Original subtitles

Let's face it, our world is downright weird...

- Oh! - LAUGHTER

..crawling with creatures you've never heard of...

I can't believe that is a living thing.

..full of the unexpected.

Like freak weather exploding out of the blue...

I thought I was going to die.

..and rocks that spontaneously combust.

I thought it was dynamite going off.

And the unexplained.

An unborn twin...

discovered inside a brain!

There was multiple hair follicles, bone and teeth.

We've scoured the globe to bring you the very weirdest stories.

MAN SHOUTS

LAUGHTER

I could feel this intense pain,

as if you were being stabbed by hundreds of syringes.

In this series, we are going to examine the evidence,

test the science and unravel the mysteries.

We are going to discover what in the weird world is going on.

In this episode, we'll uncover the secrets behind some

of the natural world's oddest occurrences.

Like what caused an Antarctic glacier

to flow blood red.

And why frogs in California started growing too many limbs.

What could possibly create this weird work of art

on an arm in Texas?

And how could a creature generate a force

so powerful it could knock down a fisherman in South America?

But first, we are going on a journey to the end of the world.

Antarctica...

..a remote, frozen wilderness.

And hidden away in this world of white

is a gaping wound in the ice.

This is Blood Falls.

A bizarre mystery that's intrigued scientists for more than a century.

And for one, it became a lifelong fascination.

The first time I saw Blood Falls was in a graduate glaciology class,

and I saw a picture of it and I got really excited

and intrigued as to what this feature was.

But Jill wasn't the first to be intrigued by Blood Falls.

This is not a new discovery.

Blood Falls, as it's known,

was first spotted by Griffith Taylor, an Australian geologist, in 1911.

And everyone thought that the incredible spectacle was down to

a phenomenon called watermelon snow.

Yes, watermelon snow is caused by algae which grow at low temperatures.

The algae produce a pigment that acts as a natural sunscreen.

And it's this pigment that gives the snow a pink appearance,

and a faint smell of watermelon.

Hence the name.

And it is a logical explanation, right? Case solved.

Well, actually, no, case not solved,

because it is a lot less to do with this, and a lot more to do with this.

But what could a rusty piece of iron have to do with a bleeding glacier?

When some chemists and glaciologists went to the site in the '60s

and '70s, they did a lot of chemical analysis on the material

and they determined that it was various iron oxides.

And this is basically rust.

So, iron oxides were found to be the cause of Blood Falls.

The water, oozing out from under the glacier, contains massive

concentrations of dissolved iron that turns the ice red.

But the big question for Jill was,

where is this huge amount of iron actually coming from?

Well, you see, some glaciers, when they are sliding downhill, grind up

the bedrock, releasing iron into the water.

But this one was hardly moving.

There's a little bit of iron there, but not enough to turn anything red.

So Jill suspected that something was going on under the glacier.

Determined to find answers, Jill and her team travelled to Antarctica's

Dry Valleys, one of the most remote

and inhospitable places on Earth.

It is a polar desert.

The first explorers walked in there, they called this the Valley of the Dead.

Feels what is must feel like to be on Mars.

I've never seen anything like it before.

But for Jill, it was the opportunity of a lifetime.

Chasing down your curiosity

and following it is...is a pretty exciting process.

In order to explore far beneath the glacier, Jill's team used a

huge antenna to measure electromagnetic forces below the ice.

This created a map of a hidden world.

What they found was more astonishing than anyone ever imagined.

A vast reservoir of salty water...

..stretching at least 5km beneath the glacier.

And it has remained untouched for at least one million years.

What they discovered was an environment that's as close

to out of this world that we're ever going to find.

Isolated for millions of years.

Frozen at minus five degrees,

deprived of oxygen, and totally dark.

Jill probed further for answers,

by taking samples from the core of the glacier.

After being intrigued her entire adult life, she was finally

in a position to solve the mystery of Blood Falls.

A world first discovery.

In a place seemingly devoid of life...

..Jill found life under the glacier.

Jill's work revealed a massive community of bacteria,

organisms that survive in a place that seems inconceivable.

Locked away in a time capsule for at least one million years.

