All language subtitles for The Universe - 2x17 - Gravity.en

ln the beginning,
there was darkness...

and then, bang...

giving birth to an endless
expanding existence...

of time, space, and matter.

Now, see further
than we've ever imagined...

beyond the limits of our existence...

in a place we call "The Universe."

lt is both mighty and meek.

Humanity's quest is to harness
its power and escape its bonds.

Holy cow!

This is what an astronaut feels.

lt creates and breaks the stars,
the planets, the galaxies...

and directs their
cosmic roller coaster ride.

Gravity is ourfriend and ourfoe.

Without it,
life as we know it would end.

The Earth would literally explode.

lt is the magnificent
and mystifying force...

that rules the universe: Gravity.

Gravity is the most pervasive
force in the universe.

lt is at work on massive
and minute scales...

on the routine and the extreme.

A surfer needs it to hang ten.

When you ride a wave, you're
going to slide down the front...

and you're going to use
that pull of gravity to get you going.

lt's your acceleration force.

lt's your accelerator.
Gravity is your accelerator.

A skier uses it
to race downhill.

A snowboarder must have it
to get big air.

lt acts on everything with mass,
including us, 24/7...

even when sleeping
or standing.

Gravity here on Earth, of course,
is always accelerating us down...

toward the center of the Earth
at 32 feet per second squared.

At a theme park,
gravity is the galactic gas...

that makes roller coasters roar
and people scream.

The gravity of the Earth
pulls us down...

and that's going to make us go
really, really fast.

All objects
with mass or energy--

particles, people, planets,
stars, and galaxies--

produce gravity.

Omnipotent and omnipresent...

gravity attracts, governs,
warps, shapes, makes...

and takes all matter and mass
in the universe.

So it's pervasive.

lt acts on all things through
extremely large distances...

and nothing escapes its pull.

lt is gravity that holds
our solar system together.

The force of gravity...

is basically that thing
that holds us on the planet...

keeps us from flying off.

lt is the cosmic glue that binds
all matter in the universe together.

lfyou were to imagine
taking two dice...

and putting them perfectly at rest
out in the middle of space...

and separating them
by a centimeter...

then what you'd see is that
over a course of an hour or so...

those two dice would slowly
come together and touch.

Gravity made ourworld.

Our Sun formed
from a vast cloud of gas...

that gravitationally contracted.

Similarly, our Earth formed
through the gravitational attraction...

of little particles,
little bitty things...

gradually growing
into a bigger and bigger object.

When it comes
to gravity's pulling power...

mass and distance matter.

lt depends on the masses
of each object...

the amount of matter
within each object.

So it's proportional to
the product of the two masses.

ln otherwords, the bigger it is...

the harder it pulls
on other objects.

But that's not all.

And it's inversely proportional...

to the square of the distance
between them.

This means ifyou double the distance
between two objects...

the attraction or pull is only
a quarter of its original strength.

The pulling power of gravity lets
it direct the motion and movement...

of all matter, however massive,
in the universe.

So you have whole galaxies,
for example...

in orbit around each other.

Clusters of galaxies all orbit
around their common center of mass.

But it is the practical potential
of harnessing this relentless force...

that has obsessed scientists
for centuries.

lt would literally fall to Galileo Galilei,
the 17th-century truth-seeker...

to first recognize
that gravity even existed.

Galileo found that objects
having a different weight...

fall at the same rate.

So here's a very heavy steel ball...

and a light ping-pong ball
of the same size.

And if l drop them
at the same time...

they hit the ground
at exactly the same time as well...

because they fall
at the same rate.

To illustrate Galileo's most profound
gravitational discovery...

that all objects, regardless of mass,
fall at the same rate...

we take a ride on the mega-fast
"Superman: The Escape"...

at Six Flags Magic Mountain
in Southern California.

The theme park ride
is the stage...

for a spectacular
free-fall demonstration.

lt will showwhat happens
when a carfull of people...

and a tennis ball fall
from 415 feet in the air.

Okay. Here we go.
All right.

Oh, my. Oh, my God.

The riders are shot up
the 41-story-tall tower...

at a hundred miles an hour.

With their eyes open, gravity
will help them see a superhero.

Oh, my God. Okay.

l'm going to drop this ball
now and--

Oh, my God,
it's floating around!

lt's floating!
lt's floating!

