All language subtitles for The Universe s07e05 Microscopic Universe.eng

Male narrator: In the beginning,
there was darkness.

And then... bang.

Giving birth to an endless expanding
existence of time, space, and matter.

Every day, new discoveries are
unlocking they mysterious,

the mind-blowing, the deadly secrets of
a place we call the universe.

As they try to unravel the
mysteries of the universe,

scientists are coming to
an astounding conclusion.

To make sense of outer space,
they need to understand

inner space-- The
microscopic matter that

forms the foundation
of everything we see.

But shrinking down billions of

times, into the realm of atoms
and subatomic particles,

takes us into a strange
unexplored world.

When we descend into the
microscopic world, we find that

it's really weird, and indeed
downright bizarre and

unbelievable.

Narrator: The stuff in this
universe is far smaller than

anything we can see with a
microscope, but it holds

the key to the cosmos.

We can only understand where we
came from if we understand

this crazy microworld.

Narrator: So let's go on a
fantastic voyage into

an uncharted world known as
the microscopic universe.

Sync and corrections by n17t01
www.addic7ed.com

When people talk about the
universe, they usually mean

the vast expanse of space,
billions of light-years across,

that they can see with radio
telescopes and cosmic imaging.

They think about stars and
galaxies and planets, and all

the big stuff out there.

You have astronomical bodies moving
under the force of gravity.

There are laws of nature, and
you think that the laws

are right, once and for all.

Narrator: However, there
is another universe--

An unseen world that governs
everything we see.

When we go down in size,
trillions of times smaller,

to the microscopic world...
The rules are much less

intuitive than the ones we're used
to from the large-scale world.

Narrator: The magic of the
microscopic universe begins

at about a ten-billionth
of a meter...

Or the size of an atom.

Matter behaves so
differently at

rules to describe
what's going on.

They call it "quantum theory."

And what it says
is extraordinary.

This baseball represents a
subatomic particle, like an

electron or a photon of light,
that routinely does all sorts

of weird, strange things in
the microscopic universe.

The subatomic version of this

baseball can be invisible, can
go through solid objects with

ease, can be in multiple places
at the same time, and can

seemingly go backwards in
time and change the past.

This means I could throw
this microscopic baseball

to first base and to home
plate at the same time...

Or change the seemingly
predetermined outcome of a play

while it's still going on.

Now this-- this is the stuff
of science fiction.

But really we know it to be
true, or at least it appears

to be true in our quantum world.

We get all sorts of weird
things happening.

Narrator: If scientists can
understand how these weird

things work, they'll be able to

put them to use in our everyday

world-- Revolutionizing modern
computing, and perhaps even

allowing us to communicate
across the cosmos instantly.

The key to making
these miracles

come true is a process called
"quantum entanglement."

And scientists are already
harnessing this astounding

discovery for both civilian
and military purposes.

In quantum physics, what happens
to an object over here

can instantly affect an object

over here-- And over here could
be millions of miles away.

Narrator: This is how it works.

When two subatomic particles
interact, they can become

entangled-- That means their
spin, position or other

properties become linked
through a process unknown

to modern science.

If you then make a
measurement of one of

the particles, then that
instantaneously determines what

the behavior of the other
particle should be.

And when the
experiment is done,

it's found that indeed the other
particle's quantum state is

exactly determined once
you've made a measurement

of the partner particle's
quantum state.

Narrator: That means if
a scientist observes

one entangled particle and
forces it to spin clockwise,

the other entangled particle will
immediately start spinning

in the opposite direction.

That seems intriguing, but
it's hardly earth-shattering

until you consider that the
two entangled particles

can be separated by billions
of light-years, and still,

the moment you observe one
particle's spin, you've dictated

the other particle's spin.

That's weird, because it may
suggest that information

has traveled instantaneously,

faster than the speed of light,

from one particle to another.

I don't understand it.

I don't know that anyone does.

"Spooky action at a distance,"

as Einstein called it.

Narrator: Quantum
entanglement is more than

a curiosity of the
microscopic world...

Because the effects
of entangled

particles can be seen and
felt in our world.

