The universe is the biggest miracle in itself. We are such a small part of the universe that it is really mind boggling. We have been looking at the sky and wondering about the universe probably through our history as humans. Slowly we’ve found that planets revolve around stars and stars too revolve around other massive objects in the sky. A galaxy is a group of stars, planets and interstellar material that are revolving around a galactic center. There are billions of galaxies in the universe and they interact with each other under the force of gravity. Smaller galaxies collide into larger ones to form even larger and more crowded galaxies.