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The human eye, one of the most
powerful instruments on Earth.

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On a clear day we can spot the
smallest detail in the widest view.

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But what the eye sees
is not the full picture.

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Alongside the world we see
is a very different world.

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An invisible world

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of hidden forces and powers that

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shapes
every aspect of life on Earth.

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Now technology can open a door
on that hidden world

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revealing its mysteries
and showing us the true wonder

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of the world we live in.

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An ordinary everyday scene,
a street, houses, people, cars,

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number 12's parked in
the wrong place, again.

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What could be more normal?

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Except this scene is incomplete.

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Our picture of it is only partial.

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There's something else going on out
here, something that the eye

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could never capture, but that's as
real as the road beneath my feet.

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The extraordinary truth is that
the picture we see is only

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the tiniest, minutest fragment
of a far, far greater reality.

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But now we can glimpse that wider
world, the invisible world, and see

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the many ways it shapes our lives.

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These men in beige gloves
are hunting a lethal force.

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HELICOPTER WHIRS

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A force that's present all over the
world, but completely invisible.

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To find it, they're doing something
of quite awe-inspiring danger,

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and I don't just mean riding
on the outside of a helicopter.

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They're about to fly

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within inches of a power line
carrying half a million volts.

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Adrenaline rush at times, yes.

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There are certain situations you can
get into that are very, very hairy.

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This might seem like
insane showing off,

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but they're doing it for a reason.

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These power lines carry a massive
and potentially lethal danger.

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There is an invisible force field.

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You cannot see it, but if you get
close enough, yes, you can touch and,

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you know, you can feel
the electricity around it.

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And it's a pretty good
potential to get you killed.

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You don't say! But now, for the
first time, specialist cameras

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can see the hidden force that could
reduce him to a pair of

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smouldering beige gloves.

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What appeared to be a normal
power line is actually revealed to

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have a violent discharge
signalling a potentially

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catastrophic leak of electricity.

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It's a phenomenon known as corona.

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So what exactly is this phenomenon?

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Inside that power line above me
hundreds of thousands of volts 

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of electricity are creating a
massive electric field radiating out

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from around the line.

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You can't see it at the moment and
that's not just because it's dark.

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Let me show you how strong
that field actually is.

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Now, right now I am the
tallest thing around here...

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Yes, all right, I just am!

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So that electric field is
going through me to the earth,

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but if I step away
it's strong enough to do this.

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Now, there's
no other power going in, it's just

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that electric field that's
switching on all of these lights.

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And these lines are perfectly normal
and well insulated, but if there's

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a leak or a fault on the line that
electrical field becomes massively

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intensified, so intense that it
charges the air around it

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and causes a discharge called
a corona.

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The more intense the invisible
corona, the bigger the leak of

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high voltage electricity.

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If it's not taken care of, it could
lead to all manner of

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unpleasantness, including power
cuts, dangerous short circuits,

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even fires.

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It needs to be fixed and that's
where this lucky chap comes in.

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So, he's next to a half
million volt power line,

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and what's he going to do now? Yep,
he's going to attach himself to it.

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OK.

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HELICOPTER WHIRS

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Right now the crew are protected
only by their mesh suits

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and the fact that they're not
earthed.

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For a few seconds, the helicopter
and the power line

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are bonded together, a huge
electrical field surging around.

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Caught by the specialist camera,
the images reveal concentrated

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hotspots of corona where the sharp
points of the rotor blade bend

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and intensify the electrical field.

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When the air reacts with
this intense electrical field

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it creates an invisible light
discharge and it's this light

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that the camera is tuned to detect.

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But to the naked eye

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it's completely invisible.

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Which, in the circumstances,
is probably for the best!

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Suffice to say it's a good
job these two blokes get on.

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Being that we know each other so
well, a lot of it is just by the way

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he may be posturing.

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If he moves his head to the left or,
you know, reaches for the left I'll

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be heading to the left.

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Basically, Tracy and I don't even
really have to talk to each other

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any more. We know each other so well
that we get all everything

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ready to go, suited up,
I give him the OK and we're on line.

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And when he says on line,
he means actually sitting

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on a live power line

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and starting the precise manoeuvre
to disconnect from the helicopter.

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And as he does that, the corona
keeps on surging around them.

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But as soon as the link is broken

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the corona on the helicopter
vanishes, leaving just a few spots

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on the lineman
just to remind him you

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he's still sitting on
a live power line!

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The corona is as real as the power
lines themselves, but it's part of a

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vast invisible world that lies
hidden from our sight.

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I will need this.

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Because although our eyes are
incredibly clever and powerful,

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they're only sensitive to a
very narrow band of light.

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If you pass light through a prism,
like a sheet of water, it splits

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what the brain sees as white light
into a spectrum of

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seven different colours,
each in a well-defined place.

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Red, orange, yellow,

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green, blue, indigo and violet,
the visible light spectrum.

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Together these seven colours
account for all the wavelengths

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of light that we can see,
but what lies beyond this spectrum,

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in other words out here past violet
or over here beyond red?

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Well,
as far as the eye is concerned,

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nothing, but that's far from true.

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In fact, the light spectrum

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stretches far beyond the
visible light we can see.

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You can think of the spectrum of
light as a bit like the notes

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on a piano.
Imagine these seven notes

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represent the visible spectrum and
the familiar colours of red, orange,

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yellow, green, blue,
indigo and violet.

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So all that we can see
accounts for this octave.

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But that, in fact, is just a tiny

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percentage
of the entire spectrum of light.

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If you want to be exact,

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it's 0.00000000001%.

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And just like this
piano has many other notes,

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light exists in many other
wavelengths

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with infrared
down here and ultraviolet up here.

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And that is just a beginning.

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If our visible spectrum is just
one octave on this piano, then

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to represent the entire spectrum
from gamma rays to X-rays

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and right through to radio waves,

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you'd need the keyboard
to extend...

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And extend...

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And extend...

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Still going...

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Still going,

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right out as far as the sun
93 million miles away.

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That's a very big piano!

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And in that huge invisible realm

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even the most familiar things
are not quite what they seem.

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Our own sun, a benign source of
warmth,

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life and the vague hope that
you might have a barbecue tomorrow.

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But go beyond what we see
and we get a very different picture

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of our nearest star.

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In ultraviolet our benign sun
becomes a writhing mass of violent

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and dangerous activity.