But what does this incredible discovery have to do with

Blood Falls?

Well, without oxygen to breathe,

these ingenious life forms have evolved a way to live

off elements in the rock, extracting minerals,

like iron, to produce energy.

In the process, iron is dissolved into the water

and it is that that turns red as it exits the glacier.

So a century after Blood Falls was first discovered,

the mystery was finally solved.

And it might actually have ramifications for the next

century beyond our planet.

Because so far, Jill and her team have only scratched the surface.

If Blood Falls is just a small component of this much larger

subsurface ecosystem,

I was wondering what it might tell us about the potential

for life on other planets, for example under the ice caps of Mars.

Jill's discovery of bacteria under the glacier proves that life can

thrive in the most unexpected places.

And now we have a clue to what life under the ice caps of distant

planets could actually look like.

All thanks to Jill's determined curiosity to investigate

the mystery of Blood Falls.

Weird forms of life can survive in the most inhospitable

environments, and who knows,

they might even occur on planets at the other side of the galaxy.

But one thing I do know for sure is that even stranger things can

happen in familiar places.

So for the next story, we are going to travel to a much more familiar

environment.

A humble pond.

In 1999, a team of scientists in California began investigating

a strange phenomena.

Reports of what appeared to be mutant frogs

with extra limbs.

It became an environmental mystery of national significance.

'When we were first working on this topic and we were starting to

'examine malformed amphibians under microscopes,'

we were trying to figure out what might be causing the deformities.

Whether it was chemical pollutants,

whether it was UV radiation,

or even whether it was just an isolated phenomenon of inbreeding.

And what happens is, if you start to put these animals under

the microscope, what you begin to notice is that right around the

base of where the limbs are growing, you find these tiny white dots.

These spots were a clue, because they allowed scientists to uncover

a link between our sadly malformed frogs

and a snail.

Just a simple freshwater snail that

lives a pretty unremarkable life,

except for the vital role it was found to

play in the mystery of the malformed frogs.

If we were to open up this snail,

what you would find inside of it is a large population of parasites.

Somewhere in the order of a few hundred to several thousand

parasites live inside this snail.

They transform the snail into a parasite factory.

Where they clone themselves by the thousand.

Then, under the cover of darkness, swarms of parasitic larvae

emerge from the snail and swim around the pond.

Having left the snail, where they multiplied,

the parasites are on the hunt for a new abode.

The next stage of the adventure is about to begin.

Because they are on the lookout for tadpoles.

They will land on the tadpole's body, they will move all over

the body until they find the exact spot where they want to infect,

which is where the hind limbs are ultimately going to develop.

And they start producing these highly specialised, but very powerful, acids.

Those acids allow the parasite to burn its way inside, and once inside,

these crafty intruders cause the tadpole's legs

to malform as it grows.

As the tadpole is turning into a frog,

the spots where there should be just one leg either have none or too many.

It is a horrific form of manipulation.

And the reason why this puppeteering parasite perpetrates with such

precision this malformation is equally

as ingeniously callous.

These deformities are going to increase the probability that that

frog is unable to escape a bird when it comes down to search for prey.

The parasite is basically playing a waiting game.

And it is waiting for that frog to eventually be eaten by a bird.

So first the parasite turns the snail into a breeding chamber,

and then it deforms the frog's legs.

These cumbersome appendages make the frog unable to escape.

Easy pickings for a bird.

But why go to so much effort just to get eaten by a bird?

Well, the bird is vital for the parasite.

Because the bird's stomach acids help the parasites mature into adults.

This stomach is the place to be,

as all the parasites gather to find a mate.

Here they reproduce sexually and release eggs into the bird's faeces.

Now I know it might not sound like the most pleasant place to raise a

family, but for these parasites, the best way to start life

is in bird poo.

Once the birds defecate in those ponds,

the parasite eggs will hatch and infect more snails.

So let's get this straight.

The parasite goes from snail to frog to bird...

to bird faeces in the pond, and then back to the snail.

It sounds absolutely exhausting,

so why would it evolve such a long and complex life cycle?

