Welcome to The Universe: An Astrophysical Tour

Evidence for the birth of the universe is raining down on you. It's called the cosmic microwave background, and it's had quite a journey. Born in the stupendous annihilation of matter and antimatter seconds after the big bang, trapped in the hot plasma of the expanding universe for 380,000 years, and then suddenly released when the universe cooled to the point that atoms could form, this echo of creation has been on an uninterrupted voyage through space for 13.7 billion years—until it reached you. The cosmic microwave background is just one of the many clues about the history and nature of our universe that make the science of cosmology a wondrous, fascinating, and philosophically profound field of study.