All language subtitles for The Secrets of Quantum Physics - 02. Let There Be Life

Welcome to a new and very strange
world of nature.

It's been taken over by
the weird subatomic particles of

quantum physics.

CHURCH BELL RINGS

As a physicist, I've spent
my working life studying

how these particles behave
in the laboratory.

But now I'm heading out
into the natural world.

I'm on a mission to prove
that quantum physics can solve

the greatest mysteries in biology.

This is a real adventure for me.

I'm very much out of my
comfort zone trying to apply

the very careful ideas I'm familiar
with in a physics laboratory

to the messy world of living things.

I believe that quantum physics
could hold many of life's secrets,

that deep in the cells of animals,

particles glide through walls
like ghosts...

..that when plants capture
sunlight...

..their cells are invaded by
shimmering waves

that can be everywhere
at the same time.

And that even our human senses

are tuning in to strange quantum
vibrations.

In the fantastic world
of quantum biology,

life is a game of chance,

played by quantum rules.

This is what I hope to
convince you of,

to show you that quantum mechanics
is essential in explaining

many of the important processes in
life, and potentially, that

quantum mechanics may even underpin
the very existence of life itself.

My quest begins with one of
the most majestic sights in nature.

Migration.

Every winter, barnacle geese
arrive right on cue

at the same Scottish river.

The end of an epic 2,000-mile
voyage from Svalbard,

high above the Arctic Circle.

Of course, many birds
head south for winter

then back home for summer.

But for decades, exactly how birds
navigated with such accuracy

was one of the greatest
mysteries in biology.

So the most recent discovery has
caused a sensation.

In the past few years,

one species of bird has helped

create a scientific revolution.

I was one of many physicists who was
shocked to discover that it

navigates using one of the strangest
tricks in the whole of science.

It utilises a quirk of
quantum mechanics,

one that bamboozled even
the greatest of physicists,

from Richard Feynman to
Albert Einstein himself.

So you might be surprised to
discover the identity of this

mysterious creature.

Say hello to the Quantum Robin.

This is the European robin.

Every year, she migrates from
northern Europe

to the tip of Spain and back.

In this laboratory in the woods,

biologist Henrik Mouritsen is
trying to solve the mystery

of how she does it.

But he's found himself in MY world,

the strange world of
quantum mechanics.

Quantum mechanics describes
the very weird behaviour of

subatomic particles.

Down in this realm
of the very small,

we have to abandon
common sense and intuition.

Instead, this is a world where
objects can spread out like waves.

Quantum particles can be
in many places at once

and send each other
mysterious communications.

I set out to understand
how the bird finds its way,

but it just turned out that the data

more and more pointed towards this as

the only explanation that could bring
all the different results together.

Henrik's investigating
a longstanding theory -

that robins navigate by
the Earth's magnetic field.

His laboratory is an ingenious
magnetic bird cage.

And these plastic cones lined
with scratch-sensitive paper

provide the key measurements.

Henrik's artificial magnetic field
is like the Earth's, except that

HE can point it in
any direction he likes.

Inside their cones, the robins
always respond to the field,

leaving scratches in
a single direction.

The big mystery is HOW.

The Earth's magnetic field
is incredibly weak,

far too weak for any
living creature to detect.

But Henrik has found
an intriguing clue

by giving the Quantum Robin a mask.

We have a little leather hood similar
to what you put on a falcon,

you know, but just for a robin,

and you have then a
hole in front of one eye

or a hole in front of the other eye.

And what we can see is that if you
cover up the right eye, you turn off

their magnetic compass processing
in the left part of the brain.

If you cover up this eye,

you turn the compass off
in this part of the brain.

The robin's magnetic compass
seems to be in her eyes.

I can show you what's going
on using my own eye.

Now, we use our eyes for vision,

but we also have a second
light-detecting mechanism.

If I shine this torch into my eye,

you can see that
my pupil closes down.

It's basically a defence mechanism
to protect my eyes.

My eye is responding to particles
of light - or photons.

The energy provided by the photons

is clearly enough to activate
chemical reactions.

After all, that's what
controls my eye muscles.

Light must be causing similar
chemical reactions

in the robin's eyes.

In fact, it's the power supply for
a unique form of magnetic compass...

