Core Concepts and Underlying Logic from I Wonder Why Stars Twinkle

I wonder why stars twinkle in other questions about space. What is the universe? The whole world and everything beyond is the universe. It is all the stars and the planets, the earth and its plants and animals, you and me, everything. You are made of the same stuff as a star. There are huge groups of stars in space, they are called galaxies and they are like gigantic star cities. The big band explosions then the young universe flying out in all directions over vast ages of time, bits came together to make galaxies. The galaxies are still speedy in the parts today and the universe is getting bigger. And did it all begin. Many astronomers think that everything in the universe was once packed together in one small lump. Then, about 14 billion years ago, there was a gigantic explosion of stuff that they called the big band. To see how the universe is getting bigger, watch the spots as you blow up a spotty balloon. To the universe ever end, some astronomers think the universe will just carry on getting bigger as the galaxies speed apart. Others think that the galaxies may one day start falling back towards each other until they crush together in a big crunch. Astronomers are scientists who study the stars and the planets. No one knows where all the material to make the universe came from in the first place. What is the Milky Way? The Milky Way is the galaxy we live in. It is made up of all the stars you can see in the sky at night and lots and lots more you cannot see. Astronomers usually give galaxies numbers instead of names. Many of you have names that tell us what they look like, the whirlpool, the sombrero, and the black eye, for example. The Milky Way got its name because at night we can sometimes see part of it looking like a band of Milky white light across the sky. The Milky Way is a bird-spirrow galaxy below you can see what it looks like from above. A bit like a whirlpool with long spiraling arms. From the side, a spiral galaxy looks like two fried eggs s