Adam Frank: evaluation

Transcript context

…Why do you think plate tectonics might be useful for the formation of complex life? There’s a bunch of different things. One is that the Earth went through a couple of phases of being a snowball planet. We went into a period of glaciation where pretty much the entire planet was under ice. The oceans were frozen. Early on in Earth’s history, there was barely any land. We were actually a water world, with just a couple of Australia-sized cratons they called them, proto-continents. We went through these snowball Earth phases. If it wasn’t for the fact that we had an active plate tectonics, which had a lot of vulcanism on it, we could have been locked in that forever. Once you get into a snowball state, a planet can be trapped there forever. Which is maybe you already had life formed, but then because it’s so cold, you may never get anything more than just microbes. What plate tectonics does, because it fosters more vulcanism, is that you’re going to get carbon dioxide pumped into the atmosphere, which warms the planet up and gets you out of the snowball Earth phase. But even more, there’s even more really important things. I just finished a paper where we were looking at something called the Hard Steps Model, which is this model that’s been out there for a long time that purports to say intelligent life in the universe will be really rare. It made all these assumptions about the Earth’s history, particularly about the history of life and the history of the planet have nothing to do with each other. It turns out, and as I was doing the reading for this, that Earth probably, early on, had a more mild form of plate tectonics, and then somewhere about a billion years ago, it ramped up. That ramping up changed everything on the planet, because here’s a funny thing. The Earth used to be flat. All the Flat Earthers out there can get excited for one second. Clip it. It still is.…

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