These are the waters off Catalina, a tiny island
20 miles off the coast of Los Angeles, California.
These are kelp forests, and they grow here in tremendous abundance
because the waters here around Catalina are rich in nutrients.
That's because of the California currents,
which brings this beautiful, rich, cold water
up from the depths of the Pacific
and allows this tremendously rich ecosystem to grow.
This...remarkable place.
Oh, look!
But I'm not here to marvel at these kelp forests.
Beautiful as they are.
I'm here to search for a little animal that lives not in this
forest of nutrients, but out there in the muddy ocean floor.
There he is, look!
HE LAUGHS
Can you see that?!
Camouflaged in its burrow on the sea floor,
the mantis shrimp is a seemingly unremarkable creature.
It's not a real shrimp, but a type of crustacean,
called a stomatapod.
I've come to see it because in one way
the mantis shrimp is truly extraordinary -
the way it detects the world.
You see these big...
eyes that they have to see.
These are some of the most sophisticated eyes
in the natural world.
Each is made up of over 10,000 hexagonal lenses.
And with twice as many visual pigments as any other animal,
it can see colours and wavelengths of light that are invisible to me.
These remarkable eyes
give the mantis shrimp a unique view of the ocean.
And this is just one of the many finely-tuned senses
that have evolved across the planet.
Sensing, the ability to detect and to react to the world outside,
is fundamental to life.
Every living thing is able to respond to its environment.
In this film, I want to show you how the senses developed,
how the mechanisms that gather information
about the outside world evolved,
how their emergence has helped animals
thrive in different environments,
and how the senses have pushed life in new directions,
and may ultimately have led to our own curiosity
and intelligence.
ACOUSTIC GUITAR
# If you feel lost
# Lost in the world
# Just like me
# Worlds are lost in me
# Worlds are lost in me. #
These are the woods of Kentucky,
the first stop on a journey across America
that will take me from the far west coast to the Atlantic,
through the heart of the country.
It's the animals that I'll find on the way
that will illuminate the world of the senses,
and I'm going to start by going deep underground.
These are the Mammoth Caves in Kentucky.
With over 300 miles of mapped passages,
they're the longest cave system in the world.
But this is also the place to start exploring our own senses.
We're normally dependent on our sight,
but down here in the darkness, it's a very different world.
I have to rely on my other senses to build a picture of my environment.
It's...completely dark in this cave.
I can't see anything at all.
You can see me because we're lighting it with infrared light.
That's at a wavelength that my eyes are completely insensitive to,
so as far as I'm concerned, it is pitch black.
And because it's so dark...
..your other senses become heightened, particularly hearing.
It's virtually silent in here.
But if you listen carefully...
DRIP OF WATER
..you can just hear the faint drop of water from somewhere
deep in the cave system.
You'd never hear that if the cave were illuminated.
But you focus on your hearing when it's as dark as this.
As well as sight and hearing,
we have of course a range of other senses.
There's touch, which is a mixture of sensations -
temperature and pressure and pain -
and then there are chemical senses,
so smell and taste,
and we share those senses with almost every living thing
on the planet today,
because they date back virtually to the beginning of life on Earth.
And even here, in water that's been collected from deep within a cave,
there are organisms that are detecting and responding
to their environment
in the same way that living things have been doing
for over a billion years.
Ah.
And there it is.
Now that is a paramecium.
It may look like a simple animal, but in fact
it's a member of a group of organisms called protists.
You'd have to go back around two billion years
to find a common ancestor between me and a paramecium.
Paramecia have probably changed little in the last billion years.
Although they appear simple,
these tiny creatures display some remarkably complex behaviour.
You can even see them responding to their environment.
The cell swims around, powered by a cohort of cilia,
tiny hairs embedded in the cell membrane.
If it bumps into something, the cilia change direction
and it reverses away.
They're clearly demonstrating a sense of touch.
