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

The following is a conversation with Dennis White,

nuclear physicist at MIT and the director

of the MIT Plasma Science and Fusion Center.

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And now, dear friends, here’s Dennis White.


Let’s start with a 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 reaction,

what happens is that 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 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 were the initial elements,

typically hydrogen,

and they had a particular mass, rest mass,

which means just the mass 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 is what E equals MC squared means.

And the conversion of this comes into kinetic energy,

namely energy that you can use in some way.

And that’s what happens in the center of stars.

So fusion is literally the reason

life 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.

It goes through a process

which is probably gets a little bit too detailed,

but it’s a somewhat complex catalyzed process

that happens in the center of stars.

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.

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 features as a nucleus,

like the interior part 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,

when you convert the hydrogen into helium,

it just wants to stay helium

and it wants to release kinetic energy.

So stars are basically conversion engines

of hydrogen into helium.

And this also tells you why you love fusion.

I mean, because our sun will last

10 billion years approximately.

That’s how long the fuel will last.

But to do that kind of conversion,

you have to have extremely high temperatures.

It is one of the criteria for doing this.

But it’s the easiest one to understand.

Why is this?

Because effectively what this requires

is that these hydrogen ions,

which is really the bare nucleus,

so they have a positive charge,

everything has a positive charge of those ones,

is that to get them to trigger this reaction,

they must approach within distances

which are like the size of the nucleus itself.

Because the nature, in fact,

what it’s really using

is something called the strong nuclear force.

There’s four fundamental forces in the universe.

This is the strongest one.

But it has a strange property

is that while it’s the strongest force by far,

it only has impact over distances

which are the size of a nucleus.

So to put that into, what does that mean?

It’s a millionth of a billionth of a meter, okay?

Incredibly small distances.

But because the distances are small

and the particles have charge,

they want to push strongly apart.

Namely, they have repulsion that wants to push them apart.

So it turns, when you go through the math of this,

the average velocity or energy of the particles

must be very high to have any significant probability

of the reactions happening.

And so the center of our sun

is at about 20 million degrees Celsius.

And on Earth, this means it’s one of the first things

we teach entering graduate students.

You can do a quick basically power balance

and you can determine that on Earth

it requires a minimum temperature

of about 50 million degrees Celsius on Earth.

To perform fusion.

To get enough fusion that you would be able to make,

get energy gain out of it.

So you can trigger fusion reactions at lower energy,

but they become almost vanishingly small

at lower temperatures than that.

First of all, let me just linger on some crazy ideas.

So one, the strong force,

just stepping out and looking at all the physics

is it weird to you that there’s these forces

and they’re very particular,

like it operates at a very small distance

and then gravity operates at a very large distance

and they’re all very specific

and the standard model describes

three of those forces extremely well and there’s.

And this is one of them.

Yeah, this is one of them.

And it’s just all kind of works out.

There’s a big part of you that’s an engineer.

Did you step back

and almost look at the philosophy of physics?

So it’s interesting because as a scientist,

I see the universe through that lens

of essentially the interesting things that we do

are through the forces that get used around those.

And everything works because of that.

Richard Feynman had,

I don’t know if you’ve ever read Richard Feynman.

It’s a little bit of a tangent, but.

He’s never been on the podcast.

He’s never been on the podcast.

He was unfortunately passed away,

but like a hero to almost all physicists.

And a part of it was because of what you said.

He kind of looked through a different lens

at these, what typically look like very dry

like equations and relationships.

And he kind of, I think he brought out the wonder of it

in some sense, right, for those.

He posited what would be,

if you could write down a single,

not even really a sentence,

but a single concept that was the most important thing

scientifically that we knew about.

That in other words, you had only one thing

that you could transmit like a future or past generation.

It was very interesting.

So, it’s not what you think.

It wasn’t like, oh, strong nuclear force

or fusion or something like this.

And it’s very profound, which was that the reason

that matter operates the way that it does

is because all matter is made up of individual particles

that interact each other through forces.

That was it.

So, just-

Atomic theory, basically.


Which is like, wow, that’s like so simple,

but it’s not so simple.

It’s because like, who thinks about atoms

that they’re made out of?

This is a good question I give to my students.

How many atoms are in your body?

Like, almost no students can answer this,

but to me, that’s like a fundamental thing.

By the way, it’s about 10 to the 28.

10 to the 28.

So, that’s a trillion, million, trillion, trillion

or something like that, yes.

So, one thing is to think about the number

and the other is to start to really ponder the fact-

That it all holds together.

Yeah, it all holds together and you’re actually that.

You’re more that than you are anything else.

Yes, exactly, yeah.

No, I mean, there are people who do study such things

of the fact that if you look at the, for example,

the ratios between those fundamental forces,

people have figured out, oh, if this ratio was different

by some factor, like a factor of two or something,

I was like, oh, this would all not work.

And you look at the sun, right?

It’s like, so it turns out that there are key reactions

that if they had slightly lower probability,

no star would ever ignite.

And then life wouldn’t be possible.

It does seem like the universe set things up for us

that it’s possible to do some cool things,

but it’s challenging.

So, it keeps it fun for us.

Yeah, yeah, that’s the way I look at it.

I mean, the multiverse model is an interesting one

because there are quantum scientists who look at it

and figure, it’s like, oh, it’s like, oh, yeah.

Like quantum science perhaps tells us

that there are almost an infinite variety

of other universes, but the way that it works probably

is it’s almost like a form of natural selection.

It’s like, well, the universes that didn’t have

the correct or interesting relationships

between these forces, nothing happens in them.

So, almost by definition, the fact that we’re having

this conversation means that we’re in one

of the interesting ones by default.

Yeah, one of the somewhat interesting,

but there’s probably super interesting ones

where I tend to think of humans as incredible creatures.

Our brain is an incredible computing device,

but I think we’re also extremely cognitively limited.

I can imagine alien civilizations

that are much, much, much, much more intelligent

in ways we can’t even comprehend

in terms of their ability to construct models of the world,

to do physics, to do physics and mathematics.

I would see it in a slightly different way.

It’s actually, it’s because we have creatures

that live with us on the earth that have cognition,

that understand and move through their environment,

but they actually see things in a way,

or they sense things in a way

which is so fundamentally different, it’s really hard.

The problem is the translation,

not necessarily intelligence.

So, it’s the perception of the world.

So, I have a dog, and when I go and I see my dog

smelling things, there’s a realization that I have

that he sees or senses the world in a way

that I can’t understand it

because I can’t translate my way to this.

We get little glimpses of this as humans, though,

by the way, because there are some parts of it,

for example, optical information, which comes from light,

is that now, because we’ve developed the technology,

we can actually see things.

I get this, as one of my areas of research is spectroscopy,

so this means the study of light,

and I get this quote-unquote see things

or representations of them from the far infrared

all the way to hard, hard x-rays,

which is several orders of magnitude of the light intensity,

but our own human eyes see a teeny, teeny

little sliver of this, so that even bees, for example,

see a different place than we do.

So, I think if you think of,

there’s already other intelligences around us in a way,

in a limited way because of the way they can communicate,

those are already baffling in many ways, yeah.

If we just focus in on the senses,

there’s already a lot of diversity,

but there’s probably things we’re not even considering

as possibilities, for example,

whatever the heck consciousness is

could actually be a door into understanding

some physical phenomena we haven’t even begun understanding.

So, just like you said, spectroscopy,

there could be a similar kind of spectrum for consciousness

that we’re just like, we’re like these dumb

descendants of apes walking around.

It sure feels like something to experience the color red,

but we don’t have, it’s the same as in the ancient times

you experienced physics, you experienced light.

It’s like, oh, it’s bright, and you know.

Yeah, yeah.

And you construct kind of

semi-religious kind of explanations.

We might actually experience this faster than we thought

because we might be building another kind of intelligence.

Yeah, and that intelligence will explain to us

how silly we are.

There was an email thread going around

the professors in my department already of,

so what is it going to look like to figure out

if students have actually written their term papers

or it’s chat, the-

Chat GPT.

Chat GPT.

It was, so as usual, we tend to be empiricists in my field.

So, of course, they were in there

trying to figure out if it could answer questions

for a qualifying exam to get into the PhD program at MIT,

which was, they didn’t do that well at that point,

but of course, this is just the beginning of it.

So, we have some interesting ones to go for.

Eventually, both the students and the professors

will be replaced by chat GPT.


And we’ll sit on the beach.

I really recommend, I don’t know if you’ve ever seen them,

it’s called The Day the Universe Changed.

Is it a movie?

James Burke.

He’s a science historian based in the UK.

He had a fairly famous series on public television

called Connections, I think it was,

but the one that I really enjoyed

was The Day the Universe Changed.

And the reason for the title of it was that,

it says the universe is what we know and perceive of it.

So, when there’s a fundamental insight as to something new,

the universe for us changes.

Of course, the universe from an objective point of view

is the same as it was before, but for us, it has changed.

So, he walks through these moments of perception

in the history of humanity that changed what we were, right?

And so, as I was thinking about coming to discuss this,

people see fusion, oh, it’s still far away,

or it’s been slow progress.

It’s like, when my godmother was born,

people had no idea how stars worked.

So, you talk about that day, that insight,

the universe changed, it’s like, oh, this is the,

I mean, and they still didn’t understand

all the parts of it, but they basically got it.

It’s like, oh, because of the understanding

of these processes, it’s like we unveiled the reason

that there can be life in the universe.

That’s probably one of those days

the universe changed, right?

And that was in the 1930s, yeah.

It seems like technology is developing

faster, and faster, and faster.

I tend to think, just like with Chad GPT,

I think this year might be extremely interesting,

just with how rapid and how profitable

the efforts in artificial intelligence are

that just stuff will happen where our whole world

is transformed like this, and there’s a shock,

and then the next day, you kind of go on,

and you adjust immediately.

You probably won’t have a similar kind of thing

with nuclear fusion with energy,

because there’s probably going to be

an opening ceremony and stuff,

an announcement, it’ll take months.

But with digital technology, you can just have

a immediate transformation of society,

and it’ll be this gasp, and then you kind of adjust,

like we always do, and then you don’t even remember,

just like with the internet and so on,

how the days were before.

And how it worked before, right?

I mean, fusion will be, because it’s energy,

its nature is that it will be,

and anything that has to do with energy use

tends to be a slower transition,

but they’re the most, I would argue,

some of the most profound transitions that we make.

I mean, the reason that we can live like this

and sit in this building and have this podcast

and people around the world is, at its heart,

is energy use, and it’s intense energy use

that came from the evolution of starting to use

intense energies at the beginning

of the Industrial Revolution up to now.

It’s like it’s a bedrock, actually, of all of these,

but it doesn’t tend to come overnight.

Yeah, and some of the most important,

some of the most amazing technology

is one we don’t notice, because we take it for granted,

because it enables this whole thing.

Yeah, exactly, which is energy,

which is amazing for how fundamental it is

to our society and way of life

is a very poorly understood concept, actually,

just even energy itself.

People confuse energy sources with energy storage

with energy transmission.

These are different physical phenomena,

which are very important.

So, for example, you buy an electric car,

and you go, oh, good, I have an emission-free car.

And, ah, but it’s like, so why do you say that?

Well, it’s because if I draw the circle around the car,

I have electricity, and it doesn’t emit anything.

Okay, but you plug that into a grid

where you follow that wire back,

there could be a coal power plant or a gas power plant

at the end of that.

Oh, really?

You mean, so this isn’t like carbon-free?

Oh, and it’s not their fault, it’s just, you know,

they don’t, like the car isn’t a source of energy.

The underlying source of energy

was the combustion of the fuel back somewhere.

Plus, there’s also a story of how the raw materials are mined

in which parts of the world, with sort of basic respect

or deep disrespect of human rights

that happens in that mining.

So, the whole supply chain, there’s a story there

that’s deeper than just a particular electric car

with a circle around it.

And the physics or the science of it, too,

is the energy use that it takes to do that digging up,

which is also important and all that.

Yeah, anyway, so.


We wandered away from fusion, but yes.

Ah, it’s a beautiful straw.

But it’s very important, actually,

in the context of this, just because, you know,

those of us who work in fusion and these other kinds

of sort of disruptive energy technologies,

it’s interesting, I do think about, like,

what is it going to mean to society

to have an energy source that is like this,

that would be like fusion, you know,

which has such completely different characteristics.

For example, you know, free unlimited access to the fuel,

but it has technology implications.

So, what does this mean geopolitically?

What does it mean for how we distribute wealth

within our society?

It’s very difficult to know, but probably profound, yeah.

We’re gonna have to find another reason

to start wars instead of resources.

We’ve done a pretty good job of that

over the course of our histories, yeah.

So, we talked about the forces of physics,

and again, sticking to the philosophical

before we get to the specific technical stuff,

E equals MC squared, you mentioned.

How amazing is that to you,

that energy and mass are the same?

And what does that have to do with nuclear fusion?

So, it has to do with everything we do.

It’s the fact that energy and mass

are equivalent to each other.

The way we usually comment to it

is that they’re just energy, just in different forms.

Can you intuitively understand that?

Yes, but it takes a long time.

I haven’t for a while,

but often I teach the introductory class

for incoming nuclear engineers.

And so, we put this up as an equation,

and we go through many iterations of using this,

how you derive it, how you use it, and so forth.

And then, usually in the final exam,

I would basically take all the equations

that I’ve used before, and I flip it around.

I basically, instead of thinking about

energy is equal to mass,

it’s sort of mass is equal to energy.

And I ask the question a different way,

and usually about half the students don’t get it.

It takes a while to get that intuition, yeah.

So, in the end, it’s interesting,

is that this is actually the source of all free energy,

because that energy that we’re talking about

is kinetic energy, if it can be transformed from mass.

So, it turns out even though we used equals MC squared,

this is burning coal, and burning gas,

and burning wood is actually still equals MC squared.

The problem is that you would never know this

because the relative change in the mass is incredibly small.

By the way, which comes back to fusion,

which is that E equals MC squared.

So, what does this mean?

It tells you that the amount of energy

that is liberated in a particular reaction

when you change mass has to,

because C squared, that’s the speed of light squared.

It’s a large number.

It’s a very large number,

and it’s totally constant everywhere in the universe,

which is another thing.

Which is another weird thing.

Which is another weird thing, and in all rest frames.

Actually, the relativity stuff gets more difficult

conceptually until you get through.

Anyway, so you go to that,

and what that tells you is that

it’s the relative change in the mass

will tell you about the relative amount of energy

that’s liberated, and this is what makes fusion,

and you asked about fission as well, too.

This is what makes them extraordinary.

It’s because the relative change in the mass is very large

as compared to what you get in a chemical reaction.

In fact, it’s about 10 million times larger,

and that is at the heart of why

you use something like fusion.

It’s because that is a fundamental of nature.

You can’t beat that.

So whatever you do, if you’re thinking about,

and why do I care about this?

Well, because mass is like the fuel, right?

So this means gathering the resources

that it takes to gather a fuel,

to hold it together, to deal with it,

the environmental impact it would have,

and fusion will always have 20 million times

the amount of energy release per reaction

that you get of those.

So this is why we consider it the ultimate

environmentally friendly energy source is because of that.

So is it correct to think of mass broadly

as a kind of storage of energy?


You mentioned it’s environmentally friendly.

So nuclear fusion is a source of energy.

It’s cheap, clean, safe, so easy access to fuel

and virtually unlimited supply,

no production of greenhouse gases,

little radioactive waste produced allegedly.

Can you sort of elaborate why it’s cheap, clean, and safe?

I’ll start with the easiest one, cheap.

It is not cheap yet because it hasn’t been made

at a commercial scale.

Time flies when you’re having fun, but yes.

Yeah, yeah.

But yes, not yet.

We’ll talk about that.

Actually, we’ll come back to that

because this is cheaper, or a more technically correct term,

that it’s economically interesting

is really the primary challenge, actually,

of fusion at this point.

But I think we can get back to that.

So what were the other ones you said?

So cheap, actually, when we’re talking about cheap,

we’re thinking like asymptotically.

Like if you take it forward several hundred years,

that’s sort of because of how much availability

there is of resources to use.

Of the fuel.

Yeah, of the fuel.

We should separate those two.

The fuel is already cheap.

It’s basically free, right?

What do you mean by basically free?

So if we were to be using fusion fuel sources

to power your, and it’s like,

that’s all we had was fusion power plants around,

and we were doing it, the fuel costs per person

are something like 10 cents a year.

It’s free, okay?

This is why it’s hard to, in some ways,

I think it’s hard to understand fusion

because people see this and go,

oh, if the fuel is free,

this means the energy source is free

because we’re used to energy sources like this.

So we spend resources and drill to get gas or oil,

or we chop wood, or we make coal,

we find coal or these things, right?

So fusion, this is what makes fusion,

and it’s also, it’s not an intermittent,

renewable energy source like wind and solar.

So it’s like, but this makes it hard to understand.

So if you’re saying the fuel is free,

why isn’t the energy source free?

And it’s because of the necessary technologies

which must be applied to basically recreate the conditions

which are in stars, in the center of stars, in fact.

So there’s only one natural place in the universe

that fusion energy occurs that’s in the center of stars.

So that’s going to bring a price to it

depending on the size and complexity of the technology

that’s needed to recreate those things.

And we’ll talk about the details of those technologies

and which parts might be expensive today

and which parts might be expensive in 200 years.

Exactly, it will have a revolution, I’m certain of it.

So about clean, so clean is, at its heart,

what it does is convert, it basically converts hydrogen

into, it’s heavier forms of hydrogen,

the most predominant one that we use on earth,

and converts it into helium and some other products,

but primarily helium is the product that’s left behind.

So helium, safe, inert, gas, you know.

In fact, that’s actually what our sun is doing.

It’s eventually going to extinguish itself

because it’ll just make so much helium

that it doesn’t do that.

So in that sense, clean because there’s no emissions

of carbon or pollutants that come directly

from the combustion of the fuel itself.

And safe.

Safe, yeah.

We’re talking about very high temperatures.

Yeah, yeah, so this is also the counterintuitive thing.

So I told you temperatures, which like 50 million degrees,

or it actually tends to be more like

about 100 million degrees is really what we aim for.

