That's correct, yes.

Okay, all right.

Gav: It looks like someone's just

pulling on space time.

- ( grunts ) - Not really sure what I'm looking at.

Dan: Bath time.

Gav: Those ducks just went--

Dan: Whoosh!

Gav: How do you feel about taking it

right in the face?

Gav: Dan, are you nervous?

- Oh. - ( water splashing )

- Gav: ( chuckles ) Oh! - ( laughter )

Well, that was a very unique

building we had access to there.

I love the fact that they just let us

mess around with it.

It's this incredibly scientific and precise

equipment and they were like, "Go wild."

Your life jacket going off,

unexpectedly, almost wet myself.

I think I even said, I was like,

- ( chuckles ) - "Huh, I'm surprised

this hasn't gone off."

and then about two seconds later it--

- ( air whooshing ) - Both: Whoa!

Both: ( laughing )

I think they're activated by salt

aren't they? Like it dissolves and

- then it activates-- - Yes, the salt in there

to make salt crystal, yeah.

Did it hurt taking the spike wave in the mouth?

- ( water splashing ) - Ooh!

Dan: I thought it was going to,

but it actually didn't.

I really liked that shot where

- ( music playing ) - it sort of tunnels

around your face, you look like you're

in a weird room that's moving.

Dan: Totally surreal. No one had done

that before, it was quite an honor really

to be the first smashed in the face with it.

Gav: Yeah.

So I think it'd be a good idea

if we learned more about waves in general,

but also learn a little bit more about the facility.

So we had a little chat with Tom.

Dr. Thomas Davey, you're the Senior Experimental Officer here.

Yeah, that's correct, yeah.

Okay, so, you can tell us all about

what you do here essentially.

Yes, so this is a facility which essentially is

just a model sea, about 20th scale.

And we we use that for lots of applications,

testing things like wave energy devices,

tidal energy devices.

Basically anything which we put in the sea.

Okay, so if you make a small wave about this big in here,

you imagine it's 20 times the size.

That's what you're imitating essentially in the ocean.

- Dr. Davey: Exactly. - Dan: So how long did it take to fill that thing?

Uh, it did take us three weeks, so--

- Three weeks? - ...we don't like taking the water out of it.

It's two and a half thousand tons of water in this tank.

And what was the choice behind making the tank

this specific size?

If you go much bigger,

things start to get very expensive.

If you go much smaller the scaling

will start to work against you, uh...

- I imagine this was cheap, then. - ( laughs )

Yeah, so you're looking at

about 6 millions pounds of investment

just to build the tank.

And actually the whole project's probably around

12 to 15 million.

Might be one of the more expensive things

- we've messed around with... - ( laughs ) Yeah.

...if I'm honest. Cool.

So how do you get the waves to do

the exact thing you want them to?

Well, this is the only large circular wave

and tidal tank in the world.

So what we have is 168 wave makers around the edge.

These are basically paddles.

So each individual paddle on its own can generate a wave.

But because we're in a circle,

you can imagine, you can actually then generate from any direction,

so you can have this one wave going in one direction,

you can have thousands of waves going from all directions.

It's a bit like playing a musical instrument.

You just combine all these notes together

to create a very complex sea in the tank.

- Whoa-ho-ho-ho! - Whoa!

( water splashing )

And then on top of that you then put tidal currents.

So you make currents as well underneath...

Dr. Davey: Yes, yes. It works a bit like a conveyer belt.

The current comes from underneath the tank,

over the top, and back around again.

- Oh, okay. - So...

You said you can replicate any part of the sea.

If I said to you, I want to replicate Brighton.

I want Brighton, could you do that for me?

As long as you got the data.

If we could get good data for a site

and we can understand the energy of that site

and the directions of the waves and so on, then yes.

That way, if you just brought in a load of sand,

and people didn't fancy the, like, eight hour drive,

you could have people just come in here

- and enjoy the-- - Yeah, we'd be in the surfing business.

( laughter )

Thanks, Tom, that was really interesting

and thanks for letting us use your very expensive pool.

Dr. Davey: No problem.

Back to you, Gav and Dan.

Thanks, us.

Why don't we learn some more about waves.

Yeah, we've invited someone along

who's travelled the world,

and written a book about all the world's

scariest, largest, fastest waves.

It's called "Tides."

Hi, Jonathan. How's it going?

- Hi, Dan. - Hey.

Could you explain to us, the difference between waves and tides?

Sure, waves, as we talked about

are generally created in the storm, right?