..inside her cells...

..in the weird world
of subatomic particles...

..a place where only quantum physics

can explain what's going on.

To see why, imagine the chemical
reactions in the robin's eye

taking place in mountains
and valleys of energy.

To get a reaction to start,

you have to push molecules
to the top of a mountain.

Thanks to Henrik's experiments,

we now know that light does
most of the hard work.

But when it reaches the very peak,

the molecule becomes incredibly
sensitive to the slightest touch.

The key point here is that
the robin's chemical compass is now

balanced on an energy peak
between two valleys.

Going one way produces one set
of chemical products -

the other, a different set.

Now, even a tiny change in the
Earth's magnetic field can tip the

molecule over the top, but the way
this happens defies common sense.

The final piece of the puzzle

depends on one of the truly

mind-boggling ideas in physics.

But don't worry if you find it

hard to understand -

even Albert Einstein

called it "spooky".

The idea is called
quantum entanglement.

It involves particles that
seem to communicate faster

than the speed of light.

In 1935, Einstein published
a famous paper

arguing that it was impossible.

But Einstein was wrong.

In recent years, extremely delicate
experiments have shown that

subatomic particles
really are entangled.

It means they can subtly

and instantaneously influence
each other across space.

And now it seems the same thing is
going on inside the robin's eye.

When a photon enters
the robin's eye,

it creates what's called an
entangled pair of electrons.

Here's how it works. Each electron
has two possible states.

For simplicity, I'm choosing to
call them Red and Green.

Now, here's the weird thing.

Until I measure it,
it's neither one nor the other,

but both at the same time.

Think of the electrons
like spinning discs.

They're simultaneously
red AND green.

But by firing a dart...

..I can force the first electron
to be one or the other.

So far, it's just a game of chance.

I don't know what I'll get
until I try it.

So I know my first electron is red.

Suppose I now measure
the second electron.

You'd think I'd have a 50/50 chance
of getting red or green.

After all, that's what you'd expect
in the normal, everyday world.

But you'd be wrong.

In quantum entanglement, the
electrons are mysteriously linked.

For example,
if I get red on the first...

..I ALWAYS get red on the second.

It's not a game of chance any more.

It's as if the first electron is
telling the second one what to do.

That's why Einstein
called it spooky.

The electrons seem to know that they
should both have the same colour,

no matter how far apart they are.

The really important part is that

the two electrons needn't be
the same colour.

They can be entangled
in a different way,

so that if the first
electron is red...

..the second one is always green.

It seems that this mysterious
connection is the ultimate secret

of the Quantum Robin's compass...

..because the direction of
the Earth's magnetic field

can influence the outcome.

Near the equator, they may be
more likely to be red-red.

But near the pole, they may be
more likely to be red-green.

And that's the vital factor
that finally tips the balance of

the robin's chemical compass.

Tiny variations in the Earth's
magnetic field change the way

electrons in the robin's eye
are entangled,

and that's just enough
to trigger her compass.

Now, finally, we can see how
something as weak as the Earth's

magnetic field can tip that
balance one way or the other.

If the message changes,

the chemical reaction
tips a different way...

..changing the robin's
compass reading.

Suddenly it looks like it's
a fundamentally quantum mechanical

phenomenon in birds.

It would be one of the first,
if not THE first, in biology.

Biologists better get used
to the weirdness of physics.

The robin is navigating by
"spooky" quantum entanglement.

To see subtle quantum effects,

even in a controlled, austere
environment of a physics lab,

is really difficult.

And yet here's the robin
doing it with ease.

These experiments are real
and verifiable, and yet even though

I'm seeing them with my own eyes,
I still find it hard to believe.

Bird navigation has brought physics

and nature together as
the science of quantum biology.

There's a whole new world
to explore.

But its pioneers have found that
it doesn't just affect birds.

It affects every single one of us.

Because the latest experiments say

you're doing quantum physics
right now.

And believe it or not,
you're doing it with your nose.

Hello, Jem!

Hello.

Hello, little girl! Hello...

Our sense of smell is remarkable,

and quite different from our other
senses of sight and hearing.

Among the thousands of scents
that we can recognise,

many of them may well trigger very
powerful memories and emotions.

It's as though our sense of smell is

wired directly to our
inner consciousness.

