The Milky Way is a large spiral whose disk is about 100,000 light-years wide and about 10,000 light-years thick at the nucleus. <br />
In addition to shape and size, one of the major differences among different types of galaxies is the age of their stars. <br />
The red shifts of distant galaxies that the universe is expanding.<br />
The big bang theory states that at one time, the entire universe was confined to a dense, hot, supermasentire ball. Then about 13.7 billion years ago, a violent explosion occurred, hurling this material in all directions. <br />
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