<i>male narrator:
A blast from space...</i> [people groaning] <i>And there's nowhere to hide.</i> <i>[dramatic music]</i> <i>It's the cosmic death beam
of a gamma-ray burst.</i> <i>♪ ♪</i> <i>- We're talking about
a silent killer</i> that has massive amounts
of radiation. <i>♪ ♪</i> [woman screaming] - Whatever survives
at this point is a roll of the dice. <i>♪ ♪</i> <i>narrator: Will you be ready...</i> <i>when doomsday strikes?</i> <i>Can any of us survive?</i> [woman shouting] [glass shattering] <i>♪ ♪</i> <i>Every week, NASA detects
deadly laser beams</i> <i>of energy in outer space</i> <i>known as gamma-ray bursts.</i> <i>♪ ♪</i> <i>Some scientists believe</i> <i>one may have struck Earth
440 million years ago,</i> <i>killing off 2/3
of all species.</i> <i>If one hit Earth today...</i> <i>would you survive?</i> - Basically, you've just
walked into Armageddon. [people screaming] - The exposure basically
starts destroying cells. Things start to shut down. <i>♪ ♪</i> - This is the last
and brightest moment you'll ever witness
in your life. [woman screaming] [ship horn blares] <i>narrator:
San Juan, Puerto Rico.</i> <i>As a container ship
heads into port,</i> <i>every eye on deck is drawn</i> <i>to the bizarre light flashes
on the eastern horizon.</i> [seagulls cawing] <i>They morph into a fantastic
light show of greens and blues,</i> <i>something usually seen
near the Arctic Circle.</i> <i>- You'll begin to see
the northern lights,</i> <i>which is really bizarre.</i> <i>The aurora borealis,</i> <i>these beautiful arcs
of red and green and violet</i> will be shimmering
through the atmosphere. What would you think happened? <i>[suspenseful music]</i> <i>♪ ♪</i> <i>narrator: Meanwhile,
7,000 miles to the east,</i> <i>in Paris...</i> <i>a much more intense
phenomenon takes place.</i> - Think about being
a tourist in Paris. <i>You see the Eiffel Tower,
and you're looking up at it,</i> <i>and then there's this
bright flash in the sky</i> <i>that's growing brighter
and brighter.</i> - This flash of light
would grow rapidly in intensity to the point where it would be
blindingly bright. [people exclaiming] - This is the brightest thing
you have ever seen <i>until your retina
stops working.</i> <i>♪ ♪</i> <i>- I think the only thing that
would be anywhere near this</i> would be
a thermonuclear bomb going off fairly close to them and looking straight at it. <i>narrator: What has triggered
this massive burst of energy</i> <i>in Earth's skies?</i> <i>♪ ♪</i> <i>Long ago, more than
1,200 trillion miles away,</i> <i>two dead stars circled
each other in deep space.</i> <i>♪ ♪</i> <i>With a combined
gravitational pull</i> <i>four billion times greater
than the Earth's,</i> <i>the two stars collided,</i> <i>triggering a devastating
gamma-ray burst.</i> <i>♪ ♪</i> <i>- There's an impact...</i> [explosion] And because of the extremely
high densities and their extremely high
gravitational force, there's just a huge amount
of energy that's released. <i>♪ ♪</i> - A gamma-ray burst
is the most colossal explosion in the universe, second only to the creation
of the universe itself, the big bang. <i>The energy released
is so titanic</i> <i>that it can outshine
an entire galaxy</i> of hundreds of billions
of stars. <i>♪ ♪</i> <i>narrator: The gamma rays,</i> <i>the most energetic type
of radiation</i> <i>in the universe,</i> <i>shot out in two powerful
concentrated beams.</i> <i>♪ ♪</i> <i>Now, after 200 years
of space travel,</i> <i>the gamma-ray burst is quickly
approaching our atmosphere,</i> <i>and planet Earth
is right in the crosshairs.</i> <i>♪ ♪</i> <i>- If the rotational axis
were pointing at Earth,</i> the results
would be devastating. <i>♪ ♪</i> <i>narrator: Since the 1990s,</i> <i>ground- and satellite-based
telescopes have spotted</i> <i>the radiation from hundreds
of distant gamma-ray bursts...</i> <i>♪ ♪</i> <i>But only at the moment
the radiation reaches Earth.</i> <i>♪ ♪</i> <i>So humanity has
no advanced warning</i> <i>of the catastrophe
that is about to strike.</i> <i>♪ ♪</i> <i>[indistinct radio chatter]</i> <i>- This is Mission Control,
Houston,</i> <i>onboard the International
Space Station.</i> <i>narrator: 250 miles
above Earth's surface,</i> <i>the International Space