Even though they're single-celled organisms,
they have no central nervous system,
they can still do what all life does.
They can sense their environment and they can react to it,
and they do that using electricity.
The mechanism that powers the paramecium's touch response
lies at the heart of all sensing animals.
It's based on an electrical phenomenon found throughout nature.
An electric current is a flow of electric charge,
and for that to happen, you need an imbalance between
positive and negative charges.
Now, usually in nature, things are electrically neutral,
the positive and negative charges exactly balance out,
but there are natural phenomena in which there is a separation
of electric charge. A thunderstorm, for example.
As thunder clouds build,
updraughts within them separate charge.
The lighter ice and water crystals become positively charged
and are carried upwards,
while the heavier, negatively charged crystals sink to the bottom.
This can create a potential difference,
a voltage between the cloud and the ground
of as much as 100 million volts.
Now, nature abhors a gradient. It doesn't like an imbalance,
and it tries to correct it by having an electric current flow.
In the case of a thunderstorm, that's a bolt of lightning.
And it's the same process that governs the paramecium's behaviour,
but on a tiny scale.
In common with virtually all other cells,
and certainly all animal cells,
the paramecium maintains a potential difference
across its cell membrane.
It does that in common with a thunderstorm by charge separation.
By manipulating the number of position ions
inside and outside its membrane, the paramecium creates
a potential difference of just 40 millivolts.
So when a paramecium is just sat there, not bumping into anything,
floating in this liquid, then it's like a little battery.
It's maintaining the potential difference across its cell membrane,
and it can use that to sense its surroundings.
When it bumps into something, its cell membrane deforms,
opening channels that allow positive ions to flood back
across the membranes.
As the potential difference falls,
it sets off an electrical pulse that triggers
the cilia to start beating in the opposite direction.
That electrical pulse spreads round the whole cell in a wave
called an action potential.
And the paramecium reverses out of trouble.
This ability to precisely control flows of electric charge
across a membrane is not unique to the paramecium.
It actually lies at the heart of all animal senses.
In fact, every time I sense anything in the world,
with my eyes, with my ears, with my fingers,
at some point between that sensation and my brain,
something very similar to that will happen.
Although the same electrical mechanism underpins all sensing,
every animal has a different suite of sensory capabilities
that is beautifully adapted to the environment it lives in.
This is the Big Black River,
a tributary of the mighty Mississippi in America's deep south.
And these dark and murky waters are home to a ferocious predator.
Even though it's impossible to see more than a couple of inches
through the water,
this predator has found a way to track down and catch its prey
with terrifying efficiency.
To help me catch one,
I've enlisted the support of wildlife biologist Don Jackson.
You go... Wrestle it. I'll wrestle it now.
He's going over right here. Is he?
There you go.
He can bite. Argh!
I'll show you the mouth of this thing.
Hang on... So you can see what the prey sees when he comes.
Anything that'll fit in that mouth, he'll grab it!
You can hold him if you just want to put your hand all the way under him.
Come all the way. All the way. Hold him up close to you. Yeah.
How about that? I've got him. Yeah.
This is the top predator in this river.
This is a, what? A 25-pound flathead catfish.
You see those protrusions from his head?
Those are barbels.
They sense a vibration in the mud, on the river bed,
but the most interesting thing about the catfish
is that she really is, in some ways, one big tongue.
There are taste sensors covering every part of her body,
and she can build up a 3D picture of the river
by detecting the chemical scents of animals.
So, her eyes are not much use.
As you can see, this river's extremely muddy,
but it's the sense of taste that does the job of
building up a picture of the world,
and that's how he hunts, and he weighs a ton.
I can feel those teeth. Ow!
I'm going to let go.
All right, you. Go on.
The sensory world of the catfish is a remarkable one.
Its map of its universe is built from the thousands of chemicals
it can detect in the water.
A swirling mix of tastes and concentrations,
flavours and gradients.
It's a world we can hardly imagine.