It's also different in another way.

The other senses of sight and
hearing rely on us detecting waves -

light and sound.

But our sense of smell
involves detecting particles -

chemical molecules.

Recently, scientists have begun to
realise that when it comes to

our sense of smell, something very
mysterious is going on.

GUNSHOT

For decades, biologists thought
they knew exactly how our noses

sniffed out different chemicals.

But physicists like Jenny Brookes
think there could be a new

ingredient in the mix.

And it smells like
quantum mechanics.

A lot of people speak of
the sense of smell and olfaction,

and the science of olfaction as
being a problem that's been solved

and we know all about it -
and we do know a lot about it.

We know about the ingredients,

we know about the equipment
that we use to smell.

But I would argue that there's
a little bit more to understand.

To understand more, I need someone
to help me with a smell test.

And Jem is going to sniff him out.

Every human being gives off
a cocktail of chemicals.

Jem's nose could detect
a single gram of it

dissolved over an entire city.

So she has no trouble finding
the man I'm looking for.

Meet Colin the gardener, a man
who's used to smelling the flowers.

Right, then, Colin, I'm going to put
your sniffing skills to the test.

Cool. I've got a selection of
chemicals here,

and I want you to tell me
what they remind you of.

OK.

I'll start you off easily.

COLIN SNIFFS

Oh, that's...

like a minty, minty vapour rub...
It is, yeah. ..sort of thing.

Yeah, this is...
Something what you'd rub...

This is men...menthol. Menthol.
Yeah. But it's that essence.

Right, here's the next one.

Ah. You should be able to
recognise this one.

That's baking with my daughter.

Mm-hm. Erm, icing sugar
sort of thing...

Vanilla. Vanilla, yeah.

When our noses detect a chemical,

they fire a nerve signal
to our brains.

But different chemicals create
different sensations.

The standard explanation for this
is to do with

the shape of the molecules.

The conventional theory
that goes back to the 1950s

says that the scent molecule has
a particular shape that allows it

to fit in to the receptor
molecules in our nose.

If it has the right shape,
it's like a hand in a glove,

or a key in a lock. In fact, it's
called the lock and key mechanism.

With the wrong shape,
it won't fit into the receptor.

But with the right shape,
it fits into the receptor,

triggering that unique
smell sensation.

Different receptors are wired to
different parts of our brains.

So, when a menthol molecule
locks into its specific receptor,

it triggers that
minty fresh sensation.

But the lock and key theory
has always had a problem...

..and Colin's next test
will show you why.

OK, how about...

this one?

Quite a strong smell.

Oh, that's...

Yeah. What does it remind you of?
What does it conjure up?

What memories?

I think Christmas.

Christmas cake. Yeah. Marzipan.

Marz...marz...yeah, that's it, yeah.

Almonds. Very, yeah.

Colin identified the smell of
marzipan or almonds.

In fact, it's due to a scent
molecule called benzaldehyde.

What I didn't give him to smell was
this other chemical - cyanide.

Both benzaldehyde and cyanide
have the same smell,

they both smell of almonds,

but these molecules are both
very different shapes,

so the lock and key mechanism,

as an explanation for how we smell,
can't be the whole story.

So why would two molecules with
different shapes smell the same?

Quantum biology has
a head-spinning explanation.

It says our noses aren't
smelling chemical molecules...

..they're LISTENING to them.

It's not just the shape of
a scent molecule that matters.

Let's take a closer look at this
model of a cyanide molecule.

The white ball here is
a hydrogen atom,

and the grey sticks are the bonds
that hold it together

with the carbon and nitrogen.

But the reality isn't
as simple as that.

I can give you a better
sense of what's going on

if we look at this
larger white ball.

You see, atoms don't just sit still.

The bonds that hold them together
are like vibrating strings,

and that gives us a whole new
way of thinking about smell.

The bizarre new quantum theory of
smell is all about vibrating bonds.

HE PLAYS HARMONICS ON GUITAR

Chemical molecules are
playing music for our noses.

Imagine a receptor molecule
in my nose is like my guitar.

Before it can make a sound, a scent
molecule has to enter my nose,

and when that scent molecule
is in place, its chemical bonds

provide the strings,
and it's ready to be played.