So how can 100 million degrees be safe?

And it’s safe because it is, this is so much hotter

than anything on earth, where everything on earth

is at around 300 Kelvin, you know,

it’s around a few tens of degrees Celsius.

And what this means is that in order to get a medium

to those temperatures, you have to completely isolate it

from anything to do with terrestrial environment.

It can have no contact, like with anything on earth,


So this means what we, this is the technology

that I just described, is it fundamentally what it does

is it takes this fuel and it isolates it

from any terrestrial conditions

so that it has no idea it’s on earth.

It’s not touching any object that’s at room temperature.

Including the walls of the containment.

Even including the walls of the containment building

or containment device, or even air or anything like this.

So it’s that part that makes it safe,

and there’s actually another aspect to it,

but that fundamental part makes it so safe.

And in the mainlines approach to fusion

is also that it’s very hot,

where there’s very, very few particles at any time

in the thing that would be the power plant.

The actually more correct way to do it is you say,

there’s very few particles per unit volume.

So in a cubic centimeter, in a cubic meter,

something like that.

So we can do this.

So right now we’re, although we don’t think of air really

as a, there’s atoms floating around us

and there’s a density, because if I wave my hand,

I can feel the air pushing against my face.

That means we’re in a fluid or a gas, which is around us,

that has a particular number of atoms per cubic meter.

So this actually turns out to be 10 to the 25th.

So this is one with 25 zeros behind it per cubic meter.

So we can figure out cubic meters about this,

the volume of this table, the whole volume of this table.

Okay, very good.

So like fusion, there’s a few of those.

So fusion, like the mainstream one of fusion,

like what we’re working on at MIT,

we’ll have a hundred thousand times less particles

per unit volume than that.

So this is very interesting because it’s extraordinarily

hot, a hundred million degrees, but it’s very tenuous.

And what matters from the engineering and safety point

of view is the amount of energy,

which is stored per unit volume,

because this tells you about the scenarios

and that’s what you worry about.

Because when those kinds of energies are released,

suddenly it’s like, what would be the consequences, right?

So the consequences of this are essentially zero

because that’s less energy content than boiling water.

Because of the low density?

Because of the low density.

So if you take, water is at about a hundred million

to a billion times more dense than this.

So even though it’s at much lower temperature,

it’s actually still, it has more energy content.

So for this reason, one of the ways that I explain this

is that if you imagine a power plant that’s like

powering Cambridge, Massachusetts, like if you were to,

which you wouldn’t do this directly,

but if you went like this on it,

it actually extinguishes the fusion

because it gets too cold immediately.


So that’s the other one.

And the other part is that it does not,

because it works by staying hot rather than a chain reaction

it can’t run out of control.

That’s the other part of it.

So by the way, this is what very much

distinguishes it from fission.

It’s not a process that can run away from you

because it’s basically thermally stable.

What does thermally stable mean?

That means is that you want to run it

at the optimization in temperature,

such that if it deviates away from that temperature,

the reactivity gets lower.

And the reason for this is because it’s hard

to keep the reactivity going.

It’s a very hard fire to keep going, basically.

Oh, so it doesn’t run away from you.

It can’t run away from you.

How difficult is the control there to keep it at that?

It varies from concept to concept,

but in generally, it’s fairly easy to do that.

And the easiest thing, it can’t physically run away from you

because the other part of it is that there’s just,

at any given time, there’s a very, very small amount

of fuel available to fuse anyway.

So this means that that’s always intrinsically limited

to this, so even if the power consumption

of the device goes up, it just kind of burns itself out

immediately, yeah.

So you are the, just to take another tangent on a tangent,

you’re the director of MIT’s Plasma Science

and Fusion Center.

That’s right.

We’ll talk about, maybe you can mention

some interesting aspects of the history of the center

in the broader history of MIT and maybe broader history

of science and engineering in the history

of human civilization.

But also, just to link on the safety aspect,

how do you prevent some of the amazing reactors

that you’re designing, how do you prevent

from destroying all of human civilization in the process?

What’s the safety protocols?

Fusion is interesting because it’s not really

directly weaponizable because what I mean by that

is that you have to work very hard to make these conditions

which you can get energy gain from fusion.

And this means that when we design these devices

with respect to application in the energy field,

is that they, you know, while they will,

because they’re producing large amounts of power

and they will have hot things inside of them,

this means that they have like a level of industrial hazard

which is very similar to what you would have

like in a chemical processing plant

or anything like that, and any kind of energy plant

actually has these as well too.

But the underlying, underneath it, core technology

like can’t be directly used in a nefarious way

because of the power that’s being emitted.

It just basically, if you try to do those things,

typically it just stops working.

So the safety concerns have to do with just regular things

that like equipment malfunctioning, melting of,

like all this kind of stuff that has nothing to do

with fusion necessarily.

I mean, usually what we worry about is the viability

because in the end we build pretty complex objects

to realize these requirements.

And so what we try really hard to do

is like not damage those components,

but those are things which are internal

to the fusion device.

And this is not something that you would consider

about like it would, as you say, destroy human civilization

because that release of energy is just inherently limited

because of the fusion process.

So it doesn’t say that there’s zero.

So you asked about the other feature of it, that it’s safe.

So it is, the process itself is intrinsically safe,

but because it’s a complex technology,

you still have to take into consideration aspects

of the safety.

So it produces ionizing radiation instantaneously.

So you have to take care of this,

which means that you shield it.

Think of like your dental x-rays or treatments for cancer

and things like this.

We always shield ourselves from this.

So we get the beneficial effects,

but we minimize the harmful effects of those.

So there are all those aspects of it as well too.

So we’ll return to MIT’s Plasma Science and Fusion Center,

but let us linger on the destruction of human civilization,

which brings us to the topic of nuclear fission.

What is that?

So the process that is inside nuclear weapons

and current nuclear power plants.

So it relies on the same underlying physical principle,

but it’s exactly the opposite,

which actually the names imply.

Fusion means bringing things together.

Fission means splitting things apart.

So fission requires the heaviest instead of the lightest

and the most unstable versus the most stable elements.

So this tends to be uranium or plutonium,

primarily uranium.

So take uranium.

So uranium-235 is one of the,

this is one of the heaviest unstable elements.

And what happens is that this is,

fission is triggered by the fact

that one of these subatomic particles,

the neutron, which has no electric charge,

basically gets in proximity enough to this

and triggers an instability effectively inside of this,

what is teetering on the border of instability

and basically splits it apart.

And that’s the fission, right?

The fissioning.

And so when that happens,

because the products that are,

it roughly splits in two, but it’s not even that.

It’s actually more complicated.

It splits into this whole array

of lighter elements and nuclei.

And when that happens, there’s less rest mass

left than the original one.

So it’s actually the same.

So it’s, again, it’s rearrangement

of the strong nuclear force that’s happening,

but that’s the source of the energy.

And so in the end, it’s like,

so this is a famous graph that we show everybody

is basically, it turns out every element

that exists in the periodic table,

all the things that make up everything have a,

remember, you asked a good question.

It was like, so should we think of mass

as being the same as stored energy?


So you can make a plot that basically shows

the relative amount of stored energy

in all of the elements that are stable

and make up basically the world, okay, and the universe.

And it turns out that this one has a maximum amount

of stability or storage at iron.

So it’s kind of in the middle of the periodic table

because this goes from, you know, it’s roughly that.

And so this, what that means is that

if you take something heavier than iron,

like uranium, which is more than twice as heavy than that,

and you split apart, if somehow just magically,

you can just split apart its constituents

and you get something that’s lighter,

because it moves to a more stable energy state,

it releases kinetic energy.

That’s the energy that we use.

Kinetic energy meaning the movement of things.

So it’s actually an energy you can do something with.

And fusion, it sits on the other side of that

because it’s also moving towards iron,

but it has to do it through fusion together.

So this leads to some pretty profound differences.

As I said, they have some underlying physics

or science proximity to each other,

but they’re literally the opposite.

So fusion, why is this?

It actually goes into practical implications of it,

which is that fission could happen at room temperature.

It’s because this neutron has no electric charge

and therefore it’s literally room temperature neutrons

that actually trigger the reaction.

So this means in order to establish what’s going on with it

and it works by a chain reaction,

is that you can do this at room temperature.

So Enrico Fermi did this like on a university campus,

University of Chicago campus.

The first sustained chain reaction was done

underneath a squash court with a big blocks of graphite.

It was still, don’t get me wrong,

an incredible human achievement, right?

But that’s, and then you think about fusion,

I have to build a contraption of some kind

that’s going to get to a hundred million degrees.

Okay, wow, that’s a big difference.

The other one is about the chain reaction,

that namely fission works by the fact

that when that fission occurs,

it actually produces free neutrons.

Free neutrons, particularly if they get slowed down

to room temperature, can trigger other fission reactions

if there’s other uranium nearby or fissile materials.

So this means that the way that it releases energy

is that you set this up in a very careful way

such that every, on average, every reaction that happens

exactly releases enough neutrons and slows down

that they actually make another reaction,

exactly one.

And what this means is that because each reaction

releases a fixed amount of energy,

you do this and then in time,

this looks like just a constant power output.

So that’s how a fission power plant works.

And so their control of the chain reactions

is extremely difficult and extremely important for fission.

It’s very important.

And when you intentionally design it

that it creates more than one fission reaction

per starting reaction, then it exponentiates away.

Which is what a nuclear weapon is.

Yeah, so how does an atomic weapon work?

How does a hydrogen bomb work?

Asking for a friend.


Yeah, so what you do is you very quickly put together

enough of these materials that can undergo fission

with room temperature neutrons.

And you put them together fast enough that what happens

is that this process can essentially grow mathematically,

like very fast.

And so this releases large amounts of energy.

So that’s the underlying reason that it works.

So you’ve heard of a fusion weapon.

So this is interesting is that it is,

but it’s just like fusion energy in the sense

that what happens is that you’re using fusion reactions

but it’s simply, it increases the gain actually

of the weapon rather than, it’s not a pure,

at its heart, it’s still a fission weapon.

You’re just using fusion reactions

as a sort of intermediate catalyst

basically to get even more energy out of it.

But it’s not directly applicable to be used

in an energy source.

Does it terrify you, just again,

to step back at the philosophical,

that humans have been able to use physics

and engineering to create such powerful weapons?

I wouldn’t say terrify.

I mean, we should be, this is the progress of human.

Every time that we’ve gotten access,

you talk, you know, the day the universe changed.

It was really changed when we got access

to new kinds of energy sources.

But every time you get access,

and typically what this meant was you get access

to more intense energy, right?

That’s, and that’s what that was.

And so the ability to move from burning wood

to using coal, to using gasoline and petroleum,

and then finally to use this is that both the potency

and the consequences are elevated around those things.

It’s just like you said, the way that fusion,

nuclear fusion, would change the world,

I don’t think, unless we think really deeply,

we’ll be able to anticipate some of the things

we can create.

There’s going to be a lot of amazing stuff,

but then that amazing stuff is gonna enable

more amazing stuff and more, unfortunately,

or depending how you see it, more powerful weapons.

Well, yeah, but see, that’s the thing.

Fusion breaks that trend in the following way.

So one of them, so fusion doesn’t work

on a chain reaction.

There’s no chain reaction, zero.

So this means it cannot physically exponentiate

away on you, because it works,

and actually this is why stars,

by the way, we know this already,

it’s why stars are so stable,

why most stars and suns are so stable.

It’s because they are regulated through their own

temperature and their heating,

because what’s happening is not that there’s

some probability of this exponentiating away,

it’s that the energy that’s being released by fusion

basically is keeping the fire hot.

And these tend to be, and when it comes down

to thermodynamics and things like this,

there’s a reason, for example, it’s pretty easy

to keep a constant temperature, like in an oven

and things like this, it’s the same thing in fusion.

So this is actually one of the features

that I would argue fusion breaks the trend

of this is that it has more energy intensity

than fission on paper, but it actually

does not have the consequences of control

and sort of rapid release of the energy,

because it’s actually, the physical system

just doesn’t want to do that.

Yeah, we’re gonna have to look elsewhere

for the weapons with which we fight World War III.

Fair enough, so what is plasma,

that you may or may have not mentioned,

you mentioned ions and electrons and so on.

So what is plasma, what is the role

of plasma in nuclear fusion?

So plasma is a phase of matter or a state of matter.

So unfortunately our schools don’t,

it’s like I’m not sure why this is the case,

but all children learn the three phases of matter, right?

So, and what does this mean?

So we’ll take water as an example.

So if it’s cold, it’s ice, it’s in a solid phase, right?

And then if you heat it up, it’s the temperature

that typically depends, sets the phase,

although it’s not only temperature.

So you heat it up and you go to a liquid,

and obviously it changes its physical properties

because you can pour it and so forth, right?

And then if you heat this up enough,

it turns into a gas, and a gas behaves differently

because there’s a very sudden change in the density,

actually that’s what’s happening.

So it changes by about a factor of 10,000 in density

from the liquid phase into when you make it

into steam at atmospheric pressure, all very good.

Except the problem is they forgot like what happens

if you just keep elevating the temperature.

You don’t wanna give kids ideas.

They’re gonna start experimenting

and they’re gonna start heating up the gas.

It’s good to start doing it anyway.

So you, it turns out that once you get above,

it’s approximately five or 10,000 degrees Celsius,

then you hit a new phase of matter.

And actually that’s the phase of matter

that is for all, pretty much all the temperatures

that are above that as well too.

And so what does that mean?

So it actually changes phase,

so it’s a different state of matter.

And the reason that it becomes a different state of matter

is that it’s hot enough that what happens

is that the atoms that make up,

remember go back to Feynman, right?

Everything’s made up of these individual things,

these atoms.

But atoms can actually themselves be,

which are made of nuclei,

which contain the positive particles in the neutrons.

And then the electrons, which are very, very light,

very much less mass than the nucleus,

and that surround us, this is what makes up an atom.

So a plasma is what happens when you start

pulling away enough of those electrons

that they’re free from the ion.

So almost all the atoms that make up us up

and this water and all that,

the electrons are in tightly bound states

and basically they’re extremely stable.

Once you’re at about 5,000 or 10,000 degrees,

you start pulling off the electrons.

And what this means is that now the medium that is there,

its constituent particles mostly have net charge on them.

So why does that matter?

It’s because now this means that the particles

can interact through their electric charge.

In some sense, they were when it was an atom as well too,

but now that they’re free particles,

this means that they start,

it fundamentally changes the behavior.

It doesn’t behave like a gas,

it doesn’t behave like a solid or a liquid,

it behaves like a plasma, right?

And so why is it disappointing

that we don’t speak about this?

It’s because 99% of the universe is in the plasma state.

It’s called stars.

And in fact, our own sun,

at the center of the sun is what clearly a plasma,

but actually the surface of the sun,

which is around 5,500 Celsius is also a plasma.

Because it’s hot enough that is that.

In fact, the things that you see,

sometimes you see these pictures from the surface of the sun

amazing like satellite photographs

of like those big arms of things

and of light coming off of the surface of the sun

and solar flares, those are plasmas.

What are some interesting ways

that this force state of matter is different than gas?

Let’s go to how a gas works, right?

So the reason a gas,

and it goes back to Feynman’s brilliance

in saying that this is the most important concept.

The reason actually solid, liquid and gas phases work

is because the nature of the interaction

between the atoms changes.

And so in a gas, you can think of this as being,

this room and the things, although you can’t see them,

is that the molecules are flying around,

but then with some frequency,

they basically bounce into each other.

And when they bounce into each other,

they exchange momentum and energy around on this.

And so it turns out that the probability

and the distances and the scattering

of those of what they do,

it’s those interactions that set the,

about how a gas behaves.

So what do you mean by this?

Well, so for example,

if I take an imaginary test particle of some kind,

like I spray something into the air

that’s got a particular color.

In fact, you can do it in liquids as well too.

Like how it gradually will disperse away from you.

This is fundamentally set because of the way

that those particles are bouncing into each other.

The probabilities of those particles bouncing.

The rate that they go at

and the distance that they go at and so forth.

So this was figured out by Einstein and others

at the beginning of the Brownian motion,

all these kinds of things.

These were set up at the beginning of the last century

and it was really like this great revelation.

Wow, this is why matter behaves the way that it does.

Like, wow.

So, but it’s really like,

and also in liquids and in solids,

like what really matters

is how you’re interacting with your nearest neighbor.

So you think about that one,

the gas particles are basically going around

until they actually hit into each other though,

they don’t really exchange information.

And it’s the same in a liquid,

you’re kind of beside each other,

but you can kind of move around.

In a solid, you’re literally like stuck

beside your neighbor, you can’t move like a man.

Plasmas are weird in the sense is that

it’s not like that.

So, and it’s because the particles have electric charge,

this means that they can push against each other

without actually being in close proximity to each other.

It’s not, that’s not an infinitely true statement,

which if you go get it, it’s a little bit more technical,

but basically this means that you can start having action

or exchange of information at a distance.

And that’s in fact, the definition of a plasma

that it says, this have a technical name,

it’s called a Coulomb collisions,

just means that it’s dictated by this force,

which is being pushed between the charged particles,

is that the definition of a plasma is a medium

in which the collective behavior

is dominated by these collisions at a distance.

So you can imagine, then this starts to give you

some strange behaviors,

which I could quickly talk about,

like for example, one of the most counterintuitive ones

is as plasmas get more hot,

as they get higher in temperature,

then the collisions happen less frequently.

Like what?

That doesn’t make any sense.

When particles go faster,

you think they would collide more often.

But because the particles are interacting

through their electric field,

when they’re going faster, they actually spend less time

in the influential field of each other.

And so they talk to each other less

in an energy and momentum exchange point of view.

It’s just one of the counterintuitive aspects of plasmas.

Which is probably very relevant for nuclear fusion.

Yes, exactly.

So if I can try to summarize

what a nuclear fusion reactor is supposed to do.

So you have, what, a couple of elements?

What are usually the elements?

Usually deuterium and tritium,

which are the heavy forms of hydrogen.


You have those and you start heating it.

And then as you start heating it,

I forgot the temperature you said,

but it becomes plasma.

About 100 million.

No, first it becomes.

Oh, first it becomes plasma.