This is a brilliant mode of dispersal,

because rather than being dependent on the movement of a snail,

which doesn't move that far, or the movement of a frog, which

might get a little bit farther but is still pretty limited,

the parasites are now being transported around by birds,

which can move miles, sometimes even hundreds or thousands of miles.

So this is an excellent way for the parasite to disperse rapidly

and pretty effortlessly across the landscape.

Let's just think about things from the parasite's point of view.

It wants to reproduce as much as possible,

to spread as widely as possible, using whatever means possible.

So it's bad news for the frog and it's bad news for the snail,

but it is great news for the parasite. Mystery solved.

It wasn't the UV radiation, it wasn't chemical pollutants, it wasn't

a malignant mutation in the frog,

it was a tiny little parasite

intent on world domination.

Don't tell me that nature is not a weirdly wonderful thing.

I'd say so.

And of course, we humans, well, we are

immune to such bizarre phenomena. Aren't we?

In the US state of Washington, when applying for benefits,

standard procedure requires DNA testing for proof of parentage.

But when one woman's family fell on hard times,

taking this routine test turned her life into a living hell.

You see, the test results stated she was not the mother

of her own children.

Getting the actual documents showing,

"Mother - 0.00%"

was just unbelievable to me.

With that evidence, they in fact can come and get my kids.

SHE SOBS

Every morning I felt like I was saying goodbye to them.

Lydia's nightmare began just a few weeks after taking the test.

I get a call from a prosecutor, who wants me to come

up to his office, concerning the DNA results.

Right away he started saying,

"Who are you, what is your real name,

"whose kids are these?"

And I said, "What are you talking about? These are my children.

"I've had them with my partner."

He goes, "Oh, well, we know he is the father,

"he came back 99.9% the father.

"But the DNA test came back that you are in no way

"possible the mother of these children."

So what was going on?

Was Lydia lying?

In my mind, I'm like, "OK, there must have been a mistake,

"let's do another test."

But the result was the same as the first DNA test.

I didn't know what was going on.

I didn't know why my DNA wasn't coming back as the mother.

It just wasn't making sense to me.

Lydia knew she was the mother,

but the test said she was lying.

And now, with no-one believing her story, her whole family was at risk.

Just imagine knowing that you are the mother

but a lab result says otherwise.

A result so powerful you could have your children taken away

and never see them again.

This nightmare became Lydia's reality.

When the prosecutor had threatened me that any day someone could

come and get my children from me, just solely on that DNA evidence alone,

going to work and dropping them off at daycare, I would pray with

my children and hug them as if it was going to be last time I was going to see them.

Yeah.

SHE SOBS

Facing charges of fraud and even kidnapping her own children,

getting to the bottom of this mystery was vital.

That just brought back memories, I'm sorry.

Lydia needed help.

When I first met with Lydia and started learning about the facts

of the case, I was very intrigued by it because it was certainly

unlike any other paternity case I had ever dealt with.

One of the things that had to be ruled out

is that there wasn't some sort of criminal thing going on.

If they're not related to her, then whose children are they?

But Lydia was about to give birth to her third child.

An opportunity for her lawyer to gather some evidence.

The court ordered someone be in that room when I give birth,

to take DNA directly from me and the baby right after birth.

That's what happened, someone was there, took DNA from me

and the child right away.

And when those tests came back, the baby came back as not mine.

Now Lydia had legal verification

that this new child was hers.

She could prove that she wasn't lying, and yet still

the DNA said otherwise.

There could only be one possible conclusion,

and that was that the DNA test was wrong.

And if this was the case,

it could have massive implications across the entire legal system.

DNA evidence is powerful evidence.

People have been sentenced to death in this country

because their DNA is at a crime scene

and other people have been released from death row

because their DNA isn't at a crime scene.

These tests aren't supposed to be inaccurate

and so it led not only to the questions of this woman's maternity,

but the larger question of whether or not these tests

could be trusted in any circumstance.

Her case was really testing the integrity of the DNA testing regime.

So there had to be some sort of scientific explanation

as to why her test did not match up.

With time running out,

Lydia's case was still baffling the experts.

But then, all of a sudden, something very similar cropped up

2,000 miles away in Boston.