The receptor molecules contain
quantum particles -

electrons.

As they leap from one atom to
another, they vibrate the bonds of

the scent molecule,

like my fingers plucking
a guitar string.

GUITAR NOTE CHIMES

What's remarkable about this
theory is that it tells us

our sense of smell is about
the vibrations of molecules,

or wave-like behaviour,

and not so much about the shape
of a particular scent molecule.

Our sense of smell may be much
more like our sense of hearing.

HE PLUCKS HIGH NOTE

A particular molecule,
say that of grass,

will vibrate at
a particular frequency.

HE PLUCKS LOW NOTE

But a different molecule,
say, that of mint,

will vibrate at
a different frequency.

HE PLUCKS MID-RANGE NOTE

PLUCKED NOTE REVERBERATES

HIGHER NOTE REVERBERATES

This would explain why
cyanide smells like almonds.

The two molecules have
different shapes,

but their chemical bonds
just happen to vibrate

at the same frequency.

The constant vibration
in the odorant is almost

literally like a particle of sound.

So, yeah, we're saying that
the process of smell could be

exactly like an acoustic
resonance event,

it could be very analogous to, erm,
hearing and seeing, actually.

But can we really
be listening with our noses?

A bizarre theory needs
a bizarre experiment to test it.

Here's how it works.

Scientists used a molecule that
smells fruity, like orange blossom.

But if the theory is right,

then I should be able to change its
smell by changing its vibrations.

The molecule contains

lots of hydrogen atoms like this,

bonded to carbon atoms, but what if
I were to replace all these atoms

with a different form
of hydrogen called deuterium?

Now, it won't change
the shape of the molecule,

but it will change
the way it vibrates.

And here's why - deuterium is
twice as heavy as normal hydrogen,

and so it vibrates more slowly.

Now, different vibrations mean
different smells,

so if I were to make
a new form of this chemical,

all packed with deuterium atoms
instead of normal hydrogen,

it should smell different.

Quantum biologists found a unique
way to carry out this experiment.

A smell comparison,

using the real experts
in fruity aromas.

INSECTS BUZZ

Fruit flies.

First, the flies were trained to
avoid the modified version

of the fruity molecule.

To be honest,

I haven't got a clue how you
go about training a fruit fly,

but apparently you can.

In the laboratory, the flies had
to pass through a kind of maze.

They were then given a choice.

Go right for the nice, fruity smell,

or left,
for the nasty, modified version.

HE STRUMS GENTLY

They could definitely
smell the difference.

They always preferred
the original and turned right.

The fruit fly experiment gives
hard evidence

that quantum smell theory
really works.

But ultimately, it works in harmony
with the lock and key theory.

First, the scent molecule
fits into the receptor...

..then those molecular
vibrations take over.

Incredible as it seems,
flies, humans

and dogs may be smelling
the sound of quantum biology.

Our sense of smell is fascinating
and mysterious as it is,

but to think that when
I encounter a particular scent

and that sets off
a whole wave of memories

and emotions in my mind,
that it's underpinned,

that it's triggered
by quantum mechanics,

I think makes it even
more remarkable.

CROWS CAW

The mysterious influence
of quantum physics

reaches into every corner
of the natural world.

In fact, it inhabits the walls

of every living cell on Earth.

Because the latest experiments
suggest a magical solution

to one of the greatest
mysteries of nature.

The miracle of metamorphosis.

The transformation of
a tadpole into a frog

has never been fully explained.

In little more than six weeks,
the tadpole breaks down,

then reassembles in its adult form.

But the big mystery
is how it happens so fast.

When you think about it,
there's nothing more extraordinary

than a tadpole turning into a frog.

Take its tail, for example.

Over a period of several weeks,
it gets reabsorbed into the body

and the proteins and fibres
that make up the flesh

get recycled to form
the frog's new limbs.

But for this to happen,

trillions and trillions of
chemical reactions work together,

breaking molecules, forming new ones
in a carefully orchestrated dance.

But the fibres that hold flesh
together are very, very strong.

They're a bit like these ropes
holding my raft together.

In order to dismantle the raft, I'd
have to undo these very tight knots.

You could think of it like this...

..a tadpole is held together
by long ropes of proteins

knotted together by chemical bonds.

