All language subtitles for Through The Wormhole S02E07 Can We Travel Faster Than Light 720p.HDTV.x264-DiVERGE

The Universe is full
of breathtaking sights.

Glimpsed through
powerful telescopes.

But will we ever travel
to these places of wonder,

and see them with our own eyes?

Now scientists
are designing warp drives,

learning how to pry open
wormholes,

and looking for cracks
in the fabric of the cosmos.

To bring the entire Universe
within our grasp,

they must break
a fundamental law of physics.

Can we travel faster than light?

Space, time, life itself.

The secrets of the cosmos
lie through the wormhole.

♪ Through the Wormhole 2x07 ♪
Can We Travel Faster Than Light?
Original Air Date on July 20, 2011

== sync, corrected by elderman ==

Humans have always gazed up
at the stars.

For thousands of years,

we thought they were as close
as the Sun and the Moon --

almost close enough
to reach out and touch.

But now we know
just how vast the Universe is.

The closest star
is about 25 trillion miles away.

The fastest spacecraft
we have today

would take more
than 10,000 years to get there.

To become true citizens
of the cosmos,

we have to do something
that physics says is impossible.

We have to travel
faster than a beam of light.

As a child, I loved to be out
under the Mississippi night sky,

warming myself by a campfire.

I'd spend hours
staring at the dancing flames.

What was this light made of?

I wondered
how it could seem solid

but then vanish
into nothingness.

[ Engine revs ]

Sean Carroll
is a theoretical physicist

from the California Institute
of Technology.

The mysterious nature of light
gets his mind racing.

The speed of light
is 186,000 miles per second,

or 670 million miles per hour.

Nothing goes faster
than the speed of light.

It really is
the maximum speed limit

for everything in the Universe.

Freeman: Light travels a million
times faster than sound.

It's fast enough to circle
the Earth seven times...

...in just one second.

But the mystery of light

goes much deeper
than its breathtaking speed.

The way it moves is different

from everything else
in the Universe.

Carroll: We're gonna pretend
for the moment

that I am not
a respectable citizen

and would do
a little bit of littering.

We're gonna add the velocity
of my car,

which is 30 miles an hour,

and if I throw this Slurpee

in the same direction
at 20 miles an hour,

since this is
an ordinary, everyday event,

the total velocity
of the Slurpee

is actually going to be
50 miles per hour.

If I'm going backwards
at 30 miles an hour

and I throw the Slurpee
forward at 20,

someone on the road
will see the Slurpee

move backwards
at 10 miles an hour.

Freeman:
The speed of Sean's car

changes the velocity
of his beverage.

But light doesn't abide
by the same laws

that govern cold drinks.

When I push a beam of light
out of the car,

the total velocity
is always the speed of light.

Light would be seen to be moving
at the same speed

no matter what my car was doing.

You don't add the speed of light
to the speed of the car.

The speed of light
is always the speed of light.

Freeman: These strange rules
for how light moves

inspired Albert Einstein

to rewrite the basic laws
of the Universe.

He realized that space and time
were not fixed and absolute

but connected and relevant.

It was an idea

that led to the most famous
equation in history --

"E" equals "MC" squared.

Carroll: Time and space

are really part
of one underlying thing

called space-time,

and how you divide up space-time
into time and space

depends on how you're moving.

So there's various corollaries
of that.

Once Einstein realized that time
and space were the same thing,

he realized that energy and mass
are the same thing.

Freeman:
"E" equals "MC" squared

implies that the more energy
you inject into a rocket,

the more mass it gains,

and the more massive it is,
the harder it is to accelerate.

Boosting it to the speed
of light is impossible

because, in the process,

the rocket
would become infinitely massive.

The energy it takes
to accelerate

increases and increases

as you come closer
to the speed of light.

If, in principle, you wanted
to go the speed of light,

you need
an infinite amount of energy

to accelerate you that fast.

Or you're gonna get
more and more energy,

but you're not going to get
that much more speed.

Freeman: Relativity makes light
both our friend and foe.

Its tremendous speed
lets us communicate

between any two points on Earth
almost instantaneously.

