All language subtitles for Stephen Hawkings Grand Design S01E01 The Meaning of Life

Hello. My name is Stephen Hawking.

Physicist, cosmologist,
and something of a dreamer.

Although I cannot move and
I have to speak through a computer,

In my mind, I am free...

Free to explore the great questions
of the universe.

Such as: is there a meaning to life?

Is there a reason that we exist
here on our pale, precious world?

Finding out those deep
into what it is to be alive...

To think...

To be a human being.
Right to the limits of reality itself.

Check it out.

We humans are curious species.

We wonder, we seek answers.

So can we answer
the greatest question of all:

Is there a meaning to life?

You might think
it is a philosophical question...

But I think philosophy is dead.

I believe science holds the key.

Science has changed everything.

Not just the world around us,
but how we see ourselves.

It's hard to overstate how profound
this discoveries are.

First up, they force us to leave
our common sense behind.

When we look at the human race
clearly and objectively,

what we see is a
pretty extraordinary creature.

We live, and love,
and enjoy ourselves.

We sometimes break the law
or behave badly.

We all have hopes,
and dreams, and desires.

But the first thing we must accept just
because searching for the meaning of life...

is that always is nothing more
than physics.

You see the entire universe works according
to the laws of nature, such as gravity.

These laws control everything.

From the working of atoms to
the collisions of colossal galaxies.

I see no reason why we tiny humans
should be the exception to the rule.

After all, we are made
of the exact same materials

operating to the very same principles.

So the challenge is to explain
what humans really are...

And how we, small insignificant
beings relate...

To the enormous, ancient
and rather beautiful universe...

that produce us?

Only then, I think, can we discover
if there is a meaning to our lives.

And perhaps,
even what that meaning is.

The first person to make any real headway
with this thorny question...

Was a man by the name of René Descartes.

You may know Descartes as the
father of modern philosophy...

But I consider him to be a pioneering
forefather of science.

Descartes propose that humans
are made of two distinct components:

The body and the mind.

He made careful anatomical drawings
of the body.

He saw it as a complex
biological machine.

But he was certain
the mind was different.

He prove this with a
simple thought experiment.

He tried to imagine that
he had no physical body.

As if he was floating around
like a ghost.

That was easy to do,
even though it's a little strange.

Then, he tried to imagine
having no mind.

But he couldn't.

After all, with no mind
how can you imagine anything?

He summed it up rather neatly
with the phrase: I think, therefore I am.

He believed that the mind and the body are
fundamentally different kinds of things.

Working out how they interconnect
is the next step

for us to find the scientific
basis for the meaning of life.

Here too, Descartes
was well ahead of his time.

He suggested the mind was connected
to the body at the pineal gland:

A small lobe at the top of the spine.

Although he wasn't entirely right,
Descartes was pretty close.

We now know that the conscious mind
is created by the brain as a whole.

An organ of such stupendous complexity,
that I find it mind boggling.

The human brain is far more
intricate than you may realize...

although you would not be able
to realize anything if it weren't.

It contains as many brain cells
as there are stars in the Milky Way:

100.000 billion.
Give or take a few.

These cells are coupled together
creating more connections...

than there are galaxies
in the known universe.

It may seem that studying the brain
is a job for neuroscience...

But since the brain is governed
by fundamental forces...

forces like electromagnetism...

then thinking itself automatically
bows down to physics.

Fast complex physics.

As a physicist, I see the human mind
as one of the universe's more

wonderful creations...

It's understanding how the mind
is aware of that universe

that will lead us to finding out whether
there is a meaning to it all.

The ancient Greeks were among
the first people to wonder...

if the mind was subject
to the laws of nature.

That was such an unsettling idea...

It was swept under the rug
for nearly 20 centuries.

After all, if we are just biological clockwork,
perhaps there is no meaning to life?

Perhaps no meaning at all?

Well, let's not be too hasty.

Take it, typical human
scene here in Cambridge.

Three people having a pleasant day out
on the River Cam...

which winds its way between
the colleges.

These people, whose body
are controlled by their brains...

Can interact with each other.

Appreciate each other
and their surroundings.

And might even decide to
play a song...

or fall in love.

Their world is not without meaning.
Quite the opposite.

Their world is full of meaning.

To them, even a simple glance
can be laden with meaning.

So much so that it's
easy to get carried away.

So finding out where the meaning is...

is a problem for science.

And it means delving into why
we have consciousness at all.

Enter one of the greatest
theories in science: evolution.

We know all life on earth
evolved from complex molecules called:

Amino Acids.