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These UV images from a space
telescope reveal supercharged gases

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a million degrees hot and solar
flares rising thousands of miles

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above the sun's surface.

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We can even see the intense magnetic
fields that create dark sunspots

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and solar storms.

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And X-ray telescopes reveal what we
could never see with the naked eye,

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the sun's outer atmosphere,

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a ring of glowing gases
hotter than the sun itself.

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Back down on Earth, it's X-rays that
have transformed our visible world,

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letting us see it
in a completely new way.

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The idea of using X-rays comes from
a very simple property of light.

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We see the world around us because
visible light bounces off objects

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and enters our eyes where receptors
in our retina can detect it.

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Switch that light off and...

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..nothing.

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To see beneath the surface of things
we need light that's powerful enough

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to pass through objects. It's a
bit like when light from a torch

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passes through your hand and sort of
hints at the shape of

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the bones beneath. But to really see
that I outline clearly,

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we need something more
powerful, much, much more powerful,

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and that's what light in the
X-ray part of the spectrum offers.

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This is one of the world's
most advanced X-ray machines

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and what it allows seems like
pure science fiction - X-ray vision

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in high speed and high definition.

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For the first time, we can see
exactly how the body works in motion

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and we can explore some of the
mysteries of the inner workings of

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everything from a man in a vest

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to a myriad of animals.

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A rat, for example, can clamber up
this chain with ease, but it's only

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with X-ray vision that the secrets
of its superb agility become clear.

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Rather than making its legs

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do all the work it flexes its back
like a caterpillar,

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bending its spine
to lift most of its body weight.

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Yeah, that's how they got the
plague on ships, like that.

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A moving X-ray shows a unique
feature of the chameleon.

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It's the only lizard that
can climb narrow branches

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because of an extraordinarily mobile
shoulder that allows it to twist its

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legs inwards to grasp the branch.

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Oh, vest man's back!

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Even a quail is quite interesting
when seen in X-ray vision.

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Look, it's carrying an egg!

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With this astonishing X-ray vision,

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we can understand the precision
engineering of a top athlete,

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like this man in a vest,
and see how it compares to some of

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the extraordinary abilities
of the animal kingdom.

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As humans, we get along by being
just good enough at a huge number

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of different things, but that's
a very different approach to the

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specialised movement of a predator
evolved to hunt and to kill.

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You might not think of your
pet cat as a supreme gymnast,

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but that's exactly what it is.

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Even the most powerful human
athletes

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struggle to jump safely
much beyond twice their height.

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But a cat can comfortably
fall more than ten times its height

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and stroll away to sleep on the shed
roof as if nothing has happened.

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Now we can see why.

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The human body has minimal
cushioning in the knees and ankles,

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little flexibility in these joints
to absorb the impact of landing.

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But a cat is very different.

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First, a cat's ear isn't just
for detecting when you're using

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a tin opener. It works like an ultra
fast gyroscope, telling it which way

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is up so it can twist in the air
and always land feet first.

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But it's in the mechanics
of the skeleton where

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the difference really lies.

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These are the first ever images to
show how a cat really works.

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The muscles holding the
shoulder joint stretch

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and then the shoulder blade comes up

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moving right up beyond the body.

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It's the perfect shock absorber

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and, like being able

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to sleep on the sofa for 18 hours,
it's unique to cats.

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The everyday world would look

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rather different if we could see
the X-ray part of the spectrum,

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and that's just one of
many invisible worlds out there.

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Just beyond violet in the rainbow
lies ultraviolet.

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It's completely invisible to us,

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but not to certain animals.

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Here's the vole.
It uses splashes

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of urine to mark out territories
in the undergrowth where it lives.

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The urine has its own smell

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of course, but to us
it is completely invisible.

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00:20:22,600 --> 00:20:28,160
The clever thing about vole wee
is that it contains special pigments

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that reflect ultraviolet light.

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What to us appears to be
an ordinary patch of grass

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is really packed with
bright markings.

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00:20:50,360 --> 00:20:56,520
The fresher the splashes of urine
the stronger the UV signature.

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The urine tells other voles
how fresh a path is,

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even the sex of the animal that
left it.

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00:21:06,040 --> 00:21:08,440
But there's a twist to this

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invisible pee talk because whilst it
is very useful to the voles, there's

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another animal taking an interest
in their secret communications.

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To the kestrel this is dinner.

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But first he's got to find it.

240
00:21:29,080 --> 00:21:33,040
A vole's visible colourings are
perfect camouflage against

241
00:21:33,040 --> 00:21:37,600
the background, which means it's
incredibly difficult to spot,

242
00:21:37,600 --> 00:21:41,240
even for a bird with eyes as good
as a kestrel.

243
00:21:43,480 --> 00:21:49,040
Unfortunately for the vole,
a kestrel can see in ultraviolet.

244
00:21:51,840 --> 00:21:58,880
And in ultraviolet, the location
of the vole is blindingly obvious

245
00:21:58,880 --> 00:22:03,840
leading the kestrel
straight to the main cause.

246
00:22:16,400 --> 00:22:18,880
The invisible world of ultraviolet 

247
00:22:18,880 --> 00:22:23,520
has many other things
to reveal about the life of animals.

248
00:22:26,440 --> 00:22:30,280
Alongside the garden that we see,

249
00:22:30,280 --> 00:22:35,040
there's an invisible garden,
a garden of hidden signs

250
00:22:35,040 --> 00:22:40,480
and codes, all designed to attract
the interest of passing insects.

251
00:22:43,480 --> 00:22:45,360
That's because insects can't see

252
00:22:45,360 --> 00:22:51,080
our world clearly at all,
but they can see ultraviolet.

253
00:22:51,080 --> 00:22:53,240
Take the honey bee.

254
00:22:53,240 --> 00:22:55,600
Many flowers need bees
in order to pollinate.

255
00:22:55,600 --> 00:22:57,120
No visits from bees, no pollination,

256
00:22:57,120 --> 00:23:01,440
no pollination, no reproduction, so
it's actually a matter of survival.

257
00:23:01,440 --> 00:23:04,720
And flowers have had to learn
to advertise themselves to bees

258
00:23:04,720 --> 00:23:06,720
in a way that bees can understand

259
00:23:06,720 --> 00:23:09,720
because to the bee this garden looks
very different.

