Eleventh ASC Lecture Series, Recent developments in cosmology suggest that the big bang was not a unique event in the cosmic history. Other big bangs constantly erupt in remote parts of the uni- verse, producing new worlds with great variety of physical properties. Some of these worlds are similar to ours, while others are strikingly different and even obey different laws of physics. I will discuss the origin of this new worldview, its possible observational tests, and some of its bizarre implications.