These molecules collided
randomly to create

the first simple living things.

Over billions of years this life forms
became ever more sophisticated.

Until eventually complex
multicellular creatures,

animals with brains, arrived.

Complex animals need brains in order
to process large amount of information.

They need to be able to react to the
world around them. And even plan ahead.

The more aware an animal is
of its environment...

The more successful it will be.

Eventually awareness became
so sophisticated...

That one animal became aware of itself.

And that is what we are:
self-aware animals.

Animals that evolution has equipped
with the ability to be conscious.

But how is this possible?

How can a biological structure
possess the ability to think, to feel...

and to assign meaning to things?

Not easy question to answer.

But there are theories about how
consciousness could arise.

Back in the 1970s, an unexpected
breakthrough was made by a mathematician

named John Conway, here in Cambridge.

He devised something
called The Game of Life

A simple simulation that shows how a
complex thing like the mind...

might come about from
a basic set of rules.

The simulation consists of a grid,
a bit like a chessboard...

extending infinitely in all directions.

Each square of the grid can either
be lit up, which he called "alive"...

or dark, which he called "dead".

Whether a given square
is dead or alive...

depends on what is happening in the
eight other squares that surround it.

For example, if a living square
like this one...

has no living squares nearby...

the rules say it'll
die of loneliness.

If a living square is surrounded by
more than three other living squares...

The square will also die
of overcrowding.

But if a dead square is surrounded
by three living squares...

It becomes lit, or is born.

Once you set an initial state of living
squares and let the simulation run...

These simple laws determine
what happens in the future.

The results are surprising.

As the program progresses, shapes
appear and disappear spontaneously.

Collections of shapes move across the grid
bouncing off one another.

There are whole kinds of objects,
species that interact.

Some can even reproduce...

Just as life does in the real world.

This complex properties
emerge from simple laws...

That contain no concepts like
movement or reproduction.

It's possible to imagine that something
like the Game of Life...

with only a few basic laws...

might produce
highly complex features.

Perhaps even intelligence.

It might take a grid with many
billions of squares, but...

that's not surprising. We have many
hundreds of billions of cells...

in our brains.

So I think the human mind and the
meaning it creates...

arise from a large complex system
operating to very simple rules.

Which means Descartes was right.
The body and mind are different.

The body and the brain are
made out of physical matter.

The mind is a product of the
ever-changing state of this matter.

Our body is the hardware.
Our mind is the software.

Just like the software that allows me
to speak these words.

But this does pose a problem:
the problem of free will.

When I was a young man, my father wanted
me to become a doctor like him.

But I chose to study physics instead.

Looking back, I'm pleased
because as things worked out...

I would have made
a pretty useless doctor.

So I made the right choice.
Or did I choose at all?

Perhaps I am deluded
about my own free will.

After all, if my mind follows the strict
rules of nature...

maybe the path I chose
was predetermined.

In fact, scientists have already discovered
that our decision to do something...

Can be affected by many things.
Not least, electricity.

Now, I do hope you're not squeamish...

But let's imagine watching
a surgical procedure called:

Awake Brain Surgery.

It's used to treat Neurological disorders.

The brain is exposed and
stimulated with electrical probes.

The urge to move... a foot, hand or face

can be artificially triggered
by electrically exciting...

appropriate regions of the brain.

All it takes is about 3.5 volts
in the right place.

The patient may "think"
he has made a choice...

but in fact, the surgeon
made it for him.

We can imagine a future where advanced
technology could allow the doctor...

to control someone's thoughts.

Perhaps even make them fall in love.

The unfortunate subject would believe
he was acting out of free will...

But the opposite would be true.

It's all just physics in the brain.

For many people,
this idea is a horrific thought.

For it seems to deny our basic humanity...

and return us not only into machines...

But machines that can be controlled...

conceivably, for evil means.

So perhaps I had no choice when I decided
between physics and biology.

Perhaps the laws of physics
determined my career?

Well... not necessarily.

Predictability isn't always a
consequence of the laws of nature.

It's hard to predict an individual
roll of the dice.

Even though it is pure physics.

Scale that up
to a really complex system...

Predictability becomes impossible.

To see such a system
you only have to look outside.

Now, as you may know, we English are slightly
obsessed by our ever-changing weather.

Especially when planning
a summer barbecue.

Wouldn't it be nice if we could be sure
of a sunny day...

before inviting our friends?

Predicting a nice day should be
relatively simple.

After all, we understand pretty well how the
atmosphere reacts to heat and pressure...

to form clouds and thunderstorm.