On the other hand,

because we can never move
faster than light,

we're stranded
in the Solar System,

with the stars
impossibly far away.

This man believes he can help us
escape our cosmic prison.

He think he's found a way
to bend Einstein's rules

and allow us to reach the stars.

Miguel Alcubierre,
a physicist in Mexico City,

has invented the warp drive.

The warp drive is a way to get
from one place to another

that's very different
from the way we normally do it.

So, normally
we just move through space

like we walk, or we fly,
or whatever,

but the warp drive,
the idea is to use space,

to let space do the motion.

Freeman: Miguel's idea
stems from another aspect

of Einstein's theory
of relativity --

that the shape of space can
be distorted by mass or energy.

So, the basic idea
is you expand space behind you,

which actually makes you
even further away

from those objects behind you,

and you contract space
in front of you,

getting closer
to the objects in front of you.

But you don't move at all.

Assume that this is a spaceship.

Normally, you would have to fly
through space like that,

and you cannot do this
faster than the speed of light.

But instead of that,
let us contract space here

and expand it here, like this.

So, you see, now the spaceship

is getting closer to this side
and further away from that side.

Bur it's actually not moving
at all

with respect to the objects
around it.

Freeman:
The beauty of Miguel's idea

is that the spaceship
actually stands still

inside the bubble of space-time.

Since it's not moving,
it doesn't gain any mass.

You can actually go
at any speed,

because there's no limit
in the laws of physics

that tells you
how fast you can warp space,

how fast you can expand
or contract space.

You can do it
at any speed you want.

Freeman: Miguel's warp drive
is an ingenious way

around Einstein's
cosmic speed limit.

But it's still theoretical,

and lacks
one crucial ingredient --

an exotic substance
called negative energy,

something that many scientists
aren't even sure exists.

But one man does believe
in negative energy.

He even claims
he's created it in his lab.

The warp drive.

It sounds like science fiction,

but the idea of surfing
across the Universe

in a warping bubble of space

would make perfect sense
to Einstein.

There is one snag.

A warp drive can only function

with a mysterious
power source --

negative energy.

And today, most scientists
believe negative energy

is just
an unproven theoretical concept.

But Steve Lamoreaux, an atomic
physicist at Yale University,

has made it his mission to track
down this exotic form of energy,

and he believes
the answer is all around us

in the fabric of space itself.

We normally think
of the vacuum of space

as being completely empty,

but, in fact, there is
energy density in empty space,

and we call that
the zero-point energy of space.

Freeman:
The theory of quantum mechanics

predicts that empty space is
actually constantly shimmering

with microscopic pulses
of energy

as particles pop
in and out of existence.

To make negative energy,

you have to find a way to
suppress this constant chatter.

Steve realized
the way to do this

was to change
the shape of space.

Lamoreaux:
There's a nice analogy.

If you have two ships
on a rough ocean,

one ship will kind of
reflect waves from it.

The other one
does the same thing.

So the wave density between the
two ships is a little bit less

compared to one by itself which
is surrounded by a rough sea.

So, you put two ships
on a rough sea,

they'll be mutually attracted,
and they'll come together.

Freeman: Steve reasoned
that if he created

a narrow-enough region
of empty space

like the area
between the two ships,

then some of
the shimmering zero-point energy

would not fit inside it.

The energy of empty space
outside the narrow region

would be stronger
and force it to shrink.

That force would be the
signature of negative energy,

and Steve set out
to create it in his lab.

It was an idea
that would consume him

for more than a decade.

We call the experiment
"The Time Machine."

Actually, the "Time Machine 2."

This is the second version
of the experiment.

We call it that because
I invested 15 years of my life

in this measurement.

That's a lot of time.

So, it's a time-wasting machine,
more accurately defined.

Freeman:
Inside this vacuum chamber

are two small metal plates

sitting less
than the width of a human hair

apart from one another.

To get them that close
and not touch,

the metal has to be
perfectly flat,

down almost to the atomic level.

The zero-point fluctuations
of free space

won't fit between those plates,
as well,

so when you bring
these two plates together,

there are fewer fluctuations
between the plates

than there are
outside the plates.

