Bang is the congeries of energy.
D) The place around the Big Bang is very hot and dense.
4.According to the passage, galaxies were formed because of ___.
A) the expansion of the universe
B) the contraction of the universe
C) background radiation
D) the force of gravity
5.The galaxies kept on moving and even today they are moving in a direction that is ___.
A) towards the center of the universe
B) away from the center of the universe
C) to wards Earth
D) away from Earth