Oh, the wind blew the ball
away that time.

While we expect all objects to fall
freely together, regardless of mass...

on a windy day,
results aren't always perfect.

All right. Oh, my God.

At the very top of the ride,
when upward motion has stopped...

gravity takes over
and the downward free fall begins.

l'm going to drop this ball...

and it's going to float.
lt's going to float.

Oh, it's floating.
lt's floating.

l'm going to
release this ball now.

And then,
for a few blissful seconds...

theme park thrill-seekers
feel weightless...

as ifthey are free of gravity,
or in what scientists call zero-G.

Oh, that one floated well.
That one floated well.

Oh, l'm going to try
dropping the ball.

But zero-G isjust an illusion.

ln reality, gravity is running this ride.

lt's the force that yanks the car,
the people, and the tennis ball...

indifferent to their mass,
back down to Earth at the same rate.

Oh, that's a fantastic ride.

l mean, feeling oneself
drop is amazing.

But what's really great
is dropping the ball...

and seeing it floating
above my face.

Now--l mean, it's falling.
l know it's falling...

but l'm falling
at exactly the same rate.

lt doesn't matter
how massive something is.

lt falls, under the force of gravity,
at exactly the same rate.

Thanks to experiments like this...

we now know that objects
all fall at the same rate.

But what would it take to launch
a cannonball into orbit?

When the famous British
physicist Sir lsaac Newton...

saw the apple fall that,
some say, hit him on the head...

it changed the world.

You got the apple
falling from the tree...

and he looks up and sees the Moon
in orbit around the Earth...

and judges that not only
is the apple falling to Earth...

so too is the Moon.

But could the Moon
really be falling?

Load!

By thinking of a cannon
and the trajectory of the ball it shoots...

Newton used math
to unlock a cosmic mystery.

lt came in his landmark publication,
"Principia Mathematica," in 1687.

lsaac Newton
has a famous drawing...

and in it, he draws a planet
and a little mountain.

There's a little projectile
first kicked off the mountain...

and it falls down a little bit.

You give it more speed,
it goes a little farther out.

Now say you could just increase
the force all you wanted.

lt can go fifty miles,
it can go a hundred miles before it fell.

By adding more gunpowder
and withjust the right angle offire...

a cannonball can be made
to go faster and farther.

lnevitably, however, gravity wins...

pulling the cannonball
back down to Earth.

The Earth is round and not flat,
so Newton realized...

that if the cannonball
is fired at sufficient speed...

the cannonball would
actually go into orbit.

For that to happen,
Newton determined...

the ball would need to be shot
out of the cannon...

at17,500 miles an hour.

lt starts curving
around the Earth...

and he realized
that there must be a speed...

where it goes completely
around the Earth...

and hits you
in the back of the head...

never actually hitting
Earth's surface.

And ifyou duck,
it'll just keep going...

and lo and behold,
you have an orbit.

But why doesn't the Moon
fall to Earth?

The Moon also has
some sideways motion...

so for every little bit
that it falls down...

it also moves off
in this direction...

and the sum of all those motions
is an orbit around the Earth.

Newton also realized that the Earth
is in a giant freefall around the Sun.

With gravity forging the path,
our planet rounds the Sun...

like an endless cosmic
roller coaster ride.

Newton cracked
the gravity code...

and physicists are still using his ideas
to solve all sorts of problems...

some ofthem
stranger than others...

like, what would happen if a person
tried to travel through a tunnel...

from one side of the planet
to the other?

ln this wild scheme...

you would have to drive
a straight-line tunnel...

right through the Earth and use
gravity alone to propel a traveler...

down this so-called
gravity express.

So, suppose you've got
one ofthese tunnels...

and youjump in.

lnitially, the Earth is pulling down.

You're going toward
the center of the Earth...

and so you're
accelerating toward it.

But as you pass through
the center ofthe Earth...

and start going out
toward the opposite side...

the gravity ofthe Earth
is trying to pull you back...

so it's decelerating you.

So gravity's actually
having a braking effect.

There's no fear
of shooting out the hole...

on the other side of the Earth
at some tremendous velocity...

and shooting yourself
back into space...

but, in fact, you reach the surface
ofthe Earth exactly.