The force builds up,

and it actually gets
stronger and stronger

as the plates
get closer together,

and that force we refer to
as arising from negative energy.

Freeman: The zero-point energy
fluctuations outside the plates

are stronger than those between,

so pressure from the outside
pushes them together.

Or think of it another way.

The negative energy between the
plates expands space around it.

Steve's years
of meticulous labor

have made him
the first person on Earth

to have measured a force
produced by negative energy.

But the amount he has detected
is miniscule.

The force is equal to the weight
of a red blood cell

in the Earth's gravitational
field, so it's tiny.

But if you add up
thousands of these plates

like we have in our experiment,

you can actually achieve
a palpable and useful force.

Freeman: Steve's discovery

may only be a baby step
towards warp drive,

but he's confirmed

that Miguel Alcubierre's
warp drive theory

does not violate
the laws of physics.

The energy needed to warp space
and propel a warp drive forward

actually exists.

But he's also opened the door
to something else --

the wormhole, a rip
in the fabric of space itself.

If this theoretical object
exists,

you could enter it in one place

and emerge moments later
clear across the galaxy.

But are wormholes more than
a science-fiction fantasy?

And, if so, how would we know
where they would take us?

Now one physicist is daring
to enter these strange portals

and plot a course
through the wormhole.

We've all heard of wormholes.

They're cosmic shortcuts

that put alien worlds
practically on our doorstep.

But how would
we actually build one?

And how would we use one?

Travel by wormhole
requires exotic technology

and the courage
to jump into the unknown.

Our planet is riddled
with passageways.

We regularly travel
through strong, stable tunnels

cut through massive mountains.

Well, here we're entering
a nice, solid tunnel.

It's made of -- looks like
concrete and reinforced steel.

Very solid.

A reliable means
of transportation.

I drive my car in.
I'm gonna come out.

I know what's happening
at all times.

Freeman: Physicist Steven Shu
is fascinated by the concepts

of stability and instability,

be they in the stock market...

Sell.

...In real-estate values...

Long.

...Or in space-time wormholes.

Shu: One of
the fundamental properties

that we look at in physics when
we look at a particular system

is whether that system
is stable or unstable.

An example would be a pen
which is balanced like this.

It might be okay
when it's exactly balanced,

but even a slight bump
will send it

into a drastically
different state.

We decided to look at whether
one could build a wormhole

that had nice properties

such as its behavior
is predictable and it's stable.

Those are two criteria

you'd like to have
for a real wormhole.

Freeman:
The rules of building wormholes

start with Einstein's theory
of relativity,

which tells you
how to bend and shape space

as if it were a flexible sheet.

Imagine this sheet of paper,

and imagine that you're an ant
living on this sheet of paper.

If you want to travel
from this point to this point,

you might have to walk
all the way from here to here.

But if the paper were curved,
the long way around

would involve walking all the
way around the paper like this.

But you can imagine that
there would be a little tube

connecting this point
directly to this point,

and the ant
could just slip through.

Narrator:
Wormholes in science fiction

have gaping entrances
that a starship can dive into.

But those
two-dimensional renderings

gloss over the true architecture
of wormholes.

In this two-dimensional analogy,

the opening of the straw
is just a circle.

But, because we live
in three dimensions,

the opening of the wormhole

would actually be like
the interior of a bubble.

Freeman:
This is what the mouth

of a real wormhole
might look like

if they are lurking
somewhere out there in space.

But Steven wondered

if we might be able to build
our own from scratch.

A cosmic engineer
would first create two mouths

and connect them.

Then, he would drag one of
the mouths light-years away --

but the tunnel between the two
mouths is not part of our space

and could remain very short.

It's a simple idea,

but the vast amount
of negative energy

needed to keep the wormhole's
mouth and tunnel from collapsing

is tricky stuff to control.

It's very challenging
to stabilize a wormhole.

All wormholes, as far as we know
from general relativity,

require this kind of special
negative energy exotic matter.

The question is whether that
matter itself can be stable.

Freeman: Steven crunched the
numbers on how negative energy

would react with normal matter
on the fringes of the wormhole

to discover whether they could
coexist in a stable way.

