Alex Filippenko: Supernovae, Dark Energy, Aliens & the Expanding Universe | Lex Fridman Podcast #137

The following is a conversation with Alex Filippenko, an astrophysicist and professor of astronomy from Berkeley. He was a member of both the Supernova Cosmology Project and the High-Z Supernova Search Team, which used observations of the extragalactic supernova to discover that the universe is accelerating, and that this implies the existence of dark energy. This discovery resulted in a 2011 Nobel Prize for Physics. Outside of his groundbreaking research, he's a great science communicator and is one of the most widely admired educators in the world. I really enjoyed this conversation and I'm sure Alex will be back again in the future. Quick mention of each sponsor, followed by some thoughts related to the episode. Neuro, the maker of functional sugar-free gum and mints that I use to give my brain a quick caffeine boost. BetterHelp, an online therapy with a licensed professional. MasterClass, online courses that I enjoy from some of the most amazing humans in history. And Cash App, the app I use to send money to friends. Please check out these sponsors in the description to get a discount and to support this podcast. As a side note, let me say that as we talk about in this conversation the objects that populate the universe are both awe-inspiring and terrifying in their capacity to create and to destroy us. Solar flares and asteroids lurking in the darkness of space threaten our humble fragile existence here on Earth. In the chaos, tension, conflict, and social division of 2020, it's easy to forget just how lucky we humans are to be here. And with a bit of hard work, maybe one day we'll venture out towards the stars. If you enjoy this thing, subscribe on YouTube, review it with five stars on Apple Podcast, follow on Spotify, support on Patreon, or connect with me on Twitter @lexfridman. And now, here's my conversation with Alex Filippenko. Let's start by talking about the biggest possible thing, the universe.

Sure.

Will the universe expand forever or collapse on itself?

Well, you know, that's a great question. That's one of the big questions of cosmology. And of course, we have evidence that the matter density is sufficiently low that the universe will expand forever. But not only that, there's this weird repulsive effect, we call it dark energy for want of a better term, and it appears to be accelerating the expansion of the universe. So if that continues, the universe will expand forever, but it need not necessarily continue. It could reverse sign in which case the universe could, in principle, collapse at some point in the far, far future.

So, like, in terms of ad- investment advice, if you were to give me, and then to bet all my money on one or the other, w- where does your intuition currently lie?

Well, right now I would say that it would expand forever, because I think that the dark energy is likely to be just quantum fluctuations of the vacuum. The vacuum zero energy state is not a state of zero energy, that is, the ground state is a, a state of some elevated energy which has a repulsive effect to it. And that will never go away because it's not something that changes with time. So if the universe is accelerating now, it will forever continue to do so.