Station flies over Europe</i> <i>at 17,000 miles per hour.</i> <i>♪ ♪</i> <i>Suddenly, there's
a power blackout.</i> <i>♪ ♪</i> <i>Deadly radiation
streams into the space station.</i> <i>The gamma-ray burst
claims its first victims.</i> - The astronauts
would be exposed to an onslaught
of energetic gamma rays. - They're gonna be sickened
and dying, and really, not much they can do about it. <i>♪ ♪</i> <i>narrator:
The side of the planet</i> <i>facing the gamma-ray burst</i> <i>is in the impact zone</i> <i>and will take a direct hit.</i> <i>♪ ♪</i> <i>That zone includes Africa,</i> <i>the Middle East,
parts of Russia,</i> <i>and all of Europe.</i> <i>[ominous music]</i> <i>♪ ♪</i> <i>In Madrid's famous Plaza Mayor,</i> <i>sightseers stroll</i> <i>beneath a hot afternoon sun.</i> <i>The open-air plaza offers
no protection from the heat</i> <i>or the danger
that's headed their way.</i> <i>♪ ♪</i> <i>At Galveston Beach, Texas,
families take advantage</i> <i>of the cool morning
temperatures.</i> <i>They are in
the non-impact zone,</i> <i>the side of the Earth opposite</i> <i>from the fast-approaching GRB.</i> <i>The beachgoers are in no danger
for the moment.</i> <i>♪ ♪</i> <i>Traveling at the speed
of light,</i> <i>the gamma-ray burst
is milliseconds from Earth,</i> <i>and our atmosphere will be
the first line of defense.</i> - We take the atmosphere
for granted. We don't even think
about it during the day. <i>But it protects all life
on the planet Earth,</i> <i>and it's extremely delicate
and very thin.</i> <i>♪ ♪</i> <i>- The atmosphere protects us</i> <i>from high-energy radiation
from space</i> that's always coming in, and so that protective blanket
really shields us <i>from a lot
of the dangerous radiation</i> <i>that's out there.</i> <i>[dramatic music]</i> <i>♪ ♪</i> <i>narrator: But this is
no ordinary cosmic radiation.</i> <i>It's the most powerful
in the universe.</i> <i>♪ ♪</i> - These gamma-ray bursts have millions of electron volts
of energy concentrated in a tiny,
narrow beam. <i>- The initial burst would be
the equivalent</i> of detonating
a one-megaton nuclear warhead over every square mile
of the impacted side. <i>♪ ♪</i> <i>narrator: A one-megaton
nuclear device</i> <i>is 80 times more powerful
than the Hiroshima bomb.</i> - The atmosphere won't be able
to hold its own. It'll be destroyed. <i>♪ ♪</i> <i>narrator: As the gamma-ray
burst slams into the Earth...</i> <i>♪ ♪</i> <i>It instantly engulfs Europe,</i> <i>Africa,</i> <i>and the Middle East</i> <i>in a blast of radiation</i> <i>that lasts just two seconds.</i> <i>♪ ♪</i> <i>In Paris,
on the Champs-Elysées...</i> <i>♪ ♪</i> <i>The massive white flash</i> <i>permanently blinds anyone</i> <i>staring directly at the blast.</i> - [coughing] <i>narrator: Within seconds,</i> <i>electrical transformers
explode.</i> <i>Cell phones and radios
short-circuit.</i> <i>Cars, buses, and trains</i> <i>come to a halt.</i> <i>- When the gamma-ray burst
hits the atmosphere,</i> at that point, electrons
are stripped off atoms, creating a wall
of electric fields that then create
the electromagnetic pulse. <i>Now we're talking about massive</i> <i>short-circuiting
on the planet Earth.</i> [both gasping] <i>♪ ♪</i> <i>Meanwhile, in the United States
of America,</i> <i>the dawn light reveals
a world unchanged.</i> <i>♪ ♪</i> <i>- If you were on the other side
of the Earth at the moment</i> <i>that the gamma-ray burst
arrives,</i> initially, you wouldn't really
notice anything. It would just be
business as usual. <i>♪ ♪</i> <i>narrator: At the National
Space Science Center</i> <i>in Huntsville, Alabama,</i> <i>a scientist is teleconferencing
with a colleague</i> <i>at the Max Planck Institute
near Munich, Germany.</i> - I want to see some numbers. <i>narrator:
The teams jointly monitor</i> <i>the Fermi Gamma-ray
Space Telescope.</i> <i>- Several years ago, NASA
launched the Fermi mission.</i> That is a satellite
specifically designed to home in on gamma-ray bursts
in outer space. We search it out. We scan the heavens,
looking for these things. <i>♪ ♪</i> <i>narrator: Suddenly, the German
video feed goes dark.</i> <i>♪ ♪</i> <i>340 miles above,</i> <i>hurtling through space
at 17,000 miles per hour,</i> <i>the Fermi telescope is hit</i> <i>by the electromagnetic pulse.</i> <i>♪ ♪</i> <i>The satellite's sensor
