What We Know (and don’t know) About the Universe
All the colors of the rainbow are but a tiny fraction of the "colors" of light the Universe sends us. Over the past 75 years, astronomers have been busy opening new windows on the cosmos by building telescopes and cameras that allow us to see all of these colors, revealing new phenomena previously unimagined. Very recently, we have opened entirely new channels of information by detecting gravity waves and by seeing the unseeable: directly imaging black holes. All of these messengers from the cosmos travel at the velocity of light, but even at this enormous speed, they take millions, or even billions of years to reach us. As a consequence, we are always seeing the past. Far from being a disadvantage, however, this allows us to read our history directly by looking out to objects at different distances.
We can watch stars being born, living out their lives, and then dying in spectacular explosions that produce the elements from which we are made as well as neutron stars and black holes. We can watch how galaxies form and grow by gobbling up their neighbors. And we can map the nearest million galaxies and trace them back to the tiny fluctuations in the early Universe from which they emerged. Replete with colliding galaxies and a fly-through of the Universe set to the Blue Danube waltz, this lecture provides one-stop shopping for a comprehensive tour of all of space and time — or at least of the whole 4% we actually understand.