Dennis Whyte: Nuclear Fusion and the Future of Energy | Lex Fridman Podcast #353

Why weren't we pushing towards economic fusion, and new materials, and new methods of heat extraction, and so forth? Because everybody knew fusion was 40 years away. And now it's four years away.

The following is a conversation with Dennis White, nuclear physicist at MIT and the director of the MIT Plasma Science and Fusion Center. This is the Lex Fridman podcast. To support it, please check out our sponsors in the description. And now, dear friends, here's Dennis White. Let's start with the big question, what is nuclear fusion?

It's the underlying process that powers the universe. So, as the name implies, it fuses together or brings together two different elements, technically nuclei, that come together. And if you can push them together close enough that you can trigger essentially a, a reaction, what happens is that the, the element typically changes. So, this means that you change from one element to another, chemical element to another. Underlying what this means is that you change the nuclear structure. This rearrangement, through E equals MC squared, releases large amounts of energy. So, fusion is the fusing together of lighter elements into heavier elements. And when you go through it, you say, "Oh, look. So, here are the initial elements, typically hydrogen, and they had a particular mass, rest mass." Which means just the mass with a, with no kinetic energy. And when you look at the product afterwards, it has less rest mass. And so you go, "Well, how is that possible? Because you have to keep mass." But mass and energy are the same thing, which, which is what E equals MC squared means. And the, the conversion of this comes into kinetic energy, namely energy that you can use in some way. Um, and that's what happens in the center of stars. So, fusion is literally the reason life is, is viable in the universe.

So, fusion is happening in our sun. And what are the elements?

The elements are hydrogen that are coming together. Um, it goes through a process, which is probably gets a little bit too detailed. But there's, it's, it's, it's a somewhat complex catalyzed process that happens in the center of stars. Um, but in the end, stars are big balls of hydrogen, which is the lightest, it's the simplest element, the lightest element, the most abundant element. Most of the universe is hydrogen. Um, and it's essentially a sequence through which these processes occur that you end up with helium. So, those are the primary things. And the reason for this is because helium has, uh, features as a nucleus, like the interior part of, of the atom, that is extremely stable. And the reason for this is helium has two protons and two neutrons. These are the things that make up nuclei that make up all of us, along with electrons. And because it has two pairs, it's extremely stable. And for this reason, it, when you convert the hydrogen into helium, it just wants to stay helium, and it wants to release, uh, kinetic energy. So, stars are basically conversion engines of hydrogen into helium. And, uh, I mean, this also tells you why you love fusion. I mean, 'cause our, our sun will last, you know, 10 billion years appro- approximately. Uh, that, that's how long the fuel will last.