does its job...</i> <i>and confirms
the gamma-ray burst</i> <i>on the other side
of the world.</i> <i>♪ ♪</i> <i>- Fermi's designed to handle
that kind of radiation,</i> but this is gonna be
an unprecedented level of that radiation. So they would immediately
record that, and the spacecraft would
send that data to the ground. <i>narrator:
The Huntsville scientists</i> <i>begin to alert
government officials,</i> <i>but there's already been
significant damage.</i> <i>♪ ♪</i> <i>In the first seconds
of the blast,</i> <i>hundreds of millions of people</i> <i>from Paris to South Africa</i> <i>have lost all
electronic communications</i> <i>and witnessed the brightest
flash of light</i> <i>ever seen on Earth.</i> [people screaming] <i>But it's what they can't see</i> <i>that now threatens
to kill them all.</i> <i>♪ ♪</i> <i>[dramatic music]</i> <i>♪ ♪</i> <i>narrator:
The Earth is under attack.</i> [lightning crashing] <i>The most powerful radiation
in the universe,</i> <i>a gamma-ray burst
from two colliding stars,</i> <i>has slammed into our planet
at the speed of light.</i> <i>♪ ♪</i> <i>Can humanity survive
a direct hit?</i> - In the few milliseconds
that a gamma-ray burst like this takes place,
it emits more energy <i>than our own sun has emitted</i> <i>through the entire history
of the universe.</i> <i>♪ ♪</i> <i>narrator: Africa,
the Middle East, and Europe</i> <i>are in the immediate
impact zone</i> <i>of the gamma-ray burst,</i> <i>and no one knows
what just happened.</i> <i>International superpowers
wonder</i> <i>if this is the first strike
of a nuclear war.</i> [explosion] <i>♪ ♪</i> <i>Off the coast of Italy,</i> <i>the U.S. ballistic missile
submarine "Louisiana"</i> <i>is on high alert.</i> - Are you picking up anything?
- Negative. [indistinct conversation] <i>narrator:
Coded communications</i> <i>instruct the commanding officer</i> <i>to raise
the launch readiness level</i> <i>and await further orders.</i> - Aye, aye. - Bring us full port
to 12 degrees. - Battle stations. <i>♪ ♪</i> [people screaming] <i>narrator: On land, in Madrid,</i> <i>a wave of panic
rushes over the crowd</i> <i>at the Plaza Mayor.</i> <i>♪ ♪</i> <i>The intense flash of light
and power outage sparks chaos.</i> - Help! - At first, you may think
this is a fantastic light show until you realize
that the worst is yet to come because of all the radiation
filling up the atmosphere. - Gamma radiation is what
we call ionizing radiation. It knocks electrons
off of atoms. <i>♪ ♪</i> - So when that happens,
there's charge buildup, and that charge has to
balance out in some way, <i>and one way that happens
is through lightning.</i> [lightning crashing] <i>♪ ♪</i> <i>narrator:
Across the hemisphere,</i> <i>brilliant bolts of lightning</i> <i>and crashing thunder
fill the skies.</i> [lightning crashing] <i>In Paris, the Eiffel Tower</i> <i>suddenly becomes
a massive lightning rod.</i> <i>♪ ♪</i> - This is like a hellscape
of a lightning storm. [thunder booming] <i>This is so much lightning
that the amount of fires</i> <i>that will be raging
out of control</i> will immediately overcome any sort of municipal
fire department. This is the beginning
of absolute chaos. <i>♪ ♪</i> [sirens wailing] <i>♪ ♪</i> [people groaning] - Help! <i>narrator: In the impact zone,</i> <i>millions suddenly cringe
in pain.</i> <i>♪ ♪</i> <i>People collapse.</i> <i>Some are dead in seconds.</i> <i>Others struggle to survive
against the inevitable.</i> <i>♪ ♪</i> <i>- If you're on
the surface of Earth,</i> you will experience
a shower of muon particles that will be several times
the lethal dose. <i>♪ ♪</i> <i>narrator:
Muons are charged particles</i> <i>created when the gamma
radiation interacts</i> <i>with atoms
high in the atmosphere.</i> <i>Deadly showers
of radioactive muons</i> <i>rain down across
the entire impact zone.</i> <i>♪ ♪</i> - Someone who gets
this blast of radiation is gonna have the same kind
of radiation poisoning <i>that we've seen
in nuclear explosions.</i> <i>The exposure basically
starts destroying cells.</i> <i>Things start to shut down.</i> <i>They're gonna have
immediate sickness.</i> Their body systems are likely
to be very damaged. Organs may start to shut down
