Astrophysicists like to talk about big concepts---like the nature of time, the universe, our very existence---but few make it understandable to the non-astrophysicist crowd. Usually these discussions leave my head spinning, unable to keep track of all of the concepts being flung my way. Which is just one reason why I found this talk from TEDxCaltech so fascinating. In the video, Sean Carroll, a Caltech theoretical physicist (and one of the writers of Cosmic Variance), discusses an array of topics: how entropy is responsible for the flow of time; that the universe is expanding at an accelerating rate and how dark energy fits into that; as well as the future of the universe. And then he suggests that the Big Bang might not have been the beginning.
The ideas fly by so fast I barely had time to ingest one before the next one arrived, and I'll probably want to watch this over a couple more times to take it all in. But I have to admire anyone who can make dark energy finally make sense for me.