More Than Meets the Eye
One way to count all the stars in the universe would be to count so many each night, but don't expect to find them in the same place at the same time. If two weeks have gone by, start looking for them an hour earlier. Many years ago people noticed that the stars seemed to be in different places from time to time, so they believed that the stars were circling our earth. Now scientists know that as the earth moves in its orbit around the sun, different areas of the sky are revealed. The North Star is the only star in the Northern Hemisphere that does not move as clusters of stars circle around it.
Some people also began to wonder what might lie beyond the stars that they could see. As they studied the stars, they came to believe that the universe, the space around them, was composed of billions of star groups and each of these groups also contained billions of stars. Some scientists wondered, could there be even more stars? Could there be another universe beyond this one?
If you find it hard to believe that there are so many stars in the universe, just think about the number of people that live on our world. You know there are only a few people in your family and not many people live in your hometown. When you watch television, you see there are many people in other countries around the world, but does it seem possible that there are billions of people on our world since you never see all of them? Did you ever ride in a plane and as it flew higher and higher, discover how much more of the world you could see? It was always there, just like our universe, but you couldn't see it! If you asked a grownup why the plane stayed up in the air, he might have told you how he thought it worked or joked about his super powers holding it up there! You wouldn't believe that story or myth, but people living thousands of years ago believed that their gods were controlling everything here on Earth and in the skies. Some thought that a god rode the sun as it traveled across the sky; others named the stars and planets after their gods, and even referred to them as “heavenly bodies,” as many people still do today. Each country developed its own myths. Some even made up stories about the shapes formed by the clusters of stars in the sky.
Scientists call the start of the universe “The Big Bang.” What do they call the theory that when the universe ends it will collapse in on itself? To learn this name, color in the letters that are not Z, Y, or X. Then read the dark letters from left to right, and top to bottom.
Imagine what your friends would say if you announced that a god lived on the moon and made the moon increase in size when it rose above the horizon and then made it shrink when it was high in the sky. Can you think of other myths you could tell each other? It does seem almost more like a story than something real, when you think about a universe born billions of years ago. Although the universe has been around for a long time, scientists think it may have formed very fast. Because the universe is constantly expanding, even the best experts can only guess how big the universe is or what shape it may be. Traveling millions and millions of light years to find the answers may take some time, but technology is getting us closer and closer each day. How big or what shape do you think the universe is?
Astronomy is the study of all things in space. The people who watch the skies for new stars or planets or changes in the ones that have already been discovered are called astronomers. Astronomy is a type of science.
The Big Picture
One way to see the world from a bird's-eye view is to visit a Web site that shows your town and house from space. At Web sites such as
How Big Is Big?
Astronomers figure that the universe has about 100 billion galaxies. If each galaxy has 100 billion stars, that adds up to a HUGE number — 10 sextillion stars! Think about it this way: Ten thousand is a 10 followed by three zeroes, and ten million is a 10 followed by six zeroes. To find out how many zeroes are in 10 sextillion, break this number substitution (A=1, B=2, etc.) code.