You would coast
to a perfect rest.

ln forty-two minutes, you'd be there.

Whichever two cities you connect
with a straight-line tunnel...

it takes gravity exactly
forty-two minutes to get you there.

Thejourney from Los Angeles
to Paris, forty-two minutes.

Suppose you wanted to go
from Los Angeles to Tokyo...

forty-two minutes.

lt doesn't matterwhich path
you take through the Earth.

Thejourney is always
forty-two minutes long.

lt takes Newton's math
to figure out why this works.

lfwe connect
Los Angeles to NewYork...

digging a tunnel, obviously...

a tunnel would not go
straight down...

but it has to go down
at an angle.

The angle slows
the speed of descent.

But the distance
is also less.

And ifyou work out
the equations...

lo and behold,
the two effects cancel...

and you still get there
in forty-two minutes.

lt takes forty-two minutes
regardless of the path you take.

That's really cool.

Newton figured out
what gravity does...

but it took the brilliance
of physicistAlbert Einstein...

to work out why it was doing it.

Einstein realized that gravity
is really caused by huge objects...

like stars and planets,
literally bending space itself.

Like a massive rubber sheet...

space is curved
where massive objects sit in it.

ln fact, Einstein proposed that the path
planets take around their stars...

their orbits, are all a direct result
of this curvature of space.

He said that what an orbit is...

is really something
traveling in a straight line.

When something is free-falling
towards another object...

it really isjust traveling
in a straight line through space-time.

However, the curvature of space-time
bends its path into a closed orbit...

but space itself
curves it back in on itself.

This revolutionary discovery came
when Einstein, in the early1910s...

realized that orbits of stars and planets
in the observable cosmos...

behavejust
as Newton's math predicted...

except one: Mercury.

lts orbit essentially wobbles.

Einstein described gravity
as a curvature in space and time...

and the orbit of Mercury works perfectly
when you take that into account.

Mercury isn't moving in flat space,
but curved space around the Sun.

Then the orbit's perfect.

This curvature of space is
at play in our own solar system.

Earth is simply following
what it thinks is a straight-line path...

the shortest distance
between two points...

in this intrinsically
curved space.

Einstein not only determined
that mass warps space...

it warps time, too.

So, henceforth,
Einstein proclaimed...

physicists should not speak
of space and time separately...

but of space-time
as one unified object.

While it's uncomfortable to many
the first time you hear it...

ifyou stop and think about it,
it's actually quite obvious.

lf l'm going to make
an appointment with somebody...

l don't say,
"l'll meet you at 3:00."

That's not enough information.

There's got to be a question
that follows that.

What is that question?

Where?

lf l say,
"Meet you in room 203."

When?

Any time you intersect
with someone's else's life...

you do so at a time
and at a place.

Einstein's realization
that space is curved...

and that time and space
are, in fact, intertwined...

is now the very definition
of gravity.

Liftoff of
the Space Shuttle "Discovery."

Unlocking the secrets of gravity...

has enabled humanity to escape
our earthly shackles...

and opened the universe
for exploration.

But how can future astronauts
on the long way to Mars...

survive the disabling effects
caused by zero-G?

Gravity is ourfriend...

and ourfoe.

lt is the fearsome force
that propels a skier...

and the snowboarder
down the mountain...

and shoots them into the air.

With enough momentum,
an airborne snowboarder...

can feel forfleeting moments...

as if they are free
of Earth's gravitational pull.

You're actually weightless
when you go offthejump.

The period ofweightlessness
is determined...

by the duration ofyour trajectory
as a function ofyour velocity...

so that the snowboarder
who gets really good big air...

may achieve a second, two seconds,
even three seconds ofweightlessness.

But in the end, gravity wins...

and the high-flying,
free-falling boarder...

just like the ball
fired from the cannon...

is eventually yanked
back down to Earth.

This free fall
for the snowboarder...

as he or she goes
over thejump...

and creates this trajectory
isjust as much free fall...

as a cannonball
going through the air...

and the trajectory
is determined...

only by the velocity
and the force of gravity.

Then, of course, what happens
on the landing is another story.

But what if a snowboarder...

aspired to reach
even greater heights?

What if he wanted
to overcome gravity...

and launch himself
right off the planet?