So it’s a gas, and then it turns into a plasma

at about 10,000 degrees.

And then so you have a bunch of electrons

and ions flying around.

And then you keep heating the thing.

And I guess as you heat the thing,

the ions hit each other rarer and rarer.


So, oh man, that’s not fun.

So you have to keep heating it.

Such that you have to keep hitting it

until the probability of them colliding

becomes reasonably high.

And also on top of that, and sorry to interrupt,

you have to prevent them from hitting the walls

of the reactor somehow.

So you asked about the definitions

of the requirements for fusion.

So the most famous one, or in some sense

the most intuitive one, is the temperature.

And the reason for that is that you can make

many, many kinds of plasmas that have

zero fusion going on in them.

And the reason for this is that the average,

so you can make a plasma at around 10,000.

In fact, if you come, by the way,

you’re welcome to come to our laboratory

at the PSFC, I can show you a demonstration

of a plasma that you can see with your eyes,

and it’s at about 10,000 degrees,

and you can put your hand up beside it

and all this, and it’s like, and nothing,

there’s zero fusion going on.

So you have, sorry, what was the temperature

of the plasma?

About 10,000 degrees.

You can stick your hand in?

Well, you can’t stick your hand into it,

but there’s a glass tube, you can basically

see this with your bare eye, yeah.

And you can put your hand on the glass tube

because it’s.

What’s the color, is it purple?

It’s purple, yeah.

It’s blue and purple.

It is kind of beautiful.

Yeah, plasmas are actually quite astonishing

sometimes in their beauty.

Actually, one of the most amazing forms

of plasma is lightning, by the way,

which is an instantaneous form of plasma

that exists on Earth but immediately goes away

because everything else around it

is at room temperature.

That’s fascinating.

Yeah, so there’s different requirements in this.

So making a plasma takes about this,

but at 10,000 degrees, even at a million degrees,

there’s almost no probability

of the fusion reactions occurring.

And this is because while the charged particles

can hit into each other, if you go back

to the very beginning of this, remember I said,

oh, these charged particles have to get to within distances

which are like this size of a nucleus

because of the strong nuclear force.

Well, unfortunately, as the particles get closer,

the repulsion that comes from the charge,

the Coulomb force, increases

like the inverse distance squared.

Oh, no.

So as they get closer, they’re pushing harder

and harder apart.

So then it gets a little bit more exotic,

which maybe you’ll like, though,

that it turns out that people understood this

at the beginning of the age

of after Rutherford discovered the nucleus.

It’s like, oh, yeah, it’s like, how are we going to,

how is this gonna work, right?

Because how do you get anything within these distances

is a good inquiry.

Extraordinary energy.

And it does.

And in fact, when you look at those energies,

they’re very, very high.

But it turns out quantum physics comes to the rescue

because the particles aren’t actually just particles.

They’re also waves.

This is the point of quantum, right?

You can treat them both as waves and as particles.

And it turns out if you get,

if they get in close enough proximity to each other,

then the particle pops through basically this energy barrier

through an effect called quantum tunneling,

which is really just the transposition of the fact

that it’s a wave so that it has a finite probability

of this.

By the way, you talk about like,

do you have a hard time like conceptualizing this?

These are, this is one of them.

Quantum tunneling is one of them.

Yeah, this is like throwing a ping pong ball

like at a piece of paper.

And then every like, you know, 100 of them

just like magically show up on the other side of the paper

without seemingly breaking the paper.

I mean, to use a physical analogy.


That phenomena is important,

is critical for the function of nuclear fusion.

Yes, for all kinds of fusion.

So this is the reason why stars can work as well too.

Like the stars would have to be much, much hotter

actually to be able to,

in fact, it’s not clear that they would actually ignite

in fact, without this effect.

And so we get to that.

So this is why there’s another requirement.

It’s not, so you must make a plasma,

but you also must get it very hot

in order for the reactions to have a significant probability

to actually fuse.

And it actually falls effectively almost to zero

for lower temperatures as well too.

So there’s some nice equation

that gets you to 50 million degrees.

Or like, or you said, practically speaking, 100 million.

It’s a really simple equation.

It’s the ideal gas law, basically almost.

So in the end, you’ve got a certain number of particles,

of these fusion particles in the plasma state.

They’re in the plasma state.

There’s a certain number of particles.

And if the confinement is perfect,

if you put in a certain content of energy,

then basically eventually they just,

they come up in a temperature and they become,

they go up to high temperature.

This turns out to be, by the way,

extraordinarily small amounts of energy.

And you go, what?

It’s like I’m getting something

to like 100 million degrees.

That’s gonna take the biggest flame burner

that I’ve ever seen.


And the reason for this is it goes back

to the energy content of this.

So yeah, you have to get it to high average energy,

but there’s very, very few particles.

This is low density.

It’s low density.

How do you get it to be low density in a reactor?

Is this?

So the way that you do this is primarily,

again, this is not exactly true in all kinds of fusion,

but in the primary one that we work on, magnetic fusion,

this is all happening in a hard vacuum.

So it’s like it’s happening in outer space.

So basically you’ve gotten rid of all the other particles,

except for these specialized fuel particles.

So you add them one at a time?

No, actually it’s even easier than that.

You connect a gas valve and you basically

leak gas into it.

In a controlled fashion?

Yeah, yeah.

Wow, this is beautiful.

It’s a gas cylinder.

How do you get it from hitting the walls?


Now you’ve touched on the other necessary requirements.

So it turns out it’s not just temperature that’s required.

You must also confine it.

So what does this mean, confine it?

And there’s two types of confinement, as you mentioned.

You mentioned the magnetic one.

Magnetic one, and there’s one called inertial as well too.

But the general principle actually has nothing to do with,

in particular, with what the technology is

that you use to confine it.

It’s because this goes back to the fact

that the requirement in this is high temperature

and thermal content.

So it’s like building a fire.

And what this means is that if you,

when you release the energy into this,

or apply heat to this, if it just instantly leaks out,

it can never get hot, right?

So you’re familiar with this, it’s like you’ve got

something that you’re trying to apply heat to,

but you’re just throwing the heat away very quickly.

This is why we insulate homes, by the way,

and things like this, right?

It’s like you don’t want the heat that’s coming

into this room to just immediately leave

because you’ll just start consuming infinite amounts

of heat to try to keep it hot.

So in the end, this is one of the requirements,

and it actually has a name.

We call it the energy confinement time.

So this means if you release a certain amount of energy

into this fuel, kind of how long,

you sit there and you look at your watch,

how long does it take for this energy

to like leave the system?

So you could imagine that in this room,

that these heaters are putting energy into the air

in this room, and you waited for a day,

but all the heat have gone to outside

if I open up the windows.

Oh, there, that’s energy confinement time.

Okay, so it’s the same concept as that.

So this is an important one.

So all fusion must have confinement.

There’s another more esoteric reason for this,

which is that people often confuse temperature and energy.

So what do I mean by that?

So this is literally a temperature,

which means that it is a system in which all the particles,

every particle has high kinetic energy

and is actually in a fully relaxed state,

namely that entropy has been maximized.

I think it’s a little bit more technical,

but this means that basically it is a thermal system.

So it’s like the air in this room,

it’s like the water, it’s the water in this.

These all have temperatures,

which means that there’s a distribution of those energies

because the particles have collided so much that it’s there.

So this is distinguished from having high energy particles,

like what we have in like particle accelerators,

like CERN and so forth.

Those are high kinetic energy,

but it’s not a temperature,

so it actually doesn’t count as confinement.

So we go through all of those.

You have temperature, and then the other requirement,

not too surprising, is actually that there has to be

enough density of the fuel.

Enough, but not too much.

Enough, but not too much, yes.

And so in the end, the way that it,

there’s a fancy name for it,

it’s called the Lawson criterion,

because it was formulated by scientists

in the United Kingdom about 1956 or 1957.

And this was essentially the realization of,

oh, this is what it’s going to take,

regardless of the confinement method.

These are, this is the basic,

what it is actually, power balances,

just says, oh, there’s a certain amount of heat coming in,

which is coming from the fusion reaction itself,

because the fusion reaction heats the fuel,

versus how fast you would lose it.

And it basically summarized,

it’s summarized by those three parameters,

which is fairly simple.

So temperature, and then the reason we say

100 million degrees is because almost all way in,

in for this kind of fusion, deuterium-tritium fusion,

the minimum in the density,

in the confinement time product is at about 100 million.

So you almost always design your device around that minimum,

and then you try to get it contained well enough,

and you try to get enough density.

So, you know, so that temperature thing sounds crazy, right?

That’s what we’ve actually achieved in the laboratory.

Like our experiment here at MIT,

when it ran at its optimum configuration,

it was at 100 million degrees.

But it wasn’t actually,

the product of the density in the confinement time

wasn’t sufficient that we were at a place

that we were getting high net energy gain,

but it was making fusion reactions.

So this is the sequence that you go through,

make a plasma, then you get it hot enough.

And when you get it hot enough,

the fusion reactions start happening so rapidly

that it’s overcoming the rate

at which it’s leaking heat to the outside world.

And at some point it just becomes like a star,

like a sun and our own sun and a star

doesn’t have anything plugged into it.

It’s just keeping itself hot

through its own fusion reactions.

In the end, that’s really close

to what a fusion power plant would look like.

What does it visually look like?

Does it look like, like you said, like purple plasma?

Yeah, actually it’s invisible to the eye

because it’s so hot that it’s basically emitting light

in frequencies that we can’t detect.

It’s invisible.

In fact, light goes through it,

visible light goes through it so easy

that if you were to look at it,

what you would see in our own particular configuration,

what we make is in the end is a donut shaped,

it’s a vacuum vessel to keep the air out of it.

And when you turn on the plasma,

it gets so hot that most of it just disappears

in the visible spectrum.

You can’t see anything.

And there’s very, very cold plasma,

which is between 10 and 100,000 degrees,

which is out in the very periphery of it,

which is kind of, so the very cold plasma

is allowed to interact with the,

kind of has to interact with something eventually

at the boundary of the vacuum vessel.

And this kind of makes a little halo around it

and it glows as beautiful purple light basically.

And these are, that’s what we can sense

in the human spectrum.

I remember reading on a subreddit called Shower Thoughts,

which people should check out.

It’s just fascinating philosophical ideas

that strike you while you’re in the shower.

And one of them was, it’s lucky that fire,

when it burns, communicates that it’s hot

using visible light.

Otherwise, humans would be screwed.

I don’t know if there’s a deep, profound truth to that,

but nevertheless, I did find it on Shower Thoughts subreddit.

Actually, I do have, this goes off on a bit of,

you’re right, this is actually, it’s interesting

because as a scientist, you also think

about evolutionary functions and how we got,

like, why do we have the senses that we do?

It’s an interesting question.

Like, why can bees see in the ultraviolet and we can’t?

Then you go, well, it’s natural selection.

For some reason, this wasn’t really particularly

important to us, right?

Why can’t we see in the infrared and other things can?

It’s like, hmm, hmm.

It’s the people that could.

It’s a fascinating question, right?

Obviously, there’s some advantage that you have there

that isn’t there, and even color distinguishing, right,

of something safe to eat, whatever it would be.

I’ll actually go back to this because it’s something

that I tell all of my students when I’m teaching

ionizing radiation and radiological safety.

Whatever you say, there’s a cultural concern

or that when people hear the word radiation,

like, what does this mean?

It literally just means light is what it means, right?

But it’s light in different parts of the spectrum, right?

And so, it turns out besides the visible light

that we can see here, we are immersed in almost

the totality of the electromagnetic spectrum.

There is visible light.

There’s infrared light.

There is microwaves going around us.

That’s how our cell phone works.

It’s way past our detection capability.

But also higher energy ones, which have to do

with ultraviolet light, how you get a sunburn,

and even x-rays and things like this at small levels

are continually being, like from the concrete

in the walls of this hotel, there’s x-rays

hitting our body continuously.

I can bring out a, we can go down to the lab at MIT

and bring out a detector and show you.

Every single room will have these.

By our body, you mean the 10 to the 28 atoms?

Yeah, the 10 to the 28 atoms,

and they’re coming in and they’re interacting

with those things.

And those, particularly the ones where the light

is at higher average energy per light particle,

those are the ones that can possibly have an effect

on human health.

So, we have, it’s interesting, humans and all animals

have evolved on Earth where we’re immersed

in that all the time.

There’s a natural source of radiation all the time,

yet we have zero ability to detect it, like zero.

Yeah, and our ability, cognitive ability

to filter it all out and not give a damn.

It would probably overwhelm us, actually,

if we could see all of it.

But my main point goes back to your thing about fire

and self-protection.

If ionizing radiation was such a critical aspect

of the health of organisms on Earth,

we would almost certainly have evolved methods

to detect it, and we have none.

And, yes.

The physical world that’s all around us is incredible.

You’re blowing my mind, Dr. Dennis White.

Okay, let’s, so you have experience

with magnetic confinement.

You have experience with inertial confinement.

Most of your work has been in magnetic confinement.

But let’s sort of talk about the sexy recent thing

for a bit of a time.

There’s been a breakthrough in the news

that laser-based inertial confinement was used

by DOE’s National Ignition Facility

at the Lawrence Livermore National Laboratory.

Can you explain this breakthrough

that happened in December?

So, it goes to the set of criteria

that I talked about before,

about getting high energy gain.

So, in the end, what are we after in fusion

is that we basically assemble this plasma fuel in some way,

and we provide it a starting amount of energy.

Think of lighting the fire.

And what you want to do is get back significant excess gain

from the fact that the fusion is making more,

is releasing the energy.

So, it’s like the equivalent of like,

we want to have a match, a small match, light a fire,

and then the fire keeps us hot.

It’s very much like that.

So, as I said, we’ve made many of the,

and what do I mean by we?

It’s like the fusion community has pursued aspects of this

through a variety of different confinement methodologies,

is that the key part about what happens,

what was the threshold we had never gotten over before

was that if you only consider the plasma fuel,

not the total engineering system,

but just the plasma fuel itself,

we had not gotten to the point yet

where basically the size of the match

was smaller than the amount of energy

that we got from the fusion.

Is there a good term for when the output

is greater than the input?

Yes, yes, there is.

Well, there’s several special definitions of this.

So, one of them is that if you, like in a fire,

if you light a match and you have it there

and it’s an infinitesimal amount of energy

compared to what you’re getting out of the fire,

we call this ignition, which makes sense, right?

This is like what our own sun is as well too.

So, that was not ignition in that sense as well too.

So, what we call this is scientific,

what the one that I just talked about,

which is for some instance,

when I get enough fusion energy released

compared to the size of the match,

we call this scientific breakeven.


Breakeven, and it’s because you’ve gotten past the fact

that this is unity now at this point.

What is a fusion gain or as using the notation Q

from the paper overview of the spark talking about,

before we talk, using just the same kind of term.

Yeah, actually, so, sorry, the technical term is Q,

capital Q.

Oh, so people actually use Q.

We actually use capital Q, or sometimes it’s called Q.

So, Q is taken.

Q sub P or something like this.

Okay, so this is, which means,

what it means is that it’s in the plasma.

So, all we’re considering is the energy balance

or a gain that comes from the plasma itself.

We’re not considering the technologies which are around it,

which are providing the containment and so forth.

So, why the excitement?

Well, because for one reason,

it’s a rather simple threshold to get over

to understand that you’re getting more energy out

from the fusion, even in a theoretical sense,

than you were from the starting match.

Do you mean conceptually simple?

It’s conceptually simple that you get past one,

that everyone, like when you’re less than one,

that’s much less interesting than getting past one

because obviously you start to get energy gain, yeah.

But it really is a scientific threshold

because what QP actually denotes

is the relative amount of self-heating

that’s happening in the plasma.

So, what I mean by this is that in the end,

in these systems, what you want is something

where the relative amount of heating,

which is keeping the fuel hot,

is dominated from the fusion reactions themselves.

And so, it becomes, it’s sort of like thinking

like a bonfire is a lot more interesting physically

than just holding a blowtorch to a wet log, right?

There’s a lot more dynamics,

it’s a lot more self-evolved and so forth.

And what we’re excited as scientists

is that it’s clear that in that experiment

that they actually got to a point

where the fusion reactions themselves

were actually altering the state of the plasma.

It’s like, wow.

I mean, we’d seen it in glimpses before

in magnetic confinement at relatively small levels,

but apparently it seems like in this experiment

it’s likely to be a dominant, dominated by self-heating.

That’s a very important, that’s a very interesting thing.

So, that makes it a self-sustaining type of reaction.

It’s more self-sustaining,

it’s more self-referential system in a sense.

And it sort of self-evolves in a way.

Again, it’s not that it’s gonna evolve

to a dangerous state, it’s just that we want

to see what happens when the fusion

is the dominant heating source.

And we’ll talk about that, but there’s also another element

which is the inertial confinement,

laser-based inertial confinement.

It’s kind of a little bit of an underdog.

So, a lot of the broad nuclear fission community

has been focused on magnetic confinement.

Can you explain just how laser-based

inertial confinement works?

So, it says 192 laser beams were aligned

on a deuterium-tritium-DT target smaller than a pea.

This is like, okay, well, you know, it depends.

Not all peas are made the same.

But this is like throwing a perfect strike

in baseball from a pitch.

This is like a journalist wrote this, I think.

This is like, oh, no, it’s not a journalist,

it’s DOE wrote this, Department of Energy.

We try to use all these analogies.

This is like throwing a perfect strike

in baseball from a pitcher’s mount

350 miles away from the plate.

There you go.

Department of Energy.

The United States Department of Energy wrote this.

Can you explain what the lasers?

What actually happens?

Actually, there’s usually mass confusion about this.

So, what’s going on in this form of energy?

So, the fuel is delivered in a discrete,

the fusion fuel, the deuterium-tritium

is in a discrete spherical, it’s more like a BB.

Let’s call it a BB.

So, it’s a small one.

And all the fuel that you’re gonna try to burn

is basically there, okay?

And it’s about that size.

So, how are you going to get,

and it’s at, literally, it’s like at 20 degrees

above absolute zero, because the deuterium

and tritium are kept in a liquid and solid state.

Oh, wow.

So, the fuel is injected not as a gas,

but as a solid.