Shu: And we've proven
mathematically they're unstable.

That would be
a very dangerous device to use,

because once you bump it
a little bit,

the entire device
could just fall apart.

If I try to get
into an unstable wormhole,

it's like trying to put
my finger into this bubble.

It'll just pop.

Freeman: The negative energy
needed to keep a wormhole open

is inherently too unstable.

A man-made wormhole
would collapse

the instant
someone tries to step inside.

But there might be another way.

Not by using cosmic shortcuts
that we have built ourselves,

but by searching
for microscopic ones

that could be hiding
all around us.

Just as empty space

is fizzing with
microscopic pulses of energy,

some theorists believe

it could also be riddled
with microscopic holes.

There could be quantum wormholes

that are just left over
from the Big Bang,

or at very, very
short distances,

you could have
little fluctuations

where space-time just connects
to itself in a funny way,

and that would be
a quantum wormhole.

If they just happened
as a little fluctuation,

they would be incredibly tiny,
like 10 to the minus-35 meters.

Freeman:
Microscopic quantum wormholes

are quantum fluctuations
in space

that perpetually appear,
disappear, and reappear again.

Since we don't have
to construct their portals,

Steven suspects
they might be safe to enter.

But before you try jumping into
one, be aware there's a catch.

Shu: Quantum mechanical things
are fuzzy.

They're intrinsically random
and unpredictable.

So if we were
in a quantum wormhole,

we might be shaken around,

and we wouldn't quite know
where we're gonna come out.

You wouldn't want to get
into a tunnel

that might end in the bottom
of the Pacific Ocean

or on a mountaintop
that you didn't want to be on.

Freeman: Quantum wormholes have
no estimated times of arrival,

and your destination is unknown.

You could end up anywhere

or anywhen.

Traveling faster than light
through a wormhole

would be a risky ride.

You've got to be willing
to roll the dice.

But there may be a safer way
for the cautious traveler.

Imagine being able to move
from here to there

without ever moving at all.

Well, mankind's first journey to
the stars looks a long way off.

We won't master the technology
of wormholes and warp drives

for centuries at least.

But there's another way
to zip around the cosmos.

We could turn our bodies
into information

and send that information
from place to place

at the speed of light.

Chris Monroe and Steve Olmschenk

are quantum physicists
at the University of Maryland.

They are pioneers
of teleportation.

Their work is
all about making connections

between events taking place
in two separate locations --

events which normally have
no connection whatsoever.

We're gonna demonstrate a simple
experiment using standard coins

just to show the randomness
of the individual coins

and the randomness
between the two coins.

All right.

Flip.

Heads.
Tails.

Tails.
Tails.

So, as you can see,
with two regular coins,

we get completely random results
between each other.

Freeman:
If Chris and Steve

could make the two coins
always land the same way,

then they would have succeeded

in teleporting the information
on the coin -- heads or tails --

from one place to the other.

And they had an idea
of just how to do this.

They would use
quantum entanglement,

a strange effect
that can create a link

between microscopic objects.

When a bomb explodes

and two pieces of shrapnel
come flying out,

each one moves independently
and is unaffected by the other.

Now imagine a bomb
in a subatomic world.

Two particles of shrapnel
fly out,

but this time,
quantum entanglement

means the way one moves

entirely dependent
on the other.

If one piece
is spinning clockwise,

you can deduce
that the other piece

is moving counterclockwise.

If Steve and Chris' coins
were entangled,

whenever Steve tosses heads,
Chris will toss tails.

If Steve tosses tails,
Chris will toss heads.

Tails.
Heads.

So, even though the coin flip on
one side is completely random,

there are correlations
between the two coins,

and this is the defining feature
of entanglement.

Freeman: Physicists have been
struggling to use entanglement

to teleport matter from place to
place for more than two decades.

Steve and Chris
are the first to succeed.

They begin with two atoms
of an element called ytterbium.

The experiment is, we start
with two trapped atoms

that are across the table
from each other.

Monroe: These atoms are sort
of levitated with fields,

like a levitated train.

They're in a vacuum chamber,
so nothing touches them.

They're almost complete--

they're as close as you can get
to perfect isolation.