There's an interesting almost philosophical point here
because it's easy to imagine that we humans perceive the world
in some kind of objective way, but that's not the case at all.
Think about the catfish.
The catfish sees the world as a kind of swarm of chemicals
in the river, or vibrations on the river bed,
whereas we see the world as reflected light off the forest,
and I can hear the sounds of animals out there
somewhere in the undergrowth.
The catfish sees the world completely differently.
So the way you perceive the world is determined by
your environment,
and no two animals see the world in the same way.
Like every animal, we have evolved the senses that enable us to live
in our environment.
But as well as equipping us for the present,
those senses can also tell us about our past.
Now we have a sense of touch like the paramecium,
and we have the chemical senses, taste and smell,
like the catfish, but for us, the dominant senses
are hearing and sight,
and to understand them,
we first have to understand their evolutionary history.
And that's why I'm in the Mojave Desert in California,
to track down an animal that can tell us something
about the origins of our own senses.
The creature I'm looking for is easiest to find in the dark,
using ultra-violet light.
Oh!
HE LAUGHS
Whoa!
Man! Did you see that?
Look at that. Absolutely bizarre.
It's glowing absolutely bright green.
Nobody has any idea what evolutionary advantage
that confers.
Although they now live in some of the driest,
most hostile environments on Earth,
like here in the desert, scorpions evolved as aquatic predators
before emerging onto the land about 380 million years ago.
They've adapted to be able to survive the extreme heat,
and can go for over a year without food or water.
Despite their fearsome reputation,
98% of scorpion species have a sting that is no worse than a bee's.
Perhaps the most fascinating thing about scorpions
from an evolutionary perspective
is the way that they catch their prey.
You see that he spreads his legs out on the surface of the sand.
And that's because he uses his legs to detect vibrations.
Scorpions hunt insects like this beetle.
It's almost impossible to see them in the dark,
so the scorpion has evolved another way to track them down,
by adapting its sense of touch.
As the insect's feet move across the sand,
they set off tiny waves of vibration through the ground.
If just a single grain of sand is disturbed
within range of the scorpion,
it will sense it through the tips of its legs.
They can detect vibrations that are around the size of a single atom
as they sweep past.
By measuring the time delay,
between the waves arriving at each of its feet,
the scorpion can calculate the precise direction
and distance to its prey.
And that ability to detect vibrations and use them
to build up a picture of our surroundings
is something that we share with scorpions.
While the scorpion has adapted its sense of touch
to detect vibrations in the ground,
we use a very similar system to detect the tiny vibrations in air
that we call sound.
And like the scorpions, ours is a remarkably sensitive system.
Our ears can hear sounds over a huge range.
We can detect sound waves of very low frequency
at the bass end of the spectrum.
But we can also hear much higher-pitched sounds,
sounds with frequencies hundreds or even a thousand times greater.
And we can detect huge changes in sound intensity...
..from the delicate buzzing created by an insect's flapping wings...
..to the roar of an engine, which can be 100 million times louder.
The story of how we developed our ability to hear
is one of the great examples of evolution in action...
..because the first animals to crawl out of the water onto the land
would have had great difficulty hearing anything
in their new environment.
These are the Everglades.
A vast area of swamps and wetlands that has covered the southern tip
of Florida for over 4,000 years.
Through the creatures we find here,
like the American alligator, a member of the crocodile family,
we can trace the story of how our hearing developed
as we emerged onto the land.
And it starts below the water, with the fish.
If you're a fish, then hearing isn't a problem.
You live in water and you're made of water,
so sound has no problem at all travelling from the outside
to the inside,
but when life emerged from the oceans onto the land,
then hearing became a big problem.
See, sound doesn't travel well from air into water.
If I make a noise now...
..over 99.9% of the sound
is reflected back off the surface of the water.
It's because of that reflection that underwater
you can hear very little from above the surface.
And it's exactly the same problem our ears face,
because they too are filled with fluid.