But no matter how hard we tried
to compete all the details...

it is impossible to say exactly what the weather
would be in any particular place and time.

Instead, we make
weather forecasts...

using simplified models that don't take
into account...

every single tiny variable.

But tiny variables can
have big consequences.

So, if a butterfly flaps its wings
too hard in the Amazon...

The barbecue might be a wash out.

It's a complex system.

I think our brains are just
another complex system...

like the earth's atmosphere.

We abide by the physical laws...

yet are impossible to fully predict.

The mind is like weather
inside our heads.

Free will is simply what we called the process that
happens when this vastly complex system faces its choice.

Let me try to explain.

Imagine a man wakes up at night
and feels thirsty.

Let's say I'm right about the human mind...

And this man's brain is working
according to the laws of nature.

Where exactly might free will
come into it?

Let's give him a choice to make.

Either orange juice or apple
juice to quench his thirst.

As he smells the apple juice, the
storm of neurons far...

and the memory kicks in.

He is reminded of a special
moment in an apple orchard...

And his mind is made up.

So his choice is not surprising.

He had to make a decision.

He chose...

And that is what we called
free will.

But it's all still a matter of physics.

Looking back, I certainly
made the choice to be physicist...

And I certainly feel like I
made free will...

because free will is what we called the
complex physics that happens when we decide.

But if our choices are just physics...

does it mean we are deluding ourselves?

And there is no meaning to life?

To find the answer, we have to go
even deeper and question the very nature...

of reality itself.

Reality.

Most of us share the same common sense
view of what reality is.

The world around us exists
independently from us.

It's full of real things
that are really there.

But science is unraveling
this basic assumption...

Which handily leech us
to the meaning of life.

Take this little girl here, walking around
through a busy market in Monza, Italy.

Her reality is a riot of
sound, color, taste and smell.

All based on the many bits
of information...

her senses are feeding her brain.

But once we accept that the mind
is like a weather system in the brain...

and governed by physics,
yet unpredictable...

Reality itself begins to break down.

It becomes subjective:

My reality is different than yours...

Or this fishes.

Its reality appears distorted
by the round fishbowl.

Everything is warped and curved.

In Monza they found it was so cruel
to keep fish in such a distorted reality

They actually banned round fishbowls.

Speaking as a scientist, now I think
such a law is unfounded.

Just because the goldfishes' view
isn’t the same as ours...

It doesn't mean that it is living
in a distorted reality.

Imagine that this goldfish
is something of a genius.

Even though he sees the world
differently than we do...

He can still work out the laws of nature.

The mathematics would be more complicated
to account for the distorted perspective...

But the physics would be the same.

If this clever fish could work out how fast
the police's motorcycle was moving...

He could calculate the right trajectory
and the right moment to escape.

I don't think that one reality
is more valid than another.

And that means that reality itself is
in the mind of the beholder.

When you think about it, even
our point of view is far from perfect

It may seem that human eyes for example, are
pretty good at seeing the world around them.

But in fact, they're not so great.

Our eyes only see a small
area with good resolution.

An area the width of your thumb
when held that arms length.

The eyes then send electrical signals
to the brain down the optic nerve.

The area where this nerve
connects to our eyes

means we have two blind
spots in our vision.

But we don't perceive a blurry world
with two black holes.

This is because of the incredible organ,
that is our brain.

Our brains fill in the gaps transforming
the crude signals from the eyes...

into a three-dimensional model
of the outside world.

It is this mental models
that each of us called reality.

So how does this realization brings
us closer to the meaning of life?

Well, at first, it would
seem to be bad news.

If reality itself is just a model
in each individual brain...

Where can the meaning be?

What's more: Perhaps there is
no real reality out there at all?

It may seem crazy to doubt that our
concept of reality as true.

But I think to find the meaning of life
we must answer the question:

Is there an independent reality or not?

Imagine a scenario that is straight
from a science fiction movie.

The world around you is actually nothing
more than an elaborate fabrication...

of some unknown superior intelligence.

Giant supercomputer provide you
with all your senses

from what you see to what
you smell, hear and touch.

But in fact you have no senses.

Your body does not exist.
You are just a brain in a jar.

It may sound bizarre, but this is
a genuine scientific hypothesis called:

The simulation theory.

For all we know, every one of
our perceived reality is simply fed to us

By some all-powerful supercomputer.

And the simulation is so perfect
that we never even notice.

But here's the cracks:
It doesn't actually matter.

It's as Descartes said:
We think, therefore we are.

The hamburger could be nothing more
than a piece of computer code.