Freeman: Steve and Chris

write quantum information
called qubits

into the first atom
using microwave radiation.

The qubits become
the atoms' heads or tails.

Then, we excite
both atoms

with this fast pulse
of light,

and if we do it right,

we can make sure
that the photon

is then entangled
with the internal state

of the atom.

The photons
become the messengers,

carrying the atoms' information
across the lab.

Chris and Steve aim the photon

from each atom
at the same target.

When they meet,
they become entangled,

which, in turn, entangles
the two atoms they came from.

They've been
nowhere near each other,

they've never seen
each other,

but now these two atoms

which are across the table
from each other

are now entangled,

and they somehow share
the information

that we first wrote
into the first atom.

That's called
quantum teleportation,

because the information,
in a sense,

never really made the trip.

There was never really
any physical interaction.

It's all because
of this magic of entanglement

that allows us
to do that.

And I think Einstein had
the best words to describe it.

He called entanglement
"Spooky action at a distance."

Freeman: Steve and Chris
have successfully transferred

the information
from one atom to the other.

In other words,
they teleported the atom.

It's the first time anyone has
ever beamed matter across space

at the speed of light.

And they're already working

on more ambitious
teleportation experiments.

Monroe:
But the good news is,

this idea works with matter more
complex than a single atom --

say, a few hundred atoms.

Freeman: A few hundred atoms
would be progress,

but the real question

is whether we will ever be
able to teleport the state

of all the 7,000
trillion trillion atoms

in an entire person
from one place to another

to turn a pile of organic matter
into a copy of you or me.

It's a tall order.

Well, we have a cherry pie,

and the pie
is in a particular state.

All the atoms, mostly carbon
and organic molecules,

make up this pie,

but they're obviously in a state

that we all recognize
as a cherry pie.

Looks pretty good.

Freeman:
In order for Chris

to teleport the atoms
inside the cherry pie,

he needs to gather information
about every single one of them,

which gets a little messy.

All the atoms in here are
representative of a cherry pie,

but it certainly doesn't look
like a cherry pie,

and the reason is
the atoms aren't arranged

in the right way.

They are about 10 to the 27
atoms in this tin.

That's a billion billion billion
atoms.

Consider the number
of possibilities

that a billion billion billion
atoms can be arranged.

It's a number
that's so ungodly huge

we don't have enough space
in the Universe

even to write it down.

Freeman:
Teleporting a human being

is far beyond
our capabilities...for now.

But Steve and Chris believe
if it is possible,

quantum entanglement
will be how it's done.

Quantum mechanics has been
verified repeatedly in the lab,

our labs
and many around the world,

over and over again
for decades.

We've continually verified
quantum mechanics

as an accurate description
of nature.

Monroe: If I am fundamentally
quantum mechanical,

teleportation better involve
quantum mechanics.

I would say
if there is a different way

to teleport objects,

then, somehow,
there's a different theory

than quantum mechanics
out there,

and we just don't know it yet.

Freeman: We are still a long way
from traveling from star to star

as fast as a beam of light.

But what if everything
we thought we understood

about light is actually wrong?

This scientist is turning
the laws of physics upside down.

And if he's right,

the speed limit
Einstein slapped on the Universe

might have to be changed.

We live in a Universe
with a speed limit --

670 million miles per hour.

Well, that's
what Albert Einstein said.

But what if Einstein was wrong?

John Webb has big plans.

He wants to rewrite
the laws of the Universe.

And it all begins
with bar codes.

Right.
So, we're in the supermarket.

I'm buying a few things.

This lettuce, for example --
we know what it is.

Has a lot of information
on the lettuce.

Tell us on the packet.
We can see what it is.

But encoded in this pattern here

and picked up by the laser
that's gonna scan it

is a set of information,

and when the cashier scans it,
the laser beam

will look at the white gaps
between the black lines,

and we get the price.

So there's a lot of information
stored in the bar code.

Freeman:
John is an astrophysicist

at the University
of New South Wales.

The bar codes he studies
are not on packages of lettuce,

but on light
coming from distant galaxies.

If you split the light

coming from these galaxies
into a rainbow,

you'll discover
that certain colors are missing.