So, if evolution hadn't found an ingenious solution to the problem
of getting sound from air into water,
then I wouldn't be able to hear anything at all.
And that solution relies on some of the most delicate moving parts
in the human body.
Have I just dropped them? Hang on a second.
Oh, I've done it again! Bloody hell! Idiot!
Just flipped out!
These are the smallest three bones in the human body,
called the malleus, the incus and the stapes,
and they sit between the eardrum and the entrance to your inner ear,
to the place where the fluid sits.
The bones help to channel sound into the ear through two mechanisms.
First, they act as a series of levers,
magnifying the movement of the eardrum.
And second, because the surface area of the eardrum is 17 times
greater than the footprint of the stapes,
the vibrations are passed into the inner ear
with much greater force.
And that has a dramatic effect.
Rather than 99.9% of the sound energy being reflected away,
it turns out that with this arrangement,
60% of the sound energy is passed from the eardrum into the inner ear.
Now, this setup is so intricate and so efficient,
it almost looks as if those bones could only ever
have been for this purpose,
but in fact, you can see their origin if you look
way back in our evolutionary history.
In order to understand where that collection of small bones
in our ears came from,
you have to go back in our evolutionary family tree
way beyond the fish that we see today.
In fact, back around 530 million years
to when the oceans were populated with jawless fish, called agnathans.
They're similar to the modern lamprey.
Now, they didn't have a jaw,
but they had gills supported by gill arches.
Now, over a period of 50 million years, the most forward of those
gill arches migrated forward in the head to form jaws.
And you see fish like these,
the first jawed fish in the fossil record,
around 460 million years ago.
And, there, at the back of the jaw, there is that bone,
the hyomandibular, supporting the rear of the jaw.
Then, around 400 million years ago, the first vertebrates
made the journey from the sea to the land.
Their fins became legs,
but in their skull and throat, other changes were happening.
The gills were no longer needed
to breathe the oxygen in the atmosphere,
and so they faded away
and became different structures in the head and throat,
and that bone, the hyomandibular, became smaller and smaller,
until its function changed.
It now was responsible for picking up vibrations in the jaw
and transmitting them to the inner ear of the reptiles.
And that is still true today of our friends over there...
the crocodiles.
Once more with alligator.
But even then, the process continued.
Around 210 million years ago, the first mammals evolved,
and unlike our friends, the reptiles here,
mammals have a jaw that's made of only one bone.
A reptile's jaw is made of several bones fused together,
so that freed up two bones,
which moved,
and shrank,
and eventually became the malleus,
the incus and stapes.
So this is the origin of those three tiny bones
that are so important to mammalian hearing.
He's quite big, isn't he?
I think this is a most wonderful example of the blind,
undirected ingenuity of evolution,
that it's taken the bones in gills of fish
and converted them into the intricate structures inside my ears
that efficiently allow sound to be transmitted from air into fluid.
It's a remarkable thought
that to fully understand the form and function of my ears,
you have to understand my distant evolutionary past
in the oceans of ancient earth.
We're hunting for the mantis shrimp.
'All sensing has evolved to fulfil one simple function - to provide us
'with the specific information we need to survive.'
There he is!
I might try and grab him.
'And nowhere is that clearer than in the sense of vision.'
He's quite tricky to catch!
'Almost all animals can see.'
'96% of animal species have eyes.'
'But what those eyes can see varies enormously.'
'So with an animal like the mantis shrimp, you have to ask what it is
'about its way of life that demands such a complex visual system.'
Got to be very quick and very careful with this.
Let him out.
The complex structure of the mantis shrimp's eyes
give it incredibly precise depth perception.
We have binocular vision.
We look with two eyes from slightly different angles,
and judge distance by comparing the differences between the two images.
Each of the mantis shrimp's eyes has trinocular vision.
Each eye takes three separate images of the same object.
Comparing all three gives them exceptionally precise range-finding,
and they need that information to hunt their prey.