260
00:23:13,800 --> 00:23:17,840
For the first time,
high-definition cameras can give us

261
00:23:17,840 --> 00:23:20,120
a bee's view of the garden

262
00:23:21,640 --> 00:23:26,320
revealing hidden patterns in flowers
that are normally invisible

263
00:23:26,320 --> 00:23:28,520
to humans.

264
00:23:28,520 --> 00:23:31,800
Patterns that to us
are completely invisible.

265
00:23:33,800 --> 00:23:39,360
Seen in ultraviolet,
new markings appear on the flowers,

266
00:23:39,360 --> 00:23:42,840
like secret ink.

267
00:23:42,840 --> 00:23:45,960
The markings are caused
by special compounds in

268
00:23:45,960 --> 00:23:47,960
the flowers called flavonoids.

269
00:23:47,960 --> 00:23:52,760
To the bees,
they're like aircraft landing lights

270
00:23:52,760 --> 00:23:54,320
guiding them straight

271
00:23:54,320 --> 00:23:57,960
into the nectar and pollen
at the heart of the flower.

272
00:24:04,040 --> 00:24:06,040
But if there's this ultraviolet
world

273
00:24:06,040 --> 00:24:10,840
all around us
why can't we see it?

274
00:24:10,840 --> 00:24:14,680
The answer lies in the evolution of

275
00:24:14,680 --> 00:24:16,720
this,

276
00:24:16,720 --> 00:24:21,720
the eye. That's not the human eye,
that is, was, a pig's eye, but

277
00:24:21,720 --> 00:24:24,280
physiologically very similar
to ours.

278
00:24:24,280 --> 00:24:28,160
So at the front there's this,
the cornea, it's a protective layer.

279
00:24:28,160 --> 00:24:30,400
And then behind it...

280
00:24:30,400 --> 00:24:34,200
It's all right, I'm cringing, too.

281
00:24:34,200 --> 00:24:37,200
Behind the protective cornea

282
00:24:37,200 --> 00:24:39,320
is the lens.

283
00:24:39,320 --> 00:24:41,840
That is what plays

284
00:24:41,840 --> 00:24:46,160
such a crucial part in determining
what light gets through to our eye.

285
00:24:46,160 --> 00:24:49,840
But it's not just about letting
light through, it's evolved

286
00:24:49,840 --> 00:24:53,960
to be a filter, filtering out
ultraviolet light that could,

287
00:24:53,960 --> 00:24:56,800
over time, harm our eye.

288
00:24:56,800 --> 00:25:00,120
That's perhaps why the
kestrel can see ultraviolet,

289
00:25:00,120 --> 00:25:02,280
because their lifespan is short.

290
00:25:02,280 --> 00:25:04,120
They wouldn't be alive long enough
for the ultraviolet light

291
00:25:04,120 --> 00:25:07,960
to harm their eyes,
so they haven't evolved the filter.

292
00:25:07,960 --> 00:25:11,560
But there are a few rare
individuals who lack that filter 

293
00:25:11,560 --> 00:25:16,400
and so can get a glimpse
right into that invisible realm.

294
00:25:26,280 --> 00:25:31,200
Alan Bradley's whole career
has been based on vision.

295
00:25:35,080 --> 00:25:39,080
As a television engineer,
he specialised in translating

296
00:25:39,080 --> 00:25:44,280
the world we can see into the pixels
of light on our television screens.

297
00:25:48,320 --> 00:25:52,600
I have always had an absolute
gripping fascination with light.

298
00:25:52,600 --> 00:25:56,160
Light has always been
the whole world to me.

299
00:26:00,000 --> 00:26:02,680
In 2003 Alan had

300
00:26:02,680 --> 00:26:07,560
an operation to remove cataracts
and replace the lenses in his eye.

301
00:26:09,640 --> 00:26:13,120
It had a rather weird side effect.

302
00:26:21,240 --> 00:26:24,560
The operation was successful,

303
00:26:24,560 --> 00:26:30,360
but something else seemed to have
happened to his sense of sight.

304
00:26:42,360 --> 00:26:45,800
I was in the store
and had gathered up a basket of fruit

305
00:26:45,800 --> 00:26:50,640
and veggies and walked up to the cash
register at the front of the store.

306
00:26:54,720 --> 00:26:58,920
As he approached the checkout
Adam was suddenly exposed to

307
00:26:58,920 --> 00:27:05,640
a strange glow of a kind he'd never
previously seen.

308
00:27:08,600 --> 00:27:11,760
The effect was like having someone

309
00:27:11,760 --> 00:27:14,360
punch you
hard on the end of the nose.

310
00:27:18,800 --> 00:27:22,440
It was like receiving an
electric shock through the eyes.

311
00:27:30,040 --> 00:27:32,680
What Alan was seeing was ultraviolet
light

312
00:27:32,680 --> 00:27:37,560
from the shop's blacklight
used to detect fake banknotes.

313
00:27:39,720 --> 00:27:44,960
Normally the lens in our
eyes blocks ultraviolet,

314
00:27:44,960 --> 00:27:52,200
but Alan's new artificial lens
was somehow allowing it through.

315
00:27:52,200 --> 00:27:56,120
One of the eyes was seeing
the bulb in a deep purple,

316
00:27:56,120 --> 00:27:59,160
as most people see a blacklight.

317
00:27:59,160 --> 00:28:02,200
To the other eye it looked
fluorescent blue,

318
00:28:02,200 --> 00:28:06,840
it had a glow around it
like blue purple neon.

319
00:28:10,200 --> 00:28:15,600
Alan suddenly has a view of the
world most of us will never share.

320
00:28:21,680 --> 00:28:26,040
I see things that I could
never have dreamed of before.

321
00:28:26,040 --> 00:28:31,040
This happens looking at the raindrops
with sun coming through them.

322
00:28:31,040 --> 00:28:37,880
In rainbows there is this shimmering
fragmented part of the spectrum,

323
00:28:37,880 --> 00:28:43,320
which is much more enhanced
than anything that I ever saw before.

324
00:28:46,040 --> 00:28:51,400
Alan Bradley's operation transformed
his sense of sight beyond

325
00:28:51,400 --> 00:28:53,360
what he'd ever imagined to be
possible.

326
00:28:53,360 --> 00:29:01,320
100 years ago, cataracts were dealt
with in a less sophisticated way.

327
00:29:01,320 --> 00:29:03,920
They simply took out
the lens altogether.