The bonds are so strong
that they should last for years,

much longer than the tadpole's
entire life span.

So how can it turn into
a frog in just a few weeks?

The explanation involves one of the
most important molecules of life.

Tiny widgets in all our cells
called enzymes.

The enzymes are the actual
machinery of the cell.

They are actually the little
machines inside cells

that do the chemical transformations
that are involved in everyday life.

They are absolutely crucial.

And the reason they're so crucial
is because what they are able to do

is to accelerate chemical
reactions by enormous amounts.

Let me show you just how quickly
enzymes get to work.

Inside this bottle is a substance
called hydrogen peroxide.

You're probably most familiar
with it

as the chemical used to bleach hair.

In fact, I obtained this sample

from my local hairdressers.

Hydrogen peroxide is also
produced in the body,

and it's the job of the liver
to get rid of it.

The way it does that
is using an enzyme

which breaks down hydrogen peroxide
into water and oxygen.

Now, to show you just how quickly
this enzyme works,

I'm going to do
a quick demonstration.

I've got some liver here
which I've chopped up

in order to release the enzyme.

Now, watch what happens when
I add this liver mixture

containing the enzyme
to the hydrogen peroxide.

Watch how quickly the oxygen
is released.

CROWS CAW

Just 100 grams of liver
fired my rocket nearly 20 feet.

Liver enzymes make the breakdown
of hydrogen peroxide

incredibly efficient.

It happens a trillion times faster.

That's a million, million times
faster than it would otherwise.

In metamorphosis, it's enzymes

that dismantle the tadpole's tail.

And that means breaking down

an incredibly tough protein

called collagen.

Collagen is one of the most important
proteins in the biological world.

It's the protein which actually gives
that resilience, that elasticity

to tendons, to cartilage,

and of course to our skin, as well.

And in the tail of the tadpole,
it provides the kind of scaffold

that supports that structure.

Now, when the tadpole is
transformed into the frog,

what you need to do is to
essentially have an enzyme,

collagenase, which will literally
snip the collagen down

into small pieces
and thereby take that scaffold apart.

But how do enzymes break chemical
bonds apart so incredibly fast?

Let me show you why it's a problem
only quantum biology can solve.

Think of it this way, all these
different parts of the knot

are like subatomic particles -
electrons, protons -

that hold the different parts
of the molecule together.

Now, to untie the knot,
enzymes have to move protons about.

But as you can see,
this takes quite a bit of effort

and a lot of time
if there are many knots to unpick.

Physicists have a fancy way
of saying

"put in effort to get
something done".

They say you have to overcome
an energy barrier.

OK, here's my energy barrier.

And here's my proton.

To break a bond apart,

it needs enough energy
to get over the barrier.

The trouble is, when we work out
how long this would take,

it's much too slow to
break down a tadpole's tale.

But this is where protons
turn into ghosts.

I wouldn't blame you for thinking
that this is an idea

that a clever theoretician
has come up with,

that it's just mere speculation -
something that we have no proof of.

But we do.
It takes place all the time.

In the quantum world,

protons don't have to go over
barriers.

They can tunnel...

straight through.

Tunnelling strikes at the very
heart of what is most strange

about quantum mechanics.

It's like nothing
we see in our everyday world.

A quantum particle can tunnel
from one place to another

even if it has to pass through
an impenetrable barrier.

They are not solid objects
like balls in our everyday world.

They have spread out, fuzzy,

wavelike behaviour that allows them
to leak through an energy barrier.

A particle can disappear
on one side of the barrier

and instantaneously
reappear on the other.

In nuclear physics,
this effect is a proven fact.

Without quantum tunnelling,
the Sun simply wouldn't shine.

But I never thought I'd see it...

..in a tadpole.

It's hard to stress just how
weird this process is.

It's as though I would approach
a solid brick wall and,

like a phantom, disappear from one
side and reappear on the other.

The most important advantage
of tunnelling is its speed.

It happens incredibly quickly -

much faster than if protons
go OVER the barrier.

As a nuclear physicist, quantum
tunnelling is my bread and butter.

Subatomic particles like protons
do it all the time.

But what has this got to do
with biology?

The answer is that without
quantum ghosts,

the metamorphosis of a tadpole
would be impossible.

