The sun releases more energy

in just 1.5 millionth of a second

than we humans on planet Earth consume in a year.

That's a lot of power.

Which is why solar will likely play a huge role

in our quest for a cleaner, more secure energy future.

The sun generates all of this energy

through a process called fusion.

But what exactly is fusion,

and how does the sun generate so much energy?

The sun is a massive nuclear powerhouse

that can raise temperatures in the Australian Outback

to an incredible 50.7 degrees Celsius.

That intense energy is perfect for fueling race cars

competing in the World Solar Challenge.

DEREK: I am in the middle of the Australian Outback.

As you can see,

this is a very inhospitable environment.

You know, it's funny being out here,

you feel the power of the sun.

It gets so stinking hot.

And of course, it is that very energy

which is propelling these cars down the road

at incredible speeds.

And in the World Solar Challenge,

cars from over 20 countries

have to power across the whole continent,

going 3,000 kilometers, over 1,800 miles,

to claim the title

of world's fastest solar vehicle.

MAREN: Incredibly, the power source

that makes all of this possible

is 150 million kilometers away

and involves subatomic particles.

You may know that atoms, which make up all matter,

have a nucleus at the center

made up of protons and neutrons,

with electrons zipping around the nucleus in a small cloud.

Fusion happens when two atomic nuclei

are forced together

in extremely high-energy conditions.

Now, keep in mind,

this is different from what happens

when atoms link together using their electrons,

like when two hydrogen atoms and an oxygen atom

come together to form water.

That's called bonding.

But in fusion,

the nuclei of the atoms themselves

need to smash together to form a single nucleus,

and this process releases massive amounts of energy.

Okay, so, now that we've got our heads wrapped around

the very basics of how fusion works,

let's take a look at how it happens in the sun.

First off, it takes a lot of energy

to force the nuclei to come together

in the first place,

because protons, all with the same positive charge,

repel each other.

You know, like magnets.

You may recall that principle

that like charges repel

while opposite charges attract.

However, the sun is so massive,

roughly 1.392 million kilometers in diameter,

that it has an insane amount of gravity,

meaning there's an incredible amount of pressure

exerted on all those hydrogen atoms

that make up the sun.

Now, solar fusion happens inside the sun's core,

where the pressure is so intense

and the density is so great

that those like-charged protons

of those hydrogen nuclei

smash together to form helium.

If we want to break things down

in even greater detail, which we do,

we'll have to talk about something

called the proton-proton cycle.

The energy radiated by the sun

is really the result of a series

of thermonuclear reactions.

The first step in the reaction...

two hydrogen nuclei collide

to produce what's called deuterium,

a hydrogen nucleus

with one proton and one neutron.

See, most hydrogen atoms have only one proton

and no neutrons.

Next, a third hydrogen proton

smashes into the deuterium nucleus

to make a tritium nucleus, or a triton,

a nucleus with one proton and two neutrons.

When two of these tritium nuclei fuse together,

they form a helium-4 nucleus

with two protons and two neutrons.

This fusion also releases two protons,

allowing the cycle to continue.

Two hydrogen protons collide,

a third hydrogen proton joins the party,

two of these tritium nuclei fuse together,

two protons are released.

Repeat, and repeat, and repeat

until the sun runs out of hydrogen.

Got it? Great.

It is a complicated process.

After all, it's literally thermonuclear physics.

So, if you want to go and run that animation back,

go ahead and rewatch

that proton-proton cycle animation.

Now, you may be asking,

how much energy does this process generate?

Well, scientists have calculated

that at any given moment,

the sun releases

an estimated 384 yotta watts of energy.

Never heard of a yotta watt before?

Because me neither.

But using scientific notation,

that's 3.84 times 10 to the 26th power.

So, 384 with 24 zeros behind it.

We barely have enough screen

to actually show all of those zeros.

Saying that's a "yotta" power

would be a gross understatement

and a groanable pun.

And because nuclear fusion doesn't produce unstable,

long-lived radioactive waste like nuclear fission does,

that's the splitting of an atom,

instead, fusion results in a stable,

non-radioactive by-product of helium.

So, scientists are exploring

how to develop this as a viable energy source.

But as many of our secret viewers have noted,

fusion technology always feels like

it's just a few decades away.

Now, while most of the sun's energy

is scattered across our solar system,

researchers have estimated that 430 quintillion joules

of the sun's energy

hits the surface of the Earth

roughly every hour, or hour-and-a-half.

With current estimates

of total world energy consumption

at 580 million terajoules annually,

that means, theoretically,

if we could effectively harness all of the sun's energy

that hits Earth for just two hours,

we could power our entire planet

for more than a year.

Clearly, this isn't a reality, at least not anytime soon,

but solar energy is helping power a worldwide shift

to cleaner, more sustainable energy.

And there have been some

incredible innovations in recent years

as the technology has become more and more efficient.

So, next up, we take a closer look at solar panels

and break down the technology

that powers our homes and cities,

and can transform sunlight into horsepower.