It’s actually, and it’s very,

and in these particular experiments,

they can introduce one of these targets

once per day, approximately, something like that.

Because it’s very, it’s a kind of amazing technology,

actually, that I know some of the people

that worked on this back in the,

is they actually make these things

at a BB size of this frozen fuel.

It’s actually at cryogenic temperatures.

And they’re almost like smooth to the atom level.

I mean, they’re amazing pieces of technology.

So, what you do in the end is think,

what you have is a spherical assembly of this fuel,

like a ball, and what is the purpose of the lasers?

The purpose of the lasers is to provide optical energy

to the very outside of this.

And what happens is that energy is absorbed

because it’s in the solid phase of matter.

So, it’s absorbed really in the surface.

And then what happens is that when it’s absorbed

in something called the ablator, what does that mean?

It means it goes instantly from the solid phase

to the gas phase.

So, it becomes like a rocket engine.

But you hit it like very uniformly.

So, all, there’s like rocket engines

coming off this surface.

Think of like an asteroid almost,

where there’s like rockets coming off almost.

So, what does that do?

Well, what does a rocket do?

It actually pushes, by Newton’s laws, right?

It pushes the other thing on the other side of it,

equal and opposite reaction.

It pushes it in.

So, what it does is that the lasers actually don’t heat.

This is what was confusing.

People think the lasers, oh, we’re gonna get it

to 100 million degrees.

In fact, you want the exact opposite of this.

What you want to do is get essentially a rocket

going out like this.

And then what happens is that the sphere,

and this is happening in a billionth of a second

or less, actually.

This rapidly, that force like so rapidly compresses

the fuel that what happens is that you’re squeezing

down on it and it’s like, what was the,

see BB, that’s bad actually.

I should have started with a basketball.

Goes from like a basketball down to something like this

in a billionth of a second.

And when that happens, I mean, scale that in your mind.

So, when that happens, and this comes from,

almost from classical physics.

So, there’s some quantum in it as well too.

But basically, if you can do this like very uniformly

and so-called adiabatically, like you’re not actually

heating the fuel, what happens is you get adiabatic

compression such that the very center of this thing

all of a sudden just spikes up in temperature

because it’s actually done so fast.

So, why is it called inertial fusion?

It’s because you’re doing this on such fast time scales

that the inertia of the hot fuel basically

is still finite, so it can’t like push itself apart

before the fusion happens.

Oh wow, so how do you make it so,

how do you make it so fast?

This is why you use lasers because you’re applying

this energy in very, very short periods of time,

like under a fraction of a billionth of a second.

And so, basically that, and then the force

which is coming from this comes from the energy

of the lasers, which is basically the rocket action

which does the compression.

Well, so is the force, is the inward-facing force,

is that increasing the temperature exponentially?

No, you wanna keep the fuel cold

and just literally just ideally compress it.

And then in something which is at the very center

of that compressed sphere, because you’ve compressed it

so rapidly, the laws of physics basically require

for it to increase in temperature.

So, the change in pressure.

The effect is like, if you know the thing,

so adiabatic cooling we’re actually fairly familiar with.

If you take a spray can, right, and you push the button,

when it rapidly expands, it cools.

This is the nature of a lot of cooling technology

we use actually.

Well, the opposite is true, that if you would take

all of those particles and jam them together

very fast back in, they wanna heat up.

And that’s what happens.

And then what happens is, you basically have this

very cold, compressed set of fusion fuel,

and at the center of this, it goes to this

100 million degrees Celsius.

And so, if it gets to that 100 million degrees Celsius,

the fusion fuel starts to burn.

And when that fusion fuel starts to burn,

it wants to heat up the other cold fuel around it,

and it just basically propagates out so fast

that what you would do, ideally, you would actually burn

in a fusion sense, most of the fuel that’s in the pellet.

So, this was very exciting, because what they had done

was, it’s clear that they propagated this,

they got this, what they call a hot spot,

and in fact, that this heating had propagated

out into the fuel, and that’s the science

behind inertial fusion.

So, the idea behind a reactor that’s based on this

kind of inertial confinement is that you would have

a new BB every like?

10 times a second or something like that.

And there’s some kind of, so there’s an incredible device

that you kind of implied that kind of has to create

one of those BBs.

So, you have to make the BBs very fast.

There’s reports on this, but about what does it mean?

The starting point is, can you make this gain?

So, this was a scientific achievement, primarily.

Right, and the rest is just engineering.

No, no, no, the rest is incredibly complicated engineering.

Well, in fact, there’s still physics hurdles to overcome.

So, where does this come from?

And it’s actually because, if you want to make

an energy source out of this, this had a gain

of around 1.5, that namely the fusion energy

was approximately, was 1.5 times the laser input energy.

Okay, this is a fairly significant threshold.

However, from the science of what I just told you,

is that there’s two fundamental efficiencies

which come into it, which really come from physics, really.

One of them is hydrodynamic efficiency.

What I mean by this is that it’s a rocket.

So, this just has a fundamental efficiency built into it,

which comes out to orders of like 10%.

So, this means is that your ability to do work

on the system is just limited by that, okay.

And then the other one is the efficiency

of laser systems themselves, which if the wall plug

efficiency is 10%, you’ve done spectacularly well.

In fact, the wall plug efficiency of the ones

using that experiment are like more like 1%, right.

So, when you go through all of this,

the approximate place that you’re ordering this

is for a fusion power plant would be a gain of 100,

not 1.5.

So, you still, you know, and hopefully we see experiments

that keep climbing up towards higher and higher gain.

But then the whole fusion power plant

is a totally different thing.

So, it’s not one BB and one laser pulse per day.

It’s like 10 times, five or 10 times per second,

like da-da-da-da-da-da-da-da-da-da, like that, right.

So, you’re doing it there.

And then comes the other aspect.

So, it’s making the targets, delivering them,

being able to repeatedly get them to burn.

And then we haven’t even talked about like,

how do you then get the fusion energy out,

which is mainly because these things are basically

micro implosions which are occurring.

So, this energy is coming out to some medium

on the outside that you’ve got to figure out

how to extract the energy out of this thing.

How do you convert that energy to electricity?

So, in the end, you have to basically convert it

into heat in some way.

So, most of the, in the end what fusion makes

mostly is like very energetic particles

from the fusion reaction.

So, you have to slow those down in some way

and then make heat out of it.

So, basically the conversion of the kinetic energy

of the particles into heating some engineered material

that’s on the outside of this.

And that’s, from a physics perspective,

is a somewhat solved problem,

but from an engineering is, it’s still, it’s still.

Yeah, physics I can draw, I can show you all the equations

that tell you about how it slows down

and converts kinetic energy into heat.

And then what that heat means, you know,

you can write out like an ideal thermal cycle,

like a Carnot cycle.

So, the physics of that, yeah, great.

The integrated engineering of this is a whole other thing.

I’ll ask you to maybe talk about the difference

between inertial and magnetic,

but first we’ll talk about magnetic.

But let me just linger on this breakthrough.

You know, it’s nice to have exciting things,

but in a deep human sense,

there’s no competition in science and engineering.

We’re all, like you said, we, we’re broad.

First of all, we are humanity altogether.

And you talk about this,

it’s a bunch of countries collaborating.

It’s really exciting.

There’s a nuclear fusion community broadly,

but then there’s also MIT.

There’s colors and logos and it’s exciting.

And there’s, you have friends and colleagues here

that work extremely hard and done some incredible stuff.

Is there some sort of,

how do you feel seeing somebody else get a breakthrough

and using a different technology?

Is that exciting?

Is this, does the competitive fire get-

All of the above.

I mean, I mean-

The ignition?

You know, I have, so, you know, to, you know,

just to wave the flag a little bit.

So, MIT was a central player in this accomplishment.

Interesting, I would say it showed our two,

some of our two best traits.

So, one of them was that the,

like, how do you know that this happened?

This measurement, right?

So, one of the ways to do this is,

if I told you is that in the DT fusion,

what it actually, the product that comes out is helium,

we call an alpha, but it’s helium,

and a free neutron, right?

So, the neutron contains 80% of the fusion,

of the energy released by the fusion reaction.

And it also, because it lacks a charge,

it basically tends to just escape and go flying out.

So, this is what we would use eventually for,

that’s mostly what fusion energy would be.

But, so what my colleagues, my scientific colleagues

at the Plaza Science and Fusion Center built

were extraordinary measurement tools

of being able to see the exact details

of not only the number of neutrons that were coming out,

but actually what energy that they’re at.

And by looking at that configuration,

it reveals enormous, I’m not gonna scoop them

because they need to publish the paper,

but it reveals enormous amounts of scientific information

about what’s happening in that process

that I just described.

So exciting, I mean, and I have colleagues there

that have worked for 30 years on this, for that moment.

Of course you’re excited for that, right?

And it’s one of those, there is nothing,

it’s hard to describe to people who aren’t,

it’s almost addicting to be a scientist,

when you get to be at the forefront of research,

of anything.

Like when you see like an actual discovery of some kind

and you’re looking at it,

particularly when you’re the person who did it, right?

And you go, no human being has ever seen this

or understood this.

It’s like, it’s pretty thrilling, right?

So even in proxy, it’s incredibly thrilling to see this.

It’s not, I don’t wanna say it’s rivalry or jealousy.

It’s like, I can tell you already, fusion is really hard.

So anything that keeps pushing the needle forward

is a good thing.

But we also have to be realistic about what it means

to making a fusion energy system.

That’s the-

And then, but that’s the fun, I mean,

these are still the early steps,

maybe you can say the early leaps.

So let’s talk about the magnetic confinement.


What is, how does magnetic confinement work?

What’s the tokamak?

Yeah, how does it all work?

So go back to that.

So why inertial confinement works on the same principle

that a star works.

So like, what is the confinement mechanism in the star

is gravity, because it’s its own inertia

of something the size of the sun

basically pushes literally a force by gravity

against the center.

So the center is very, very hot, 20 million degrees.

And literally outside the sun, it’s essentially zero

because it’s a vacuum of space.

How the hell does that do that?

It does that by, and it’s out of,

like, why doesn’t it just leak all of its heat?

It doesn’t leak its heat because it all is held together

by the fact that it can’t escape because of its own gravity.

So this is why the fusion happens

in the center of the star.

Like we think of the surface of the sun as being hot.

That’s the coldest part of the star.

So if our own sun, this is about 5,500 degrees,

a beautiful symmetry, by the way, it’s like,

so how do we know all this?

Because we can’t, of course, see directly

into the interior of the sun,

but by knowing the volume and the temperature

of the surface of the sun,

you know exactly how much power it’s putting out.

And by this, you know that this is coming

from fusion reactions occurring at exactly the same rate

in the middle of the sun.

Is it possible as a small tangent

to build an inertial confinement system like the sun?

Is it possible to create a sun?

It is, of course, possible to make a sun,

although we do have stars,

but it is not impossible on Earth

because for the simple reason that it takes,

the gravitational force is extremely weak,

and so it takes something like the size of a star

to make fusion occur in the center.

Well, I didn’t mean on Earth.

I mean, if you had to build like a second sun,

how would you do it?

You can’t, there’s not enough hydrogen around.

So the limiting factor is just the hydrogen.

Yeah, I mean, the forces and energy that it takes

to assemble that is just mind-boggling.

All right, to be continued.

Yeah, to be continued.

So what are we doing it with?

So in the one that I just described,

it’s like you say, so you have to replace this

with some force which is better than that.

And so what I mean by that is it’s stronger than that.

So when I talked about the laser fusion,

this is coming from the force,

which is enormous compared to gravity,

like from the rocket action of pushing it together.

So in magnetic confinement, we use another force of nature,

which is the electromagnetic force.

And that’s very, it’s orders and orders of magnitude

stronger than the gravitational force.

And the key force that matters here

is that if you have a charged particle,

that namely it’s a particle that has an electric,

net electric charge,

and it’s in the proximity of a magnetic field,

then there is a force which is exerted on that particle.

So it’s called the Lorentz force

for those who are keeping track.

So that is the force that we use

to replace physical containment.

So this again, how do you hold something

at a hundred million degrees?

It’s impossible in a physical container.

This is not like, you know,

it’s not this plastic bottle holding in this liquid

or a gas chamber.

What you’re doing is you’re using,

you’re immersing the fuel in a magnetic field

that basically exerts a force at a distance.

This comes back again to again,

like why plazas are so strange.

It’s the same thing here.

And if it’s immersed in this magnetic field,

you’re not actually physically touching it,

but you’re making a force go onto it.

So that’s the inherent feature of magnetic confinement.

And then magnetic confinement devices

are like a tokamak, are basically configurations

which exploit the features of that magnetic containment.

There’s several features to it.

One is that the stronger the strength

of the magnetic field, the stronger the force.

And for this reason is that if you increase

the strength of magnetic fields,

this means that the containment,

because namely the force which you’re pushing against it

is more effective.

And the other feature is that there is no force.

So for those who remember magnetic fields,

what are these things?

They’re also invisible.

But if you think of a permanent magnets

or your fridge magnet, there are field lines

which we actually designate as arrows,

which are going around.

You sometimes see this in school

when you have the iron filings on a thing

and you see the directions of the magnetic field lines

or when you use a compass, right?

So that’s telling you north because we’re living

in an immersed magnetic field made by the earth,

which is at very low intensity magnetic,

but it’s strong enough

where we can actually see what direction is it.

So this is the arrow that the magnetic field is pointing.

It’s always pointing north and for us.

So an interesting feature of this force

is that there is no force along the direction

of the magnetic field.

There’s only force in the directions

orthogonal to the magnetic field.

So this, by the way, is a huge deal

in a whole other discipline of plasma physics,

which is like the study of our near atmosphere.

So the study of aurora borealis,

what’s happening in the near atmosphere,

what happens when solar flares hit the magnetic field.

In fact, remember I said fusion is the reason

that life is responsible in the universe?

Well, you could also argue so is magnetic confinement

because the charged particles which are being emitted

from the galaxy and from our own star,

would be very, very damaging on Earth.

So we get two layers of protection.

One is the atmosphere itself,

but the other one is the magnetic field

which surrounds the Earth

and basically traps these charged particles

so they can’t get away.

It’s the same deal.

How do you create a strong magnetic field?

Yeah, so.

With a giant magnet.

Giant magnet, yeah.

So it’s basically true.

Engineering is awesome.

There’s essentially two ways to create a magnet.

So one of them is that we’re familiar

with like fridge magnets and so forth.

These are so-called permanent magnets.

And what it means is that within these,

the atoms arrange in a particular way

that it produces, the electrons basically arrange

in a particular way that it produces

a permanent magnetic field that is set by the material.

So those have a fundamental limitation

how strong they can be.

And they also tend to have this like circle

or shape like this.

So we don’t typically use those.

So what we use are so-called electromagnets.

And what is this?

So the other way to make a magnetic field,

also go back to your elementary school physics

or science class, is that you take a nail

and you wrap a copper wire around it

and connect it to a battery.

Then it can pick up iron filings.

This is an electromagnet.

At its simplest, what it is, it’s an electric current

which is going in a pattern around and around and around.

And what this does is it produces a magnetic field

which goes through it by the laws of electromagnetism.

So that’s how we make the magnetic field

in these configurations.

And the key there is that it’s not limited

by the magnetic property of the material.

The magnetic field amplitude is set

by the amount of the geometry of this thing

and the amount of electric current

that you’re putting through.

And the more electric current that you put through,

the more magnetic field that you get.

The closest one that people maybe see

is one of my favorite skits, actually,

was Super Dave Osborne on, it’s probably past,

he was in a show called Bizarre.

Super Dave Osborne, which is a great comedian called,

he was a stuntman and one of his tricks

was that he gets into a car and then one of those things

in the junkyard comes down and picks up the car

and then puts it into the crusher.

This is his stunt, which is pretty hilarious.

Anyway, but that thing that picks him up,

how does that work?

That’s actually not a permanent magnet,

it’s an electromagnet.

And so you can turn, by turning off and on the power supply,

it turns off and on the magnetic field.

So this means you can pick it up

and then when you switch it off,

the magnetic field goes away and the car drops, okay?

So that’s what it looks like.

Speaking of giant magnets,

MIT and Commonwealth Fusion Systems, CFS,

built a very large, high-temperature,

superconducting electromagnet that was ramped up

to a field strength of 20 tesla,

the most powerful magnetic field of its kind

ever created on Earth.

Because I enjoy this kind of thing,

can you please tell me about this magnet?

Yeah, sure.

Oh, it’s fun, yeah.

There’s a lot to parse there.

So maybe, so we already explained an electromagnet,

which in general is what you do is you take electric current

and you force it to follow a pattern of some kind,

typically like a circular pattern,

around and around and around and around.

It goes the more time, the more current

and the more times it goes around,

the stronger the magnetic field that you make of it.

And as I pointed out, it’s like really important

in magnetic confinement because it is the force

that’s produced by that magnet.

In fact, technically it goes like the magnetic field squared

because it’s a pressure which is actually being exerted

on the plasma to keep it contained.

Just so we know, for magnetic confinement,

what is usually the geometry of the magnet?

The geometry, yeah, so the geometry is typically

that typically is what you do is you want to produce

a magnetic field that loops back on itself.

And the reason for this was, goes down to the nature

of the force that I described, which is that there’s no,

there’s no containment or force along the direction

of the magnetic field.

So here’s a magnetic field.

In fact, what it’s more technically

or more graphically what it’s doing is that

when the plasma is, here’s plasma particles here,

here’s a magnetic field, what it does is it forces

all those, because of this Lorentz force,

it makes all of those charged particles execute

circular orbits around the magnetic field.

And they go around like this, but they stream freely

along the magnetic field line.

So this is why the nature of the containment is that

if you can get that circle smaller and smaller,

it stays further away from Earth, temperature materials.

That’s why the confinement gets better.

But the problem is, is that because it free streams along,

so we just have a long straight magnetic field,

okay, it’ll just keep leaking out the ends like really fast.

So you get rid of the ends.

So you basically loop it back around.

So what these look like are typically donut shaped

or more technically toroidal shape,

but donut shaped things where this collection

of magnetic fields loops back on itself.

And it also, for reasons which are more complicated

to explain, basically it also twists slowly around

in this direction as well too.