Despite appearances,
it is a dangerous animal. He has one of the hardest punches in nature.
Those yellow appendages you can see on the front of his body
are called raptoral appendages.
They're actually highly evolved from legs,
and they can punch with tremendous force.
The mantis shrimp's punch
is one of the fastest movements in the animal world.
Slowed down by over a thousand times, we can clearly see its power.
It can release its legs with the force of a bullet.
In the wild,
they use that punch to break through the shells of their prey.
But it could easily break my finger.
The need to precisely deploy this formidable weapon
is one of the reasons the mantis shrimp has developed
its complex range-finding ability.
And that punch can also help explain their sophisticated colour vision.
Because the coloured flashes on their body warn other mantis shrimp
that they may be about to attack.
While other colour signals have a quite different meaning.
Yet reading these signals in the ocean can be surprisingly difficult.
In the deep ocean, colours shift from minute to minute,
from hour to hour, with changing lighting conditions,
changing conditions in the ocean,
but it's thought that
even though the light quality can change tremendously,
the mantis shrimp can still identify specific colours very accurately,
because of those sophisticated eyes.
The mantis shrimp's eyes are beautifully tuned to their needs.
But they're very different from our eyes.
With their thousands of lenses and their complex colour vision,
they have a completely different way of viewing the world.
And yet there's strong evidence that the mantis shrimp's eyes
and ours share a common origin.
Because on a molecular level,
every eye in the world works in the same way.
In order to form an image of the world,
then obviously the first thing you have to do is detect light,
and I have a sample here of the molecules that do that,
that detect light in my eye.
It's actually, specifically, the molecules that's in the black
and white receptor cells in my eyes, the rods.
It's called rhodopsin.
And the moment I expose this to light,
you'll see an immediate physical change.
There you go.
Did you see that? It was very quick.
It came out very pink indeed, and it immediately went yellow.
This subtle shift in colour is caused by the rhodopsin molecule
changing shape as it absorbs the light.
In my eyes, what happens is
that change in structure triggers an electrical signal
which ultimately goes all the way to my brain,
which forms an image of the world.
It is this chemical reaction
that's responsible for all vision on the planet.
Closely related molecules lie at the heart of every animal eye.
That tells us that this must be a very ancient mechanism.
To find its origins, we must find a common ancestor
that links every organism that uses rhodopsin today.
We know that common ancestor must have lived
before all animals' evolutionary lines diverged.
But it may have lived at any time before then.
So what is that common ancestor?
Well, here's where we approach the cutting edge of scientific research.
The answer is that we don't know for sure,
but a clue might be found here,
in these little green blobs,
which are actually colonies of algae, algae called volvox.
We have very little in common with algae.
We've been separated in evolutionary terms for over one billion years.
But we do share one surprising similarity.
These volvox have light-sensitive cells that control their movement.
And the active ingredient of those cells
is a form of rhodopsin so similar to our own
that it's thought they may share a common origin.
What does that mean?
Does it mean that we share a common ancestor with the algae,
and in that common ancestor, the seeds of vision can be found?
To find a source that may have passed this ability to detect light
to both us and the algae,
we need to go much further back down the evolutionary tree.
To organisms like cyanobacteria.
They were among the first living things to evolve on the planet,
and it's thought that the original rhodopsins may have developed
in these ancient photosynthetic cells.
So the origin of my ability to see
may have been well over a billion years ago,
in an organism as seemingly simple as a cyanobacteria.
The basic chemistry of vision
may have been established for a long time,
but it's a long way from that chemical reaction
to a fully functioning eye that can create an image of the world.
The eye is a tremendously complex piece of machinery,
built from lots of interdependent parts,
and it seems very difficult to imagine how that could have evolved
in a series of small steps, but actually,
we understand that process very well indeed.
I can show you, by building an eye.
The first step in building an eye
would need to take some kind of light-sensitive pigment,
rhodopsin, for example, and build it on to a membrane.
