aren't the brightest events in the Universe?

Gamma-ray bursts are.

They shine hundreds of times brighter

and only last for several minutes at most.

But even a second would be enough

for them to mess up all complex life

on the planet.

Gamma-ray bursts, or GRBs,

are the most violent explosions

in the Universe.

They occur when two neutron stars collide and form a black hole.

Or when a black hole swallows a neutron star.

Or when a star goes supernova.

They're outside the spectrum of visible light.

That's why you can't see them with your naked eye.

But you'd feel their effect

if they were to hit the planet.

One of those bursts might have already

triggered a mass extinction here on Earth.

But that mighty event was 450 million years ago,

long before even the first dinosaurs

started roaming the planet.

If a gamma-ray burst hit us today,

we might have a chance to make it out alive.

Maybe...

Even though the Earth would absorb

most of the radiation the blast emitted,

the only things that would be in danger down here

would be our satellites.

Some of them would get knocked offline permanently.

You might lose your internet connection, but...

it wouldn't take long until

most of the malfunctioning satellites were restored.

It would change the game completely.

The radiation that would rain down on Earth

would destroy our ozone layer.

Almost all of our plant species would die.

There wouldn't be enough of them left to sustain photosynthesis

and with that, the amount of oxygen in our atmosphere.

Plant-eating animals would starve,

and the rest of them would be left to suffocate.

Humans could try to save ourselves with oxygen masks, but...

even that wouldn't help us last too long.

The damage from it would be equivalent to the Earth

getting hit by an asteroid.

First, it would immediately destroy our atmosphere.

Without the atmosphere,

we'd be bathing in UV rays,

getting severe sunburns,

and trying to figure out how to restore the planet's atmosphere

before this hostile environment killed us completely.

There is good news.

Gamma rays have such a short wavelength that,

with a bit of luck, the beam could pass relatively close

and do no significant damage.

But have we ever been so lucky?

Nothing would be as devastating

as the direct hit of a gamma-ray burst

from within our galaxy, the Milky Way.

If it makes you feel any better,

our satellites would detect the GRB immediately.

But what could we do once we found ourselves in the crosshairs

of this all-natural galactic phaser?

As the burst was approaching the planet,

photons would be pulling the ozone layer away

and causing chemical reactions on Earth.

You'd see a cloud of photochemical smog covering the planet.

We'd be blasted with all sorts of cosmic rays.

They'd damage our electronics

and bring us lethal doses of radiation.

You'd witness another wave of mass extinction on Earth.

The good thing is that

it doesn't look like an event like this

is likely happen for another billion years.

By that time, we might have figured out

how to move the Earth out of the danger zone.

But that's a story for another WHAT IF.