Remember,
chemical bonds are basically knots.

Tunnelling unties them - fast.

Have a look at these two knots.

Now, on the face of it
they look identical,

but there's a subtle difference.

This knot has the two short ends

of the rope on the same side.

Whereas this one

has the two short ends
on opposite sides.

Now, you'd think that wouldn't make
a difference, but it does.

You see, THIS knot...

..is very hard to break,

whereas THIS one...

..is easy.

Quantum tunnelling...

..turns strong knots
into weak ones.

So in a tadpole,

the entire collagen scaffold
breaks apart easily.

And finally, other enzymes rebuild
it in the shape of a frog.

The quantum tunnelling of particles
is one of those weird features

of the subatomic world

that a physicist like me is very
familiar with.

After all, it's
responsible for radioactive decay

and it goes on inside the Sun.

It's the reason why the Sun
and all stars shine.

But to discover this going
on inside every cell of every

living organism on the planet,
because every cell contains enzymes,

now, THAT I find truly amazing.

Quantum biology casts its spell
over every living creature.

We've seen that birds,
mammals, insects

and amphibians are governed
by the strangest laws in science.

But the most dramatic recent
breakthrough concerns

the single vital process on which
all these forms of life depend.

The conversion of air and sunlight

into plants.

This fine specimen is
a Larix decidua, or European larch.

It's about 100 feet high
and right at this moment,

passing just this side
of the planet Venus,

is a bullet with this tree's
name on it.

The bullet is a photon

nearing the end of its long
journey from the Sun.

Its ultimate destiny
is to kick-start

a series of chemical reactions that
underpins all life on Earth...

..photosynthesis.

Every second of every day,

16,000 tonnes of new plant life
are created on Earth.

And for me, it's incredible to think
that our existence

on this planet depends
on what happens

in the next trillionth
of a second.

The crucial first stage
of photosynthesis

is the capture of energy
from the Sun.

It's nearly 100% efficient,

vastly superior to any human
technology.

But the way that every plant
on Earth achieves this

is one of the great puzzles
in biology.

When it turned out that quantum
weirdness might hold the answer,

physicists could hardly believe it.

It was like a revelation.

It was very exciting, because I was

used to working on problems

that were quite abstract experiments.

I am a theoretician,
but I always related my theory

to experiments that were very clean
in the lab,

things that you can control.

But now, finding out that the
things that I knew can help me

to understand better how
nature works,

really, scientifically,
it was like a...

a new inspiration to my life,

so I would say I fell in love with
this field.

Textbook biology says
the colour of green plants

comes from chlorophyll molecules.

Inside the living cells,
they absorb light from the Sun.

This energy is then transferred
incredibly quickly

to the food-making factory
at the heart of the cell.

The entire event takes

just a millionth of a millionth
of a second.

When the photon hits the cell,

it knocks an electron out of the
middle of a chlorophyll molecule.

This creates a tiny packet
of energy called an exciton.

The exciton then bounces its way

through a forest of
chlorophyll molecules

until it reaches what is
called the reaction centre.

Now, that is where its energy is
used to drive chemical processes

that create the all-important
biomolecules of life.

The problem is, the exciton needs to
find its way to the reaction centre

in the first place.

Textbook biology can't explain
how the exciton does this.

Because, of course, it doesn't
know where it's going.

It just bounces around
like a pinball

in a process called a random walk.

Sooner or later,

it will pass through every
single part of the cell.

But this isn't the most
efficient way to get around.

Because when the exciton eventually
does reach the reaction centre...

..it's by pure chance.

If the exciton just blindly
and randomly

hops between the chlorophyll
molecules,

it would take too long to reach
the reaction centre

and would have lost
its energy as waste heat.

But it doesn't. Something very
different must be going on.

The vital clue comes from recent
experiments

that stunned the world of science.

Chemists fired lasers at plant cells

to simulate the capture of light
from the Sun.

They confirmed the exciton wasn't
bouncing along a haphazard route

through the cell.

This original understanding
didn't explain what

we were observing in the lab.

So the mystery lies in, OK,

so then, what is the explanation
for what we are observing in the lab?

The solution is that plants
obey the most famous law

in all of quantum mechanics...

..the uncertainty principle.