328
00:29:13,200 --> 00:29:17,640
This is a work by the French
impressionist painter Claude Monet,

329
00:29:17,640 --> 00:29:21,200
famous for his use of
blazing, swirling colours.

330
00:29:24,360 --> 00:29:28,520
Late in Monet's life,
a cataract in his right eye began to

331
00:29:28,520 --> 00:29:34,520
affect his sight and he agreed to
an operation to remove the lens.

332
00:29:34,520 --> 00:29:38,840
You can see in his paintings
that it completely changed

333
00:29:38,840 --> 00:29:41,960
his perception of colour.

334
00:29:41,960 --> 00:29:46,080
With his left eye, he painted this,

335
00:29:46,080 --> 00:29:50,040
but in the right eye
that was missing the lens

336
00:29:50,040 --> 00:29:51,760
that same garden looked

337
00:29:51,760 --> 00:29:56,480
very different,
swathed in a bluey-white wash.

338
00:29:56,480 --> 00:30:00,400
Maybe he'd run out of red paint!

339
00:30:00,400 --> 00:30:05,680
The more likely answer is that he
too was able to see in ultraviolet.

340
00:30:13,720 --> 00:30:18,560
Being able to see the invisible
spectrum beyond the naked eye

341
00:30:18,560 --> 00:30:22,440
has shown us the wider world
all around us.

342
00:30:25,600 --> 00:30:33,280
How cats work, how flowers are
really tiny advertising hoardings.

343
00:30:33,280 --> 00:30:37,760
These are the secrets
X-rays and ultraviolet can reveal.

344
00:30:41,200 --> 00:30:47,200
But further along the spectrum,
just beyond red, lies infrared

345
00:30:47,200 --> 00:30:52,200
and if we could see this part of
the spectrum, it would transform

346
00:30:52,200 --> 00:30:54,120
our understanding of the world.

347
00:31:04,400 --> 00:31:10,280
This, as you can probably tell,
is a forest fire.

348
00:31:13,800 --> 00:31:17,080
It's one of the most
frighteningly destructive

349
00:31:17,080 --> 00:31:19,680
forces of nature on the planet.

350
00:31:19,680 --> 00:31:21,400
'Hundreds of homes have been...'

351
00:31:21,400 --> 00:31:25,160
'Bush fires are raging out of control
across thousands of acres...'

352
00:31:26,680 --> 00:31:32,320
Once it takes hold, a fire like this
is almost impossible to put out.

353
00:31:48,600 --> 00:31:51,840
That is terrifying.

354
00:31:51,840 --> 00:31:55,600
It really is terrifying in there,
but I know I'm perfectly safe. 

355
00:31:55,600 --> 00:31:59,480
I'm wearing protective gear,
I know the name of the pyrotechnic

356
00:31:59,480 --> 00:32:03,680
guy who's controlling the flames,
but fire, it is the most elemental

357
00:32:03,680 --> 00:32:07,600
and destructive force on the
planet so we see it, we're scared.

358
00:32:07,600 --> 00:32:11,840
But just the sight of it is not
the full story. To really appreciate

359
00:32:11,840 --> 00:32:15,760
what's going on in there
we need to see into the invisible.

360
00:32:20,280 --> 00:32:23,600
Even before the fire reaches, say,

361
00:32:23,600 --> 00:32:29,200
a branch on a tree, something's
already happening that we can't see.

362
00:32:29,200 --> 00:32:34,920
Seen in infrared, the branch
looks like it's already on fire.

363
00:32:34,920 --> 00:32:39,640
What we're seeing here is a build-up
of heat before any flames appear,

364
00:32:39,640 --> 00:32:44,080
but what's really crucial it's
what's happening around the branch.

365
00:32:46,920 --> 00:32:48,440
Super hot gases

366
00:32:48,440 --> 00:32:53,440
in the air catch fire first
and they ignite the branch.

367
00:32:53,440 --> 00:32:54,960
There it goes.

368
00:33:04,800 --> 00:33:06,680
Watching something burn
it's easy to think that

369
00:33:06,680 --> 00:33:11,200
the flames are actually on the thing
that's burning, eating away at it,

370
00:33:11,200 --> 00:33:14,520
because that's what it looks like,
but it's not that simple.

371
00:33:18,160 --> 00:33:22,040
What's happening is the heat
is causing the object to give off

372
00:33:22,040 --> 00:33:26,080
combustible gases and as they escape
it's those combustible gases

373
00:33:26,080 --> 00:33:29,880
in contact with the oxygen
in the air that cause the fire.

374
00:33:35,520 --> 00:33:38,000
So those flames are not in
the thing that's burning,

375
00:33:38,000 --> 00:33:40,480
they're in the air around it.

376
00:33:45,800 --> 00:33:51,560
That's why fire can spread so
quickly as waves of super hot gases,

377
00:33:51,560 --> 00:33:55,840
fanned by the wind,
set fire to everything they touch.

378
00:34:06,000 --> 00:34:10,120
HELICOPTER WHIRS

379
00:34:12,800 --> 00:34:16,960
Stopping a forest fire before
that can happen is vital.

380
00:34:24,360 --> 00:34:27,600
We can head over to our left and
look at what's along that clearing.

381
00:34:27,600 --> 00:34:31,360
Here in the wilds of Alberta

382
00:34:31,360 --> 00:34:33,080
firefighters fly over the forest 

383
00:34:33,080 --> 00:34:36,720
looking for the
first signs of trouble.

384
00:34:36,720 --> 00:34:39,800
We try and catch the wildfire while
it's small so that it doesn't grow to

385
00:34:39,800 --> 00:34:41,880
a size that we can no longer manage.

386
00:34:44,960 --> 00:34:48,160
It could be just as small
as one tree burning, so

387
00:34:48,160 --> 00:34:51,480
we have to spot one tree in a forest.

388
00:34:55,640 --> 00:34:59,600
It's not what you'd call
a relaxing job,

389
00:34:59,600 --> 00:35:01,400
but seeing into the invisible could

390
00:35:01,400 --> 00:35:07,160
make it a lot easier, and that's
where this small animal comes in.

391
00:35:12,000 --> 00:35:14,920
This is the jewel beetle
and, weirdly, while every

392
00:35:14,920 --> 00:35:17,880
other animal is fleeing the blaze

393
00:35:17,880 --> 00:35:22,880
this extraordinary creature
has travelled miles to find it.