You see, a lady there needed a kidney transplant,

but when they DNA tested her three sons,

they found no maternal compatibility -

a very similar thing to what was going on with Lydia.

So could this finally give her the answer she needed?

Her lawyer sent some samples to Harvard University,

hair, blood, a mouth swab and a cervical smear.

And it was this last sample that proved conclusive

with absolutely astonishing results.

You see Lydia was, in fact, a chimera.

Chimera is a word from Greek mythology,

describing a creature made of different animals.

Something that simply could not exist in the real world.

But for Lydia, her condition was very real indeed.

Unbeknown to Lydia, she started life in the womb as a twin,

but her sibling never fully developed and Lydia absorbed those cells.

So when she was born, Lydia was made up of two sets of genes

instead of the usual one.

And in her case, her ovaries

contained her sister's DNA.

Her twin,

that she never knew existed,

was technically the biological

mother of her children,

which is why the DNA test results

were so confusing.

Lydia is one of only 30 people in the US confirmed to have this condition,

but any one of us could be a chimera.

As most of us are unlikely to take a DNA test, we'll never know.

It's an amazing story.

It seems unreal. But...these things can happen.

I mean, it happened to me.

From alien life forms under the ice to malformed frogs,

and a case of deceitful DNA,

the tiniest things in nature can have enormous consequences.

Where next?

Well, we're going to take you on a romp

through a manifestation of your worst possible nightmares.

From a never-ending tropical storm of enormous magnitude

to a close encounter with a zombie cockroach.

But first, let's get to grips

with one of nature's most powerful forces.

Lightning. THUNDER CRASHES

Shocking and unpredictable.

Out here, it can strike without warning.

But, of course, they do say

that lightning never strikes twice in the same place.

But what if I told you there is a place where lightning never ends?

It must be a place like no other, a true hell on Earth.

Actually, it's the Catatumbo region in Venezuela.

Now, it might look like an idyllic, tranquil haven,

but every evening, the atmosphere changes dramatically.

It's one of the world's most violent and frightening natural spectacles.

These storms are so frequent, they happen on such a regular basis

and for such a long period of time, they've been nicknamed

everlasting storms.

The storms develop about 160 days of the year

and we can see 280 strikes of lightning in just an hour.

And the local fishermen actually use it

as a way of directing themselves back into shore.

This is the eternal lightning storm of Catatumbo.

It's been going on for centuries.

It's the stuff of legend.

In 1595, Sir Francis Drake

was planning a surprise attack on this location.

He waited for night-time when it was dark, but at midnight,

the sky lit up and his whole surprise attack was just foiled.

But what's going on in Catatumbo

that makes these ferocious storms everlasting?

Well, it's all down to geography.

Electrical storms require two basic ingredients -

warm, moist air and cold air.

Being located just above the equator,

Catatumbo's weather is pretty much the same all year round,

with a constant supply of warm, moist air

blowing in from the Caribbean Sea.

It's also supplied with a constant source of cold air that cascades down

from the snow-capped mountains that surround the area on three sides.

But the final and vital ingredient

that creates these never-ending storms

arises because of the massive lake nearby.

During the day, the hot tropical sun evaporates

huge volumes of water from the lake,

but every night, winds rush in from the mountains.

They're known as a low level jet.

And it's this which

forces the air to rise,

boosting the formation

of electrical storms.

Which is why these storms develop from about midnight

and then drop away at dawn time when this low level jet dissipates.

So the location really pulls all the ingredients together

to make this the perfect storm generating system.

Catatumbo is a delicately balanced

lightning generating machine,

and it's one that could run eternally...

..providing all the ingredients remain in place.

But extreme forces of nature can sometimes combine

to create even stranger things.

Back in 2011 in Texas,

whilst his girlfriend Daphne was out of town,

electrician Winston Kemp spent a weekend in the garden,

tending his prize pumpkins.

When I went outside that day,

my mind was pretty much on the pumpkins.

But it turned out to be a very weird weekend for Winston.

When Daphne returned, he had something very strange to show her.

An impossibly intricate work of art on his arm.

When it happened, I was back home in St Angelo visiting my family.

When I came back, I saw his arm

and I took a picture and I posted it online and I asked,

"So, what does your boyfriend do when you go out of town?