It says it you can never be certain

that the exciton is
in one specific place.

Instead, it behaves like
a quantum wave,

smearing itself out across the cell.

The exciton doesn't simply
move from A to B.

In a bizarre but very real sense,

it's heading in every direction
at the same time.

It's spreading itself out as a wave

so that it can explore all possible
routes simultaneously.

This strikes at the very heart

of what's so strange about
quantum mechanics.

The exciton wave isn't just
going this way or that way,

it's following all paths
at the same time.

That's what gives it such
incredible efficiency.

The beauty of it is...

..if the exciton is trying
every route

to the reaction centre at once...

..it's bound to find the fastest
possible way to deliver its energy.

It's hard to express how
incredible this discovery seems

to physicists like me.

Biological cells are full
of the random jiggling

of billions of atoms and molecules.

But somehow, excitons
maintain their form

as beautiful, perfect quantum waves,

transporting the energy that
guarantees life on Earth.

It opened a whole new
scientific path for me.

And I really enjoy the fact that

to be able to understand fully what
is happening there or in the plants,

you have to interact with scientists

that have completely
different approaches,

like biologists and chemists.

But we all have to come together

to actually understand what
is the relevant of this,

the relevance of this.

So, for me, this is one of the most
exciting parts of this field.

Real scientific experiments
leave no doubt.

The strange hand of
quantum mechanics has shaped

the entire living world.

It's not a surprise that you should
find quantum tricks being used

in biological systems.

The reason is,
because they're better.

Quantum entanglement
is normally seen

in the tightly-controlled
conditions of the physics lab.

But now, we know that robins use it

to navigate with
extraordinary precision.

Quantum vibrations mean our noses
LISTEN to chemicals...

..enhancing our perception
of the world around us.

The living cells of all animals
depend on protons

that vanish and reappear
like ghosts...

..speeding up
the vital processes of life.

And photosynthesis reveals
the big picture.

A shimmering world

where quantum waves capture
the Sun's energy in an instant.

Sometimes, people say,
"Ah, but physicists have been

"looking for this for decades."

Well, biology has
had millions of years.

The ultramodern science
of quantum mechanics

is an ancient fact of life.

For the end of my journey,

I want to take these ideas
to their logical conclusion.

Of course, as a scientist,

any speculations I have have to be
backed up by careful experiments.

So I want to concoct a thought
experiment that helps me

to answer the biggest biological
question I can think of.

Does quantum physics play any role

in the mechanism of
evolution itself?

In 1859, Charles Darwin
stunned the world

with his Theory Of Evolution
By Natural Selection.

He went on to explain
the differences

between humans and other apes.

150 years later, there's
no doubt that Darwin's theory

accounts for every living organism

on land and sea.

But I'd like to explore the latest,

extraordinary
interpretation of his ideas.

STIRRING STRINGS

Could there be a quantum theory
of evolution?

MUSIC: Adagio of Spartacus and
Phrygia from Spartacus Suite No.2
by Aram Khachaturian

Can quantum evolution explain
how the snail got its shell?

The snails I'm used to seeing
in my back garden

tend to have
rather bland, boring shells.

So have a look at this beauty.

The patterns on its shell
very perfectly match

the lines on the stem.

It's called a banded snail.
Cepaea nemoralis.

And the pattern isn't
there by accident.

Come and have a look at this.

Less well adapted snails

are more likely to be found here.

This stone is called
a thrush's anvil.

The song thrush is
the snail's main predator.

It catches the snail

and smashes its shell against
the stone to get to the snail.

Now, what I can see here

is that there aren't many
banded snail shells,

suggesting that its colours
camouflage it very well,

hiding it from the bird.

Darwin's theory says

that evolution depends
on variation within a species.

Snails with camouflage are more
likely to survive and reproduce...

..passing on their shells
to the next generation

so that the species as a whole
becomes better adapted.

So, variation - the random
differences between snails -

is the driving force
behind their evolution.

Now, all species evolve and adapt
to their environment.

But the question
I'd like to explore is

whether quantum mechanics
plays a role in this.

The only way to find out

is by scientific experiments.

So, my adventures in quantum biology
finally bring me home...

..to the University of Surrey.

Here, in the laboratories,

I'm planning a new analysis of the
most celebrated molecule in science.