394
00:35:26,480 --> 00:35:30,040
It has a strange fire-detecting
super sense

395
00:35:30,040 --> 00:35:33,560
that no human could match.

396
00:35:34,880 --> 00:35:40,880
We look at this and see, well,
trees, but look at it in infrared

397
00:35:40,880 --> 00:35:44,200
and a
fire is screaming its presence.

398
00:36:03,480 --> 00:36:07,560
The visible fire may be hidden
deep within the forest,

399
00:36:09,080 --> 00:36:13,560
but even a small fire
has an infrared signature.

400
00:36:13,560 --> 00:36:19,400
Close up, we can sense
this radiation as heat,

401
00:36:19,400 --> 00:36:24,320
but the fire is transmitting
infrared much further than this.

402
00:36:27,400 --> 00:36:32,440
Long-wave infrared from the
fire travels vast distances

403
00:36:34,200 --> 00:36:39,640
and it's this a beetle can detect,
allowing it to sense fires from

404
00:36:39,640 --> 00:36:42,960
as far as 50 kilometres away.

405
00:36:45,360 --> 00:36:50,840
The jewel beetle is tuned to this
long-range infrared light thanks to

406
00:36:50,840 --> 00:36:57,440
two tiny pit organs on its chest,
each containing some 70 sensors.

407
00:36:59,920 --> 00:37:04,240
Now scientists are copying the
beetle's extraordinary infrared

408
00:37:04,240 --> 00:37:11,120
super sense to spot the very first
sign of forest fires from the air.

409
00:37:11,120 --> 00:37:14,200
And even from space.

410
00:37:17,080 --> 00:37:21,480
Thousands of miles above the Earth
infrared sensors on satellites

411
00:37:21,480 --> 00:37:26,840
can detect forest fires,
showing them clearly as hotspots.

412
00:37:28,640 --> 00:37:30,960
If firefighters could routinely

413
00:37:30,960 --> 00:37:37,360
harness this new technology,
it would revolutionise their job.

414
00:37:37,360 --> 00:37:39,120
Ideal situation is if we

415
00:37:39,120 --> 00:37:42,760
did have eyes in the sky essentially
so that we can try and catch the fire

416
00:37:42,760 --> 00:37:47,040
early enough to be able to
put it out at a small size.

417
00:38:03,960 --> 00:38:06,440
Infrared is also bringing to light

418
00:38:06,440 --> 00:38:10,920
some amazing things
about the natural world.

419
00:38:11,200 --> 00:38:15,200
Take the honey bee. You might think
of these as

420
00:38:15,200 --> 00:38:17,600
just slightly annoying creatures
that can ruin a picnic.

421
00:38:19,120 --> 00:38:24,360
But with its worker bees, drones
and queen a beehive is like mine,

422
00:38:24,360 --> 00:38:29,320
a collective intelligence
as powerful as the biggest computer,

423
00:38:29,320 --> 00:38:32,600
except that your PC doesn't make
honey.

424
00:38:42,640 --> 00:38:45,200
Bees are amazing.

425
00:38:45,200 --> 00:38:46,840
It might look like chaos in there,

426
00:38:46,840 --> 00:38:50,160
but in fact inside that humble
wooden box is one of

427
00:38:50,160 --> 00:38:53,520
the most sophisticated living things
in the history of evolution.

428
00:38:53,520 --> 00:38:57,920
One bee on its own
might not add up to much,

429
00:38:57,920 --> 00:39:02,240
but taken together a very different
picture emerges.

430
00:39:04,240 --> 00:39:06,040
To really appreciate the brilliance

431
00:39:06,040 --> 00:39:09,680
of this super organism, of how it
works and controls the environment

432
00:39:09,680 --> 00:39:14,560
around it, you need to see
into the invisible realm.

433
00:39:19,200 --> 00:39:23,760
Seen normally,
all these bees may look the same,

434
00:39:23,760 --> 00:39:27,240
but go beyond the visible
into the infrared

435
00:39:29,160 --> 00:39:32,720
and some bees are
warmer than others.

436
00:39:41,000 --> 00:39:44,320
Some glow bright orange

437
00:39:44,320 --> 00:39:48,840
like hot coals, radiating heat
to their surroundings,

438
00:39:48,840 --> 00:39:52,240
others are dark and cool.

439
00:39:56,320 --> 00:40:00,200
Looking beyond what our eyes
can usually see into the realms

440
00:40:00,200 --> 00:40:04,160
of the invisible reveals it's the
precise control of heat that allows

441
00:40:04,160 --> 00:40:08,520
a bee colony to be such a unique
and successful form of organisation.

442
00:40:15,280 --> 00:40:19,520
But what exactly is
all this heat for?

443
00:40:19,520 --> 00:40:24,680
Well, look closely and the
infrared camera reveals how heat

444
00:40:24,680 --> 00:40:29,440
is concentrated in one central area,
the brood nest at the heart of

445
00:40:29,440 --> 00:40:34,000
the hive
where young bee pupae are growing.

446
00:40:36,760 --> 00:40:43,320
This bee might seem relatively
still, but seen in infrared

447
00:40:43,320 --> 00:40:48,720
it's bright orange, revealing its
role as a specialist heater bee.

448
00:40:50,360 --> 00:40:54,000
The bee warms itself up by
vibrating its flight muscles,

449
00:40:54,000 --> 00:40:58,240
vibrations that allow it to reach
up to 44 degrees centigrade, 

450
00:40:58,240 --> 00:41:02,600
previously thought
to be high enough to kill it.

451
00:41:05,080 --> 00:41:10,320
Others that seem like they
might be grabbing a quiet snooze

452
00:41:10,320 --> 00:41:13,360
are actually
tight little balls of fire.

453
00:41:15,080 --> 00:41:19,720
They're doing this because they have
a special role to mother these young

454
00:41:19,720 --> 00:41:23,240
by keeping them warm,
because without that warmth

455
00:41:23,240 --> 00:41:25,880
these babies can't grow and develop.

456
00:41:30,560 --> 00:41:35,360
And now we know why bees much spend
so much time foraging for the nectar

457
00:41:35,360 --> 00:41:39,040
that will be turned into honey,

458
00:41:40,800 --> 00:41:44,480
because it's honey that
fuels these heater bees.

