The Bridge

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 delves 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 these 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 that 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 inner-workings 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 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 boils 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 a 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 bodies are the hardware. Our minds are 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 would turn us not only into machines,

but machines that can be controlled.

Conceivably, for evil means.