"Well, this is what happens to mine."

A lot of people thought it was a fake.

They were like, no, this didn't happen to him.

They thought it was, like, henna or a tattoo.

But Winston hadn't made an ill-advised trip

to the tattoo parlour.

No, what had actually happened was far weirder.

I was trying to save my pumpkins from all the rain we were having.

So I went outside to try and divert some of the water away from them.

I heard a really loud noise and I saw a flash.

There was a lot of shock and my arm started to burn.

Winston had been struck by lightning.

But rather than killing him,

he'd been left with a remarkable temporary tattoo,

a bizarre branching pattern etched from shoulder to elbow.

But how could the lightning have made such a such a beautiful design?

It was raining heavily on the night

that Winston was trying to save his precious pumpkins,

so a layer of water was running across his skin.

And this water may just have saved his life.

You see, when he was struck by lightning,

conditions combined in a perfect way.

Thousands of volts of electricity discharged through the water,

bypassing his vital organs

and instead dispersing across the surface of his skin.

Heat and pressure created what's known as a Lichtenberg figure.

The pattern on his arm showed exactly where the lightning moved

as it found the path of least resistance.

To demonstrate how this happens,

let's substitute rain with a metal Faraday suit.

Metal and water are more conductive than skin,

so if you're fully covered, lightning will flow around you.

It's called the skin effect.

Which is why this man is able to play with lightning,

and why Winston got away with only a pattern on his arm to show for it.

Quite extraordinary and Winston was so extremely lucky

to walk away with just a work of art on his arm,

because every year in the US,

hundreds of people are struck by lightning.

Around 40 are killed and many more have permanent injuries.

But in South America,

it's not always danger from above that you have to worry about.

Hiding in the mud beneath rivers and swamps is a shocking secret.

They are legendarily unpleasant to encounter.

They have a fearsome reputation

and it's pretty well earned.

The local fishermen call them arimna,

which means to deprive of motion.

So exactly what is lurking beneath the surface of the water?

In 2013, in South America, one unlucky fisherman discovered

first hand whilst reeling in his line.

HE YELLS

He'd caught an Electrophorus electricus...

..otherwise known as an electric eel.

The obvious thing about them

is they're giving off this unusual force.

What I kind of call the weapons of mass destruction.

In terms of voltage,

they can give off 600 volts for a very large eel.

It's a very significant current.

600 volts... That's nearly three times the amount

we get out of our electrical sockets.

But how can a fish produce such deadly power?

All muscle cells can generate some electricity.

Think of a heart monitor - that spike is a wave of electrical charge

generated by a muscle.

But electric eels have evolved a way of amping up their muscle cells

to create a massive charge.

A shock powerful enough to immobilise a horse!

An animal that can generate 600 volts, that is just incredible.

If that didn't exist and I said it could exist,

you would never believe me, right?

Ken's fascination with electric eels

led him to make a ground-breaking discovery.

It's using electricity to sort of

reach into other animals' nervous systems

and activate the neurons in their bodies as a way of remote control.

It's just phenomenal.

But how does the eel do this?

So when the electric eel gives off its high voltage pulses,

it's a lot like the signal that comes through our nerves.

It can either stop you moving or make you move

depending on what its purpose is at the time.

So really what it's doing is remotely controlling

the nervous system of the animal that's nearby.

The eel mimics the signals running through your own nerves.

So you can't even control your own body.

And if you're a fish in the Amazon,

nowhere is safe from the eels' electrical weaponry.

Let's say you're hidden in the mud, for example.

What it does is it gives off two of these pulses.

And what that causes is a massive whole-body involuntary twitch.

You can't help it,

because your nervous system is remotely activated.

And the eel in turn is very sensitive to water movement

so it detects that twitch.

And then it's game over.

After you've been forced to give away your location,

in a flash, the eel unleashes its highest setting.

When the eel starts its high voltage output,

within three milliseconds - that's three one thousandths of a second -

the prey is completely frozen up.

You get massive contraction of all the muscles,

essentially imitating what a Taser does,

but sort of a super-powered Taser.

And once paralysed, you're easy pickings for the eel.