459
00:41:44,480 --> 00:41:48,080
Two thirds of the hive's honey
goes on that central heating

460
00:41:48,080 --> 00:41:50,720
to keep the young warm.

461
00:41:54,080 --> 00:41:59,560
This rarely-seen moment captured
in infrared shows how exhausted

462
00:41:59,560 --> 00:42:06,240
heater bees are topped up with fresh
reserves of honey by refuelling bees

463
00:42:06,240 --> 00:42:12,120
before, recharged, they return to
their task of providing that warmth.

464
00:42:16,840 --> 00:42:20,600
These images have revealed
something extraordinary.

465
00:42:20,600 --> 00:42:24,720
By precisely controlling the
temperature, these heater bees

466
00:42:24,720 --> 00:42:27,880
control the destiny of the young.

467
00:42:35,720 --> 00:42:38,480
Incubated at 34 degrees

468
00:42:38,480 --> 00:42:43,160
this newly-born bee is likely
to become a humble housekeeper,

469
00:42:45,960 --> 00:42:51,200
but kept just 1.5 degrees higher,
it may instead turn into

470
00:42:51,200 --> 00:42:56,360
an intelligent forager,
living up to ten times longer.

471
00:43:02,640 --> 00:43:05,480
None of these amazing new
discoveries would have been possible

472
00:43:05,480 --> 00:43:10,240
without that ability to see
beyond our visible spectrum

473
00:43:10,240 --> 00:43:12,120
into the secrets of the hive.

474
00:43:22,280 --> 00:43:24,560
It's not just the behaviour of

475
00:43:24,560 --> 00:43:28,360
honey bees that the infrared
spectrum helps to reveal.

476
00:43:28,360 --> 00:43:32,080
Right across the animal kingdom
there are creatures we can only

477
00:43:32,080 --> 00:43:37,200
fully understand by looking into
this part of the invisible world.

478
00:43:45,960 --> 00:43:50,320
These caves in the southern
United States have been home to

479
00:43:50,320 --> 00:43:54,760
the free-tailed bat
for over 5,000 years.

480
00:43:54,760 --> 00:44:00,720
But what they get up to in here
has always been a mystery

481
00:44:00,720 --> 00:44:03,640
because as soon as scientists
turn on a light to see them,

482
00:44:03,640 --> 00:44:06,920
their natural behaviour changes.

483
00:44:06,920 --> 00:44:10,440
BAT WINGS FLUTTER

484
00:44:10,440 --> 00:44:13,360
Every evening, at dusk, tens of
thousands of bats 

485
00:44:13,360 --> 00:44:17,360
pour out of the
cave entrance to search for food.

486
00:44:17,360 --> 00:44:20,000
It looks like utter chaos,

487
00:44:22,880 --> 00:44:28,400
but infrared cameras have made it
possible to see through the darkness

488
00:44:28,400 --> 00:44:31,960
and it turns out that
this isn't chaos at all.

489
00:44:31,960 --> 00:44:36,520
Instead, the bats stick to specific
flight paths as they climb in

490
00:44:36,520 --> 00:44:40,800
a spiral out of the cave
and return back again.

491
00:44:45,240 --> 00:44:47,160
Once inside the cave,

492
00:44:47,160 --> 00:44:50,880
the infrared camera reveals
how these bats really live.

493
00:44:53,880 --> 00:44:56,000
The bright orange bits are actually

494
00:44:56,000 --> 00:44:59,920
hundreds of thousands of bats
hanging from the cave ceiling.

495
00:45:02,560 --> 00:45:09,200
That's half a million bats
crammed into just 200 square metres.

496
00:45:09,200 --> 00:45:12,520
But it's not
that they're short of space.

497
00:45:12,520 --> 00:45:16,680
The intense orange shows that
they're regulating their temperature

498
00:45:16,680 --> 00:45:18,840
by huddling together for warmth.

499
00:45:23,240 --> 00:45:28,560
And looking into the infrared gives
a new insight into bat behaviour.

500
00:45:30,160 --> 00:45:34,440
These colder
dark blue areas are their wings.

501
00:45:36,080 --> 00:45:40,360
We know that they need to stretch
and beat them in a vital warm-up

502
00:45:40,360 --> 00:45:42,280
before taking to the air.

503
00:45:51,720 --> 00:45:57,360
In every street of every town, the
invisible world is all around us.

504
00:46:02,040 --> 00:46:06,280
If our eyes could see into
the infrared part of the spectrum

505
00:46:06,280 --> 00:46:08,880
your kitchen would suddenly become
an insane world

506
00:46:08,880 --> 00:46:12,240
of hidden forces and actions.

507
00:46:14,040 --> 00:46:18,400
These are swirling air currents
propelled by the heat of our bodies.

508
00:46:18,400 --> 00:46:22,080
And here, beyond our normal vision,

509
00:46:22,080 --> 00:46:25,760
is the very moment
an egg transforms.

510
00:46:25,760 --> 00:46:30,760
Around 80 degrees Celsius,
the proteins in the egg crumple.

511
00:46:30,760 --> 00:46:35,800
It's this that turns the
white of an egg, well, white!

512
00:46:43,480 --> 00:46:46,560
We can see the dull red
glow of a heating element,

513
00:46:46,560 --> 00:46:51,360
but what we can't see is the vast
outpouring of infrared light...

514
00:46:54,560 --> 00:46:56,520
..triggering the formation

515
00:46:56,520 --> 00:47:01,800
of a molecule called
acetyl tetrahydropyridine...

516
00:47:02,720 --> 00:47:05,360
giving us toast.

517
00:47:10,040 --> 00:47:11,920
Toasting, boiling, cooking -

518
00:47:11,920 --> 00:47:17,560
things that are only possible thanks
to the invisible world of infrared.

519
00:47:22,520 --> 00:47:27,200
Infrared and ultraviolet are quite
close to the visible spectrum.

520
00:47:27,200 --> 00:47:30,560
Now we're travelling
much further along it,

521
00:47:30,560 --> 00:47:34,240
right out to the far reaches
of the invisible world

522
00:47:34,240 --> 00:47:36,280
to a part of the light spectrum

523
00:47:36,280 --> 00:47:39,160
that has utterly changed
our modern world -

524
00:47:39,160 --> 00:47:40,960
radio waves.

525
00:47:40,960 --> 00:47:44,280
Yes, they're part of
the light spectrum, too.