If scientists can overcome some
fundamental obstacles, quantum

entanglement could someday help
humans communicate across

vast distances instantly.

People sometimes think
that quantum entanglement

will achieve the desired goal
of transferring information

at a speed faster
than that of light.

I don't think this will be achieved,
because to set up these systems,

you had to have brought them
there at speeds slower than

the speed of light.

But then what do I know?

A hundred years ago, they didn't think
that we'd be going to the Moon.

Narrator: Quantum entanglement
is far more likely

to transform modern computing.

Scientists hope to use the magic
of the microscopic universe to

build powerful new computers.

We're going to see
what this baby can do.

Narrator: At the
Massachusetts Institute of

Technology, Professor Seth Lloyd
has helped create a prototype of

a quantum computer, which uses
quantum bits rather than

traditional computer bits to
perform its calculations.

This lab has the world's best
superconducting quantum bit

or "Q-bit" in it.

And when we do quantum
computations with Q-bits, we

can have the quantum computer do
multiple tasks simultaneously--

It can do this, it can do
that at the same time.

It can add two plus two, it
can add one plus three,

and it can add those two
things simultaneously.

Narrator: The fact that a
single Q-bit can perform many

calculations at the same time
gives the quantum computer

the potential to be far more powerful
than any computer ever imagined.

Like traditional computers in the 1950s...
Quantum computers are in their infancy today.

The machines take up large rooms and can
do only the most basic calculations.

But they hold great
promise for the future.

Quantum physics is notoriously weird,
strange, and counterintuitive.

And so quantum computers use
this weirdness to compute in

ways that classical
computers can't.

Narrator: The major stumbling
block is figuring out how

to effectively code classical
information-- the ones and zeros

that computers use-- in a way the
microscopic universe can process

it using entangled particles.

But when scientists figure that
out, quantum computers could

transform the planet.

Even if you have a quantum
computer with not that very many

bits, you might still be able
to do things like break all

the codes that people use to
communicate on the Internet.

Or you could solve very
difficult problems having

gajillions of variables, like try to
figure out what happened at the Big Bang.

Narrator: That may be hard to
believe, but the microscopic

universe gets even stranger.

In fact, the most famous
experiment in quantum physics

shows how one object can be in
two places at the same time--

A result that startled...
the great Albert Einstein.

Narrator: As scientists explore the
microscopic universe, they find it's

governed by rules that are often
incomprehensible to those of us

in the normal world.

At the smallest scales
imaginable, not only does

information appear to travel
faster than the speed of light,

but human observation often
seems to decide what happens.

It seems like the behavior
of quantum mechanical stuff

is different when we're looking at it
than when we're not looking at it.

Narrator: This profound
conclusion comes from performing

the double-hole experiment.

Scientists first conducted this
experiment a century ago,

firing photons of light through
a metal plate with two slits.

The light that went through the holes
hit a screen behind the plate.

I'm going to demonstrate the
results of this amazing

experiment, with a bunch of
baseballs and a barrier

that we've set up which
has two holes in it.

Now normally, in the everyday
world, if I throw baseballs

through one hole or the other,
they'll form a predictable

pattern on a screen that we've
set up behind home plate.

They'll be in one
place or the other.

Now let's make that pattern with
a whole bunch of baseballs.

I'm going to use this
pitching machine.

Here's the first one.

Let's see what happens.

Now you see the balls landed
on the screen in two bunches,

pretty much along a direct line
from each of the two holes.

That's natural-- that's
what we expect.

But when we descend into
the microscopic universe

and use electrons, which are 10
trillion times smaller than

baseballs, we get a very
different odd result when

we perform this experiment...
A pattern that you would expect

if these were waves going
through both holes at the same

time and interfering
with themselves.

Well, we usually think of
electrons as being particles.

So how can they exhibit
wavelike properties?

Narrator: These test
results were confounding.

The electron was a particle
before it was fired at the

screen, yet it formed a pattern
on the screen as if this single

electron had gone through
both holes at the same time.

Does a microscopic particle
spontaneously clone itself in midair?

After years of study,
scientists still don't know

exactly what's happening.