pretty quickly, within minutes, <i>and basically fatality
right away.</i> <i>♪ ♪</i> There's not much anyone
could really do. <i>Your first responders, they're
gonna be getting sick too.</i> <i>♪ ♪</i> <i>narrator:
In Madrid, Paris, Cairo,</i> <i>and across
the entire impact zone,</i> <i>people taking refuge
in office buildings and homes</i> <i>find there is no escape
from the gamma-ray burst.</i> - [wheezing] - Muons are very penetrating. They'll pass right through
buildings, no problem. - [gasping] <i>♪ ♪</i> <i>narrator:
30,000 feet in the air</i> <i>isn't any safer.</i> <i>High above the burning
landscape of Europe</i> <i>and the Mediterranean,</i> <i>hundreds of commercial aircraft
are still in flight</i> <i>without navigation systems
to guide them.</i> <i>♪ ♪</i> <i>The showers of muon radiation
are so powerful,</i> <i>they penetrate the aircraft,</i> <i>killing everyone onboard.</i> <i>♪ ♪</i> <i>How far will this deadly
gamma radiation</i> <i>spread across the globe?</i> <i>Will any of us survive?</i> <i>[dramatic music]</i> <i>narrator: 25 years ago,</i> <i>scientists began monitoring
gamma-ray bursts,</i> <i>deadly radioactive beams
that come from deep space.</i> <i>♪ ♪</i> <i>What if one slammed
into planet Earth today?</i> [people exclaiming] <i>Without warning,
hundreds of millions</i> <i>have already died
in the impact zone</i> <i>that includes Africa,
the Middle East,</i> <i>and Europe...</i> - [coughing] <i>narrator: Many of them victims</i> <i>of overwhelming
radiation poisoning.</i> - Basically, you've just
walked into Armageddon. - [gasping] <i>- Gamma radiation
is what we call</i> <i>ionizing radiation.</i> It destroys the compounds
and the tissues of your body and kills you almost instantly. <i>♪ ♪</i> <i>- So immediately,
the central nervous system</i> will obliterated and destroyed. So life as we know it
on that part of Earth will disappear immediately. <i>♪ ♪</i> <i>narrator: The U.S. navy
ballistic missile</i> <i>submarine, "Louisiana,"</i> <i>preparing for what
military leaders</i> <i>think might be nuclear war,</i> <i>cruises submerged
off the coast of Italy.</i> <i>♪ ♪</i> <i>The vessel is on high alert,</i> <i>poised to launch
a retaliatory missile strike</i> <i>on an unknown enemy.</i> <i>But the launch
will never happen...</i> [alarm blaring] <i>Because everyone aboard...</i> <i>is dead.</i> <i>♪ ♪</i> <i>High-energy
muon radiation particles</i> <i>can penetrate water</i> <i>up to a depth
of nearly one mile.</i> <i>♪ ♪</i> <i>Even the heartiest creatures
in Earth's oceans</i> <i>are not safe.</i> - The more complex organisms
like whales, dolphins, large fish-- <i>they're gonna experience
a really immediate impact.</i> <i>Their systems are gonna
start shutting down</i> <i>just like people's would.</i> <i>♪ ♪</i> <i>narrator:
On the vast grasslands</i> <i>of Africa's Serengeti,</i> <i>mammals suffer the same fate.</i> <i>But not everything perishes.</i> - Insects are extremely
resistant to radiation, so they have a tremendous
capability to repair the damage. <i>A big fraction of the radiated
population will survive.</i> <i>♪ ♪</i> <i>narrator:
Deep below the impact zone,</i> <i>a handful of humans</i> <i>have also survived
the gamma-ray burst.</i> <i>♪ ♪</i> <i>From the Boulby Mine,</i> <i>the second-deepest
hard rock mine in Europe,</i> <i>a group of workers
doesn't realize</i> <i>that the 4,000 feet of earth
and solid rock</i> <i>has saved their lives.</i> <i>♪ ♪</i> <i>When they arrive
on the surface,</i> <i>they emerge to a vision
of hell on Earth.</i> - [coughing] [lightning crashing] <i>♪ ♪</i> <i>narrator: Now their survival
depends on finding</i> <i>sources of food and water</i> <i>in a burned
and lifeless continent.</i> [thunder booming] <i>♪ ♪</i> <i>As lightning storms
illuminate the skies</i> <i>over Mumbai's famous Colaba
Causeway street market...</i> [lightning crashing] <i>♪ ♪</i> <i>Shoppers are unaware
of the cosmic radiation</i> <i>that's falling
all around them.</i> <i>♪ ♪</i> [thunder booming] <i>♪ ♪</i> <i>While mankind in the impact
zone is nearly extinct...</i> [lightning crashing] <i>Those living on the edges
have better odds of surviving.</i> <i>♪ ♪</i> <i>narrator:
From the streets of Mumbai...</i> - Try.