You want to leave Earth
entirely and forever?

Earth has what we call
the escape velocity...

this magic speed
where ifyou pass that speed...

you will escape Earth forever,
never to return.

Escape velocity, the minimum speed
any object needs to reach...

in order to escape
from the Earth...

is about seven miles a second.

That's 25,000 miles an hour.

ln theory, even a snowboarder...

with enough momentum
and aimed in the right direction...

can take offjust like a rocket.

Escaping Earth's gravity may
not be realistic for a snowboarder...

but it has proven possible to launch
people and projectiles into orbit.

You can leave systems.

Youjust need
enough energy to do so.

And we've garnered enough energy
and technological know-how...

to dojust that
in ourvoyages to the Moon.

And our hope is that that will
continue on to Mars and beyond.

To get to Mars and beyond...

mankind will have to harness
gravity's energy...

just like we always do when
we're seeking thrills to the extreme.

Gravity gives us
two types of energy...

potential...

and kinetic.

Potential isjust that.

lt is energy that's being stored...

while kinetic is the result
of all that pent-up potential energy.

This fantastic phenomenon
works on a roller coaster.

As you're winched up on a hill,
your potential energy is increasing.

You literally have more energy...

at the top of the roller coaster
than at the bottom.

lt's notjust a weird,
abstract thing.

You actually possess
higher energy at the top...

and that's turned into speed,
into kinetic energy...

as you go down that hill
on the roller coaster.

Pretty soon, l'll be converting
my potential energy to kinetic energy.

When a surfer hits
that sweet spot on a wave...

they're using
energy's double act.

NASA also uses
this energy exchange principle...

to add some speed
to their missions.

As a spacecraft
nears the orbit of a planet...

it, too, gathers kinetic energy
at the expense of potential energy.

Then as it rounds the planet
on its cosmic coaster ride...

the craft gets a slingshot effect...

that punches it onward
with more kinetic energy.

When the Voyager spacecraft
visited Jupiter in 1979, 1980...

it flew past Jupiter,
and Jupiter tugged on it...

giving it extra motion,
sort of a slingshot effect...

not only changing
its direction of motion...

so that it was aimed
towards Saturn...

but also speeding it up.

Knowing how to use
the power of gravity...

will enable humanity to travel
further and faster across the universe.

Having the physics formulated
and the technology available...

isjust one part of the preparation
for extraterrestrial travel.

Readying people for the rigors
of space is the other.

Far away from Earth's
gravitational pull...

in a spaceship on the long
journey to Mars, for example...

future astronauts will have to
learn to live, work, and play...

in an environment free
of Earth's sizeable gravity...

one where they
effectively feel weightless...

and all objects
move equally and freely.

One fun way to experience...

the astronautical thrills
and spills of space travel...

is to simulate it
on a zero-G flight.

l'm really looking forward to this.

This is going to be
an incredible experience.

By riding the ultimate
roller coaster...

a specially modified
zero-G Boeing 727 aircraft...

astrophysicist Alex Filippenko
is about to go on the ride of his life.

This is going to be like a ball
thrown up in the air...

weightless because it will be
in free fall...

so l'll be floating around as though
there's no ground holding me up.

The zero-G flight flies between
24,000 and 32,000 feet.

This is about the same altitude
as a regular commercial jet...

but that is where
the similarity ends.

The water's the next one?

The path it follows is a series
of coaster-like rolling hills...

in the stratosphere.

Just like "Superman: The Ride"...

the super zero-G plane
gathers potential energy...

as it climbs up at forty-five degrees.

Passengers feel this
as an increase in weight.

Oh, yeah.

Gravity is measured
in terms of g-forces.

One G is the amount
of gravitywe feel...

standing on the surface
ofthe Earth.

l'm going to get back down
like this and get ready.

As the plane steeply climbs,
accelerating upward...

the gravity G count rises
and people feel heavier.

All right.

The plane
is accelerating us upwards...

at about1.8 G at its maximum.

As the flight approaches, then eases
around the apex of the arc...

the plane, as well
as all the people inside it...

are, in effect, in free fall.

Zero-G comin' up.

Oh, man,
what an indescribable feeling.

Holy cow!

Oh, l'm out in free space.

Floating, just floating.

This is what an astronaut feels.

