Lex Fridman: evaluation

Transcript context

…The following is a conversation with Lisa Randall, a theoretical physicist and cosmologist at Harvard. Her work involves improving our understanding of particle physics, supersymmetry, baryogenesis, cosmological inflation, and dark matter. This is the Lex Friedman podcast. To support it, please check out our sponsors in the description. Now, dear friends, here’s Lisa Randall. One of the things you work on and write about is dark matter. We can’t see it, but there’s a lot of it in the universe. You also end one of your books with a Beatles song quote, “‘Got to be good-looking because he’s so hard to see. ” What is dark matter? How should we think about it given that we can’t see it? How should we visualize it in our mind’s eye? I think one of the really important things that physics teaches you is just our limitations, but also our abilities. The fact that we can deduce the existence of something that we don’t directly see is really a tribute to people that we can do that. It’s also something that tells you, you can’t overly rely on your direct senses. If you just relied on just what you see directly, you would miss so much of what’s happening in the world. We can generalize this, but just for now to focus on dark matter, it’s something we know is there, and it’s not just one way we know it’s there. In my book, Dark Matter and the Dinosaurs, I talk about the many different ways. There’s eight or nine that we deduce not just the existence of dark matter, but how much is there, and they all agree. Now, how do we know it’s there? Because of its gravitational force. Individually, a particle doesn’t have such a big gravitational force. In fact, gravity is an extremely weak force compared to other forces we know about in nature, but there’s a lot of dark matter out there. It carries a lot of energy. Five times the amount of energy as the matter. We know that’s in atoms, et cetera. You can ask, how should we think about it? It’s just another form of matter that doesn’t interact with light, or at least as far as we know. It interacts gravitationally, it clumps, it forms galaxies, but it doesn’t interact with light, which means we just don’t see it. Most of our detection, before gravitational wave detectors, we only saw things because of their interactions with light in some sense.…

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