Google Tech Talk August 13, 2010 ABSTRACT Presented by Sean Carroll. One of the most obvious facts about the universe is that the past is different from the future. We can remember yesterday, but not tomorrow; we can turn an egg into an omelet, but can’t turn an omelet into an egg. That's the arrow of time, which is consistent throughout the observable universe. The arrow can be explained by assuming that the very early universe was extremely orderly, and disorder has been increasing ever since. But why did the universe start out so orderly? I will talk about the nature of time, the origin of entropy, and how what happened before the Big Bang may be responsible for the arrow of time we observe today. Speaker Info: Sean Carroll I'm a theoretical physicist at Caltech in sunny Pasadena, California. My research interests include theoretical aspects of cosmology, field theory, and gravitation. I want to learn about fundamental physics by studying the structure and evolution of the universe. These days I'm especially interested in inflation, the arrow of time, and what happened at or before the Big Bang. I've done a bunch of work on dark matter and dark energy, modified gravity, topological defects, extra dimensions, and violations of fundamental symmetries. I recently finished writing a popular-level book on cosmology and the arrow of time: From Eternity to Here: The Quest for the Ultimate Theory of Time, which I expect all of you to buy. I previously wrote a graduate textbook