Probably the most magical thing
is that in quantum physics

an object can be in more than
one place at the same time.

It actually can sense both
slits and actually go through

and quantum-mechanically feel
the structure of both slits in

the experiment.

Most physicists agree that
the math is quite solid,

and leads to solutions that are
undeniable and can be confirmed

with experimental measurements.

But exactly what is happening,
and how, is a matter of debate.

Narrator: To try to grasp
this amazing experimental

result, scientists decided to
observe how individual electrons

behaved when they went
through the double slit.

How exactly could a particle go
through both holes at the same time?

Scientists got a front-row
seat to observe the strange

behavior of these electrons or
other subatomic particles,

or even photons of light-- Doesn't
really matter as long as they're small.

They didn't just look at where
they landed on the screen

back there, they also watched
the behavior of the particles

as they went through the holes.

And then they saw
something amazing.

When scientists were watching
the holes, the electrons behaved

like particles, forming the
baseball-like pattern

on the screen back there.

But when the scientists weren't

watching, then the electrons
behaved like waves.

They formed a pattern that
looked like the interference

pattern produced by
waves on a screen.

That's really strange.

What you see depends on whether
you're watching or not.

If you're watching, you see the
particle-like behavior like baseballs.

If you're not watching, you
see a wavelike behavior.

But not both at the same time.

Narrator: This was nothing
less than astounding.

Observation seems to change the
nature of subatomic particles.

Mysteriously, when we're not
looking, things are waves.

When we are looking, they
look like particles.

So even an electron, which
seems to us like a particle,

has wavelike properties when
we're not looking at it.

The fact that when we don't
look, the electron appears

to go through both holes, but when we
do look we always see it go through

one hole or the other, is what
we call the "quantum enigma."

Narrator: How could our decision
about whether to observe something

change how that something acts?

There is a technical
explanation.

To make an observation, you
somehow have to interact

with a system-- For example, you
have to shine light on it,

which then bounces off and
you observe the light.

That's how we can tell that a
baseball is here or there--

We bounce light off of it.

Well, for macroscopic particles,
that doesn't disturb them very much.

But for microscopic particles,
the act of bouncing the light

off of the particle changes where
it is and how it's moving.

Narrator: So in the microscopic universe,
where photons of light are about

the same size as subatomic
particles, these photons

have a big impact when they illuminate
the particles so we can see them.

But this doesn't answer the
question "why doesn't the light

simply change the direction
of the subatomic particles?

Why does observation actually change
the nature of what is being observed?"

The short answer is
"we don't know."

This is the fundamental mystery
of quantum mechanics,

the reason why quantum
mechanics is difficult.

Mysteriously, when we look at
things, we see particles.

And when we're not looking,
things are waves.

This is something we scientists
have argued passionately about now

for almost a hundred years.

And there's still no consensus.

Narrator: When they were first
released a century ago...

These test results were enough to
unsettle the brightest mind in science.

Einstein said, "I don't
believe in quantum physics,

because I believe the Moon is there
even when I'm not looking at it."

Einstein was of course referring
to the implications of

the theory that the Moon really
isn't anywhere until it's observed.

Narrator: However, the double-hole
experiment's mind-boggling conclusions

don't end there.

In recent years, technology has
allowed scientists to perform

a fascinating variation
of the test.

Its results call into question
our perception of time itself.

This is like a high-tech version
of the double-hole experiment.

Electrons are being fired toward
a barrier with two holes in it.

But the scientists can delay
their decision about whether to

observe the electrons until
after they've passed through

the holes, but before
they hit the screen.

It's as though I'm on a baseball
field and there's a baseball

being pitched toward the
barrier with the holes in it.

But my eyes are closed, so it goes
through and it behaves like a wave.

But then, at the last second
before it hits the screen,

I open my eyes and
decide to observe it.

Narrator: At that moment,
the electrons, in essence,

become particles-- and seemingly
always were particles from the

time they left the electron gun.

So it's as though they went back
in time to before they went

through the holes, and decided to
go through one or the other--

Not through both as they would have
had they been behaving like waves.

That's really crazy!