So that’s what it looks like.

That’s what the plasma looks like,

because that’s what the fuel looks like.

So then this means is that the electromagnets

are configured in such a way that it produces

the desired magnetic fields around this.

So the-

How precise does this have to be?

You were probably listening to our conversation

with some of my colleagues yesterday.

So it’s actually, it depends on the configuration

about how you’re doing it.

The configuration of the plasma, sorry.

The configuration of the electromagnets

and about how you’re achieving this requirement.

It’s fairly precise, but it doesn’t have to be,

particularly in something like a tokamak,

what we do is we produce planar coils,

which just mean they’re flat, and we situate them.

So if you think of a circle like this,

what does it produce?

If you put current through it, it produces a magnetic field,

which goes through the circle like this.

So if you align many of them like this, this, this, this,

there’s things online, you can go see the picture.

You keep arranging these around in a circle itself.

This forces the magnetic field lines

to basically just keep executing around like this.

So you tend to align.

That one tends to, well, it requires good alignment.

It’s not like insane alignment

because you’re actually exploiting the symmetry

of the situation to help it.

There’s another kind of configuration of magnetic,

of this kind of magnetic confinement called a stellarator,

which is, we have these names for historic reasons.

Which is different than a tokamak.

It’s different than a tokamak,

but actually works on the same physical principle,

that namely, in the end, it produces a plasma,

which loops in magnetic fields,

which loop back on themselves as well.

But in that case, the totality, basically,

the totality of the confining magnetic field

is produced by external three-dimensional magnets,

so they’re twisted.

And it turns out the precision of those is more stringent.

So are tokamaks by far more popular

for research and development currently than stellarators?

Of the concepts which are there,

the tokamak is by far the most mature

in terms of its breadth of performance

and thinking about how it would be applied

in a fusion energy system.

And the history of this was that many,

in fact, you asked, if we go back to the history

of the Plasma Science and Fusion Center,

the history of fusion is that people,

scientists had started to work on this in the 1950s.

It was all hush-hush and Cold War and all that kind of stuff.

And it’s like, they realized, holy cow,

this is really hard.

We actually don’t really know what we’re doing in this,

because everything was at low temperatures,

they couldn’t get confinement.

It was interesting.

And then they declassified it,

and this is one of the few places

that the West and the Soviet Union

actually collaborated on was the science of this.

Even during the Cold War.

Even during the middle of the Cold War.

It was really, and this actually perpetuates

all the way to now for, we can talk about the project

that that has sort of captured in now.

But, and the reason they declassified it

was because everything kind of sucked, basically,

about trying to make this confinement

in high-temperature plasma.

And then the Russians, then the Soviets,

came along with this device called a tokamak,

which is a Russian acronym,

which basically means magnetic coils

arranged in the shape of a donut.

And they said, holy cow, like everyone was stuck

at like a meager, like half a million degrees,

half a million degrees, which is like infusion

in terms of zero, basically.

And then they come along and they say,

oh, we’ve actually achieved a temperature

20 times higher than everybody else.

And it’s actually started to make fusion reactions.

And everyone just go, oh, you know, no way.

It’s just hype from the, it’s like, there’s no way

because we’ve failed at this.

It’s a great story in the history of fusion is that then,

but they insisted, they said, no, look,

you can see this from our data.

It’s like, this thing is really hot

and it seems to be working.

This is, you know, late 1960s.

And there was a team that went from the United Kingdom’s

fusion development lab and they brought this very fancy,

amazing new technology called a laser.

And they use this laser and they shot the laser beam

like through the plasma.

And by looking at the scattered light that came from that,

they go, basically the scattered light gets more broadened

in its spectrum if it gets hotter.

So you could exactly tell the temperature of this.

And even though you’re not physically touching the plasma,

it’s like, holy cow, you’re right.

It is like, it is 10 million degrees.

And so this was one of those explosions of like everyone

in the world then wanted to build a tokamak

because it was clearly like, wow, this is like so far ahead

of everything else that we tried before.

So that actually has a part of the story to MIT

and the Plasma Science and Fusion Center was,

why is there a strong fusion

and a major fusion program at MIT?

It was because we were host

to the Francis Bitter Magnet Laboratory,

which is also the National High Field Magnet Laboratory.

Well, you can see where this goes, right?

From this, we’re kind of telling the stories

backwards almost, but the advent of a tokamak

along with the fact that you could make

very strong magnetic fields with the technology

that had been developed at that laboratory,

that was the origins of sort of pushing together

the physics of the plasma containment

and the magnet technology and put them together

in a way that I would say is a very typical

MIT success story, right?

We don’t do just pure science or pure technology,

we sort of set up this intersection between them.

And there were several pioneers of people at MIT,

like Bruno Coppi, who’s a professor

in the physics department and Ron Parker,

who was a professor in electrical engineering

and nuclear engineering.

It’s like even the makeup of the people, right?

Has got this blends of science and engineering in them.

And that’s actually was the origin

of the Plasma Science and Fusion Center

was doing those things.

So anyway, so back to this.

So why, so yes, tokamaks have been,

have achieved the highest in magnetic fusion by far,

like the best amounts of these conditions

that I talked about.

And in fact, pushed right up to the point

where they were near QP of one.

They just didn’t quite get over one.

So can we actually just linger on the collaboration

across different nations?

Just maybe looking at the philosophical aspect of this.

Even in the Cold War,

there’s something hopeful to me besides the energy

that these giant international projects

are a really powerful way to ease

some of the geopolitical tension,

even military conflict across nations.

There’s a war in Ukraine and Russia.

There’s a brewing tension and conflict with China.

Just the world is still seeking military conflict,

cold or hot.

What can you say about sort of the lessons

of the 20th century in these giant projects

in their ability to ease some of this tension?

So it’s a great question.

So as I said, there was a reason because it was so hard,

that was one of the reasons they declassified it.

And actually they started working together

in some sense on it as well, too.

And I think it was really, there was a heuristic

or altruistic aspect to this.

It’s like, this is something that could change

the future of humanity and its nature

and its relationship with energy.

Isn’t this something that we should work on together?

Right, and that went along in those ones.

And in particularly, that any kind of place

where you can actually have an open exchange

of people who are sort of at the intellectual frontiers

of your society, this is a good thing, right,

of being able to collaborate.

I’ve had the, I mean, I have had an amazing career.

I’ve worked with people from, it’s like hard

to throw a dart at a country on the map

and not hit a country of people

that I’ve been able to work with.

How amazing is that?

And even just getting small numbers of people

to bridge the cultural and societal divides

is a very important thing.

Even when it’s a very teeny fraction

of the overall populations, it can be held up

as an example of that.

But it’s interesting that if you look at then

that continued collaboration, which continues to this day,

is that it was, this actually played a major role, in fact,

in East-West relations or like Soviet-West relations,

is that back in the Reagan-Gorbachev days,

which of course were interesting in themselves

of all kinds of changes happening on both sides, right?

But still like a desire to push down the stockpile

of nuclear weapons and all that, within that context,

there was a fairly significant historic event

that at one of the Reagan-Gorbachev summits

is that they had really, they didn’t get there.

Like they couldn’t figure out how to bargain

to the point of some part of the tree

to get any more of the details of it anymore.

But they needed some kind of a symbol almost to say,

but we’re still gonna keep working

towards something that’s important for all of us.

What did they pick?

A fusion project.

And that was in the mid-1980s

and actually then after,

so they basically signed an agreement

that they would move forward

to like literally collaborate on a project

whose idea would be to show large net energy gain

in fusion’s commercial viability and work together on that.

And very soon after that,

Japan joined as did the European Union.

And now that project, it evolved over a long period of time

and had some interesting political ramifications to it.

But in the end, this actually also had South Korea,

India, and China join as well too.

So you’re talking about a major fraction of,

and now Russia, of course, instead of the Soviet Union.

And actually that coalition is holding together

despite the obvious political turmoil

that’s going around on all those things.

And that’s a project called ITER,

which is under construction in the South of France

right now.

Before we turn to the giant magnet

and maybe even talk about Spark

and the stuff going, all amazing stuff going on at MIT,

what is ITER?

What is this international nuclear fusion megaproject

being built in the South of France?

So its scientific purpose is a worthy one

that it’s essentially in any fusion device,

the thing that you want to see

is more and more relative amounts of self-heating.

And this is something that had not been seen,

although we have made fusion reactions

and we’d seen small amounts of the self-heating,

we never got to a dominant,

this actually goes to this QP business, okay?

The goal of ITER,

and it shifted around a little bit historically,

but fairly quickly became,

we want to get to a large amount of self-heating.

So this is why it has,

its primary feature is to get to QP of around 10.

And through this, this is a way to study this plasma

that has more higher levels of self-determination

around on it.

But it also has another feature,

which was let’s produce fusion power at a relevant scale.

And actually they’re linked together,

which actually makes sense when you think about it,

is that because the fusion power

is the heating source itself,

this means that they’re linked together.

And so ITER is projected to make

about 500 million watts of fusion power.

So this is a significant amount,

like this is what you would use for powering cities.

So it’s not just the research,

it is the development of really trying to achieve scale here.

So self-heating and scale.

Yeah, yes.

So this meant then, too,

is the development of an industrial base

that can actually produce the technologies

like the electromagnets and so forth.

And to do it with, it is a tokamak.

It is one of these, yes.

But very interesting,

it also revealed limitations of this as well, too.

Like what?

Well, it’s interesting is that

it is clearly on paper,

and in fact, and in practice as well, too,

the world, and very different political systems,

and you consider at least geopolitical

or economic rivals or whatever you want to use.

Like working towards a common cause,

and one that we all think is worthy,

is very like, okay, that’s very satisfying.

But it’s also interesting to see the limitations of this.

It’s because, well, you’ve got seven chefs in the kitchen.

So what has this meant in terms of the speed of the project

and the ability to govern it and so forth?

It’s just been a challenge, honestly, around this.

And this is, I mean,

it’s very hard technically what’s occurring.

But when you also introduce such levels of,

I mean, this isn’t just me saying it.

There’s like GAO reports from the US government

and so forth.

It’s hard to like steer all of this around.

And what that’s tended to do is make it,

it’s not the fastest decision-making process.

My own personal view of it was,

it was interesting, because you asked,

you said about the magnet and commonwealth fusion systems.

It was, I worked most of my career on ITER,

because when I came into the field in the early 1990s,

when I completed my PhD and started to work,

this was one of the most,

you can’t imagine being more excited about something.

We’re going to change the world with this project.

We’re going to do these things.

And we just poured an entire generation,

and afterwards as well, too,

just poured their imagination and their creativity

about making this thing work.

Very good.

But also at some point, though,

when it got to being another five years of delay

or a decade of delay, you start asking yourself,

well, is this what I want to do?

Right, am I going to wait for this?

So it was a part of me starting to ask questions

with my students.

I was like, is there another way

that we can get to this extremely worthwhile goal

that maybe it’s not that pathway?

And the other part that was clearly frustrating to me,

because I’m an advocate of fusion.

You asked me about, was I, you know,

I was like, well, it’s a laser fusion

or inertial fusion or magnetic fusion.

I just want fusion energy, okay?

Because I think it’s so important to the world is that,

but the other thing, if that’s the case,

then why do we have only one attempt at it

on the entire planet, which was ITERF?

It’s like, that makes no sense to me, right?

We should have multiple attempts at this

with different levels of whatever you want to think about it,

technical, schedule, scientific risk,

which are incorporated in them,

and that’s going to give us a better chance

of actually getting to the goal line.

With that spirit, you’re leading MIT’s effort

to design SPARC, a compact, high-field,

DT-burning tokamak.

How does it work?

What is it?

What’s the motivation?

What’s the design?

What are the ideas behind it?

At its heart, it’s exactly the same concept as ITER.

So it’s basically a configuration of electromagnets.

It’s arranged in the shape of a donut.

And within that, we would do the same thing

that happens in all the other tokamaks

and including in ITER and in this one,

is that namely, you put in gas,

make it into a plasma, you heat it up,

it gets to about 100 million degrees.

The differentiator in SPARC is that

we use the actual deuterium-tritium fuel,

and because of the access to very high magnetic fields,

it’s in a very compact space.

It’s very, very small.

What do I mean by small?

So it’s 40 times smaller in volume than ITER,

but it uses exactly the same physical principles.

So this comes from the high magnetic field.

So in the end, why does this matter?

What it does is it does those things,

and it should get to the point where

it’s producing over 100 million watts of fusion power,

but remember, it’s 40 times smaller.

So ITER was 500 megawatts.

Technically, our design is around 150 megawatts,

so it’s only about a factor of three difference

despite being 40 times smaller,

and we see QP large,

order of 10 or something like this.

At that state, it’s very important scientifically

because this basically matches what ITER is looking to do.

The plasma’s dominated by its own heating.

It’s very, very important,

and it does that for about 10 seconds,

and the reason it’s for 10 seconds is that

that basically allows everything to settle

in terms of the fusion in the plasma equilibrium.

Everything is nice and settled,

so you know you have seen the physical state

at which you would expect a power plant

to operate basically for magnetic fusion.

Like, wow, right?

But it’s more than that, and it’s more than that.

It’s because about who’s building it

and how it’s being financed.

So that scientific pathway was made possible

by the fact that we had access

to a next generation of magnet technology.

So to explain this real quick, why do we call it,

you said it in the words, a superconducting magnet.

What does this mean?

Superconducting magnet means that the materials

which are in the electromagnet

have no electrical resistance.

Therefore, when the electric current is put into it,

the current goes around unimpeded,

so it could basically keep going around and around

technically for infinity, or for eternity.

And what that means is that when you energize

these large electromagnets,

they’re using basically zero electrical power

to maintain them, whereas if you would do this

in a normal wire, like copper,

you basically make an enormous toaster oven

that’s consuming enormous amounts of power

and getting hot, which is a problem.

That was the technical breakthrough

that was realized by myself and at the time,

my students and postdocs and colleagues at MIT,

was that we saw the advent of this new superconducting

material, which would allow us to access

much higher magnetic fields.

It was basically a next generation of the technology,

and it was quite disruptive to fusion,

but namely what it would allow,

that if we could get to this point

where we can make the round 20 Tesla,

we knew by the rules of tokamaks

that this is going to allow us to vastly shrink

the sizes of these devices.

So it wouldn’t take, although it’s a worthy goal,

it wouldn’t take a seven nation international treaty

basically to build it.

You could build it with a company and a university.

So same kind of design,

but now using the superconducting magnets.

Yeah, and if in fact, if you look at it,

it’s like if you just expand the size of it,

they look almost identical to each other

because it’s based on the,

and actually that comes for a reason, by the way,

is that it also looks like a bigger version

of the tokamak that we ran at MIT for 20 years,

where we established the scientific benefits,

in fact, of these higher magnetic fields.

So that’s the pathway that we’re on.

So we say, so what does this mean?

The context is different because it was made,

because it’s primarily being made

by a private sector company spun out of MIT,

because the way that it raised money

and the purpose of the entity, which is there,

is to make commercial fusion power plants,

not just to make a scientific experiment.

This is actually why we have,

it’s why we have a partnership, right?

Is that our purpose at MIT is not to commercialize directly,

but boy, do we want to advance the technology

and the science that comes along with this,

and that’s the reason we’re sort of doing it together.

So it’s MIT and Commonwealth Fusion Systems.

So what’s interesting to say about financing?

And this seems like, from a scientific perspective,

maybe not an interesting topic,

but it’s perhaps an extremely interesting topic.

I mean, you can just look at the tension

between SpaceX and NASA, for example.

It’s just clear that there’s different financing mechanisms

can actually significantly accelerate

the development of science and engineering.

It’s great that you brought that up.

We use several historic analogs,

and one of them is around SpaceX,

which is an appropriate one

because space, putting things into orbit

has a minimum size to it

and integrated technological complexity

and budget and things like this.

So our point when we were talking about

starting a fusion commercialization company,

people look at you like,

isn’t this still really just a science experiment?

But one of the things that we pointed to was SpaceX

to say, well, tell me, like 25 years ago,

how many people would have voted

that the leading entity on the planet

to put things into orbit’s a private company?

People would have thought you were nutso, right?

And what is interesting about SpaceX

was that it proved it’s more than actually just financing.

It’s really the purpose of the organization.

So the purpose of a,

and I’m not against public finance or anything like that,

but the purpose of a public entity like NASA

correctly speaks to the political,

because the cost comes from the political assembly

that is there and I guess from us eventually as well too,

but its purpose wasn’t about making a commercial product.

It’s about fundamental discovery and so forth,

which is all really great.

It’s like, why did SpaceX,

it’s interesting, why did SpaceX succeed so well

is because the idea was,

it’s like the focus that comes in the idea

that you’re going to relentlessly reduce cost

and increase efficiency is a drive

that comes from the commercial aspect of it, right?

And this also then changes the people in the teams

which are doing as well too.

And in fact, trickles throughout the whole thing

because the purpose isn’t,

while you’re advancing things,

like it’s really good that we can put things in orbit

a lot more cheaply.

Like it advances science,

which is an interesting synergy, right?

And it’s the same thing that we think

is gonna happen in fusion, that namely,

this is a bootstrap effect that actually,

that when you start to push yourself

to think about near-term commercialization,

it allows the science to get in hand faster,

which then allows the commercialization to go faster

and up we go.

By the way, we’ve seen this also in another,

again, you have to watch out with analogies

because they can go so far,

but like biotech is another one.

Like you look at the Human Genome Project,

which was, it’s sort of like,

to me, that’s like mapping the human genome

is like that we can make net energy from fusion.

Like it’s one of those, like in your drawer that you go,

this is a significant achievement by humanity,

right, in this century.

And there’s the Human Genome Project,

fully government funded.

It’s gonna take 20, 25 years

because we basically know the technology.

We’re just gonna be really diligent,

keep going, da, da, da, da.

And then all of a sudden, what comes along?

Disruptive technology, right?

You can sequence, you know,

shotgun sequencing and computer recognition patterns.

And basically, oh, I can do this 100 times faster.

Like, wow, right?

So that’s really the, you know,

to me, the story about why we started,

why we launched Commwith Fusion Systems

was more than just about another source of funding,

which it is a different source of funding

because it’s also a different purpose,

which is very important.