You don't stand a chance.

A good reason to never get out of the boat

should you venture up the Amazon.

And as strange as tasering your meal might sound,

I have to tell you, there is one other tiny species

that goes to far more extraordinary lengths

to bring food to its table.

For our next story, we travel to Hawaii

where in 2011, a film-maker captured this extraordinary

David and Goliath contest,

a tiny jewel wasp dragging along a cockroach five times its size.

The cockroach is one of the fastest and toughest insects around.

With a strong exoskeleton and powerful mandibles,

it's a formidable beast to deal with.

The jewel wasp is a beautiful creature, but on size alone,

it's no match for the cockroach, which should easily win this battle.

But instead, it's being led by the wasp without putting up a fight.

So how does the wasp get the cockroach to follow it?

And what's it going to do with it?

Take it for a walk?

Well, obviously not.

But the truth is far weirder than you could ever imagine.

It's a process that takes some careful planning.

To begin, the wasp hunts down a cockroach

and administers a sting to the thorax.

Now, that's a risky move for the wasp, but it's one that pays off.

This first hit temporarily paralyses the cockroach's front legs,

vital for the next stage in the fight.

The cockroach needs to be almost motionless

while the wasp administers the much more accurate second sting.

This second sting needs to be to a specific part

of the cockroach's brain.

And it does that almost with the precision of a surgeon's scalpel.

This second hit goes straight to the cockroach's brain.

Instead of fighting back,

the cockroach responds with some strange behaviour.

It starts to groom obsessively,

but I'll come back to that in a moment.

And then, as the wasp's venom takes over,

it knocks out the cockroach's ability to fight back or even run away.

It's been turned into a zombie completely under the wasp's control.

But the cockroach's ordeal isn't over yet.

The wasp leads it like a puppet to its dark lair,

where the true purpose behind this brutal clash is finally revealed.

The cockroach has become a larder for the wasp's larva.

So, initially, the wasp larva feeds outside

on the body of the cockroach.

But after a few days, it tunnels into the cockroach's abdomen,

then it feeds on its internal organs.

And to keep the cockroach alive as long as possible,

it feeds on the organs sequentially

so it leaves the most important organs until last,

effectively keeping the cockroach alive for as long as it can.

As dark and twisted as it sounds,

everything the wasp does has a purpose.

Remember that excessive grooming?

Well, now that comes into its own.

The cockroach is keeping itself clean so that the wasp larvae survive.

Imagine that. Keeping yourself in tiptop condition

just so that some other animal can eat you alive from the inside.

Not very nice. By committing that cockroach to such a miserable end,

the female wasp insures that her larvae will survive,

and that's what it's all about.

And it's astonishing the lengths that some species will go to,

just to ensure that their kids get the very best start in life.

The lightning never ends in Venezuela,

but leaves its mark on skin in Texas.

Eels use electricity to make underwater weapons,

and wasps rewire the circuitry of their cockroach slaves.

The forces that shape our world are not only weird,

but they're also deadly.

And finally, I'm going to tell you a story

which I can absolutely promise you

will change the way you think about our weird and wonderful world,

from some eye-opening dentistry to a cyborg with an ear for colour.

So let's start with something that really has to be seen to be believed.

In 1998, Ian Tibbetts from Shropshire

began having problems with his eyes.

I went blind in my right eye.

My left eye slowly going what the right one did.

Gradually, I got to being able to only see shadows.

As his eyesight got worse,

it slowly robbed him of everything that he liked doing.

Worse still, Ian and Alex had recently had twin boys,

but Ian had never seen their faces.

It was quite scary in the fact that..

..I'd never be able to see my children...

..or the wife again.

Or anybody again, actually.

Then, one day, at his lowest,

Ian stumbled across a lifeline.

I saw this picture on the TV, on the news,

this miraculous cure to help people who were going blind.

It was my last chance, really, the last chance saloon.

Ian reached out to a very specialist eye surgeon.

I did a very detailed assessment and told him there was a good chance

I could help him regain his sight.

Ian was in luck,

but Professor Liu's solution

was weirder than he could have ever have imagined.

With Ian's eyes, the outside of his eyes was the problem.