Deoxyribonucleic acid, or DNA.

Its double helix holds the genetic
code for every living organism.

It's a remarkable fact that Darwin
himself had no idea

what created variation
in the species.

The structure of DNA wasn't
discovered until 1953

by Francis Crick and James Watson.

The most famous feature of DNA
is of course

its beautiful double helix
structure.

But that's just scaffolding.

The real genetic secret
lies in between.

The four different-coloured
molecules are called bases.

The colour code on one side -
say blue, red, blue -

forms a gene that parents
pass on to their offspring.

A gene is a bit like a jigsaw
puzzle.

It fits together like this.

A full strand of the double helix
forms a coloured pattern.

But the other strand always
pairs up the same way.

A blue base always goes with yellow

and green always goes with red...

..because only those colours have
the right shape to fit together.

What Crick and Watson realised
was that this provides

a mechanism for passing
on the genetic code.

When cells reproduce,
the two strands of DNA separate,

ready to be copied.

But red still goes with green...

..and yellow still goes with blue.

So bit by bit,

the cell creates two new strands.

Two perfect copies of the entire
genetic code.

So far, there's
no genetic variation.

This new copy is
identical to the original.

But here's the interesting bit.

During the copying process,
something very important can happen.

Sometimes, mistakes creep in.

They're called mutations.

Let's have a look at
these two bases here.

The two prongs that hold them
together are subatomic particles.

They're protons.

They're basically the bonds
between the strands of DNA.

These protons can jump across
to the other side.

If the strands split
when the protons have jumped across,

they find themselves
in the wrong position.

Now, this red base will no longer
bind to a green base.

Instead,
it has to bond to a yellow base.

Slotting this back in,

we see that now this copy is no
longer identical to the original

because I have a yellow base here
instead of a green one.

We've brought in a genetic mutation.

Jumping protons would change
the snail's DNA.

It could make a new gene
for camouflaged shells.

The question is,
how do protons jump?

It's my belief that quantum's
spookiness can take over.

Now, for these mutations
to take place,

the protons have to overcome
an energy barrier.

And if you remember
what happened with enzymes,

well, you can probably
guess what's coming next.

Protons can behave
as if barriers don't exist.

They tunnel straight through.

But does this ghostly effect
really happen?

My colleagues in biology
are already looking

for the very first evidence
of quantum mutations.

Biologists didn't really even
know about quantum mechanics,

so when you tell them that particles
can be in two places at once,

they kind of say,
"Well, not in my cells, they can't!"

Our experiment
involves samples of bacteria.

The first sample is
prepared in normal water,

containing hydrogen nuclei,
or protons.

When the bacteria reproduce,
we simply count the mutations.

But if our theory is correct,

then we should be able to change
the rate at which mutations occur.

Remember how we tested
the quantum theory of smell?

What if I replaced the proton
with its big brother, the deuteron?

This is the nucleus
of an atom of deuterium.

Now, crucially, a deuteron is
twice as heavy as a proton

and this should influence
how easy it is for

the deuteron to quantum tunnel.

Quantum mechanics is
full of surprises.

Protons tunnel easily.

Deuterons...don't.

These heavier particles are much
more likely to bounce straight back.

So the second sample of bacteria is
prepared in heavy water,

which is full of deuterons.

Our theory says you should get
far fewer mutations.

And, so far, the results
are extremely encouraging.

The preliminary experiments that
we've done gives us a hint

that the mutation rate is indeed
depressed in deuterated water.

We find that it is lower.
So my hunch is that we're right,

but we'll have to wait a little
while before we're sure.

Final proof lies in the future.

Even if we're right,

quantum tunnelling is a rare
form of mutation.

But our results promise
hard evidence

for a new explanation of one of the
most fundamental processes of life.

Even the merest possibility
of a new quantum mechanism

for evolution itself is
tremendously exciting.

In fact, the story of quantum
biology is only just beginning.

What the frog, the robin, the fruit
fly and the tree have shown us

is that real quantum effects
are going on in nature all the time.

And if there's anything
we've learnt

from the history of
quantum mechanics, it's this -

we can never be certain where
new discoveries will take us next.

Quantum biology is
a revolution in science.

But it's time I got back to
the physics department.