Here. [thunder booming] <i>♪ ♪</i> <i>narrator: To the container ship
in Puerto Rico,</i> <i>the radiation falling down
is far less damaging.</i> <i>♪ ♪</i> - [breathing heavily] <i>narrator: For those
that act quickly,</i> <i>there is a way to beat the odds
of cancer onset.</i> <i>♪ ♪</i> <i>Removing clothes and shoes</i> <i>eliminates about 90%
of external contamination.</i> <i>♪ ♪</i> <i>Washing with soap and water</i> <i>also removes radiation
particles from the skin.</i> <i>♪ ♪</i> <i>narrator:
As millions fight to survive</i> <i>on the edges
of the gamma-ray inferno,</i> <i>in North and South America,</i> <i>massive food shortages</i> <i>threaten to take down
the rest of humanity.</i> - As time goes by, as the hours
turn to days and weeks, <i>eventually, the chaos envelops</i> <i>the entire planet.</i> <i>♪ ♪</i> <i>[dramatic music]</i> <i>narrator:
Some scientists believe</i> <i>that 440 million years ago...</i> <i>♪ ♪</i> <i>Earth was hit
by a gamma-ray burst,</i> <i>or GRB,
a deadly beam of radiation</i> <i>that devastated life
on the planet.</i> <i>♪ ♪</i> <i>Could you survive
if we were struck</i> <i>by a gamma-ray burst again?</i> <i>♪ ♪</i> - [gasping] <i>narrator: In the first minutes
after the disaster,</i> <i>billions of people
are already dead or dying</i> <i>in the impact zone,</i> <i>an area including Africa,</i> <i>Europe, and the Middle East.</i> - Essentially, life
on the side of the impact has been extinguished. <i>♪ ♪</i> [lightning crashing] - [coughing] <i>narrator: In northern England,</i> <i>the lone survivors
are a group of miners</i> <i>who weathered the blast under
4,000 feet of earth and rock.</i> <i>♪ ♪</i> <i>Now they travel
the countryside,</i> <i>living off canned
and other preserved goods,</i> <i>but they don't realize
that the gamma-ray burst</i> <i>has poisoned their food supply.</i> <i>♪ ♪</i> <i>- So gamma-ray bursts</i> at these intensities
can produce radioactive or activated isotopes
from the food that can be very dangerous. <i>♪ ♪</i> <i>narrator:
The miners' lifeline is thin,</i> <i>and it's only a matter of time.</i> <i>♪ ♪</i> <i>In the Americas,</i> <i>on the side of Earth
opposite the impact zone,</i> <i>the situation is desperate.</i> <i>♪ ♪</i> <i>After the gamma-ray burst's
electromagnetic pulse</i> <i>zapped electronics...</i> <i>♪ ♪</i> <i>A global power blackout
went into effect.</i> <i>♪ ♪</i> <i>narrator:
For people in Atlanta,</i> <i>Seattle,</i> <i>Rio de Janeiro,</i> <i>and every large
North and South American city</i> <i>in the non-impact zone,</i> <i>power grids are down,</i> <i>and commerce is frozen.</i> <i>- You are literally left
in the dark,</i> <i>without heat, without light,
without food.</i> You're basically thrown back
a hundred years into the past. <i>♪ ♪</i> [water trickling] <i>narrator: Municipal
water supplies are severed.</i> <i>Without electricity,</i> <i>the pumps can't
distribute the water.</i> [people shouting] <i>Grocery stores are mobbed,</i> <i>and desperation sets in</i> <i>as people fight over
a shrinking food supply.</i> <i>♪ ♪</i> <i>Ventilators, dialysis machines,</i> <i>and backup systems fail,</i> <i>all but ensuring the deaths</i> <i>of thousands
of hospital patients.</i> <i>- We live in a bubble.</i> <i>This bubble is energized
by electricity.</i> <i>But what happens if something
pops that bubble?</i> [electricity sparking] <i>Without backups,
without heat, without food,</i> <i>then you begin to realize
that civilization itself</i> will begin to degenerate
as a consequence. <i>♪ ♪</i> <i>When the gamma-ray burst</i> <i>slammed into
Earth's atmosphere,</i> <i>it ripped apart
the ozone layer,</i> <i>exposing the survivors
to a new radiation threat.</i> <i>♪ ♪</i> - The ozone layer
in our atmosphere is one of the most beneficial