That's the enigma-- That our choice
of what experiment to do determines

the prior state of the electron.

Somehow or other we've had an
influence on it which appears

to travel backwards in time.

Narrator: Scientists are only
beginning to grasp what these

microscopic mysteries mean for
time travel, and changing

the past in our everyday world.

But one thing is clear.

The rules that govern this
subatomic world hint at

a universe that's just as
mysterious as science fiction.

In fact, quantum physics may
suggest that reality is simply

a figment of our imagination.

Narrator: After discovering
mysteries in the microscopic

universe, scientists wanted to quickly
unravel, study, and solve them.

But as they tried to figure out
exactly what was going on in

this strange subatomic realm...
They found something completely

unexpected...
Nature refused to tell them.

When we descend into the
microscopic world, we find

that there's a fundamental
uncertainty in essentially

all quantities that
we wish to measure.

And it's not a problem with the
measurement process, it's that

nature herself does not know.

Narrator: Scientists call this
the "uncertainty principle."

And as strange as it is, it
may be the most profound

concept to emerge from the
microscopic universe.

We simply cannot know anything
with absolute certainty.

In our everyday world, we
think we know a lot about

the things around us.

We can actually locate, for
example, the position of this

cue ball, and strike it at a
certain speed which we know.

And we can use that to collide
it into other balls, and go

ahead and play a game of pool.

But what actually happens if
we shrink everything down

trillions of times...
In that world, these pool balls

are now actually like
subatomic particles.

Narrator: In this microscopic

realm, quantum physicists have
found they simply cannot

determine with any precision
where these particles are

located... Because of their
wavelike qualities.

And what's even stranger-- If
scientists try to box in

a particle, it will always
generate enough energy to break

out of the box before its
position and speed have been

determined.

The uncertainty principle says
nature will not allow its

fundamental elements
to be boxed in.

So because in the microscopic
world, because particles will

interact with a completely
different set of rules--

The rules of quantum physics--
Microscopic pool will be

a completely different game.

Narrator: The uncertainty of
the microscopic universe

extends far beyond the
location of particles.

It applies to everything,
including a particle's energy.

And this gives rise to a
stunning phenomenon called

"quantum tunneling."

In classical physics, if you
throw a ball at a wall and

you don't throw it hard enough,

it won't go through the
wall, it will bounce back.

But if it's an electron, and you
don't throw it hard enough

to go through the wall...
It might go through anyway.

We call that quantum tunneling.

Narrator: How can
this be possible?

It may sound bizarre, but one

way to explain quantum tunneling
is that the uncertainty of

the microscopic universe
allows a particle to borrow

energy from the future to
breach the barrier, and then

pay it back after it
gets to the other side.

The electron actually already
is on the other side

of the wall, and therefore it
can go through it and appear

on the other side of the wall.

Narrator: Ever since these wonders
of the microscopic world

were discovered a century ago,
people have asked if quantum

tunneling-- being in multiple
places at the same time, and

what appears to be traveling
backwards in time-- can be

achieved in our everyday world.

Some scientists say we'll never
be able to throw a baseball

through a solid barrier.

A baseball is a huge
number of particles.

You would need all of them to
collectively suddenly appear in

another place for the baseball, as a
whole, to appear in another place.

And that's just
extraordinarily unlikely.

A single electron or a
single proton can do this.

But the bigger your particle
or the bigger the collection

of particles, the more difficult
that process of tunneling is.

Narrator: However, a growing
number of physicists are

developing a more outrageous
theory for what's going on.

We know that these tiny particles can
be in two places at the same time.

But, hey, I'm made of
these kinds of particles.

So if they can be in two
places at once, so can I.

Narrator: Scientists call this the "many-worlds
interpretation" of quantum physics.

They say, just like the electron
in the double-hole experiment,

human beings are all in multiple
places at the same time.

They say any time anyone makes
a decision, we don't actually

choose one option over another...
Instead we do them both,

in slightly different
versions of reality.

What happens when you use
your mind and your will

to decide things is you end up
actually making many choices at

once, and all of them become realized
in different parallel universes.

