Transcript: The cosmological anthropic principle connects the existence of life in the universe to the global geometry of the universe. The universe we live in has a spatial geometry very close to flat, and has a matter density within a factor of three of the critical density at which the cosmic expansion is slowly decelerated over cosmic time. The universe could have any value of the mass density. For hypothetical universes with much larger values of the matter density, these universes would have closed and re-collapsed a long time ago. In most of these hypothetical universes, there would not have been time for stars to form, evolve, and create carbon; they would have re-collapsed after millions of years. So, these would have been universes without biological life. In another set of hypothetical universes with much lower values of the mass density than the universe we live in, the early expansion would have been so rapid that stars and galaxies could not have formed out of the rapidly expanding material. Once again, with no stars, no carbon could have been created, and so no biological life would have been possible. Thus, out of the vast range of possible and physically plausible universes, only those with matter density in a particular narrow life could have biological life as we understand it. This is a fine-tuning argument on a cosmological scale.