Those dark bands,
called spectral lines,

are caused
by the chemical elements

in clouds of interstellar gas

absorbing certain frequencies
of starlight.

Webb: You can learn a great deal
from spectral lines.

From their positions,
you can identify elements

that have
particular frequencies,

so you can see where things
like hydrogen or helium

or other elements are present.

Freeman: But John realized
his starlight bar codes

could tell him about something
much more important

than what stars were made of.

It could give him a glimpse

into one of the most fundamental
constants of the Universe --

the strength
of the electromagnetic force.

In physics, every force

has a particle that carries it.

Electromagnetic force
is carried by light, or photons.

The electromagnetic force
keeps atoms glued together

with a constant exchange
of photons

that bounce from the nucleus
to its orbiting electrons.

When light passes through atoms
of interstellar gas,

it can interfere
with this exchange of photons

and knock an electron
out of its orbit,

but only if the light

has exactly the right amount
of energy.

The bar code of missing light

tells you precisely how strong
the electromagnetic force is.

Webb:
Over the last decade or so,

there's been an amazing change
in technology.

One can now measure the things
in distant astronomical objects

more precisely than
ever been measured on Earth.

That provides
a very strong motivation

for studying the early Universe,

because we can measure
what the conditions were like,

we can measure
what physics was like,

whether the laws of physics

there in very remote regions
of the Universe

are the same
as they are on Earth.

That's pretty amazing.

Freeman: So John began searching
the heavens

for glowing clouds of gas
billions of light-years away.

He used the Keck Telescope
in Hawaii

to look at the northern sky,

and a very large telescope
in Chile

which looks out
on the southern sky.

And when he looked
at his bar codes,

he discovered something
totally unexpected.

This is what a cloud of gas
would look like

if we were looking at it
in the laboratory on Earth.

When we look
in the Southern hemisphere,

something slightly different --

this line has moved towards
the red end of the spectrum,

and another line here

has moved towards the blue end
of the spectrum.

So there's a change
in the relative spacing

of the spectral lines.

It looks slightly different
in the Southern hemisphere.

If you now go
to the Northern hemisphere,

the exact opposite direction
on the sky,

this line has now shifted,

instead of to the right,
to the left,

and this line has shifted to the
right instead of to the left.

So the patterns
now look different.

It's a little bit as if
you're in a supermarket drunk,

looking at the bar code,
and the pattern has changed.

Freeman:
These shifting bar codes

can only be caused
by one thing --

something
that seems impossible...

A change in one of
the fundamental laws of physics.

When we first saw the results,

it was hard to accept
that they were correct.

What we found is when you look
in one direction on the sky,

the strength
of the electromagnetic force

appears to decrease with
increasing distance from us,

and when you look in exactly the
opposite direction on the sky,

the converse is true.

The strength of electromagnetism

seems to increase
as you move to greater distance.

Freeman:
Electromagnetism is the force

that is transmitted by light.

So if the strength
of electromagnetism

is not constant,

it means that the properties
of light itself are changing.

If John Webb is right,

he's overturned one of
the basic laws of the Universe.

Once the laws of physics

are allowed to vary
in those equations,

things have to be rewritten.

So it's back
to the drawing board

for certain fundamental
principles in physics.

Freeman:
Could Einstein be wrong?

Could the speed of light
be different

in different parts
of the cosmos?

On the other side of the world,

one cosmologist is sure
the answer is "yes."

He believes that light can move
much faster than we think,

and that, out there
in the Universe,

there are superhighways
to the stars.

Back at the dawn
of the space age,

it was all about
having the right stuff.

The first people who journey
to the stars will need it, too.

They will be venturing
into the absolute unknown,

and, perhaps for the first time,
traveling faster than light.

Theoretical physicist
Joao Magueijo

thinks that there may be regions
of outer space

where faster-than-light travel
is possible.

He developed this radical theory
because without it,

he couldn't explain
the way the Universe looks.

Magueijo: When we look out
into the Universe,

everything looks the same
in every direction.

This is a problem,

because during the time
the Universe has lived,

there really isn't enough time
for light to travel around

for features to be shared
around the Universe,

and this we call
the homogeneity problem.