The many-worlds hypothesis of
quantum physics says that when

I throw a curveball, I do
so only in this universe.

In another universe I might
be throwing a fastball.

And in still another one, I
throw a knuckleball for the

first time in my life.

And in yet another universe, I
heave this ball to the outfield.

In the many-worlds hypothesis,
all of these choices are

outcomes that occur in universes
that are parallel to our own--

Just not in ours, but
in parallel universes.

That's what the many-worlds
hypothesis tells us.

Narrator: This may sound
far-fetched, but an impressive

array of theoretical physicists
believe it's the way

the microscopic world works.

If it's true, the implications of
this startling theory go far

beyond the baseball diamond.

In essence, it suggests there
are universes parallel to our

own in which...
The Nazis won World War II.

And in another, the American
government foiled the 9/11 hijackers.

So the World Trade Center
still stands in Manhattan.

If you take quantum mechanics
absolutely at face value, it

says that every time you observe
something quantum-mechanical,

you become two different
copies of yourself...

There's the copy that got one answer,
and a copy that got another answer.

It just implies there's a huge
number of other copies of you

that saw slightly different
things happen in the universe.

These days it's completely accepted
that the microworld is weird.

Many people had hoped that this
weirdness could be confined

to the microworld, so that big
things like us would be immune

to it and always be
in a single place.

But it's become clear now that
that hope [Laughs] was naive.

The weirdness
can't be confined.

Narrator: The fascinating debate about
the many-worlds interpretation

of quantum physics will rage
until physicists finally solve

the mysteries of the
microscopic universe.

However, some astronomers are
concluding that we will never be

able to fully explain
any of these mysteries.

Because, according to their calculations,
the vast majority of matter

holding the universe together
exists in a higher dimension

that we can never explore.

Narrator: If there's anything
in the microscopic universe

stranger than quantum particles,
it's the mysterious matter that

scientists have never seen but
that plays a crucial role

in the formation of planets,
solar systems, and galaxies.

Astronomers know that there's
all sorts of matter out there

that exerts a gravitational
influence but that we can't see.

We call that "dark matter."

I wouldn't exist if it weren't
for dark matter, because

dark matter has this nurturing
force of bringing things

together to form structure,
to form galaxies which are

absolutely necessary for life.

Narrator: Dark matter makes
up a staggering 85% of

the gravitationally attractive
stuff in the universe.

If the dark matter is some kind of
particle, then typically, millions of

dark matter particles will
pass through me every second.

Narrator: But even though they
know dark matter exists,

astronomers have been confounded by
a microscopic mystery-- What is it?

At first, they thought it was
ordinary matter that, for some

reason, they couldn't see.

But what happened was astronomers
went and took an inventory.

We know how much ordinary matter
there is in the universe.

By "ordinary matter" we
basically mean atoms-- Things

that are made out of protons,
neutrons and electrons,

the elementary particles that go into
making you, me, everything on Earth.

And it just doesn't measure up.

There's not nearly enough
ordinary matter in the universe

to make up the total.

Narrator: This
conclusion was bizarre.

How could most of the matter
in the microscopic universe

not be made of protons,
neutrons, and electrons?

It's been quite shocking to
discover that these atoms

actually make up just a small minority
of all the stuff in the universe.

There's six times more of an
altogether different substance

which is invisible to us.

It's interesting to think
that science has brought us

to the point where we realize
not only are we not the center

of the universe, we're not
even made of the same stuff

as the universe is made
of, for the most part.

Most of the stuff in the
universe is this dark matter,

and it's some small particle beyond
the reach of our direct detection.

Narrator: Some theoretical
physicists speculated that

dark matter might be made of
neutrinos-- Tiny particles

a thousand times smaller than
an electron, that fit many

of the known characteristics
of dark matter.

We know neutrinos exist.

And they have mass, they contribute
weight, so maybe we're done.

But now it's turned out
that they're not neutrinos.

Most of the dark matter is
probably not normal neutrinos,

because they travel
very, very quickly.

And they wipe out the formation
of what's called "large-scale

structure"-- The clumping of
material on the scale of

galaxies, early in the
universe's history.