The plane's trajectory induces
weightlessness again and again...

by flying a series
of these parabolic arcs.

Even though they are
within the cabin of a plane...

the zero-G passengers are freely falling
towards the Earth just like skydivers.

But what creates the sensation
ofweightlessness?

lt goes back to Galileo...

who showed that all objects
fall at the same rate.

So, as the plane and the people inside
fall freely toward Earth...

they maintain the same position
relative to each other...

and that is why
they feel weightless.

The feeling lasted
twenty-five full seconds...

because, for twenty-five seconds,
we were essentially in free fall.

lt was like Superman
just flying through the air.

Oh, l cannot believe
how it feels.

When thejet's engines reengage
and end the free fall...

the passengers
feel theirweight return.

As Einstein would say,
weightlessness is but an illusion.

This is so awesome!
So awesome!

The zero-G plane
takes advantage...

of something Einstein
worked out back in 1916...

in his general theory of relativity...

that acceleration is essentially
the same as gravity.

When you are thrust upward
in a rocket or the zero-G plane...

the G-forces you experience...

are the same as you would feel
being tugged downward...

by the gravity of a massive object
like a planet.

So gravity and acceleration
create the same sensation.

That's how the passengers
on a zero-G flight...

can feel like an astronaut...

and can experience
thejoys ofweightlessness.

The ball and l
arejust freely falling...

according to our natural path
through curved space-time.

This is what Einstein's theory says.

lndependent ofthe mass,
we all follow the same path.

Oh, yeah, this is unbelievable.

On the twenty-minute,
fifteen-parabola flight...

there's time in between
the frights and delights...

to further taunt
the laws of gravity.

Look at that.
Look at that water.

Oh, look at that water.
l'm going to catch some.

Okay, here we go.

As well as entertaining
weekend warriors...

the parabolic flights...

also inauspiciously called
"The Vomit Comet"...

have a practical purpose.

They prepare NASA astronauts
forworking and living...

in the zero-G environment of space.

With these sensational
parabolic flights...

humans have learned how to
simulate the absence of gravity.

But is it also possible to create
artificial gravity in the lab?

These experiments will lead
to a successful exploration of Mars.

lt is in ourfuture.

At the dawn of the 21st century,
overcoming the bonds of gravity...

and escaping Earth's sizeable
tug have been realized.

The next step is to design
and build the technology...

that will allow humans
to travel, work, and live...

on exotic alien planets.

And we've garnered
enough engineering know-how...

to dojust that
in ourvoyages to the Moon.

Thanks to state-of-the-art
technology...

humanity is on the brink of
a new era in space exploration.

The trip to Mars is beginning
here at our laboratory at MlT.

Artificial gravity may be one
of the ways that we overcome...

the debilitating effects
ofweightlessness.

Since the advent
of the space age...

scientists have been
concerned with minimizing...

the life-threatening risks
and damaging effects...

of being weightless at zero-G.

The issues originally had to do
with human survivability.

We didn't even know
back in the Apollo period...

how people would react
to stays in space...

of more than a few hours.

There was all kinds of concern
about humans' ability...

to control a vehicle after
being exposed to weightlessness...

for a long period of time.

A mission to Mars
would require astronauts...

to be away from Earth's gravity
for at least two, maybe three years.

The human frame
is simply not designed...

for the absence
of terrestrial one-G gravity.

The architecture of our bodies
is designed to withstand ourweight...

under the forces of gravity.

Gravity determines how our
cardiovascular system reacts...

so when you get out of bed...

and you go from being supine
to upright...

there's a regulatory system
that keeps the blood pressure...

reacting
against the forces of gravity.

Experience has shown that
being weightless for long periods...

leads to bone loss,
muscle deterioration...

and life-threatening blood clots.

Aeronautical engineers
at NASA and MlT...

are testing a personal
centrifuge system...

that may mitigate
the very real dangers.

They protect the heart,
the bones, their muscles.

And even in these early experiments,
we have every reason to believe...

that artificial gravity
with short-radius centrifuges...

may be the universal antidote
that we're looking for...

to protect people
on the long trip to Mars.

Just like a theme park ride...

spinning a subject
artificially creates g-forces.

To prevent motion sickness
in the MlT ride...

astronauts are conditioned
to keep their head still.

