Richard Hammond's Invisible Worlds

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

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

But what the eye sees is not the full picture.

Alongside the world we see is a very different world.

An invisible world of hidden forces and powers.

This shapes every aspect of life on Earth.

Now, technology can open a door on that hidden world,

revealing its mysteries, and showing us the true wonder of the world we live in.

In our vibrant, hectic world, we think we spot everything.

But right in the midst of this busy world, there's a whole other world going on,

it's just that we can't see it.

To us, it's invisible.

Our eyes are too slow to see everything that's really going on.

The world is full of things that happen too fast for us to notice.

Things we miss in the blink of an eye.

The blink of an eye takes about 15 milliseconds,

and it takes the human brain about 150 milliseconds to process what we see.

We're not aware of this time lag going on,

but in those few milliseconds, there are things happening,

extraordinary things that were never see.

This is the invisible world of speed...

..where thin air...

can shatter rock

and water can tear through metal.

Where the fastest thing on Earth is right beneath our feet.

And where we'd see spectacular events that some thought were UFOs.

If we could stretch time, we could solve some of the biggest mysteries of our planet.

Now, using the latest camera technology, we CAN stretch time, making the invisible visible.

We can overcome the limitations of our eyes to see whole new worlds.

Lightning. A billion volts and hotter than the sun.

But there's even more danger in what you CAN'T see.

This is Rapid City, South Dakota.

In the middle of America's lightning belt,

it gets hundreds of strikes every year.

But there is something strange about the lightning here...

..something that's becoming a bigger and bigger problem.

Something too fast to see.

Lightning travels at over 100,000 miles an hour.

So only with super slow-motion cameras can experts begin to understand what's going on.

When you view a flash in real time, it's like seeing a title of a book.

You can see that there was a flash there that reached the ground,

maybe it flickered a little bit, but that's all you know.

You come and record this same flash with these high-speed cameras,

it's like a novel.

It tells a unique story every time you play it back. Incredible.

In slow motion, we can see what gives lightning the shape that launched a thousand horror movies.

Fingers of electricity hunting for the ground.

And now, these high-speed cameras are allowing us to catch something

completely invisible to the naked eye.

The strange lightning that's found not in the plains, but right in the heart of Rapid City.

There's a storm brewing.

Specialist cameras set to record at nearly 300 times slow-motion are waiting to capture it.

And there it is.

At first it looks like a normal lightning strike

but the technology reveals something else.

Instead of lightning shooting downwards, this lightning is travelling upwards.

When I played this for the first time, I was just blown away.

It was just amazing to see it.

And this strange, upside-down lightning is powerful, it carries more charge than normal lightning.

But what's really extraordinary is that upward lightning is created by us.

Because it's these tall transmission towers that are triggering

the vast bolts of lightning firing up into the clouds.

Now, you might think that because it is going away from the town,

this lightning is harmless.

Unfortunately not.

When the upward bolt hits the storm clouds, it triggers more lightning

that fires straight back down to the city.

And it is not just here, in Rapid City.

As we build more tall buildings,

this new form of lightning is spreading across the world.

In this high-speed world, there are surprises hidden in even the most everyday things we think we know.

Take this, for example.

On the face of it, that's just one small firework designed to make people go, "Ahh!"

But in fact, there's an invisible force at work here,

one hidden in all explosions, and it's powerful enough

to destroy buildings or tear through solid rock.

Even this little candle unleashes a force too fast for us to see,

that reaches way beyond the pretty sparkle.

And that's what this special camera shows,

something our eyes can never see.

It's a shockwave -

super-fast, devastating, potentially deadly, and yet it's just thin air.

I want to take a closer look at this devastating force in action.

To do that, I need to blow something up.

So, this rock face, it's about 100 metres long.

That's what we're going to blow up,

which will mean shifting about 20,000 tons of rock.

Up here on the top, we're filling not one, but 20, separate holes with explosives.

You see, our experiment is a bit more sophisticated than just creating one massive explosion.

Each one of these 20 separate explosions needs to be

choreographed to go off at 25 millisecond intervals.

That way, each explosion will fragment the rock,

and open up a face that can then be hit by subsequent explosions.

At least, that's the theory.

This whole event is going to be over in about half a second.