The insides were fine.

He'd need to consider an artificial cornea.

Professor Liu wanted to replace the entire front of Ian's eye.

That would be his cornea, his iris and his lens.

But, of course, that sort of surgery is anything but standard.

When I went to see him and he told me

what he would like to try and do to me...

..I just thought in the back of my mind, "He must be crazy."

But this new part of Ian's eye

wasn't going to be totally artificial.

Oh, no.

It was going to be made out of something very strange indeed.

The implant consists of two parts.

One is the lens, or optical cylinder,

and that is like a camera lens.

The other part is made

from the patient's tooth, root and surrounding jawbone.

Yes, you heard right!

Professor Liu wanted to use one of Ian's teeth

to rebuild his eye.

It must be one of the most bizarre treatments

for blindness you can imagine.

What's putting a tooth in the back of the eye going to help me see?

Can't work. I thought he was delusional.

The procedure that Professor Liu wanted to perform

has got a bit of a name.

It's called osteo-odonto-keratoprosthesis.

Yeah, it's a bit of a mouthful.

But the big question is, why did he need to use a bit of a tooth?

Well, it's all about fooling Ian's eyes.

If you just put the plastic lens onto the eye

then it will just reject it.

If we surround it with a picture frame

made with the patient's own tooth and surrounding jawbone,

it can trick the eye into accepting it.

So, to help Ian see again, Professor Liu needed to use

something from Ian's body with the perfect structure

and blood supply to hold an artificial lens,

and a tooth happens to be just right for the job.

But this surgery wasn't without risk.

If it went wrong, Ian could be plunged into darkness forever.

Professor Liu performed the operation in two parts.

First, a tooth was removed and shaped to hold the lens.

It was then implanted for four months under Ian's cheek

to grow soft tissue around it.

In the second part of the surgery,

the front of the eye was removed

and replaced with the new artificial lens embedded in the tooth.

All in all, it's an incredibly complex and delicate procedure.

But there was no way to know if it had worked

until the bandages were removed 24 hours later.

When they took the bandages off,

I couldn't see a thing.

It was worse, actually, than it was before.

I couldn't actually see at all.

I thought I was going to be blind for life.

I just started crying.

I sat down on the floor and cried.

And that's about all I can remember of that part.

But a few weeks later, something truly remarkable happened.

Callum comes in and I look at him

and I could actually see his face clearly.

By then, Ryan had come running in and I could see him, too.

It made me feel ecstatic, over the moon.

That I could actually see them.

My little boys.

He could see his sons for the very first time.

And none of it would have been possible

without this incredible surgery.

It's wonderful, because it's given him some life again.

You know, some quality.

It's changed my life for the better.

What about that?

That's really something, isn't it?

A real life-changing moment.

I suppose you could say that the phrase "seeing is believing"

has never been more apt.

But then we all experience what we see in slightly different ways.

Double rainbow! Oh, my God.

It's a double rainbow, all the way.

We've all been excited when we've spotted rainbows.

Double complete rainbow...

in my front yard.

LAUGHTER

But perhaps some more than others.

Oh, my God, it's so bright and vivid. Oh!

In 2010, Paul Vasquez saw a double rainbow

from his California back yard near Yosemite National Park.

Double rainbow all the way across the sky!

Oh, my God.

Whoo!

Yeah!

Oh...

He recorded his dramatic reaction and the clip went viral

and has been viewed by millions around the world.

What does this mean?

Paul, Paul, calm down. There's a perfectly logical explanation.

So how does a double rainbow work?

The answer lies in a single drop of water.

A rainbow is created when light refracts as it enters a raindrop.

It then bounces off the back of the droplet

and refracts again as it exits the water.

This splits the colour spectrum and causes a rainbow to appear

at an angle of around 42 degrees relative to the incoming light.

OK, that explains a single rainbow.

But some light bounces twice before it exits the drop,

this time at an angle of around 53 degrees,

creating a second rainbow just above the first one.

Scale all of this up with millions of water drops

and you get a double rainbow.

And the way to know that your eyes aren't deceiving you?

Well, because of this second reflection,

the colours in a second rainbow are reversed.