There's a one pulse that makes the wave

and then the waves travel away from that.

But a tide is actually also a wave,

but it's the largest wave on the planet.

And it's a long low wave

that travels about 450 miles per hour around the globe.

We don't experience it as a fast moving phenomenon

because if we're on the coast, we have to stay there all day

to watch it pass, right?

Six hours of trough, which is low tide,

and then about six hours later, the crest, high tide.

So you could potentially be on a plane,

unknowingly flying at the same speed

- as a tide rolling through. - That's right.

The oceans actually aren't deep enough

for this free wave, this wave of tide, to travel

as fast as it wants to travel.

So essentially it drags its legs

on the bottom of the ocean,

and slows down and creates friction.

Friction against the entire Earth?

- That's right. - Wow, yeah.

'Cause I've heard that they occasionally

will add like a leap second to the clocks

to compensate for the Earth slowing down.

Tides have literally slowed down the rotation of the Earth.

Acted as a break.

'Cause the tides are slowing down the world

by friction on the bottom of the sea.

That means every millions of years,

there's changes to the amount of hours in a day?

Yeah, about 400 million years ago,

our day 21 hours long, not 24.

Because of the tide.

I'm okay with it, because I feel like

I'd struggle to fit everything into a 21 hour day.

Yeah, so you're thinking that millions of years

when it's a 30 hour day,

- people are gonna be like... - ( laughs )

( sputters ) ...a long day.

Yeah, the days got longer and then people started having longer meetings.

- ( laughs ) - That's what happened.

Yeah.

So when we filmed the footage in the wave pool,

it looked a bit like a sound wave in 3D space.

And you've done experiments before with vibrations and frequency

to try and show what's happening with the tides

and you've asked us to get this stuff here.

Yes, this is the Chladni experiment

and uh, that little device over there

is a sign wave signal generator.

And it's gonna function like the sun and the moon.

The vibrations from the sun and the moon.

And this area here, this is the ocean.

and we're gonna put some salt on that

and it's gonna demonstrate how the salt

will dance around or resonate with

the various signals from the sun and the moon.

When scientist look at tides,

it's really all about the oceans responding

to the vibrations, or pulses, or beats

from the sun and the moon.

So what I've got here is a way to look at that.

So go ahead and pour the salt on there...

- Okay. - ...and as you turn the signal generator on,

You wanna do it?

Well, you're the sun and the moon.

- That's fair. - Yeah.

Jonathan: So as you turn the signal generator on

you'll start to see patterns form here.

Gav: Why don't we start with 60?

Oh, I see a bit moving around the edges.

Dan: Gibberin'.

- It's gibbering - I like that.

Whoa.

- Jonathan: Oh, wow, it's bouncing. - Dan: Oh, wow. That's cool.

Gav: An "X." Get more salt on there.

Sure, let's get that on there.

None of that salt wants to be in the middle,

that's interesting.

- Dan: Oh, that's really weird. - ( Gav laughs )

Dan: It looks like static from a TV.

Oh, it's spreading. Circle's getting bigger.

Do it again.

- Oh. - Gav: Yeah.

This made two lines perfectly.

And that's not a huge jump,

and now that's two completely parallel lines.

As the frequency alters, so does the pattern.

Which is an indication of how the patterns

and the tide change with frequencies

from the sun and the moon.

78, here we go.

- ( grunts ) - Steady on.

Oh.

I need to put more on, eh?

- Oh, it's making like a-- - Gav: Like a plus sign.

All right, go then.

I'm gonna run out of salt here.

Oh, quick.

- Oh, it's making a circle. - It's a circle.

Dan: A bit of acorn that one.

Do you like the little tappy technique?

- Gav: Yeah. - Dan: That is so weird looking,

the middle part.

So this shows how the ocean tide is basically

a response to the vibrations of the sun and the moon.

A patterned response.

You know, it might be worth whipping out the Phantom

for some of this.

- It's what we do after all. - Yeah.

Okay, the Phantom's set up 1,000 frames a second in 4K.

Dan, what would be your preference for frequency?

Well, I-- I think we started at 60 and went to 67

and there was a lot of activity and jumping around.

Yeah, there was a lot in the middle,

so I think we can contain it.

And also the sides were pretty cool as well

'cause it just went crazy on the sides and everything that--

Yeah. Well, as you can see we've got the whole thing in the shot,

so whenever you're ready.

Okay, I'm gonna whip it on

and crank it up.

- Are we ready? - Yeah.

- So this is sixty. - Yeah.