things on the planet. <i>We have this star in the sky,</i> <i>the sun,</i> <i>that dumps
ultraviolet radiation</i> <i>at us all the time.</i> It keeps us alive,
but without the ozone, it would cook us and kill us. <i>♪ ♪</i> <i>- The side of earth facing it</i> <i>gets completely depleted
of ozone.</i> <i>♪ ♪</i> <i>All the ozone gets destroyed.</i> <i>Essentially zero left.</i> Now, you've still got
100% percent on the other side of Earth, but as the atmosphere
mixes together in the ensuing days and weeks, effectively, what you'll have is 50% of the normal ozone
throughout the world. <i>♪ ♪</i> <i>- If you go out in the weeks
after this event</i> with any kind
of unprotected skin, you're getting doses
of UV radiation that would take you
normally hours in minutes. <i>♪ ♪</i> <i>You're talking
a serious sunburn</i> <i>in 10, 15, 20 minutes.</i> <i>Life-threatening
if you're exposed for hours.</i> This is a "get inside or perish"
situation. <i>♪ ♪</i> <i>- The long-term effects</i> are that UV is coming through and interacting
with living cells. <i>- That much larger dose
of ultraviolet radiation</i> will change DNA
and can create cancers. Skin cancers
will rise dramatically. <i>narrator:
The only form of protection</i> <i>is to avoid the sun.</i> <i>- They're gonna have to put on
extra heavy-duty clothing.</i> <i>They're gonna have
to put on sunglasses.</i> <i>They're gonna have to cover
every inch of their body,</i> <i>realizing that the sun that
gives us life and nourishment</i> <i>is now bathing us
in a ultraviolet radiation</i> that can eventually kill us. <i>♪ ♪</i> <i>- Lifestyles will change</i> <i>because you have to
in order to survive.</i> Think of living the entirety
of the remainder of your life inside or underground. This is what we will
have to do to survive. <i>narrator: As the ultraviolet
radiation threatens mankind,</i> <i>Earth's ecosystems
begin to collapse.</i> - Ultraviolet radiation will,
over time, sterilize the upper meters
of the Earth's oceans. <i>♪ ♪</i> <i>- The phytoplankton</i> <i>in the ocean are basically</i> <i>little green plants,
single-celled plants,</i> <i>and they produce
about half the world's oxygen,</i> which means they're the base
of the food chain in the ocean. Larger things eat them
and so on up the food chain. <i>♪ ♪</i> - Fishermen accustomed
to harvesting large bounties of fish from the ocean would see something
very different. <i>They would see
a massive die-off.</i> <i>♪ ♪</i> <i>narrator:
Without adequate food and water</i> <i>or electrical power,</i> <i>North and South American cities</i> <i>in the non-impact zone
are now in peril.</i> <i>♪ ♪</i> - Food supply. Average city, community has,
at most, about two weeks' worth
of food on hand. <i>You go without any significant
caloric intake</i> <i>after about two weeks,</i> <i>then you start becoming
more susceptible</i> <i>to disease and dying.</i> <i>♪ ♪</i> <i>narrator: New York,</i> <i>San Francisco,</i> <i>Mexico City,</i> <i>and Bogotá</i> <i>are soon to be...</i> <i>cities of the dead.</i> <i>[dramatic music]</i> <i>♪ ♪</i> <i>narrator: Earth's future
hangs in the balance...</i> <i>♪ ♪</i> <i>When a massive gamma-ray burst</i> <i>showers the planet
in deadly radiation.</i> <i>♪ ♪</i> <i>Half the world's population
is dead.</i> <i>narrator: Like every other
population center</i> <i>in the impact zone,</i> <i>Madrid is a city of corpses.</i> <i>The blistering UV radiation
hardens the skin,</i> <i>preventing decomposition.</i> <i>♪ ♪</i> <i>The bodies in the streets
are now mummies.</i> <i>♪ ♪</i> <i>Indoors, where the UV rays
don't penetrate,</i> <i>the bodies become food
for insects</i> <i>that survived
the radiation blast.</i> - A gamma-ray burst