526
00:47:46,760 --> 00:47:51,880
When German physicist Heinrich Hertz
discovered radio waves in 1857

527
00:47:52,160 --> 00:47:55,840
his students may have been
impressed, but he wasn't.

528
00:47:55,840 --> 00:47:57,200
This is what he said,

529
00:47:57,200 --> 00:48:00,400
though he actually said it
in German, obviously.

530
00:48:00,400 --> 00:48:03,440
"We just have these mysterious
electromagnetic waves

531
00:48:03,440 --> 00:48:06,640
"that we cannot see with the naked
eye, but they are there.

532
00:48:06,640 --> 00:48:10,000
"They're of no use whatsoever".

533
00:48:17,320 --> 00:48:21,720
Yeah, mobile phones, television,
radio, all these things

534
00:48:21,720 --> 00:48:25,560
use something
that's of no use whatsoever.

535
00:48:30,800 --> 00:48:33,120
Radio waves have
changed the world we live in,

536
00:48:33,120 --> 00:48:37,920
transmitting conversations, music,
pictures, information

537
00:48:37,920 --> 00:48:42,680
sometimes over thousands of miles
and in thousands of different ways,

538
00:48:42,680 --> 00:48:46,240
but, because we can't see,
or smell, or feel them,

539
00:48:46,240 --> 00:48:49,600
it's easy to forget
just how fundamental they are

540
00:48:49,600 --> 00:48:51,560
to our modern way of life.

541
00:48:51,560 --> 00:48:54,200
INDISTINCT RADIO TRANSMISSIONS

542
00:48:54,200 --> 00:48:57,120
The air around us might look
completely empty

543
00:48:57,120 --> 00:48:58,880
when, in fact, it's anything but.

544
00:48:58,880 --> 00:49:02,880
If we could actually see it,
we'd realise just how crowded

545
00:49:02,880 --> 00:49:06,040
our 21st century airwaves
have become.

546
00:49:06,040 --> 00:49:08,880
And, happily,
scientists like this man

547
00:49:08,880 --> 00:49:13,040
can precisely measure those signals
so that we can visualise

548
00:49:13,040 --> 00:49:16,120
this invisible world all around us.

549
00:49:16,120 --> 00:49:18,160
Mum, hello.

550
00:49:18,160 --> 00:49:19,760
Yes.

551
00:49:20,960 --> 00:49:25,120
This is a world that's
almost entirely man-made.

552
00:49:25,120 --> 00:49:28,360
Natural sources of radio
waves on Earth are very rare,

553
00:49:28,360 --> 00:49:31,400
they're mostly made by extreme
weather like lightning, but the

554
00:49:31,400 --> 00:49:37,080
air around us is crammed with the
radio traffic of the 21st century.

555
00:49:37,080 --> 00:49:41,320
Every mobile phone
is its own little radio transmitter.

556
00:49:41,320 --> 00:49:46,160
Things as varied as microwave ovens
and the WiFi for your computer

557
00:49:46,160 --> 00:49:48,920
all work by radio.

558
00:49:48,920 --> 00:49:53,920
Whenever you lock or unlock your car
that's a radio pulse in action.

559
00:49:59,400 --> 00:50:03,760
In fact, there are now hundreds
of different applications

560
00:50:03,760 --> 00:50:05,640
pouring out radio waves.

561
00:50:05,640 --> 00:50:09,600
At any one time, there could be
thousands, hundreds of thousands

562
00:50:09,600 --> 00:50:13,200
or even millions of discrete
messages being transmitted.

563
00:50:13,200 --> 00:50:18,880
BABBLE OF MIXED RADIO TRANSMISSIONS

564
00:50:18,880 --> 00:50:22,360
Radio has turned
the empty air around us

565
00:50:22,360 --> 00:50:26,600
into a dense,
crowded web of invisible signals,

566
00:50:26,600 --> 00:50:31,200
which really isn't bad for
something with no use whatsoever(!)

567
00:50:37,440 --> 00:50:39,960
Seeing into this part
of the spectrum

568
00:50:39,960 --> 00:50:43,280
is helping us understand
more than our own planet.

569
00:50:43,280 --> 00:50:47,680
It's revealing the mysteries
of the entire universe,

570
00:50:47,680 --> 00:50:51,800
answering some of the most
fundamental questions of all.

571
00:50:51,800 --> 00:50:55,720
Look up into the night and, even if
you're lucky and it's a clear one,

572
00:50:55,720 --> 00:50:57,800
there's not really
that much to see.

573
00:50:57,800 --> 00:51:00,280
Stars, a few galaxies maybe.

574
00:51:02,640 --> 00:51:06,920
But that image we have of the night
sky is very limited

575
00:51:06,920 --> 00:51:09,840
because beyond that visible picture

576
00:51:09,840 --> 00:51:13,080
there's another
far more detailed one.

577
00:51:14,800 --> 00:51:18,320
But to see that for yourself
you need help.

578
00:51:18,320 --> 00:51:23,920
You need one of these, a telescope
designed to see the invisible.

579
00:51:29,640 --> 00:51:32,920
Telescopes
like this one at Jodrell Bank,

580
00:51:32,920 --> 00:51:35,720
are transforming
our view of the universe...

581
00:51:40,120 --> 00:51:44,280
..allowing scientists for the first
time to see into the depths of space

582
00:51:44,280 --> 00:51:46,920
far beyond what our eyes can see.

583
00:51:53,960 --> 00:51:58,040
This is an image of our Milky Way
in the visible spectrum.

584
00:51:58,040 --> 00:52:01,000
Visible telescopes can do
much better than the naked eye,

585
00:52:01,000 --> 00:52:04,720
but there are still large areas
of it that appear entirely dark.

586
00:52:04,720 --> 00:52:09,320
That's because much of space is
filled with, well, dust basically,

587
00:52:09,320 --> 00:52:14,200
cosmic debris from dead stars,
and this dust blocks our view,

588
00:52:14,200 --> 00:52:17,000
so this is pretty much the limit
of what we can see

589
00:52:17,000 --> 00:52:20,560
with a bit of assistance
in the visible part of the spectrum.

590
00:52:22,680 --> 00:52:26,440
But now, a new generation of
telescopes are able to look at

591
00:52:26,440 --> 00:52:29,720
that very same image of our visible
Milky Way

592
00:52:29,720 --> 00:52:32,040
in other parts of the spectrum.