So it would be much harder to
produce galaxies if the universe

is filled with lots and lots
of neutrinos zooming around.

So the dark matter is not
ordinary matter, it's not

neutrinos-- It's some wholly new
kind of particle that we haven't

detected yet.

It has to be some sort of weird
subatomic particle left over

from the Big Bang, when the
universe was very hot and dense.

A whole zoo of
particles was created.

Most of them annihilated or
decayed into other particles.

But some were left over, and
they are what are thought

to be the dark matter.

Narrator: But what could this
exotic microscopic particle be?

Since it's nothing known to
science, astronomers proposed

an entirely new particle that
embodied all of dark matter's

characteristics, and then began
searching the universe for it.

They call it a "WIMP"-- A "weakly
interacting massive particle."

One of the problems with the
WIMP hypothesis is that

we've never actually detected
a WIMP in a laboratory.

In fact, there's several
experiments going on right this

minute to look for WIMPs in
underground laboratories.

And you'd also like to make
them in particle accelerators,

like the large hadron
collider in Geneva.

So there's a multipronged attack
to detect WIMPs directly if

they're the right answer.

Narrator: If scientists find
evidence of dark matter, will

they also find evidence of another
world of dark planets...

dark life-forms...
and a dark matter table of elements?

I don't think they are like
us, in that the dark matter

particles can form
planets and so on.

Because if they could, then we
would expect most of the planets

in our Solar System to actually
be made of dark matter.

But I think it's much more
likely that the dark sector

is many different kinds of
particles that are much more

complex than just one.

Narrator: However, modern
science still has not found

evidence of this mysterious
microscopic material.

And a growing number of
scientists argue that's because

it's not something else...
It's somewhere else,

like other dimensions.

People have taken very
seriously the idea that the

dark matter comes from other
dimensions, or represents

ordinary particles that are actually
moving in the other dimensions.

The thing about other dimensions
are we don't see them, we don't

interact with them very
strongly, so they're a natural

place to put the dark matter.

It's conceivable that the
gravitational influence

in galaxies and clusters of
galaxies that we attribute to

dark matter in our own universe,
is actually caused by

concentrations of matter in
other dimensions that are

felt within our dimensions, but
will never be discovered within

our dimensions, because they're
actually somewhere else.

Narrator: Whatever or wherever
it is, many physicists

are confident they'll eventually
discover a complete solution

to the dark matter mystery...
Unless, they say, it simply

exists at an incredibly small
size-- Far smaller than humans

have ever been able to explore.

That raises the question...
"What does exist at the smallest

scales of the
microscopic universe?"

That's what viewer Jason L., from
Houston, Texas, wanted to...

Jason, I'm glad you
asked that question.

The smallest things in the
universe are the fundamental

subatomic particles-- like
electrons, or the quarks

that make up protons and
neutrons or neutrinos.

Now all these particles are
thought to be different

vibrational modes of a little
tiny entity called a "string"--

A little tiny package of energy.

And that then is the smallest thing
from which everything else is made.

Narrator: Scientists have just
started trying to explore

strings, and other incredibly small
stuff in the microscopic universe.

And what they found offers
tantalizing clues... to a world beyond.

Narrator: As they delve into
smaller and smaller spaces

in the microscopic universe,
scientists have successfully

looked inside atoms.

But what exists if we continue
our fantastic voyage still

deeper into this
subatomic netherworld?

Even scales that are smaller
than the electron are really

a vast unexplored territory,
more so than solar systems or

galaxies or even the universe.

Because we can make observations
of planets and stars and

galaxies and the universe, but
it's hard to conduct experiments

that allow us to directly explore
tiny scales in time and space.

Essentially what you need to
examine the microscopic world is

a sharper and sharper tool,
something that actually allows

you to distinguish the details
down at that very small level.

Narrator: But as scientists try
to probe spaces smaller than

the atom, they cannot possibly focus
enough light to illuminate them.

They need something
more powerful.

To look more finely,
you need more energy.

We can go to incredibly small
details, using high-energy

devices of various kinds.

Now the state-of-the-art are
actually particle accelerators.