But there’s also something about

a mechanism that creates culture.

So giving power to like a young student,

ambitious student, to have a tremendous impact

on the progress of nuclear fusion

creates a culture that actually makes

progress more aggressively.

Like you said, when seven nations collaborate,

it gives more incentive to the bureaucracy

to slow things down, to kind of have,

let’s first have a discussion,

and certainly don’t give voice to the young,

ambitious minds that are really pushing stuff forward.

And there’s something about like the private sector

that rewards, encourages, inspires young minds

to say in the most beautiful of ways,

F you to the boss, to sort of like,

we’ll make it faster, we’ll make it simpler,

we’ll make it better, we’ll make it cheaper.

And sometimes that brashness doesn’t bear out.

That’s an aspect that you just take

a different risk profile as well too.

But you’re right, it’s this, of the,

I mean, it was interesting, our own trajectory

at the fusion center was, like we were pushed

into this place by necessity as well too

because I told you we have, and we had operated

for a long time, a tokamak on the MIT campus,

achieved these world records,

like 100 million degree plasma,

and so I was like, wow, this is fantastic.

But somewhat ironically, I have to say,

is that it was like, oh, but we’re not,

this isn’t the future of fusion anymore.

Like we’re not, we’re just gonna stop

with small projects because it’s too small, right?

So we should need, we need to really move

on to these much bigger projects

because that’s really the future of fusion.

And so it was defunded, and this basically

put at risk, like we were going to essentially

lose MIT in the ecosystem, really, of fusion,

both from the research, but also clearly important

from the educational part of it.

So we, you know, we pushed back against this,

we got a lifeline, we were able to go,

and it was in this time scale that we basically

came up with this idea, it’s like, we should do this.

And in the end, it was all of those,

the people who were in the C level of the company

were all literally students who got caught in that.

They were PhD students at the time.

So you talk about enabling another generation,

it’s like, yeah, there you go, right?

So SPARC gave-

A lifeline, yeah.

A lifeline, gave fuel to the future center at MIT

that it continues.

But it’s way more than that.

It wasn’t just about like surviving

for the sake of surviving, it was like,

in the end for me, it became like this,

I remember the moment, you talk about these moments

as a scientist, and we were just like,

we were working so hard about figuring out,

like, does this really, will this really work?

Like, and it’s complex.

Like, does the magnet work?

Does the interaction with the plasma work?

Does all these things work?

And it was just a grind, push, push, push, push.

And I remember the moment,

because I was sitting in my office in Brookline,

and there was just like, I read like,

and I was in, I don’t know, whatever,

the 20th or 40th slide or something into it.

And it was sort of that moment,

like it just came together.

And I like, I got, I couldn’t even sit down,

because all it was just like, my wife was like,

why are you walking around the apartment like this?

Like, I just couldn’t, I said, it’s going to work.

Like, it’s going to work.

Like, holy, that moment of realization is like,

kind of amazing, but it also brings the responsibility

of making it work as well.

Yeah, how do you make it work?

So you mean like that magic realization

that you can have this modern magnet technology,

and you can actually, like, why do we need to work

with ITER, we can do it here?

Yeah, yeah.

But it’s interesting that ITER is,

that one of the reasons that, like,

we started with a group of six of us at MIT,

and then once we got some funding

through the establishment of the company,

it became a slightly larger.

But in the end, we had a rather small team.

Like, this was like a team of,

order of like 20 to 25 people designed Spark

in like about two years, right?

How does that happen?

Well, we’re clever, but you have to give ITER

its due here as well, too.

Again, this is an aspect always of the bootstrap up.

Like, I go back to the Human Genome Project.

So modern day genomics would not be possible

without the underlying basis that came

from setting that up.

It had to be there.

It had to be curiosity-driven public program.

It’s the same with ITER, but because we had the tools

that were there to understand ITER,

we also had the tools to understand Spark.

So we parlayed those in an extremely powerful way

to be able to tell us about what was going to happen.

So these things are never simple, right?

It’s like people look at this, go,

oh, this means we should, like,

should we really have a public-based program about fusion,

or should we have it all in the private?

It’s like, no, the answer is neither way,

because in all these complex technologies,

you have to keep pushing on all the fronts

to actually get it there.

So, you know, the natural question when people hear

breakthrough with the inertial confinement,

with the magnetic confinement is,

so when will we have commercial reactors, power plants

that are actually producing electricity?

What’s your sense, looking out into the future,

when do you think you can envision a future

where we have actual electricity coming from nuclear fusion?

Partly driven by us, but in other places as well, too.

So there’s the advent, what’s so different now

than three or four years ago.

Like, we launched around four years ago.

What’s so different now is the advent of a very nascent,

but seemingly robust, commercial fusion endeavor.

So it’s not just Commonwealth Fusion Systems,

there’s something like 20-plus companies.

There’s a sector now.

There’s a sector.

They actually have something called

the Fusion Industry Association,

which if your viewers want to go see this,

this describes the different,

and they’ve got this plethora of approaches.

Like, I haven’t even described all the approaches,

I’ve basically described the mainline approaches.

And they’re all at varying degrees of technical

and scientific maturity with very huge,

different balances between them.

What they share is that because they’re going out

and getting funding from the private sector

is that their stated goals are about getting fusion

into place so that both it meets the investors’ demands,

which are interesting, right, and the timescales of that,

but also it’s like, well, there’s gonna, and why?

It’s because it’s easy.

There’s this enormous push, driver,

about getting carbon-free energy sources

out into the market.

And whoever figures those out is going to be both very,

it’s gonna be very important geopolitically,

but also economically as well too.

So it’s a different kind of bet, I guess,

or a different kind of gamble that you’re taking with fusion

but it’s so disruptive that it’s like,

there’s essentially a class of investors and teams

that are ready to go after it as well too.

So what do they share in this?

They typically share getting after fusion on a timescale

so that could it have any relevance

towards climate change, battling climate change.

And I would say this is difficult,

but it’s fairly easy because it’s math.

So what you do is you actually go to some target

like 2050 or 2060, something like this,

and say, I wanna be blank percent

of the world’s market of electricity

or something like that.

And we know historically what it takes to evolve

and distribute these kinds of technologies

is every technology takes some period of time.

It’s so-called S-curve, it’s basically,

everything follows a logarithmic curve,

exponential type curve.

It’s a straight line, a log plot.

And like you look at wind, solar, fission,

they all follow the same thing.

So it’s easy, you take that curve and you go,

that’s slope and you work backwards and you go,

if you don’t start in the early 2030s,

like it’s not gonna have a significant impact

by that time.

So all of them share this idea.

And in fact, it’s not just the companies now,

the US federal government has a program

that was started last year that said,

we should be looking to try to get like the first,

and what do I mean by like, what does it mean to start?

That you’ve got something that’s putting electricity

on the grid, a pilot, what we call it.

And if that can get started like in the early 2030s,

the idea of ramping it up makes sense, it’s math, right?

So that’s the ambition, then the question is,

and actually this is different

because the government program,

and they vary around in this.

So for example, the United Kingdom’s government idea

was to get the first one on by 2040.

And China has ambitions probably middle 2030s

or maybe a little bit later.

And Europe, continental Europe is a little bit,

I’m not exactly sure where it is, but it’s like later,

it’s like 2050 or 2060,

because it’s mostly linked to the Eater timeline

as well too.

The fusion companies, which makes sense,

it’s like, of course,

they’ve got the most aggressive timelines.

It’s like, we’re gonna map the human genome faster

as well too, right?

So it’s interesting about where we are.

And I think, we’re not all the way there,

but my intuition tells me we’re probably gonna have

a couple of cracks at it actually on that timeline.

So this is where we have to be careful though,

you say commercial fusion, what does that mean?

Commercial fusion to me means that you’re actually

have a known quantity about what it costs,

what it costs to build and what it costs to operate,

the reliability of putting energy on the grid.

That’s commercial fusion.

It’s like, so it turns out that that’s not necessarily

exactly the first fusion devices

that put electricity on the grid.

Cause you got it, there’s a learning curve

to get like better and better at it.

But that’s probably, I would suspect the biggest hurdle

is to get to the first one.

The work I’ve done, the work I continue to do

with autonomous vehicles and semi-autonomous vehicles.

There’s an interesting parallel there

where a bunch of companies announced a deadline

for themselves in 2020, 2021, 22.

And only a small subset of those companies

have actually really pushed that forward.

There’s Google with Waymo or Alphabet rather.

And then there’s Tesla with semi-autonomous driving

in their autopilot, full self-driving mode.

And those are different approaches.

So Tesla is achieving much, much higher scale,

but the sort of the quality of the drive

is semi-autonomous, right?

I don’t know if there’s a metaphor, an analogy here.

And then there’s Waymo that’s focusing

on very specific cities, but achieving real full autonomy

with actual passengers, but the scale is much smaller.

So I wonder, like, just like you said,

there’ll be these kinds of similar

kind of really hard pushes.


So actually, this is why I’m encouraged about Fusion.

So Fusion’s still hard, let’s let everyone be clear,

because of the science underneath it

of achieving the right conditions for the plasma

basically is a yardstick that you have to put up

against all of them.

What’s encouraging that I see in this,

and it’s actually what happens

when you sort of let loose the creativity of this

is maybe I’ll go back to first principles.

So Fusion is also a fairly strange,

so if you think about building a coal plant,

like burning wood and coal and gas

is actually not that much different from each other,

because they’re kind of about the same physical conditions

and you get the fuel and you light it.

Fusion is very, remember I told you

that there’s this condition of the temperature,

which is kind of universal.

But if you take the density of the fuel

between magnetic fusion and inertial fusion,

they’re different by about a factor of 10 billion.

So this, and the density of fuel really matters,

and actually so does the,

and this means energy confinement time

is also different by a factor of 10 billion as well too,

because it’s the product of those two.

So one’s really dense and short-lived,

and the other one’s really long-lived

and actually under-dense as well too.

So what that means is that the way to get

the underlying physical state is so different

among these different approaches,

what it lends itself to is,

does this mean that eventual commercial products

will actually fill different needs in the energy system?

So it sort of goes to your comment about,

I have to suspect this, because anything that is high-tech

and is like a really important thing in our economy

tends to never find its way as one, only one manifestation.

Like look at transportation as well too.

We have scooters, Vespas, overland trucks, cars,

electric cars, of course we have these

because they meet different demands in it.

So what’s interesting that I find fascinating now

is that we have, in fusion it’s going to look like that,

that probably there’s, while the near-term focus

is on electricity production,

there might even be different kinds of markets

that actually make sense in some places less than others.

It comes to trade-offs,

because we haven’t really talked about the engineering yet

but engineering really matters,

like to the operation of the device.

And so it could be that, I suspect what we’ll end up with

is several different configurations

which have different features,

which are trade-offs basically in the energy market.

What do you see as the major engineering

or general hurdles that are in the way?

So the first one is just the cost of building a single unit.

So fusion has, and it’s actually interesting,

you talked about the different models that you have.

So fusion has, one of its interesting limitations

is that it’s very hard,

it almost at some point becomes physically impossible

to actually make small power units,

like a kilowatt, 1,000 watts,

which is like a personal home,

like this is about 1,000 watts,

or your personal use of electricity

is about like 1,000 watts.

This is basically impossible for a single unit to do this.

So like you’re not gonna have a fusion power plant

like as your furnace or your electric heater in your home.

And the reason for this comes from the fact

that fusion relies on it being,

it’s not just that it’s very hot,

it’s that the fusion power

is the heating source to keep it hot.

So if you go too small,

it basically just cannot keep it hot.

So it’s interesting is that this,

so this is one of the hard parts.

So this means that the individual units,

it varies from concept to concept,

but the National Academy’s report that came out last year

sort of put the benchmark as being

like probably the minimum size

looks like around 50 million watts of electricity,

which is like enough for like a small to mid-sized city,


So that is, so that’s sort of like a scale challenge.

And in fact, it’s one of the reasons why

in Commonwealth and in other private sector ones,

like they try to push this down actually

of trying to get to these smaller units

just because it reduces the cost of it.

Then probably, obviously, I would say it’s an obvious one,

like achieving the fusion state itself

and high gain is a hard one,

what we already talked about.

What kind of hurdle, what kind of challenge is that?

That’s achieving the right temperature, density,

and energy confinement time in the fuel itself,

in the plasma itself.

And so some of the configurations

which are being chosen are actually,

have quite a ways to go, in fact, of seeing those.

But what their consideration is,

oh, yes, but by our particular configuration,

the engineering simplicity confers

like an economic advantage, even if we’re behind

in sort of a science sense.

Okay, which is fine, that’s also what you get

when you get an explosion in the private sector,

you basically are distributing risks in different ways,

right, which makes sense.

All of that good, so what I would say

is that the next hurdle to really overcome

is about making that electricity.

So like we need to see a unit or several units,

like put using fusion in some way

to put a meaningful amount of energy on the grid,

because this starts giving us real answers

as to like what this is going to look like.

The full end-to-end process.

The full end-to-end thing.

So Commonwealth’s goal is that,

I’ll just comment to Commonwealth

because I’ll take some, you know,

I guess some credit for this,

is that the origins of Commonwealth

were in fact in examining that.

Like we could see this new technology coming forward,

this new superconducting material,

and the origins of our thought process

were really around designing, effectively,

the pilot plant or the commercial unit.

It’s called ARC, which is actually

the step forward after SPARC.

And that was the origins of it.

So all the things that were other parts of the plan,

like SPARC and the magnet,

were actually all informed totally by building

something that was going to put net electricity on the grid.

And the timing of that, we still hope,

is actually the early 2030s.

So SPARC is the design of the Takamak

and ARC is the actual full end-to-end thing.

Is like a thing that actually puts that energy

on the grid.

So SPARC is named, you know, intentionally,

that it’s like, it’s on for a short period of time

and it doesn’t have a, it has, yeah, you know,

it’s the spark of the fusion, you know,

revolution or something like that,

I guess we could call it.

Yeah, so those are sort of the programmatic

challenges of doing that.

And, you know, you asked about,

you talked about SpaceX.

So what has evolved even in the last year or so

was, in fact, in March of 2022,

the White House announced that it was going to start

a program that kind of looks like a SpaceX analogy,

that namely, wow, we’ve got these things

in the private sector.

We should leverage the private sector

and the advantages of what they obtain,

but also with the things, like this is going to be hard

and it’s going to take quite a bit of financing.

So why don’t we set up a program where we don’t really

get in the way of the private sector fusion companies,

but we help them finance these difficult things,

which is how SpaceX basically became successful

through the COTS program, fantastic, right?

And that’s evolving as well too.

So like the fusion ecosystem is almost unrecognizable

from where it was like five years ago

around those things.

How important is it for the heads of the companies

that are working on nuclear fusion to have a Twitter account

and to be quite, you said you don’t use Twitter.

I don’t use Twitter.

Very much.

I mean, there is some element to,

and I don’t think this should be discounted,

whatever you think about figures like Jeff Bezos

with Blue Origin or Elon Musk with SpaceX.

There is a science communication, to put it in nice terms,

that’s kind of required to really educate the public

and get everybody excited and sell the sexiness of it.

I mean, just even the videos of SpaceX,

just being able to kind of get everybody excited

about going out to space once again.

I mean, there’s all kinds of different ways of doing that,

but I guess that’s what companies do well,

is to advertise themselves, to really sell themselves.

It is, yeah.

Well, actually, I feel like one of the reasons

on this podcast, and so I don’t have an official role

in the company.

And one of the reasons for this was also that,

it’s interesting, because when you come from,

like you’re running a company, it makes sense.

They’re promoting their own product and their own vision,

which totally makes sense.

But there’s also a very important role for academics

who have knowledge about what’s going on,

but are sufficiently distant from it

that they’re not fully only self-motivated

just by their own projects or so forth.

And for me, this is, I mean, we see particularly

the problems of the distrust in technology,

and then honestly in the scientific community as well too.

It will be one of the greatest tragedies, I would say,

that if we go through all of this and almost pull off

what looks like a miracle, like technologic

and scientific-wise, which is to make a fusion power plant,

and then nobody wants to use it because they feel

that they don’t trust the people who are doing it

or the technology.

So we have to get so far out ahead of this.

So I give lots of public lectures or things like this

of accessing a larger range of people.

We’re not trying to hide anything.

You can come and see, come do tours of our laboratory.

In fact, I want to set those up virtually as well too.

You might look at our Plasma Science and Fusion Center

YouTube channel.

So we are reaching out through those media,

and it’s really important that we do those things.

But it’s also, but also then realizing,

setting up the realistic expectations

of what we need to do.

We’re not there.

We don’t have commercial fusion devices yet.

And you asked, like, what are the challenges?

I’m not going to get into any deep technical questions

about what the challenges are, but it is,

the pathway, not just to make fusion work technically,

but to make it economically competitive and viable

so that it’s actually used out in the private sector

is a non-trivial task.

And it’s because of the newness of it.

Like, we’re simultaneously trying to evolve the technology

and make it economically viable at the same time.

Those are two difficult coupled tasks.

So my own research and my own drive right now

is that fantastic Commonwealth Fusion Systems is set up.

We have a commercialization unit of that particular kind,

which is going to drive forward a token back.

In fact, I was just, there’s discussions,

or there’s dialogues going on around the world

with other kinds of ones, like stellarators,

which prefer different kinds of challenges

and economic advantages.

But what we have to, I know what we have to have.

What we have to have is a new generation

of integrated scientists, technologists, and engineers

that understand, like, how, what needs to get done

to get all the way to the goal line.

Because we don’t have them now.

So like a multidisciplinary team.

Yeah, exactly.

What’s required, I mean, you’ve spoken about,

you said that fusion is, quote,

the most multidisciplinary field you can imagine.

Yes, yeah.

Why is that?

What are the differences?

Well, because most of our discussion that we’ve had so far

is really like a physics discussion, really.

So don’t neglect physics is at the origin of this.

But already we touched on plasma physics

and nuclear physics, which are basically two,

somewhat overlap, but independent disciplines.

Then when it comes to the engineering,

it’s almost everything.

So why is this?

Well, let’s build an electromagnet together, okay?