But our desire to eat it,
is still our own desire.

We still feel hunger...

Our minds still exist,
even if we are in a simulation.

So doubting the true nature of reality
serves no purpose.

It's simpler to just accept that there are
fundamental limits to what we can known.

Take this table, for example.

How do you know if a table
still exists if you go out of the room...

And can no longer see it?

For all you know, the table could pack up
and disappear out the window.

It could take a visit to
the International Space Station.

Perhaps even fly to the moon.

All this before returning to the exact same
spot an instance before you reenter the room.

This, of course is a
pretty unlikely scenario.

But one we can't rule out.

It is much simpler to assume that
the table stays put when we are not there.

It is our best fit model of reality.

This is essentially what we do in science.

To create best fit models
of how we believe

the universe actually works.

The ancient Greeks were the first...

to built such scientific models.

They suggested that the earth
was a large sphere, motionless...

And fixed at the center of the universe.

But later pioneering scientists
like Copernicus and Galileo...

found a much simpler and completely revolutionary
model to describe this same observations.

They proposed that the earth itself was spinning
and orbiting the sun at the same time...

Along with all the other planets.

But neither can be said
to actually be true.

Because they, like all models,
are just a models in our heads:

The best fit of
reality we perceive.

In fact, physicist are forever
creating ever more sophisticated models...

And the truth of those models
is impossible to establish.

A good example of this came in the 1960s.

Physicists devised a theory of
really tiny bits of matter, called quarks.

These quarks were proposed to be the building
blocks of the subatomic particle called:

A proton.

The theory our model
suggested that...

these quarks were held together
by a force...

that got stronger as you tried to
separate them.

If the quarks were bound
by tiny rubber bands.

This model also implied that there is no way
one can ever see a single isolated quark.

At first, some people were skeptical.

If something by its very
definition can never be seen,

Can it be said to exist?

Does it make sense to say
that quarks are real or not?

In vast particle accelerators like this one
at CERN in Switzerland...

Scientists are on the hunt for
quarks and other subatomic particles.

By smashing protons together
at incredible speed...

We can study the behavior of the
tiniest particles in nature.

Although we haven't enable
to directly observe quarks,

we have seen evidence of particle
behavior predicted by the quark model.

So do Quarks exist?

The answer is they exist
only as a model that works.

Measure we do not know

This is called the concept of
model dependent reality.

And I believe that lead us directly
to the meaning of life.

To my mind, science has taught us
something pretty remarkable:

We humans are highly complex biological
machines behaving in accordance

with the laws of nature. Our brains
create and sustain our conscious mind

through an extraordinary network
of interacting neurons.

That consciousness creates a
three-dimensional model...

of the outside world:

a best fit model
that we call reality.

This reality is much more than what
we see around us in our everyday life.

A vast array of ground and space telescopes
have extended our senses.

Allowing us to see deep into space...

And build a much bigger model
than ever before.

As we peer further
and further into the cosmos...

our reality has grown bigger
and bigger still...

where once we saw a chink
in heaven's flow...

We now see distant stars like our sun.

Many with their own planets and moons.

Then we discovered distant
galaxies, home to billions more stars.

We have peered back in time.

All the way to the birth
of the universe itself.

All this, the entire 13.7 billion year
history of the universe...

exists as a model inside our minds.

So where does this leave us with
finding a meaning to life?

The answer, I think, is pretty clear.

Meaning itself is simply
another piece of the model of reality...

that we each built inside our own brains.

Take this mother and child.

They each create their own little bubbles
of reality in their conscious minds.

The youngster, can create
a detailed mental model

of his surroundings.

Even though he may not fully appreciate
the fact he's on the fifth floor.

The mother's reality is
also produced by her mind.

And for her, her love for her boy
is as real as the telephone in her hand.

In short: the brain is responsible
for not only the reality we perceive...

but for our emotions and meaning, too.

Love and honor, right and wrong...

are part of the universe we create
in our minds

just as a table, a planet or a galaxy.

It's pretty remarkable to
think that our brains...

which are essentially a collection of
particles working to the laws of physics...

have this wonderful ability to not
only perceive reality...

but to give it meaning, too.

The meaning of life is
what you choose it to be.

Personally, I like to think that it is everyone
of us that gives meaning to the universe.

We are, as cosmologist
Carl Sagan once said:

The universe contemplating itself.

Meaning can only ever exist within the
confines of the human mind.

And in this way, the meaning of life
is not somewhere out there...

but right between our ears.

In many ways, this makes us
The Lords of Creation.