Now the blue is on the outside and the red on the inside,

just like the double rainbow that was so intense for Paul.

Oh!

Oh, my...

Oh, my God, look at that.

It's starting to look like a TRIPLE rainbow.

Oh, my God, it's full-on.

Double rainbow all the way across the sky.

Oh, my God!

So a double rainbow had given Paul Vasquez the moment of his life.

But try and imagine this -

try and imagine that you can't see any colour at all.

A whole world without colour,

a world made up only of shades of grey.

What then would you give to see that world in colour?

Something that we all take for granted.

New York City. And this is Neil Harbisson.

He has never seen colour.

Born with a condition called achromatopsia,

he only sees a world of black and white.

But despite this limitation, Neil became an artist,

and in 2004 began an incredible journey

to bring him closer to the world of colour.

There's lots of red things.

Very F street.

This is more F sharp.

The woman sounded... very high-pitched E.

I was always curious about colour

cos everyone is using it

in daily life.

They are mentioning it every single day.

So I was always interested in sensing colour.

Not because I wanted to change my sight,

but because I wanted to have this element of colour in my life.

With the help of a team of engineers and doctors,

he created something straight out of science fiction.

Neil had an electronic device implanted inside his skull.

So this is a colour sensor. It picks up light frequencies.

It sends the light frequency to a chip

and the chip transforms the light frequency to a real vibration

that moves inside the skull.

So the vibration inside my skull

becomes a sound in my inner ear and each colour

has a different vibration, so it creates a different note.

So now the antenna is picking up

the light frequencies of this colour.

People can see the light frequencies and they say it's blue.

I can say it's blue

because the light frequencies are being converted

into a vibration in my skull.

In the same way that people can see this frequency,

I can sense it through vibrations in my head.

So, for example, red is very low. It's an F.

And then blue sounds C sharp and the green sounds A.

So when I look at this wall, I hear lots of music.

So it's a musical wall.

And there's lots of sound coming out of these colours.

So let's get this absolutely straight.

When Neil looks up at a clear blue sky,

he doesn't see the colour blue, he hears a note.

MID-RANGE NOTE

And if he were here, looking at this green tree, he wouldn't see green.

He'd hear another note.

HIGHER NOTE

But he's not happy.

He's not happy just being able to transpose colours into sounds.

Oh, no, he wants a technical upgrade.

I didn't see why I should stop to only human colour perception.

I could also sense colours that other animal species sense.

Just like some species of snake, Neil can sense infrared light.

For example, I can go in a shop and detect

if the alarms are on or off, because if there is infrared,

it means that there's movement detectors.

At the other end of the light spectrum,

Neil can also sense ultraviolet...

..just like many birds can.

Male and female bluetits look identical to us,

but they can see UV light.

It's how they tell each other apart

because males like this one have brighter UV patches than females.

But for Neil, the ability to see UV light

has even more useful ramifications.

On a day like today, with all the UV light pouring out of the sun

potentially damaging me,

Neil could hear whether it was safe enough to go out.

And what's even more astonishing

is that he can perceive parts of the spectrum that we will never see.

And even more amazing

is what's actually going on inside his brain.

The next stage that was a big stage

was when I started to dream in colour.

So when I sleep, my brain creates the sound of colours,

so I dream in colour, and that was also a very big emotional step.

There's something absolutely amazing going on here.

You see, the pathways in Neil's brain

have adapted to these new sensory inputs.

And over time, it's got to the extent

that he doesn't need to even hear a particular sound

to relate it to a specific colour.

It's happening automatically.

To the extent that, when he goes to sleep and the machine is turned off,

his brain can still produce those sounds,

so that he can dream in colour.

What about that?

The technology has fused to the circuitry in his brain,

effectively making Neil a cyborg.

A cyborg!

From sight-saving surgery,

to a mind-bending double rainbow

and music creating a cacophony of colour in a world of grey,

we may all see things differently, but one thing is certain.

This world of ours it just wonderfully weird.

Next time...

How did this man find himself in the middle of a waterspout?

And what creates this underwater wonderland?

Are these the world's weirdest worms?

And just why has this rat developed a death wish?