Bang Goes The Theory (2009) s04e04 Episode Script

On today's show 'Dallas is in Oalifornia looking at earthquake science.
' This basically acts as a fuse, if it's overloaded then this bit is going to go and the bridge is saved.
That's the theory.
'And l'm in Hawaii, witnessing the power of Mother Nature.
' A magnitude 8.
8 moment.
'That's Bang Goes The Theory' Welcome to Bang Goes The Theory.
The tragic events in New Zealand in February were yet another reminder of how unpredictable and destructive Earth can be.
What can we do to limit the damage? Dallas went to Oalifornia to find out.
'The San Andreas Fault, 'the line where two of Earth's tectonic plates meet 'and rub up against each other.
' The land over there is moving north, an eye-watering 55mm per year on average.
lf l waited here for 15 million years or so, l'd see Los Angeles gently passing me by northwards to where Alaska is.
'Unfortunately, all this geological rubbing 'can result in major earthquakes.
' (OAR HORN HONKS) 'l spent a bit of time living in Los Angeles 'and often wondered if today was the day l would experience 'the earthquake everyone dreads - ''the big one'', 'a magnitude 7 on the famous Richter scale.
'ln LA, people take this threat very seriously.
'This truck is designed to give people the experience 'without it injuring them.
'l admit l'm a little nervous, so l've enlisted an earthquake expert 'to hold my hand.
' Welcome to earthquake country.
How are you feeling? Slightly sweaty palms.
Not quite sure what to expect.
At what number on the Richter scale would you perceive an earthquake? You could feel it at a magnitude three, depending on what kind of rock you're on.
lt would be good to put on safety glasses.
- Really? - You never can tell.
Better to be safe.
All right.
We're on.
Oh.
OK, so that's quite That's quite violent.
My tea's almost A typical southern Oalifornia earthquake.
Magnitude 4.
5 or so.
Very much like what happened in the last few days - a 4.
7, 4.
1 - near the earthquake site.
- You actually had that sort of level recently? - Exactly.
OK, this is much bigger.
Where are we at now?.
Around a 7.
5 now.
This is where buildings collapse, people get killed.
lt's the big one.
Stop! Turn it off! Turn it off! 'Well, that was alarming, 'but it does make Oalifornians take earthquake resistance seriously, 'particularly in the engineering of bridges, 'the lifelines to major cities.
'When a big one does hit, there'll be no reaching for the off button.
' Somewhere the Oalifornians know that is in San Francisco.
Just over a century ago, the city was shaken to its foundations by a magnitude 8 earthquake that killed 3,000 people and left over 200,000 homeless.
Then in 1989, it was hit by another massive earthquake.
At magnitude 6.
9, it claimed 63 lives, and the city's Bay Bridge, little brother to the Golden Gate Bridge, was one fatal location.
The bridge is built on wooden pilings, Douglas fir trees that are driven into the bay mud.
lt's hats off to the engineers that this bridge has lasted so long.
After 80 years, it's time to replace it.
Ourrently under construction is a new Bay Bridge.
Naturally, earthquake protection is at the forefront of its design.
'To cope with the way earthquakes make the ground behave like a liquid 'the bridge is being built with strong footings that splay out '100 metres deep into the mud below.
'lt's just one feature that means this remarkable bridge 'will withstand that 7.
5 magnitude earthquake 'and, more importantly, stay open afterwards.
' What is it about the engineering of this bridge that's special? This bridge is built to ''lifeline criteria''.
That means that after a large-scale earthquake, this bridge will remain available to emergency service vehicles - fire trucks, police - then, without a complete rebuild, will open back up to public service.
'This $5 billion bridge is being engineered 'to withstand a freak earthquake, the likes of which 'might only be seen once in 1 ,500 years.
'One way to do that is by building the bridge in sections, 'with a gap between them that allows for free movement.
' Wow! This is amazing! So we're at a junction point between two separate bridges? Yeah.
Why can't you have one bridge? Why do you need spaces? lf you don't have the bridge broken up into sections, an earthquake can cause a lot of damage.
lmagine we're in a big earthquake situation.
What would be going on here? These bridges are going to hit each other.
That rubberised grommet there will take the first impact.
Then this hinged pipe beam will allow the bridge to move in and out.
Like doweling when you're putting your lkea furniture together.
- They work as connectors.
- That's a fantastic analogy.
We don't want the bridges to skew or move sideways.
The pipe beams keep the bridge together.
All the energy will be transferred into what we call a fuse here.
This acts as a fuse.
lf it's overloaded, then this bit is going to go - and the bridge is saved.
- That's the theory.
'A similar device can be found up the bridge's only tower, 'which will support the road below.
' l'm 65 metres up in the heart of the tower.
lt's actually not one tower.
There's four independent legs which are joined together by these connecting beams, which you can see down here.
These beams, on a non-earthquake day like today, give the bridge its rigidity.
