But why the Big Bang?

Why do most scientists believe this model to be the most accurate? There are two major pieces of evidence that support this model. They are redshift and the cosmic microwave background. For the remainder of this session, you will learn about the first of these phenomena at a World Wide Web site produced by the National Center for Supercomputer Applications called "Cosmos in a Computer". You will be exploring a page titled "Expanding Universe". You should spend about 15 minutes investigating this site. When you reach the end of the "Expanding Universe" page, return to this page and continue on. Remember, if you get lost, use your browser "back" button to return to this page, and then start again.

Good luck, and off you go!

When you return from "Expanding Universe", take this quiz!