So imagine this is such a membrane, with the pigment cells attached,
then immediately you have something that can detect
the difference between dark and light.
Now, the advantage of this arrangement
is that it's very sensitive to light.
There's no paraphernalia in front of the retina to block light,
but the disadvantage, as you can see,
is that there is no image formed at all.
It just allows you to tell the difference between light and dark.
But you can improve that a lot by adding an aperture,
a small hole in front of the retina, so this is a movable aperture,
just like the sort of thing you've got in your camera,
And now, we see that the image gets sharper.
But the problem is that in order to make it sharper,
we have to narrow down the aperture,
and that means that you get less and less light,
so this eye becomes less and less sensitive.
So there's one more improvement that nature made,
which is to replace the pinhole, the simple aperture...
With a lens.
Look at that.
A beautifully sharp image.
The lens is the crowning glory of the evolution of the eye.
By bending light onto the retina, it allows the aperture to be opened,
letting more light into the eye, and a bright, detailed image is formed.
Our eyes are called camera eyes, because, like a camera,
they consist of a single lens
that bends the light onto the photoreceptor
to create a high-quality image of the world.
But that has a potential drawback,
because to make sense of all that information,
we need to be able to process it.
Each one of my eyes contains
over 100 million individual photoreceptor cells.
That's about five or ten times the number
in the average digital camera.
So if my visual system works
by just taking a series of individual still images of the world
and transmitting all that information to my brain,
then my brain would be overwhelmed.
It's just not practical, so that's NOT what animals do.
Instead, their visual systems have evolved
to extract only the information that is necessary.
And this is wonderfully illustrated in the toad.
The toad has eyes that are structurally very similar to ours.
But much of the time, it's as if it isn't seeing anything at all.
It seems completely oblivious to its surroundings.
Until something, like a mealworm, takes its interest.
If you think about what's important to a toad visually,
then it's the approach of either pray or predators,
so the toad's visual system is optimised to detect them,
So, there, we've put a worm in front of the toad, and did you see that?
Incredibly quickly, the toad ate the worm.
As soon as the mealworm wriggles in front of the toad,
its eyes lock onto the target.
Then it strikes in a fraction of a second.
It's an astonishingly precise reaction,
but it's also a very simple one.
Because the toad is only focusing on one property of the mealworm -
the way it moves.
These 1970s lab tests
show how a toad will try and eat anything long and thin.
But only if it moves on its side, like a worm.
And that's because the toad has neural circuits in its retina
that only respond to lengthwise motion.
If, instead, the target is rotated into an upright position,
the toad doesn't respond at all.
At first sight, the visual system of the toad
seems a little bit primitive and imperfect.
It is true that if you put a toad in a tank full of dead worms,
it'll starve to death, because they're not moving,
so it doesn't recognise them as food.
But it doesn't need to see the world in all the detail that I see it.
What it needs to focus on is movement,
because if it can see movement then it can survive,
because it can avoid predators, and it can eat its prey.
I suppose, in a sense, if it moves like a worm, in nature,
then it's likely to be a worm.
This ability to simplify the visual world
into the most relevant bits of information
is something that every animal does.
We do it all the time.
We also have visual systems that detect motion.
Others identify edges and faces.
But extracting more information takes more processing power.
That requires a bigger brain.
And to see the results of this evolutionary drive
towards greater processing power,
I've come to the heart of Metropolitan Florida.
You know, it may not look like it, but underneath this flyover,
just out in the shallow water,
is one of the best places in the world
to find a particularly interesting animal.
It's an animal that's evolved
to make the most of the information its eyes can provide.
Well, what we're going to do is find some octopus.
And it's, as you say in physics, nontrivial.
Because they've developed a beautiful way
of camouflaging themselves.
They change colour. Their cells and their skin change colour
to match their surroundings.
It's an ability that we don't possess, of course.
