How the Universe Works

An invisible danger hurtles towards Earth

at close to the speed of light.

These are intergalactic alien interlopers on our Milky Way.

Cosmic rays.

Getting hit by a cosmic ray is like

getting hit by a cosmic bullet.

Cosmic rays are billions of times more energetic than any

other types of particles,

vastly more energetic than anything

we can even create in

a laboratory, in a nuclear fusion reactor, anywhere.

They pierce spaceships, putting our astronauts

in danger.

But the source of their power is a mystery.

Are they coming from other galaxies?

Are they coming from things in between the galaxies?

Where do cosmic rays come from?

Truth is, the most powerful ones,

we haven't got a clue.

The race is on to solve the mystery

of the fastest particles in the universe.

If I were to make a list of the dangers of space,

it would be a long list.

You know, there's hard vacuum, huge swings in temperatures,

micro meteorites, all kinds of things.

But probably at the very top of that list, cosmic rays.

These space invaders are not what they seem.

When you hear the name cosmic rays,

you might think it's like a beam,

like a laser beam of light. No, no, no, no, no, no.

It's a tiny little death particle.

To fight them,

we must first understand them.

April 2019.

NASA's Parker probe flies closer to the sun than

ever before.

We know the sun produces some of

the cosmic rays that fill the solar system,

but we don't know how.

Our sun looks like a beautiful glowing orb,

bringing energy and light to Earth and allowing life

to thrive.

But if you look at it up close,

you'll see a tumultuous storm of events.

The amount of energy the sun is emitting every

second is the equivalent of 100 billion one megaton bombs.

It's a dangerous neighborhood.

Suddenly, the probe is caught head-on

in a powerful blast.

It's perfectly positioned to monitor

the outburst from the inside.

The entire outer third of the sun is a boiling

cauldron, and tied up in that plasma are magnetic fields.

They get tied and twisted, and energy is stored in them,

so they rise towards the surface, and there,

they rearrange, they reconnect, they twist, they spin.

When the magnetic field lines snap,

energy bursts out.

And sometimes, that energy release is explosive

and that's what results in flares,

which are these huge bursts of light.

The probe discovers that after a solar flare,

the sun's surface stores electrically charged particles.

But sometimes, there's a second explosion called

a coronal mass ejection, releasing superheated,

electrically charged gas called plasma.

These giant balls of plasma go flying off the surface of

the sun, and in those balls of plasma

are contained these charged particles.

The charged particles move fast, but they hit a roadblock,

a cloud of slower-moving particles

that always surrounds the sun, the solar wind.

Well, the coronal mass ejection is moving into the solar wind

much faster than the wind is moving.

So it sort of runs into it and creates this shockwave

and ends up piling up particles at the edge.

The shockwave and particles

slam together... In the collision,

the particles steal energy and speed,

like a baseball accelerating off a bat.

The particles transform into something far more powerful...

A solar cosmic ray.

They're light, but they're moving

incredibly fast.

The Earth is on average 93 million miles away from

the sun, and these guys reach us in about an hour.

That's 93 million miles an hour.

That's pretty fast.

The cosmic rays speed towards Earth.

We're under attack.

Cosmic rays are, by far, the most energetic

particles that we know to exist in the universe.

And when things with very high energy, no matter how small

they are, impact something else,

they deposit that energy, right, and so cosmic rays

can be very dangerous.

Solar cosmic rays aren't the only threat we face.

Other space bullets arrive from beyond our solar system.

There are different kinds of cosmic rays,

just like there are different kinds of bullets.

At the lowest end of the spectrum

are these solar cosmic rays.

These are like the BBs, and when a BB hits you,

it might sting for a little bit, but you're not gonna get

too worried about it.

A bigger concern... Galactic cosmic rays.

They travel faster and have more energy.

If solar rays are like BBs,

the galactic cosmic rays are like rifle bullets.

They're far more dangerous.

They're moving a lot faster.

But they're also more rare.

Faster still are the universe's most wanted...

Ultra-high-energy cosmic rays.

If you thought galactic cosmic rays were bad, it's

because you haven't met an ultra-high-energy cosmic ray.

These are the biggest, baddest,

meanest cosmic rays in the universe.

These ultra-high-energy cosmic rays

are like hypersonic missiles.

They are screaming, and they come from

the most energetic events in the universe.

The ultra-high-energy cosmic missiles

are the rarest but also the swiftest.

These cosmic ray particles are moving fast.

These mysterious particles are moving incredibly

close to the speed of light.

I'm not talking about 99 percent the speed of light.

They're moving through space at

like 99.999...

- 9999... - 9999...

- 99999... - 999999...

99999... 21 nines.

That's fast.

That's wild. That's scary.

All three types of cosmic rays

are racing through the solar system.

If I were to hold up a golf ball in the middle of space,

almost 100 cosmic rays pass through that golf ball every

single second.

It's a deadly hail of particle bullets,

and out in space,

our astronauts are caught in the crossfire.

Cosmic rays represent one of

the greatest dangers for human space flight.

NASA plans to send astronauts back to the moon,

where radiation levels Liftoff.

From cosmic rays are 200 times greater than

on Earth, and that is just the start.

One of NASA's big goals is to send humans to Mars,

and that is a long way away,

at least a six-month journey, and more often,

about a nine-month journey. That's a big problem.

I am hoping that one day, I can go to Mars as an astronaut,

but I'm definitely afraid of cosmic rays,

and the more that I read about it,

the bigger of a threat it seems.

So I think that NASA and other space organizations

are going to need to work on

how to protect their astronauts in these

really dangerous situations.

Only one group of people have been

exposed to these high levels of cosmic rays,

the crew members of the Apollo missions

July 1969.

That's one small step for man,

one giant leap for mankind.

One of the astronauts, Buzz Aldrin,

sees something strange.

During Apollo 11,

Buzz Aldrin reported seeing tiny little

flashes sometimes when he was looking around.

That's pretty weird.

But what's weirder is that he saw them

when his eyes were closed.

Later missions also report seeing odd flashes of light.

A streak in the lower left side of the...

left eye, moving down.

The astronauts describe the flashes as spots,

streaks, and clouds.

Apollo 15 Commander David Scott reported seeing one that

was blue with a white cast, like a blue diamond.

What's happening is that a cosmic ray is entering

the eyeball

and then striking molecules and giving off

a flash of light.

An alternative theory is that it triggers the layer of

sensitive cells in your retina,

so you perceive a streak of light even though

no light ever actually existed.

The cosmic rays cause long-term damage.

Inside of the eye's lens,

there are these fiber cells that are transparent.

Well, when a cosmic ray travels through them,

it can damage those cells and make them cloudy,

causing cataracts.

When NASA examines the astronauts' helmets,

they find tiny tracks etched through them,

evidence of cosmic ray impacts.

When we say that cosmic rays are like tiny little bullets,