can be thought of as a cosmic silent assassin that arrives with no warning, exterminates much of life
on Earth, and then leaves
no real trace behind. <i>♪ ♪</i> <i>narrator: Meanwhile,</i> <i>people on the side
of the planet</i> <i>facing away from the burst</i> <i>survive the initial onslaught,</i> <i>but the danger
is far from over.</i> <i>♪ ♪</i> <i>Across America,
there is no electricity.</i> <i>♪ ♪</i> - The average major urban center in an industrialized nation
has, at most, two to three weeks' worth
of food on hand. <i>That's what you have
in your pantry,</i> <i>in your fridge.</i> <i>In the supermarket,</i> <i>most of it is
climate-controlled or frozen.</i> Turn off the electricity,
no food. <i>♪ ♪</i> <i>After we've lost
our power grid,</i> <i>you have a city that is
starving to death...</i> <i>♪ ♪</i> Starving the way people
once did, say, in the Siege of Leningrad
in World War II. <i>♪ ♪</i> - The police force,
the EMP crews, the firemen. All our emergency systems
are down. <i>narrator:
Across the non-impact zone</i> <i>from Los Angeles
to Washington, D.C.,</i> <i>food is the biggest problem.</i> <i>The supermarkets were
cleaned out weeks ago,</i> <i>and on farms,
there is nothing to harvest.</i> <i>♪ ♪</i> <i>- The crops that we rely on</i> <i>are gonna be affected
by the UV,</i> so there's gonna be
a lot less wheat, corn, soybeans, rice. <i>- So without
the protective ozone layer,</i> <i>agriculture as we know it
will collapse,</i> which means there'll be
massive food riots as people start
to kill each other for whatever scraps of food that are still left. <i>narrator: Humans aren't
the only ones affected.</i> <i>Livestock also suffer.</i> <i>♪ ♪</i> <i>- They, too, will begin to die,</i> <i>meaning that we're gonna have
a lack of protein.</i> We're not gonna see animals
that we can harvest and fish that we can take
from the oceans. We're gonna see the fact that
we're facing mass starvation. <i>♪ ♪</i> <i>narrator:
Deaths begin to rise sharply.</i> <i>More than 50%
of the United States'</i> <i>population has perished.</i> <i>♪ ♪</i> <i>The survivors eke out a living</i> <i>scavenging scraps of food</i> <i>and avoiding the harmful
UV rays.</i> - Some of the population
will be able to survive in, say, an underground setting. You're got hardened
military shelters. You're got underground
survivalist-type silos. <i>♪ ♪</i> - This is life on Earth trying to survive. This kind of event,
this gamma-ray burst, is a reset button
for the planet. <i>Whatever survives at this point
is a roll of the dice.</i> <i>Natural selection becomes</i> the ultimate decider of what evolves
and what goes extinct. <i>♪ ♪</i> <i>narrator: But even
the strongest survivors</i> <i>could be out of luck</i> <i>when the same gamma-ray burst</i> <i>that destroyed half the Earth</i> <i>comes back to finish the job.</i> <i>♪ ♪</i> <i>[dramatic music]</i> <i>narrator: It's been two years
since a gamma-ray burst,</i> <i>a deadly beam of radiation
from space,</i> <i>wiped out half
of Earth's population.</i> <i>♪ ♪</i> <i>On the other side of the Earth,</i> <i>hundreds of millions
in the non-impact zone</i> <i>of North and South America</i> <i>are now dead.</i> <i>The failure of the power grids</i> <i>has turned the clock back
to the Dark Ages.</i> <i>♪ ♪</i> <i>As food supplies dwindle,</i> <i>can any survivors</i> <i>prevent the end
of the human race?</i> <i>♪ ♪</i> [lightning crashing] <i>♪ ♪</i> <i>Omaha, Nebraska,</i> <i>once part
of America's breadbasket,</i> <i>lies barren.</i> <i>A steady rainfall</i> <i>falls over what was once
a cornfield.</i> <i>But this is no ordinary rain.</i> <i>♪ ♪</i> <i>It is acid rain,
heavy with nitrogen dioxide</i> <i>because of the gamma-ray
burst's radiation.</i> [thunder booms] <i>Strangely, this acid rain</i> <i>offers a glimmer of hope