By spinning a person
at thirty revolutions a minute...

the centrifuge imparts one G...

the same force felt pulling down
a person standing on Earth.

Scientists hope that one day,
a trip to Mars will be a reality.

Onboard, they believe there should be
a personal centrifuge.

To get their Earthly gravity fill-up,
21st-century astronauts...

could then just spend
one hour a day on the machine.

We get onto it
for a brief period every day...

and get spun up quite fast...

spun up in what l'll call
a spin in the gym.

You go foryour exercise,
you go foryourworkout...

you get your G tonic,
your gravity tonic.

While a trip to Mars
may still be decades away...

astrophysicist and seasoned
skier Larry Young...

can dream of big air
in the liberating gravity of Mars.

On the surface, there is three-eighths
the tug of Earth's gravity.

Everyone likes
to get some air.

Everybody likes a little bit.

Just think ifwe were on Mars.

A person who weighs
100 pounds on Earth...

would feel as if they weigh
38 pounds on Mars.

Although a Martian skier
would fly down Olympus Mons...

at a third of the speed
theywould on Earth...

the lower gravity also means
that theywould get...

at least three times the big air.

ln the case of gravity,
it's mass that matters.

The more mass you have,
the stronger the pull of gravity.

So when you think about what
yourweight would be on the Earth...

versus something more massive
than the Earth, it's pretty direct.

lf something were twice
as massive as the Earth...

you'd weigh
about twice as much.

The Big Kahuna
in our solar system is Jupiter.

On that planet,
a 100-pound person...

would weigh
a whopping 254 pounds.

Even if Jupiter
had a solid surface...

a skier there would have
to fight for big air.

What we already know
about gravity, how it works...

and how it can be used
for practical purposes...

could, in theory,
even save the planet...

from its
ultimate cataclysmic fate.

Here's how gravity
can come to our rescue.

Gradually,
in about five billion years...

our Sun will brilliantly flare,
turn into a red giant...

gloriously burn up and die.

As this comes to pass,
our inner solar system is engulfed...

and Earth's gravity and atmosphere
will be radically altered.

At that point, life
on the blue planet will end.

But astrophysicist
Greg Laughlin has a plan...

to use gravity to save Earth.

This environment
that we have here now...

would look very similar
to the environment...

that is holding sway
on Venus right now.

A crushing carbon dioxide
atmosphere...

temperatures hot enough
to melt lead.

But rest assured,
if the worst hypothetical happens...

gravitational science
could save mother Earth.

The one thing that we could do
over the very long term...

is to somehow move
the Earth's orbit...

out to a larger distance
from the sun...

where the temperature
isn't so hot.

And a way that you can do that,
ifyou have enough time...

ifyou have billions ofyears
available to you...

is to use a comet
or an asteroid.

This mega move would require
astronauts and engineers...

aboard a spacecraft to maneuver
the comet or asteroid...

just in front ofthe Earth.

ln order to be most effective...

the comet has to fly
very close to the Earth...

within orbital radius or so
ofthe Earth.

Then on the cosmic roller coaster...

potential and kinetic energy are
roused and gravity does the rest.

lf that happens, then the comet
pulls the Earth forward...

the Earth pulls
the comet backward...

and the net result is that
the Earth is given a boost.

lt's given a boost
to a slightly higher orbital radius...

slightly larger distance from the Sun.

And ifyou make
one of these adjustments...

one of these passages
every10,000 years or so...

then the Earth,
over a period of a billion years...

can move
at a fast enough pace outward...

to keep track with
the steadily brightening sun.

lf however, the experts
get the math wrong...

and the big gamble doesn't work,
all bets are off.

And ifyou screw that up,
then you can have a collision...

between the comet
and the Earth.

So a hundred-kilometer object
crashing into the Earth...

is absolutely
an extraordinary disaster.

lt's the kind of thing
that causes huge extinctions...

of gigantic numbers of species.

Of course, this is only
an extreme hypothetical scenario...

but what is known for sure...

is that our continued existence
today here on Earth...

is contingent
on the presence of gravity.

lt allows for the perfect
conditions for life...

and the pursuit of happiness.

One G produces the surfer's dream:
A perfect wave.

But the wild waters
enjoyed on Earth...

are not the only kind
of gravity-generated waves.