593
00:52:33,160 --> 00:52:37,040
From radio to gamma rays,

594
00:52:37,040 --> 00:52:38,800
X-rays and infrared.

595
00:52:38,800 --> 00:52:41,440
These aren't just a series

596
00:52:41,440 --> 00:52:44,760
of cool images,
they offer a more revealing picture

597
00:52:44,760 --> 00:52:49,280
of our universe.
Take this area of space.

598
00:52:49,280 --> 00:52:53,560
The visible spectrum
reveals a shadowy gas cloud...

599
00:52:55,600 --> 00:52:59,840
..but seeing into the infrared
reveals a dense concentration

600
00:52:59,840 --> 00:53:01,600
of stellar material.

601
00:53:01,600 --> 00:53:07,200
This is the very process
that forms new stars.

602
00:53:07,200 --> 00:53:08,880
Five, four,

603
00:53:08,880 --> 00:53:14,600
three, two, one and liftoff
of the Space Shuttle Discovery.

604
00:53:14,600 --> 00:53:17,880
The dawn of the Space Age
has allowed scientists to see

605
00:53:17,880 --> 00:53:20,120
even further
into the invisible sky.

606
00:53:23,360 --> 00:53:26,920
Telescopes in orbit
around the Earth can detect light

607
00:53:26,920 --> 00:53:31,360
from the furthest parts of space,
like X-rays and gamma rays.

608
00:53:38,800 --> 00:53:42,800
Here's another image
of the visible sky,

609
00:53:42,800 --> 00:53:46,120
but seen in X-ray it revealed this.

610
00:53:46,120 --> 00:53:48,320
This extraordinary image

611
00:53:48,320 --> 00:53:52,000
shows nothing less
than the death of a star.

612
00:53:54,000 --> 00:53:57,160
You'd think that space
was empty and quiet.

613
00:53:57,160 --> 00:54:01,720
Actually, it's violent
and dynamic and explosive.

614
00:54:03,000 --> 00:54:06,400
This is the control room
at Jodrell Bank,

615
00:54:06,400 --> 00:54:08,760
still at the forefront
of modern astronomy,

616
00:54:08,760 --> 00:54:12,320
but on top of the discoveries
of this generation of telescopes

617
00:54:12,320 --> 00:54:15,360
there's a whole new generation
of monster telescopes

618
00:54:15,360 --> 00:54:18,360
being built to see even further
into the invisible.

619
00:54:23,120 --> 00:54:26,120
And now they're helping probe
one of the most fundamental

620
00:54:26,120 --> 00:54:29,080
and intriguing mysteries
of the universe,

621
00:54:29,080 --> 00:54:32,240
the presence of black holes.

622
00:54:32,240 --> 00:54:34,840
Now, I don't wish to be alarmist

623
00:54:34,840 --> 00:54:40,520
but, according to theory, there
should be a super massive black hole

624
00:54:40,520 --> 00:54:43,920
right at the centre
of our own galaxy.

625
00:54:45,960 --> 00:54:47,560
A central dark mass

626
00:54:47,560 --> 00:54:52,680
around which the galaxy was formed,
but, well, how do you find it?

627
00:54:52,680 --> 00:54:57,000
It sounds obvious when you think
about it, but seeing a black hole

628
00:54:57,000 --> 00:55:00,560
is an immense challenge for the
simple reason a black hole

629
00:55:00,560 --> 00:55:03,920
doesn't emit ANY light
from ANY part of the spectrum.

630
00:55:03,920 --> 00:55:07,480
In a sense,
it's the ultimate invisible object.

631
00:55:11,560 --> 00:55:16,520
So, finding it is,
as you'd imagine, quite tricky

632
00:55:16,520 --> 00:55:18,440
unless of course you've got

633
00:55:18,440 --> 00:55:22,200
one of the world's most powerful
invisible telescopes.

634
00:55:22,200 --> 00:55:26,680
And here in the high Andes of Chile,
that's exactly what this is.

635
00:55:27,840 --> 00:55:31,120
Looking into the infrared,
astronomers began probing

636
00:55:31,120 --> 00:55:37,360
deeper and deeper into one tiny
and precise patch of sky.

637
00:55:37,360 --> 00:55:39,560
And, finally,

638
00:55:39,560 --> 00:55:45,920
they discovered a collection of
stars apparently locked in orbit

639
00:55:45,920 --> 00:55:48,600
around a vast area

640
00:55:48,600 --> 00:55:50,120
of nothing.

641
00:56:02,160 --> 00:56:05,600
They'd found it,
a super massive black hole,

642
00:56:05,600 --> 00:56:09,240
three million times bigger
than the Sun,

643
00:56:09,240 --> 00:56:13,960
right at the heart
of our own Milky Way.

644
00:56:13,960 --> 00:56:17,040
Being able to see
what was once invisible

645
00:56:17,040 --> 00:56:21,040
helps us to unlock the great
mysteries of the universe -

646
00:56:21,040 --> 00:56:23,640
where it came from,
where it's heading

647
00:56:23,640 --> 00:56:26,640
and the sheer scale
of a cosmos where our Sun

648
00:56:26,640 --> 00:56:31,200
is just one lonely star
in a galaxy of 100 billion,

649
00:56:31,200 --> 00:56:33,160
and our galaxy just one

650
00:56:33,160 --> 00:56:37,440
of 100 billion others
across the known universe.

651
00:56:37,440 --> 00:56:41,400
But even if planet Earth
is just one tiny planet

652
00:56:41,400 --> 00:56:43,200
in that vast, vast universe,

653
00:56:43,200 --> 00:56:45,800
seen across that invisible spectrum

654
00:56:45,800 --> 00:56:48,120
from ultraviolet...

655
00:56:49,880 --> 00:56:52,840
to infrared and beyond...

656
00:56:55,280 --> 00:56:59,080
..it's shown to be a rather
wonderful and remarkable one.

657
00:57:09,280 --> 00:57:12,640
So the next time you step out of
your front door into the world,

658
00:57:12,640 --> 00:57:16,160
remember, there's whole lot more
going on around us

659
00:57:16,160 --> 00:57:17,800
if only we could see it.

660
00:57:32,200 --> 00:57:34,080
Thank you.

661
00:58:03,120 --> 00:58:06,160
Subtitles by Red Bee Media Ltd.

662
00:58:06,160 --> 00:58:09,200
E-mail subtitling@bbc.co.uk