It makes them difficult to find.
There he is, look.
Ha-ha!
He went flying into there,
and a crab and a load of fish are flying out, and look at his ink.
A defence mechanism. I don't know where he is.
He's hiding somewhere in there.
Look at those colours!
What a remarkable creature.
'Although the octopus is a mollusc, like slugs and snails,
'in many ways, it seems more similar to us.'
Whoa!
'It's believed to be the most intelligent invertebrate.'
It's like he's holding his fists up.
Look at that.
'Its brain contains about 500 million nerve cells,
'about the same as a dog's.'
What are you doing?
You know, if you want an example of an alien intelligence
here on earth..
that must surely be it.
'And it's used that brain to develop some remarkable abilities.'
'It's become a skilled mimic.'
'It can rapidly change not only its colour,
'but its shape, to match the background.'
'Some species even do impressions of other animals.'
'They become cunning predators, and adept problem-solvers.'
'They've even been reported to use tools.'
'All these skills are signs of great intelligence,
'but they also rely on an acute sense of vision.'
Look at those big eyes surveying the surroundings.
Checking us out.
Camera eyes, just like mine, and they're vitally important
for allowing the octopus to live the lifestyle it does,
so a visual animal in the same way that I'm a visual animal.
'The octopus is one of the only invertebrates
'to have complex camera eyes.'
'Like our eyes, they capture detailed images of the world.'
'And their brains have evolved
'to be able to extract the most information from those images.'
'The optic lobes make up about 30% of the octopus' brain.'
'The only other group
'that is known to devote so much of its brain to visual processing
'is our group.
'The primates - the most intelligent vertebrates.'
I think it's a fascinating thought
that that intelligence is a result
of the need to process all the information
from those big, complex eyes.
'What's so compelling about the octopus' intelligence
'is that it evolved completely separately to ours.'
'We last shared a common ancestor 600 million years ago.'
'An ancestor that had neither eyes nor a brain.'
'But we've both evolved sophisticated camera eyes,
'and large, intelligent brains.'
'It suggests a tantalising link between sensory processing
'and the evolution of intelligence.'
Sensing has played a key role in the evolution of life on Earth.
The first organisms
were able to detect and respond to their immediate environment,
as paramecia do today.
But as animals evolved, and their environments became more complex,
their senses evolved with them.
Developing the mechanisms to let them decode vibrations
and detect light.
Allowing them to build three-dimensional pictures
of their environments,
and stimulating the growth of brains that could handle all that data.
But for one species,
the desire to gather more and more sensory information
has become overwhelming.
That species is us.
This is the closest thing to hallowed ground that exists
in a subject that has no saints,
because that telescope is the one that Edwin Hubble used
to expand our horizons, I would argue,
more than anyone else before or since.
In 1923, Edwin Hubble took this photograph of the Andromeda galaxy.
You can see his handwriting on the photograph.
He did it by sitting here night after night for over a week,
exposing this photographic plate.
Now, at the time,
it was thought that this misty patch you see in the night sky
was just a cloud, maybe a gas cloud in our own galaxy,
but Hubble, because of the power of this telescope,
identified individual stars, and crucially,
he found that it was way outside our own galaxy.
In other words,
Hubble had discovered this is a distant island of stars.
We now know it's over two million light years away,
composed of a trillion suns like ours.
Hubble demonstrated that there's more to the universe
than our own galaxy.
He extended the reach of our senses further than we could have imagined.
With the help of the telescope,
we could perceive and comprehend worlds billions of light years away.
There's a wonderful feedback at work here,
because the increasing amounts of data delivered by our senses
drove the evolution of our brains,
and those increasingly sophisticated brains became curious
and demanded more and more data.
And so we built telescopes
that were able to extend our senses beyond the horizon
and showed us a universe that's billions of years old
and contains trillions of stars and galaxies.
Our insatiable quest for information is the making of us.
Subtitles by Red Bee Media