What is this gonna take?

It’s gonna take, it’s basically electrical engineering,

computer, so you understand how it goes together,

what happens.

Computational engineering to model

this very complex integrated thing.

Materials engineering, because you’re pushing materials

to their limit with respect to stress and so forth.

It takes cryogenic engineering,

which is sort of a subdiscipline,

but cooling things to extremely low temperatures.

There’s probably some kind of chemistry thing in there too.

Well, actually, yeah,

which tends to show up in the materials.

Then that’s just one of the sub components of it.

Like almost everything gets hit in this, right?

So you’re, and you’re also in a very integrated environment

because in the end, all of these things,

while you isolate them from each other in a physics sense,

in an engineering sense,

they all have to work like seamlessly together.

So it’s one of those, I mean, in my own career,

I’ve basically done atomic physics, spectroscopy,

plasma physics, ion etching.

So this includes material science,

something called MHD, even magnetohydrodynamics.

And now all the way through, like,

I’m not even sure how many different careers I’ve had.

It’s also, by the way, this is also a recruiting stage

for like young scientists thinking to come in.

My comment to scientists, if you’re bored in fusion,

you’re not paying attention

because there’s always something interesting to go and do.

So that’s a really important part of what we’re doing,

which isn’t new in fusion, actually,

and in fact is in the roots of what we’ve done at MIT.

But holy cow, like the proximity of possibility

of commercial fusion is the new thing.

So my catchphrase is like,

you may be wondering like,

why weren’t we doing all these things?

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.

There is a history, like you said, 40, 30, whatever,

that kind of old joke.

There’s a history of fusion projects

that are characterized by cost overruns and delays.

How do you avoid this?

How do you minimize the chance of this?

You have to build great teams is one of them.

It tends to be that the smaller the,

there’s sort of an, I’m not an expert in this,

but I’ve seen this enough integrated engineering teams.

Is there any equations?

Yeah, well, there’s almost,

I’ve seen this from enough teams.

Like I’ve seen also the futility of lone geniuses

trying to solve everything by themselves, like no.

But also organizations that have 10,000 people in them

is just not, doesn’t lend itself at all to innovation.

Like one of our original sponsors and a good friend,

Vinod Khosla, I don’t know if you’ve ever talked

to Vinod Khosla, he’s a venture guy.

He’s got fantastic ideas about the right sizes of teams

and things that really innovate, right?

And there is an optimum place in there

is that you get enough cross-discipline and ideas,

but it doesn’t become so overly bureaucratic

that you can’t execute on it.

So one of the ways,

and this was one of the challenges of fusion

is that everything was leading towards,

like I have to have enormously large teams

just to execute because of the scale of the project.

The fact that now through both technology

and I would argue financing innovation,

we’re driving to the point where it’s smaller focused teams

about doing those things.

So that’s one way to make it faster.

The other way to make it faster is modularize the problem

or parse the problem.

So this is the other difficulty in fusion

is that you tend to look at this as like,

oh, it’s really just about making the plasma

into this state here that you get this energy gain.

No, because in the end,

if you can parse out the different problems of making that

and then make it as separate as possible

from extracting the energy

and then converting it into electricity,

the more separate those are,

the better they are because you get parallel paths

that basically mitigate risk.

This is not new in fusion, by the way,

and this is the way that we attack

most complex technological,

integrated technological challenges.

Have you by any chance seen some of the application

of artificial intelligence reinforcement learning?

A DeepMind has a nice paper,

has a nice effort on basically using reinforcement learning

for a learned control algorithm

for controlling nuclear fusion.

Do you find those kinds of,

I guess you throw them under the umbrella

of computational modeling.

Do you find those interesting, promising directions?

They’re all interesting.

So when people, I’ll pull back,

maybe a natural question is like,

why is it different in fusion?

Like there’s a long history to fusion, right?

It was going on for, like I told you,

like stories from the late 1960s,

like what’s different now, right?

So I think from the technology point of view,

there’s two massive things which are different.

So one of them, I’ll be parochial,

it’s the advent of this new superconducting materials

because the most mature ways that we understand

about how we’re gonna get to fusion power plants

are magnetic fusion.

And by the fact that you’ve got access

to something which like changes the economic equation

by an over an order of magnitude is just a totally,

you know, and that wasn’t that long ago.

It was only September of 2021

that we actually demonstrated the technology.

That changes the prospects there.

And the other one is computing.

And it’s across the whole spectrum.

It’s not just in control of the fusion device.

It’s actually in the,

we actually use machine learning and things like this

in the design of the magnet itself.

It’s an incredibly complex design space.

So you use those tools.

The simulation of the plasma itself is actually,

we’re at a totally different place than we were

because of those things.

So those are the two big drivers that I see actually

that make it different.

And actually, and it’s interesting,

both those things self-enforce

about what you asked about before,

like how do you avoid delays and things?

Well, it’s by having smaller teams

that can actually execute on those.

But now you can do this

because the new magnets make the devices all smaller.

And the computing means your human effectiveness

about exploring the optimization space is way better.

It’s like, they’re all interlinked to each other.

Plus the modularization, like you said,

and it’s everything just kind of works together

to make smaller teams more effective, move faster.

And it’s actually,

and it’s through that learned experience.

I mean, you know, of the things that I’m the most proud of

about what came out.

In fact, the origins of thinking

about how we would use

the high-temperature superconducting magnets

came out of my design class at MIT.

And in the design class,

like one of the features that I kept,

I mean, it was interesting.

I actually learned,

I really learned along with the students about this,

but like this insistence on the features,

like we can’t have so many coupled,

integrated, hard technology developments.

Like we have to separate these somehow.

So we worked and worked and worked at this.

And in fact, that’s what really, in my opinion,

the greatest advantage of the arc design

and built into the Commonwealth Fusion System idea

is like to parse out the problems.

Like how can we attack these in parallel?

Yeah, and so it really comes to,

we talked about philosophy.

It’s like a design philosophy.

Like how do you attack these kinds of problems?

And you do it like that.

And also, like you mentioned offline,

that there’s a power to,

you know, as part of a class,

to design a nuclear fusion power plant.

And then make it a reality.

And it’s hard to imagine a more powerful force

than like 15 MIT PhD students,

like working together towards solving a problem.

And what I always, in fact,

we recently just taught the most recent,

you know, I say I teach it.

I mean, I guide it, actually.

The most recent version of this,

where they actually designed, you know,

based on this National Academies report,

they actually designed like a pilot plant

that has basis and similarities to what we had done before.

But, you know, I kept wanting to like push the envelope

in where they are.

It’s like the creativity and the energy

that they bring to these things is kind of like,

it keeps me going.

Like, you know, I’m not gonna retire anytime soon.

When I keep seeing that kind of dedication

and it’s wonderful around on that.

It almost, not to overuse a,

or to paraphrase something, right,

which is that, you know, the famous quote by Margaret Mead,

you know, never doubt that a small group

of dedicated, you know, persons will change the world.

Indeed, it’s the only thing that ever has.

I mean, that’s just such a powerful

and inspiring thing for an individual.

Find the right team, be part of that.

And then you, yourself, your passion,

your efforts could actually make a big change.

Big impact.

I gotta ask you, so it’s,

it’s a whole nother different conversation,

I’m sure, to have.

But nuclear power as it currently stands,

so using fission is extremely safe,

despite public perception.

It is the safest, actually.

So that’s a whole nother conversation.

But almost like a human, bureaucratic,

physics, engineering question of what lessons

do you draw from the catastrophic events

where the power plants did fail?

So Chernobyl and Three Mile Island.

Chernobyl, what lessons do you draw?

Actually, Three Mile Island wasn’t really a disaster

because nothing escaped from the thing,

but Chernobyl and Fukushima were,

have been, you know, had obvious consequences

in the populations that live nearby.

What lesson do you draw from those

that you can carry forward to fusion?

Now, I know there’s, you can say that you’re not gonna have

the same kind of issues, but it’s possible

that the same folks also said they’re not gonna be,

have those same kind of issues.

We humans, the human factor.

We haven’t talked about that one quite as much,

but it’s still there.

So to be clear, it’s, so fusion has intrinsic safety

with respect to it can’t run away.

Those are physics basis.

Technology and engineering basis of running a complex,

again, anything that makes large amounts of power

and heats things up has got intrinsic safety in it.

And by the fact that we actually produce

very energetic particles, this doesn’t mean

that there’s no radiation involved in ionizing radiation

to be more accurate.

In fusion, it’s just that it’s in a very different

order of magnitude, basically.

So what are the lessons in fusion?

So one of them is make sure that you’re looking at aspects

of the holistic environmental and societal footprint

that the technology will have.

As technologists, we tend not to focus on these,

particularly in early stages of development.

Like we just want something that works, right?

But if we come with just something that works,

but doesn’t actually satisfy the societal demands

for safety and for, I mean, we will have materials

that we have to dispose of out of fusion.

But there’s technological questions

about what that looks like.

So will this look like something that you have to put

in the ground for a hundred years or five years?

And the consequences of those are both economic

and societal acceptance and so forth,

but don’t bury those.

Like bring these up front, talk to people about them

and make people realize that you’re actually,

the way I would look at it is that you’re making fusion

more economically attractive by making it

more societally acceptable as well too.

And then realize is that, you know,

I think there’s a few interesting boundaries, basically.

So one of them, speaking of boundaries,

that successful fusion devices, I’m pretty sure

will require that you don’t have to have an evacuation plan

for anybody who lives at the site boundary.

So this has implications for what we build

from a fusion engineering point of view,

but has major implications for where you can site

fusion devices, right?

So in many ways, it becomes more like, well, you know,

we have fences around, you know, industrial heat sources

and things like this for a reason, right?

For personal safety.

It looks more like that, right?

It’s not quite as simple as that,

but that’s what it should look like.

And in fact, we have research projects going on right now

at MIT that are like trying to push the technologies

to make it more look like that.

I think that those are key.

And then in the end, as I said, like,

so Chernobyl is physically impossible,

actually, in a fusion system.

From a physics perspective.

From a physics perspective, you can’t run away

like it did at Chernobyl, which was basically human error

that, you know, of letting the reactors,

like, run out of control, essentially.

Human error can still happen with fusion-based reactors.

Yeah, so, but in that one, if human error occurs,

then it just stops and this is done.

And all of those things, this is the requirement

of us as technologists and developers of this technology

to not ignore that dimension, in fact, of the design.

And that’s why me personally, I’m actually pouring myself

more and more into that area because this is going to be,

I actually really think it is an aspect

of the economic viability of fusion

because it clearly differentiates ourselves

and also sets us up to be about what we want fusion to be

is that, again, on paper, fusion can supply

all of our energy, like all of it.

So this means I want it to be like,

like really environmentally benign.

But this takes engineering ingenuity, basically, to do that.

Let me ask you some wild out there questions.


So for-

We’ve been talking too much, you know.

It’s a very-

Simple, practical things in everyday life.

No, only revolutionizing the entire energy infrastructure

of human civilization, yes.

But, so cold fusion, this idea, this dream,

this interesting physical goals seem to be impossible,

but perhaps it’s possible.

Do you think it is possible?

Do you think down the line, somewhere in the far distance

it’s possible to achieve fusion at low temperature?

It’s very, very, very unlikely.

And this comes from, so this would require

a pretty fundamental shift in our understanding

of physics, as we know it now.

And we know a heck of a lot

about how nuclear reactions occur.

By the way, what’s interesting is that there’s,

they actually have a different name for it.

They call it leaner, like low energy nuclear reactions.

But we do have low energy nuclear reactions.

We know these, it’s because these come from,

particularly the weak interaction,

the weak force, nuclear force.

And so, it’s at this point, as a scientist,

you always keep yourself open,

but you also demand proof, right?

And that’s the thing.

It almost requires a breakthrough

on the theoretical physics side.

So, some deeper understanding about quantum mechanics,

so the quantum tunneling, some weird.

Yeah, and people have looked at that,

but even something like quantum tunneling

has a limit as to what it can actually do.

So, there are people who are genuine,

that really want to see it make,

but it sort of goes to the extort,

I mean, we know fusion happens at these high energies.

Like, we know this extremely accurately,

and I can show you a plot that shows that

as you go to lower and lower energy,

it basically becomes immeasurable.

So, if you’re going down this other pathway,

it means there’s really a very different

physical mechanism involved.

So, all I would say is that I actually poke in my head

once in a while to see what’s going on in that area.

And as scientists, we should always

try to make ourselves open.

But in this one, it’s like,

but show me something that I can measure

and that is repeatable,

and then it’s gonna take more extraordinary effort.

And to date, this has not met that threshold,

in my opinion.

So, even more so than just mentioning,

or in that question, thinking about people

that are claiming to have achieved cold fusion,

I’m more thinking even about people

who are studying black holes,

and they’re basically trying to understand

the function of theoretical physicists.

They’re doing the long haul,

trying to investigate, like,

okay, what is happening at the singularity?

What is this kind of holographic projections on a plate,

these weird freaking things

that are out there in the universe,

and somehow, accidentally,

they start to figure out something weird.

And then, all of a sudden.

There’s weirdness all over the place already, yeah.

Somehow, that weirdness will,

I think on a timescale probably of 100 years or so,

that weirdness will open.

It just seems like nuclear fusion

and black holes and all of this are too,

they’re next-door neighbors a little bit too much

for you’ll find something interesting.

Well, let me tell you a story about this.

It’s a real story, yeah.

So, there were really, really clever scientists

in the end of the late 1800s in the world.

You talk about, like, James Clerk Maxwell,

and you talk about Lord Kelvin,

and you talk about Lorentz, actually,

who named after these other ones,

and on and on and on, and like Faraday,

and they discovered electromagnetism, holy cow.

And it’s like, they figure out all these things,

and yet, there were these weird things going on

that you couldn’t quite figure out.

It’s like, what the heck is going on with this, right?

But we teach this all the time in physics classes, right?

So, what was going on?

Well, there’s just a few kind of things unchecked,

but basically, we’re at the end of discovery

because we figured out how everything works

because we’ve got basically Newtonian mechanics

and we’ve got Maxwell’s equations,

which describe basically how matter gets pushed around

and how electromagnetism works.

Holy cow, what a feat.

But there are these few nagging things.

Like, for instance, there’s certain kinds of rocks

that for some reason,

like if you put a photographic plate around it,

it gets burned or it gets an image on it.

Like, well, where’s the electromagnetism in that?

There’s no electromagnetic properties of this rock.

Oh yeah, and the other thing, too,

is that if I take this wonderful classical derivation

of something that is hot, about how it releases radiation,

everything looks fantastic.

Perfect match, oh, until I get to high frequencies

of the light, and then it basically just,

the whole thing falls apart.

In fact, it gives a physical explanation,

which is total nonsense.

It tells you that every object should basically

be producing an infinite amount of heat.

And by the way, here’s the sun,

and we can look at the sun,

and we can figure out it’s made out of hydrogen.

And Lord Kelvin actually made a very famous calculation,

who was basically one of the founders of thermodynamics.

So you look at the hydrogen.

Hydrogen has a certain energy content.

You know the latent heat, basically, of hydrogen.

We know the mass of the sun,

because we knew the size of it.

And he conclusively proved that basically,

the sun could only make net energy

for about 2,000 or 3,000 years.

So therefore, all this nonsense about deep,

because clearly, the sun can only last

for 2,000 or 3,000 years.

If you think about the,

and this is basically the chemical energy content

of hydrogen, and what comes along.

In one decade, basically, one guy sitting

in a postal office in Switzerland,

figures out that all these, Einstein, of course,

which was, figured out all this,

took these seemingly unconnected things,

and it’s like, boom, there it is.

It wasn’t just him, but it was,

like, there’s quantum physics.

Like, this explains this other disaster.

And then this other guy, my hero,

Ernest Rutherford, experimentalist,

did the most extraordinary experiment,

which is like, which was that,

okay, they had these funny rocks.

They emitted these particles.

In fact, they called them alpha particles.

Alpha, just A in the alphabet, right?

Because it was the first thing that they discovered.

And what were they doing?

So they were taking these alpha particles,

and by the way, I do this to all my students,

because it’s a demonstration of what you should be

as a good scientist.

So he took these alpha things,

and he was a classically trained physicist,

knew everything about momentum scattering,

and so forth like that.

And he took this, and these alpha,

which clearly were some kind of energy,

but they couldn’t quite figure out what it was.

So he said, let’s try to figure that,

we’ll actually use this to try to probe the nature of matter.

So he took this, took these alpha particles,

and a very, very thin gold foil.

And so what you wanted to see was that,

as they were going through,

the way that they would scatter,

in fact, the Coulomb collision,

based on classical mechanics,

this will tell me, reveal something

about what the nature of the charge distribution is

in matter, because they didn’t know.

Where the hell is this stuff coming from?

Even though they’d solved electromagnetism,

they didn’t know what made up charges.

Okay, very interesting.

Through it goes, and so what did you set up?

So it turns out, in these experiments,

what you did was, because these so-called alphas,

which actually now we know is something else,

as they go through, they would deflect,

how much they deflect tells you

how strong an electric field they saw.

So you put detectors,

because if you put like a piece of glass in front of this,

what will happen is that when the alpha particle hits,

it literally gives a little boop,

a little boop of light like this.

It scintillates, a little blue flash.

So he would train his students or postdocs

or whatever the heck they were at the time,

you have to train yourself,

because you have to put yourself in the dark for like hours

to get your eyes adjusted.

And then they would start the experiment

and they would sit there and literally count the things.

And they could see this pattern developing,

which was revealing about what was going on.

But there was also another part of the experiment,

which was that, it’s like, here’s the alphas,

here’s the source, they’re going this way.

They could tell they were going in one direction only,

basically, they’re going in this direction.

And you put all these over here,

because you want to see how they deflect

and bend through it.

But you put a control in the experiment,

but you basically put glass plates back here,

because obviously, everything should just deflect,

but nothing should bounce back.

So it’s a control in the experiment.

But what did they see?

They saw things bouncing back.

Like, what the hell?

Like, that fit no model of any idea, right?

But Rutherford refused to ignore what was a clear,

they validated it, and he sat down,

and based on classical physics,

he made the most extraordinary discovery,

which was the nucleus,

which is a very, very strange discovery.