to survivors.</i> <i>♪ ♪</i> - The presence of nitrogen
in this acid rain acts the same
as the type of fertilizer we might throw on our grass
or our crops. [rain falling] <i>♪ ♪</i> <i>narrator: The acid rain</i> <i>is actually the first sign</i> <i>of Earth returning to balance.</i> <i>♪ ♪</i> <i>It cleanses the atmosphere</i> <i>and allows Earth's ozone layer
to reform.</i> <i>This begins to block out</i> <i>the sun's hazardous
ultraviolet rays again.</i> <i>♪ ♪</i> <i>Life slowly begins
to repopulate the oceans.</i> <i>- We could be seeing
a new equilibrium</i> <i>being established,</i> <i>so there is some hope.</i> <i>Even though civilization
as we know it</i> <i>has been destroyed,</i> perhaps with the atmosphere
re-stabilizing itself, perhaps we can start
all over again. <i>♪ ♪</i> <i>narrator:
As agriculture returns</i> <i>and fish populations
are replenished...</i> <i>♪ ♪</i> <i>Mankind slowly returns
from the brink of extinction.</i> <i>♪ ♪</i> <i>But the rebirth
is destined to fail.</i> <i>♪ ♪</i> <i>♪ ♪</i> <i>Five years after
the gamma-ray burst impact...</i> - [coughing] <i>narrator:
Survivors begin to drop dead.</i> - [exclaiming] <i>narrator: A sudden rush
of radioactive particles</i> <i>is pouring in
from outer space.</i> - [choking] <i>♪ ♪</i> <i>narrator:
It's another wave of radiation</i> <i>from the same star collision</i> <i>that caused
the gamma-ray burst...</i> <i>but this blast takes longer
to travel through space</i> <i>and reach the Earth.</i> - A gamma-ray burst
produces not only gamma rays but also charged particles. - Particles
that would be emitted along with these gamma rays <i>travel at a slower speed.</i> <i>- So it's possible
that an onslaught</i> <i>of energetic particles
will arrive</i> years after the onslaught
of photons from the gamma-ray burst. <i>♪ ♪</i> <i>narrator: Earth's rotation
has placed the Americas</i> <i>directly under
the particle burst</i> <i>when it arrives.</i> <i>Across the new impact zone,</i> <i>humans succumb to
the second assault from space.</i> <i>♪ ♪</i> <i>Once again, Earth's ozone layer
is stripped away,</i> <i>and without protection
from our atmosphere,</i> <i>there is no chance of survival.</i> - As the particles
continue to arrive, we're going to get this
enhancement in radiation over a long time scale. <i>[eerie music]</i> <i>♪ ♪</i> <i>narrator: The Earth is now
a radioactive wasteland.</i> <i>♪ ♪</i> <i>The only remaining life:</i> <i>radiation-resistant insects.</i> <i>♪ ♪</i> <i>It's a catastrophic scene</i> <i>scientists believe
has happened before.</i> <i>- 440 million years ago,</i> during what we call
the Ordovician period, there was an extinction-level
event that wiped out about 75% of all life
on Earth. <i>- So we don't have
a smoking gun</i> <i>that the gamma-ray burst
was the cause</i> <i>of this late Ordovician
mass extinction,</i> but there's a lot
of correlations that seem to make the case
pretty strong. <i>♪ ♪</i> <i>narrator: Could another
cataclysmic extinction event</i> <i>happen again?</i> <i>♪ ♪</i> <i>And could planet Earth
and mankind</i> <i>become the victims
of a gamma-ray burst?</i> <i>♪ ♪</i> <i>- We know that the gamma-ray
bursts happen all the time.</i> <i>They're rare
in any given location,</i> <i>but we know that they happen,</i> and we know that the Earth would be profoundly
affected by one. <i>♪ ♪</i> <i>- We are children
when it comes to understanding</i> <i>gamma-ray bursts,
their history.</i> Maybe, just maybe, it's happened many times
in our history. We don't know. <i>♪ ♪</i> <i>We didn't think
that there could be</i> <i>rocks from heaven coming down,</i> <i>killing the dinosaurs.</i> <i>But now we know better.</i> <i>♪ ♪</i> How many more gamma-ray bursts are just waiting to fire? <i>♪ ♪</i>