So to stand a chance of seeing this,

we're going to need to film it at high-speed.

We're using a remote trigger with a short travel,

so I need to be 100 metres away from the explosion - in that.

Yeah, I know.

But it does mean I'll get to experience very much at first hand

the impact of 20 separate explosions detonating within half a second

of one another to try and shift 20,000 tons of rocks.

So in that sense, I'm lucky to be in there.

Nice!

Oh, yeah.

I feel safe.

So, I arm it with that. BEEP

That means it's now armed.

Counting down from five, four, three, two, one.

20,000 tons of rock, gone in a second.

And I'm still safe, which is a bonus.

That was quite a rumble.

I really felt that.

Yeah, just to actually feel the earth move

because of something you have just triggered, that's quite a sensation.

Yeah.

A little lie-down is needed.

But it's only when we slow down in the film 40 times that

we can see more of what just happened

and why I wasn't turned into mush.

There's a flash as the detonation cable ignites.

And now we can see the blast going off. One every 25 milliseconds.

But the real force is not the blast.

It's the shockwaves that each blast releases.

Deep in the quarry face, the shockwaves are forcing their way through sheer rock,

eventually erupting at the top.

The shockwaves keep on expanding outwards,

powerful enough to crumble the rock

and finally tear apart the entire face.

But thankfully, not mine.

By choreographing the explosions,

we were able to drive and steer the shockwaves through the rock,

rather than let them spill out into the air around,

which is why I was able to get so close.

Not sure I'd want to get much closer.

So, how can a shockwave cause such awesome destruction?

To find out, we're going to trigger one almighty explosion.

We're going to attempt to see a shockwave.

It'll be over in the blink of an eye,

but high-speed cameras will capture every millisecond.

At least, that's the plan.

First, thousands of pounds of gunpowder are loaded.

That's a lot of gunpowder.

The fuse is set.

To be safe, everyone needs to be over a mile away -

that's why they're running away in pick-up trucks.

Except for these guys -

the detonators.

They'll be less than half a mile from the blast zone,

which is why they get the armoured car.

Everybody ready? Are you ready, sir?

Range control to security checkpoint, are you clear? 'All clear.'

Obs one, are you clear? 'We're all clear.'

10/4, stand by for counting. I'll say it again, stand by for counting.

Five, four, three, two, one...

In an instant, thousands of pounds of gunpowder explode.

But the shockwave is completely invisible.

So we need to slow it down over 100 times,

and then watch it back repeatedly - from several angles.

Stand by for counting. I'll say it again, stand by for counting.

Five, four, three, two, one...

The fuse races towards the site.

In a thousandth of a second, the gunpowder ignites.

In one millionth of a second it changes from solid to gas.

And there it is. Finally, we can see the shockwave.

A wall of intense high pressure in the air.

It's travelling at over 300 metres every second.

So fast that anything in its path is punched aside.

And now we can see amazing detail.

The shockwave reignites unburnt fuel, triggering a secondary shockwave at the tip.

It's the shockwave, not the explosion itself, that causes devastation.

In the high-speed world, thin air can create brute force and destruction.

But it can also allow us to do some pretty amazing things.

OK, right, so go for the off, yeah.

A nice bit of back pressure as you take-off, plenty of left pedal.

And a bit more.

That's it.

There she goes.

Now, bear with me, I am still learning this.

Now, it's something that we take for granted, but essentially

nearly two tons of helicopter and me are being held up by air.

Just very, very fast-moving air.

The rotor above pushes air downwards, that creates the lift that keeps me up in the sky.

It's one of the basic principles of aerodynamics.

But step into the world of the invisible,

and this benign and useful force suddenly looks very different.

These planes are flying close to the speed of sound.

But at this speed, the air moves so fast

it's about to become a potentially dangerous force.

Slowed down by nearly 200 times, just watch what happens on the wing.

At these super high-speeds, the moisture in the air suddenly condenses into water.

A cloud forms.

I know that doesn't sound very scary - a cloud -

but that cloud is like suddenly dumping the weight of a car on the wings.

Only the most skilled pilots, like these, can cope.

We may think that we've conquered flight,

but compared to the natural world,

our mastery of the air is basically rubbish.

Engineers have been wrestling with the problem of flight