We use elementary particles to
actually probe the structure

of other elementary particles
by colliding them together...

Letting them interact with each
other, and then seeing what

comes out at various
energy scales.

So we can continue this process
of examining smaller and

smaller distances in space and
time, by actually going to

higher and higher energy
with collider experiments.

[Explosion]

Narrator: However, the world's largest
particle accelerators have not yet

generated enough energy to probe
things much smaller than

the elementary particles
inside atoms.

Even so, scientists believe something
exists at even smaller scales...

At a size so tiny, the human mind
cannot possibly comprehend it.

Physicists are now trying to
understand what's called

the "planck length"-- 10 to the
minus-33-power centimeters.

That's 20 factors of 10-- 20 orders of
magnitude smaller than an electron.

Now an electron is yea big,
and I exaggerate a lot.

So the planck length is just
almost unimaginably smaller

than any objects we
can actually measure.

Nevertheless, physicists are
trying to deal with these scales.

And that's what string
theory is all about.

String theory says that
everything that we think of as

a particle is actually a tiny
vibrating loop of string.

To get an idea of how tiny it
is, I have here an eyedropper.

We're going to put out
one drop of water.

That has about a trillion trillion
atoms of hydrogen and oxygen.

Now imagine taking one hydrogen
atom and blowing it up

by 10 billion times.

It becomes about 1/2
a meter across.

You might say, "can we now see
the individual strings inside

that hydrogen atom?"

But the answer is no.

We can continue to make it
bigger-- make one hydrogen atom

the size of the Solar System.

The strings are still
too small to be seen.

It's only when we make that atom
the size of our observable

universe, that a string becomes
macroscopically large.

If one hydrogen atom is as
big as the whole observable

universe, how big is a string?

Only about the size of
one of these trees.

The amazing thing is that we
human beings can even talk

sensibly about what exists
at this microscopic scale.

Narrator: Not only can
scientists talk sensibly,

they've also formulated theories
about what happens down there.

This is really one of the "holy
grails" of all of science.

We think that ordinary space and time
cease to exist at the planck length.

What we don't know is
what takes their place.

We need to replace our idea of
space itself by something more

fundamental...
Something that might involve

different numbers of dimensions or
just a different concept entirely.

Narrator: One possibility is
that space at the planck length

resembles the grid
on a football field.

The yard lines are the fabric of
our universe, and there's simply

nothing in between.

It could be that time jumps
from one discrete point to

another, and there are
no steps in between.

And, like, little quantum
mechanical ants could tunnel

from one spot on the grid to
another spot on the grid

without ever going into the
intervening space in between.

Why? 'Cause there isn't any
intervening space in between.

Narrator: Whatever exists at
this incredibly small scale,

most scientists believe that the
concepts of space and time

segue into another kind of
universe where shrinking smaller

is a meaningless concept.

It could be that time and space
are what we call "emergent

properties" of the universe, but
that if you go to very small

spatial scales, or very small
intervals of time, the concepts

of time and space break
down-- they don't make sense.

Narrator: Scientists say the
conditions of the planck length

may be very similar to
those that existed before

the Big Bang, when everything
in our universe was probably

concentrated in a
microscopic pinpoint.

Maybe the same answers to the
question about "what happens

to the universe at the very
smallest scales" may also be

connected to knowing "what was the
universe like before the Big Bang?"

Did it just come into
being at the Big Bang?

Or was there something different
which then turned into the

universe that we're familiar
with at the Big Bang?

These are all questions we
don't know the answer to,

but are all connected to the issue of
what's going on at the planck scale.

You might think that these
tiny planck-scale things have

nothing to do with us
who are much bigger.

But actually it has
everything to do with us.

It's our origins.

Our entire universe, if we
extrapolate backwards,

would have been smaller
than the planck length.

Narrator: Whatever exists at
the smallest scales of the

subatomic world, and however
these things behave, scientists

say they must make sense of it
all before they can possibly

comprehend the cosmos above,
human behavior, and what

might have existed
before the Big Bang.

It's a mind-boggling amount
of information tucked inside

an unimaginably small space
of our microscopic universe.

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