What I mean by that,

because what he could figure out from this

is that in order for these particles

to bounce back and hit this plate,

they were hitting something that must be heavier than them.

And that basically something like 99.999% of the mass,

of the matter that was in this gold foil

was in something that contained

about one trillionth of the volume of it.

And that’s called the nucleus.

And until, and you talk about, so how revealing is this?

It’s like, this totally changes your idea of the universe,

because a nucleus is a very unintuitive,

non-intuitive thing.

It’s like, why is all the mass in something

that is like zero,

like, basically it was the realization

that matter is empty.

It’s all empty space.

And that changes everything.

And it changes everything.

Until you had that, like you had steam engines,

by the way, you had telegraph wires,

you had all those things.

But that realization opened up,

those two realizations opened up everything,

like lasers, all these things about the modern world

of what we use.

And that set it up.

So all I would point out is that there’s a story already

that sometimes there’s these nagging things

at the edge of science that,

we pat ourselves on the back

and we think we got everything under control.

Of course, by the way, that was the origin of also that,

think about this, that was 1908.

It took like another 20 some years

before people put that together with,

that’s the process that’s powering stars,

is the rearrangement of those nuclei, not atoms.

That’s why Kelvin wasn’t wrong,

he just was working with the wrong assumptions, right?

So fast forward to today, like what would this mean?

There’s a couple of things like this

that sit out there in physics.

And I’ll point out one of them, which is very interesting.

We don’t know what the hell makes up 90%

of the mass in the universe.

So the search for dark matter, right?

What is it?

We still haven’t discovered it.

90% of the mass of the universe is undetectable.

Like what?

And then, and dark energy, and again,

black holes are the window into this,

the edge of the black hole.

I mean, in some sense,

black holes are way better understood

than those things as well too.

So all it tells us is that we shouldn’t have hubris

about the ideas that we understand everything.

And when we, who knows what the next major

intellectual insight will be

about how the universe functions.

And actually, I think Rutherford is the one

who’s attributed at least that quote,

that physics is the only real science,

everything else is stamp collecting, right?

So there’s, I’m sorry, he’s my hero,

but I’ll slightly disagree with that, yes.

Well, no offense to stamp collecting,

that’s very important too.

But you know, you have to have humility

about the kind of disciplines that make progress

at every stage in science.

Yeah, exactly.

Physics did make a huge amount of progress

in the 20th century, but it’s possible

that other disciplines start to step in.

Yeah, but Rutherford couldn’t imagine

like mapping the human genome

because he didn’t even know about DNA.

Yeah, or computers really.

Or computers.

He probably didn’t think deeply about computation.

Who knows, it’s like, here’s a wild one,

what if like the next great revelation to humanity

about the universe is not done by the human mind?

That seems increasingly more likely.

And then you start to ask deep questions

about what is the purpose of science?

For example, if AI system will design

a nuclear fusion reactor better than humans do,

but we don’t quite understand how it works,

and the AI can’t, we know that it works,

we can test it very thoroughly,

but we don’t know exactly what the control mechanism is,

maybe what the chemistry of the physics is.

AI can’t quite explain it.

They just can’t.

It’s impenetrable to our consciousness, basically,

trying to hold it all together.

And then, okay, so now we’re living in that world

where many of the biggest discoveries

are made by AI systems.


As if we weren’t growing bigger.

I say, again, I will point out,

like when my godmother was born,

none of this was in front of us, right?

It’s like we live in an amazing time.

It’s like my grandfather plowed fields with a horse.

I get to work on designing fusion reactors.


Yeah, pretty amazing time.

But still, there’s humans, so we’ll see.

We’ll see if that’s around 100 years.

Maybe it’ll be cyborgs and robots.

I think we’re pretty resilient, actually.

Yeah, I know.

One lesson from life is it finds a way.

Let me ask you a bigger question.

As if those weren’t big enough,

let’s look out maybe a few hundred years,

maybe a few thousand years out.

There’s something called the Kardashev scale.

It’s a method of measuring civilization’s level

of technological advancement

based on the amount of energy it’s able to use.

So type one civilization,

and this might be given all your work,

is no longer a scale that quite makes sense,

but it very much focuses on the source of fusion,

natural source of fusion, which is, for us, the sun.

And type one civilizations are able to leverage,

sort of collect all the energy that hits Earth.

And then type two civilizations

are the ones that are able to leverage

the entirety of the energy that comes from the sun

by maybe building something.

Like a Dyson sphere.

Dyson sphere, yeah.

So when will we reach type one status?

Is get to the level, which we’re, I think,

maybe a few orders of magnitude away from currently.

And in general, do you think about this kind of stuff,

is where energy’s so fundamental to the,

like, of life on Earth,

but also the expansion of life into the universe?

Oh yeah, so one of the fun, on a weekend,

I sat down and figured out what would it mean

for interstellar travel, like, to have a DT fusion.

In fact, one of the, I talked about my design class.

One of my design classes was how you use,

essentially, a special configuration of a fusion device

for not only traveling to, but colonizing Mars.

So, because what would it,

you talk about energy use being

at the heart of civilizations, like,

so what if you want to go to Mars not to just visit it,

but actually, like, leave people there

and make something happen?

Needs massive amounts of energy.

So, what would that look like?

And it actually transforms how you’re thinking

about doing that, as well, too.

Oh yeah, so we do all those kinds of fun.

And actually, it was a fairly quasi-realistic, actually.

So, do you think it’ll be nuclear fusion

that powers the civilization on Mars?

Well, what we considered was something,

so it turns out that there’s thorium,

which is a heavy element,

so it’s a so-called fertile element,

that we know, we still know fairly little

about the geology of Mars, in the deep sense,

and we know that there’s a lot of this

on the surface of Mars.

So, one of the things we considered

was what would happen,

that it’s basically a combination of a fusion device

that actually makes fuel from the thorium.

But the underlying energy one

was fission itself, as well, too.

So, this is one of the examples of being,

trying to be clever around those things.

Or what is it, you know, this also means

it’s like interstellar travel.

Oh, yeah, that looks almost impossible, basically,

from an energy balance point of view,

just because the energy required

that you have to transport to get there,

almost the only things that would work

are DT fusion and basically annihilation.

It’s like Star Trek, right?

That’s what it is.

So, your sense is that interstellar travel

will require fusion power?

Oh, it’s almost even impossible

with fusion power, actually.

It’s so hard.

It’s so hard.

Because you have to carry the fuel with you,

and the rocket equation tells you

about how much fuel you’ll use to take.

So, what you end up with is, like,

how long does it take to go to these places?

And it’s, like, staggering, you know, periods of time.

So, I tend to believe that there’s alien civilizations

dispersed all throughout the universe.

Yeah, but we might be totally isolated from them.

So, you think we’re not, there’s none in this galaxy?

So, like, I guess, and the question I also have

is what kind of, do you think they have nuclear fusion?

Is it all, is the physics all the same?

Yeah, oh, the physics is all the same.

Yeah, right.

So, this is the, and this is the Fermi paradox.

Like, where the hell is everybody in the universe?

Well, there’s some, you know, the scariest one of those

is that, I would point out that there’s been, you know,

there’s, you know, order of many tens of millions

of species on the planet Earth,

and only one ever got to the point

of sophisticated tool use

that we could actually start essentially leveraging

the power of what’s in nature to our own will.

Does this mean that basically this means,

so almost, look, there is almost certainly life

or DNA equivalents or whatever would be somewhere.

I mean, just because you just need a soup

and you need energy and you get organics

and whatever the equivalent of amino acids are.

But, you know, most of the life on Earth

has been that, those are still amazing,

but it’s still, like, it’s not very interesting.

Are we actually the accident of history?

This is a very interesting one.

Super, super rare accident.

Super rare.

And then, of course, the other part is that also just,

the other scary part of it,

which is if you look at the Fermi paradoxes,

good, we got to this point, how long has it been

in humans, so humans, homo sapien has been around

for whatever, 100,000 years, 200,000 years, something like that.

Our ability in that timeline to actually make an imprint

on the universe by emitting radio waves

or by modifying nature in a significant way

has only been for about 100 of those 100,000 years.

And, you know, are we, it’s a good question.

So, is it by definition, by the fact

that when you are able to reach that level

of being able to manipulate nature,

for example, discover, you know, discover, like, fission

or burning fossil fuels and all this,

is that what it says, oh, you’re doomed,

because by definition, any species that gets to that point

that can modify their environment like that,

they’ll actually push themselves, you know, past,

that’s one of the most depressing scenarios

that I can imagine.

Yeah, so the…

So, basically, we will never line up in time

because you get this little teeny window in time

where civilization might occur and you can never see it

because you never, these sort of, like,

scatter like fireflies around the galaxy

and you never, yeah.

It goes up, goes up, goes up, goes up,

and then explodes, destroys itself

because of the exponential.

And when we say destroy ourselves,

all we’d have to do is that we basically go,

if humans are all left

and we’re still living on the planet,

but all we have to do is go to the technology

of, like, you know, 1800

and we’re invisible in the universe again.


So, it was, when I listened to the podcast,

I thought I wanted to talk about this as well, too,

because it’s, it comes from,

well, it comes from a science point of view, actually,

of what it means.

But also, to me, it’s like another compelling driver

of telling us, it’s like,

why we should try really hard not to screw this up.

Like, we’re in this unique place

of our ability to discover and to make it.

And I just don’t want to give up

about thinking that we can get through.

Yeah, I tend to see

that there is some kind of game theoretic force,

like with mutually assured destruction,

that ultimately, in each human being,

there’s a desire to survive

and a willingness to cooperate,

to have compassion for each other in order to survive.

And I think that, I mean, maybe not in humans,

but I can imagine a nearly infinite number of species

in which that overpowers

any technological advancement that can destroy

or rewind the species.

So I think if humans fail, I hope they don’t.

I see a lot of evidence for them not,

but it seems like somebody will survive.

And there, you start to ask questions

about why we haven’t met yet.

Maybe it’s just space is large.

Oh, space is, it’s, I think in logarithms,

and I can’t even fathom space,

this is extraordinary, right?


It’s extraordinarily large, yeah.

I mean, there’s so many places on Earth.

I just recently visited Paris for the first time.

And there’s so many other places I haven’t visited yet.

There’s so many other places.

Well, I like to, you know,

it’s interesting that we have this fascination

with alien life.

We have what is essentially alien life on Earth already.

Like you think about the organisms

that develop around deep sea, like thermal vents.

One of my favorite books of all time from Stephen Jay Gould.

If you’ve never read that book,

it kind of blows your mind.

It’s about the Cambrian explosion of life.

And it’s like, oh, you look at these things

and it’s like, the chance of us existing as a species,

like the genetic diversity was larger back then.

You know, this is about 500 million years ago

or something like that.

It is a mind-altering trip

of thinking about our place in the universe,

I have to say.

Plus the mind itself is a kind of alien,

almost a mystery to ourselves.

We still don’t understand it.

The very mechanism that helps us explore the world

is still a mystery.

So understanding that will also unlock,

quite possibly unlock our ability to understand the world

and maybe build machines that help us understand the world,

build tools that help us understand the world.

Yeah, I mean, it already has.

I mean, our ability to understand the world

is ridiculous almost, actually.

And post the bot on TikTok.

It’s almost unbelievable where we’ve gotten all this to.

So what advice would you give to young folks

or folks of all ages who are lost in this world,

looking for a way, looking for a career

that they can be proud of

or looking to have a life they can be proud of?

Yeah, oh, the first thing I would say is don’t give up.

I get to see multiple sides of this

and there seems to be a level of despair

in a young generation.

It’s like, no, it’s almost like the Monty Python skit.

I’m not dead yet, right?

I mean, we’re not there.

We’re in a place that,

don’t say the world’s gonna end in 300 days or something.

It’s not, okay?

And what we mean by this is that we have a robust society

that’s figured out how to do amazing things

and we’re gonna keep doing amazing things.

But that shouldn’t be complacency about what our future is

and the future for their children as well too.

And in the end, I mean, it’s a very,

it’s a staggering legacy to think of what we’ve built up

primarily by basically using carbon fuels.

Like people almost tend to think of this

as an evil thing that we’ve done.

I think it’s an amazing thing that we’ve done

but we owe it to ourselves

and to this thing that we’ve built.

I mean, talking about the end of the world is just nonsense.

What it is is it’s the end of this kind of lifestyle

and civilization at this scale

and the ability to execute on these kinds of things

that we are talking about today.

Like we are extraordinarily privileged.

We are in a place where it’s just,

it’s almost unfathomable compared to most of the misery

that humans have lived in for our history.

So don’t give up about this, okay?

But also roll up your sleeves and let’s get going

at solving and getting real solutions

to the problems that are in front of us

which are significant.

Most of them are linked to what we use in energy

but it’s not just that.

It’s around all the aspects of like,

what does it mean to have a distributed energy source

that lifts billions of people out of poverty

particularly outside of like the Western nations, right?

That seems to me a pretty compelling moral goal

for all of us.

But particularly for this upcoming generation.

And then the other part is that

we’ve got possible solutions in front of us.

Apply your talents.

That you’re passionate about

and it’s gonna make a difference.

And that’s only possible with optimism, hope and hard work.


What, easy question.

Certainly easier than nuclear fusion.

What’s the meaning of life?

Why are we here?


Is it 42?

No, no.

We already discussed about the beauty of physics.

That there’s almost a desire to ask a why question

about why the parameters have these values.

It’s very tempting, yeah.

It’s an interesting hole to go down as a scientist

because we’re a part of what people have a hard time,

people who aren’t scientists have a hard time

understanding what scientists do to themselves.

And a great scientist does a very non-intuitive

or non-human thing.

What we do is we train ourselves to doubt ourselves.

Like how?

Like that’s a great scientist.

We doubt everything we see.

We doubt everything that we think

because we basically try to turn off the belief valve, right?

That humans just naturally have.

So when it comes to these things,

like I can make my own comments to this.

It’s like, personally, you see these things

about the ratios of life.

And I made a comment where I said,

well, you know, some part of my brain that just goes,

yeah, well, yeah,

because we’re the only interesting multiverse

because by definition, it has to look like this.

But I have to say, there’s other times,

I can say in the history of the whole,

of what has happened over the last 10 years,

there have been some pretty weird coincidences,

like coincidences that like you look at it and just go,

is that really, was that really a coincidence?

Is something like pushing us towards these things?

And it’s a natural, it’s a human instinct

because since the beginnings of humanity,

we’ve always assigned human motivation and needs

to these somewhat empirical observations.

And in some sense, the stories,

before we understand the real explanations,

the stories, the myths serve as a good approximation

for the thing that we’re yet to understand.


And in that sense, you said the antithesis

to sort of scientific doubt is having a faith

in these stories.

They’re almost silly when looked at

from a scientific perspective,

but just even the feelings of,

it seems that love is a fundamental fabric

of human condition.

And what the hell is that?

Why are we so connected to each other?

As a physicist, I go, this is a repeatable thing

that’s due to a set of synapses

that fire in a particular pattern and all this.

That’s kind of like, okay, man,

what a drag that is to think of it this way.

And you can have an evolutionary biology explanation,

but there’s still a magic to it.

I mean, I see scientists, some of my colleagues

do this as well too, like what is spirituality

compared to science and so forth?

I, my own feeling in this is that as a scientist,

because I’ve had the pleasure of being able

to both understand what my predecessors did,

but I also had the privilege of being able

to discover things, right, as a scientist.

And I see that, and you just,

in just the range of our conversations,

like that is my, in a weird way,

it’s the awe that comes from looking at that.

That is, if you’re not in awe of the universe and nature,

you haven’t been paying attention.

I mean, my own personal feeling is that I feel,

if I go snorkeling on a coral reef,

I feel more awe than I could ever feel like in a church.

You kind of notice some kind of magic there.

There’s something about the way

the whole darn thing holds together

that just sort of escapes your imagination.

And that’s, to me, this thing of,

and then we have different words,

we call them holistic or spiritual,

the way that it all hangs together.

In fact, one of the interesting,

you asked about like what I think about,

one of the craziest things that I think

that how does it hold together is like our society.

Like what?

Like how, because there’s no way,

like you just think of the United States,

there’s 330 million people kind of working like this engine

about going towards making all these things happen,

but there’s like no one in charge of this, really.


How the heck does this happen?

It’s kind of like, it’s, so these things,

these are the kinds of things mathematically

and organization-wise that I think of

just because they’re sort of, they’re awe-inspiring.


And there’s different ideas that would come up together

and we share them.

And then there’s teams of people

that share different ideas and those ideas compete.

Like there was, the ideas themselves

are these kinds of different organisms

and ultimately somehow we build bridges and nuclear reactors.

And do those things.

Well, I have to give a shout out to my daughter,

by the way, who’s interesting.

She’s an applied math major and she’s amazing at math.

And over the break, she was showing me

she was doing research and it’s basically

about how ideas and ethos are transmitted within a society.

So she’s building an applied math model

that is explaining like, she was showing me

in this simulation, she goes, oh, look at this.

And I said, oh, oh, that’s like how political parties

like evolve, right?

And even though it was a rather, quote unquote,

simple mathematical model, it wasn’t really.

It’s like, oh, wow.

Well, maybe she has a chance to derive mathematically

the answer to what’s the meaning of life.

There we go.

And maybe it is indeed 42.

Well, Dennis, thank you so much for just doing,

creating tools, creating systems, exploring this idea

that’s one of the most amazing magical ideas

in all of human endeavor, which is nuclear fusion.

I mean, that’s so interesting.

You know, it’s almost like my, one of my lifelong goals

is like to make it, it’s like, it’s not magic.

It’s like, it’s boring as all heck.

And this means we’re using it everywhere, right?


And the magic is then built on top of it.

Well, thank you for everything you do.

Thank you for talking to me.

It’s a huge honor.

This was a fascinating and amazing conversation.

Thank you.

Thanks for listening to this conversation

with Dennis White.

To support this podcast, please check out our sponsors

in the description.

And now let me leave you with some words

from Albert Einstein.

There are two ways to live your life.

One is as though nothing is a miracle.

The other is though everything’s a miracle.

Thank you for listening.

I hope to see you next time.



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