Freeman:
The homogeneity problem,

the fact that all galaxies
and all matter

are evenly spread
around the Universe

no matter where we look,

is one of the biggest puzzles
in cosmology.

The problem is, scientists don't
think there has been enough time

since the big bang for matter
to spread out so evenly.

Imagine the Big Bang
was a big party.

[ Cork pops,
indistinct conversations ]

As soon as the party starts,

everyone instantly has a glass
of the same kind of wine.

How would a waitress have time

to serve everyone
a glass of wine so quickly?

Magueijo: If she can only move
at the speed of light,

she won't have time to reach
everyone before they disperse,

like the Big-Bang Universe.

Freeman: Most scientists
solve this problem

with a theory
called cosmic inflation.

The idea is
that the room stayed small

for longer
at the beginning of time,

giving the waitress enough time
to serve everyone.

Then, a mysterious
magnifying force

inflates the room very rapidly.

Everyone gets a drink, and the
waitress hardly breaks a sweat.

Magueijo: Cosmic inflation
says the Universe

started as
an unimaginably small pinpoint

concentrating all the energy
of the Universe,

and that in the first trillions
of trillions

of trillions of a second,

the Universe doubled, doubled,
and doubled in size.

The initial smoothness
of that single point

then spread to the vast
distances we can see nowadays.

Freeman:
But inflation is not proven.

It's just a theory.

And Joao has
an alternative to it --

a provocative theory

that might bring the Universe
within our reach.

What if, instead of changing
the rate of expansion,

we change the speed limit --
the speed of light?

That's what we call the varying
speed of light theory.

Under the varying speed of light
theory,

our waitress simply served
everyone faster

in the beginning of the Universe

and then slowed down
to the current speed,

leaving us latecomers
wondering how she managed

to serve such a large Universe
in such a short time.

Freeman: Joao's theory solves
the homogeneity problem

just as effectively
as cosmic inflation.

But it also thumbs its nose
at Einstein's golden rule.

This does not exactly contradict
Einstein's principle

that the speed of light
is the speed limit.

We're only saying
that the speed limit

changed throughout
the life of the Universe.

Freeman: And Joao's theory
means there might be a way

to break
today's cosmic speed limit,

because there could be pathways
through space

where the speed of light
remains faster.

These pathways
are called cosmic strings.

Magueijo: Under the varying
speed of light theory,

light traveled faster in
the beginning of the Universe,

and cosmic strings
could be regions

where this higher speed limit
is still in force.

Freeman: The idea
is that, in the first moments

of the Universe,

tiny fractures
formed in space-time.

Since then, these fractures

expanded along with
everything else in the cosmos

and are now billions
of light-years long.

Cosmic strings might serve
as high-speed lines

cutting across regions

where you would otherwise
be moving at a crawl.

You could think
of cosmic strings

like the tube in London...

...Where, on the surface,
there is a speed limit,

but obviously down there
there isn't one.

Freeman: On the surface,
Einstein's limit is the law.

The tube below
is the cosmic string --

a faster way across town.

If you could fit a spacecraft

into the corridor
of high speed limit

created around
the cosmic string,

fast travel throughout the
Universe would become possible.

Freeman: Cosmic strings
have yet to be found,

and the variation in the speed
of light is still just a theory.

But slowly and steadily,

scientists like Joao Magueijo
and John Webb

are chipping away at
Einstein's cosmic speed limit.

Carroll:
You begin to wonder,

what if it changes from place
to place in the Universe,

or maybe it was different early
on in the Universe's history,

and if the speed of light
is changing,

then a lot
of what we think about physics

could be different
in the early Universe to today.

Freeman:
Around the world,

scientists are testing
new technologies

and probing deep
into the heart of physics

to uncover new laws
of the Universe,

to find a way for us
to escape our island Earth.

We are still a long way from
becoming citizens of the cosmos.

The stars remain
almost unimaginably far away.

But wherever science goes next,

our hopes to explore this final
frontier will never be dimmed.

And, one day, we will reach it,

because what man can imagine,
man can do.

== sync, corrected by elderman ==