There are cosmic waves so large
they roll across the entire universe.

Tidal torrents of gravity-boosted
particles roll across the cosmos.

According to Einstein...

these gravitational waves
wash through the universe.

But what are they?

Any change in the gravity...

sends a ripple through
that fabric of space...

then moves
at the speed of light.

That would be a gravity wave.

And why do they happen?

lfyou have two objects,
two compact stars...

each ofwhich
curves space around them...

and they're orbiting one another...

then the result is, is that
these two curved regions...

create a wave,
a ripple in the structure...

in the shape of space
that moves outwards...

carrying energy with it.

That's called a gravitational wave.

l mean, literally, you can
think about space and time...

having a wave,
just like an ocean wave in it...

that travels
through the universe.

Gravitywaves
arejust the same.

Any type of mass in motion,
big or small...

generates a gravitational wave.

And like the Earth's ocean tides...

gravitational waves roll
ceaselessly across the cosmos.

ln theory, a surfer launched
into space could experience...

an out-of-this-world
wipeout and warp.

lf a gravitational wave was
created in space or somewhere...

and went through you,
what would happen...

is you'd get fat
and then you'd get skinny...

meaning that space
was distorted.

Space in one direction
made you fatter.

ln the other direction,
it squashed you.

And it goes back and forth.

But for earthbound scientists
to detect any faint G-wave signals...

the disturbance
needs to be propagated...

by a massive cosmic object.

Black holes and spinning
neutron stars can do it.

Another thing
that can make a gravity wave...

is an explosion,
say, a supernova.

A star explodes
and it goes--whack--

and that actually pushes
a gravity wave forward.

The tool to catch the light-like signal
from a wave is the LlGO...

the Laser lnterferometer
Gravitational Wave Observatory.

There are two identical,
ground-based LlGO labs.

One is in Hanford, Washington...

and the other is more
than 2,000 miles away...

near Baton Rouge, Louisiana.

lf a wave comes by, each lab's results
will be vital to confirm the event.

Here's how it works.

Super polished glass mirrors are
at the fulcrum of the interferometer...

which is a tool that basically...

compares two
light wave measurements...

and identifies the differences
between them.

Precision laser light
is fired back and forth...

and split between
two calibrated mirrors.

ln normal circumstances,
as the light bounces up and down...

the 2 1/2-Mile long,
L-shaped vacuum tubes...

the two laser beams
are basically in sync.

This means the beams effectively
cancel each other out...

and no light escapes the tunnel.

But when a gravity wave
rolls through...

space is ever so slightly stretched
or squashed.

As a result, the laser beams
are thrown out of phase...

and only then a small amount
of light is emitted...

a tiny signal, less than
the diameter of a human hair...

1/1000th the size
of a proton will register.

Converted into a sound
and a light signal...

it will be seen and heard.

The scientists' greatest hope...

is to catch the most massive event
that ever occurred in the universe...

the Big Bang.

Gravitywaves may be
our best chance to look...

very, very close to
the beginning of the universe.

About 300,000 years
after the Big Bang...

the universe was so dense,
it was actually opaque to light.

Light could not travel through it.

So if light can't travel
through the universe, what can?

A gravity wave.

The problem is a miniscule signal
from a gravitywave...

has yet to be caught.

lt's clearly hard.

ln fact, when Einstein predicted them,
he thought it was a nice idea...

but no one would ever
be able to detect them.

lt's only the advances of technology
that give us a chance.

LlGO scientists,
like astrosurfers...

live for the day
when they can hang ten...

and ride theirvery own
perfect wave of gravity.

We've seen what we think
are the effects of gravity waves...

the loss of energy from a system
by way of gravity waves...

but we never
directly detected one.

That's one of the last frontiers.

lf the LlGO scientists' quest
is successful...

and they catch a wave,
it could change science.

So, l think that long term,
it's first to understand gravity...

and then, even more interestingly,
to understand the universe.

The force of gravity
has domain over our universe.

lt created and can destroy
the cosmos, the stars...

the planets, and the people.

lt controls our lives,
our play, and our endeavors.

And therein
is this cosmic ballet.

Our collective future depends
on the grace and greatness...

ofthe mighty ruler
of the cosmos, gravity.