They're also designed to bow and flex.
lf the earthquake's bad enough, they'll buckle.
The clever bit is that whole section can be replaced with these bolts.
They just unscrew and you can put a whole new section on.
'Four legs are better than one in an earthquake because if one breaks, 'the others will be strong enough to keep the bridge up.
'lt's due to be completed in 2013.
'To get an idea of what it's going to look like, 'l'm taking a look from the top.
' How high are we going? 1 12 metres above the water.
1 12 metres above the water.
This is not for the faint-hearted.
- You're not faint-hearted? - No! He's all right.
Good.
lf you get a bit nervous, l'm here for you.
l appreciate it.
You've got to have a head for heights for this! To take stock, over towards San Francisco, is the San Andreas Fault, which is capable of serving up a magnitude 8.
1 earthquake.
Over there, towards Berkeley, is the Hayward Fault, which is capable of serving up a 7.
1 magnitude earthquake.
l'm right in the middle! And it's a question of not ''if'' but ''when''.
'According to the US Geological Survey, there's a 70% chance 'of a big earthquake striking here some time in the next 20 years.
' At least for the 280,000 people who drive across there every day, it's reassuring to know their bridge will be safe.
That is a beautiful build! What's happened to the old bridge? - Simple.
- Being sold for scrap.
lt's solid steel.
That is a lot of steel.
Are they going to hold on to it while the price of scrap goes up? - l'm not sure.
What is the price of steel.
- £150 a tonne? That is worth a lot of money scrap.
- lt did fare well for 80 years, that old one.
- lt's amazing.
lt's a beautiful bridge.
That's part of the deal.
lt wasn't, ''We've got to put up a new bridge.
'' The aesthetics of it are vital.
They are vital but, for $6 billion, you expect a few aesthetics.
- You want it to look pretty! - l've got a present for you, Jem.
This is an actual bolt from the new Bay Bridge.
l was thinking about you up there, about you as an engineer.
Missing you! The exciting thing about this bolt, in honour of our visit from the BBO, they've put BBO Oan you see that? - .
.
on every single bolt! - No way?! - BBO? - BBO.
British Broadcasting Oorporation? Either that or the Bay Bridge Oompany.
One of Goodness sake! - That's for you.
- Thank you.
- l like it.
- To use wisely.
- Did you bring me anything? - Moving swiftly on Now, it is time for Dr Yan.
Matt from Brighton sent in a really intriguing question.
lf a caterpillar has a scratch on it, will the butterfly have a scar after it's metamorphosed? Firstly, what is metamorphosis? Many insects have different-looking stages to their life cycle.
They often start out as a form that's specialised for feeding.
Then they end up as something that's adapted for breeding.
The change between these forms is called metamorphosis.
Even grasshoppers metamorphose.
lt's not so obvious because the babies look like the adults.
lt's more noticeable in dragonflies.
Their young are specialised for living in water whereas the adults fly around.
ln both cases, the changes happen step by step.
That's called incomplete metamorphosis.
But insects like beetles, flies, bees and butterflies do something more extraordinary.
That's called complete metamorphosis.
The eggs hatch out as larvae, which feed voraciously.
Think of maggots or caterpillars on the vegetable patch.
Those then seal themselves up as a pupa, which looks a bit like this.
They emerge completely transformed as the sexually mature adult, like this butterfly.
ln fact, this insect's been through four major stages in its life cycle.
Egg, larva, pupa and, finally, butterfly.
Although we call this a butterfly, it's spent much more of its life as a caterpillar.
This stage as a flying and mating machine is much more visible to us.
So, the question.
What if there's a scratch on the caterpillar? We need to look carefully at the caterpillar's life cycle.
lnsects have a tough outer skin.
As the caterpillar grows, it needs to repeatedly shed its outer layer and grow a bigger one.
The caterpillar doesn't stop eating, so it has to moult and regrow skin four or five times.
lf a caterpillar suffers a scratch on the outermost skin, it'll get rid of it by moulting.
The new skin won't have a scratch and the butterfly won't be affected.
What if the scratch went into the muscle? That's where complete metamorphosis comes in.
l set up a camera to capture caterpillars going through their pupal stage, but don't worry, l didn't harm them.
Once the caterpillar is finishing its final moult, it attaches itself onto a branch and grows a rigid case that looks nothing like a caterpillar.
This is the pupal stage.
lnside, it undergoes its final transformation into a butterfly.
l'm going to demonstrate with this jelly caterpillar.
ln the pupa, the caterpillar secretes digestive enzymes and kind of liquefies itself.
The cells of what was the caterpillar die and disintegrate.
lt's called apoptosis, kind of like melting the jelly.
Even when it liquefies, a few vital structures do remain.
l've represented those by sweets.
The central nervous system, the gut, and the innermost layer of skin cells.
Most importantly, it also includes the imaginal cells.
They're arranged down the body in a series of discs.
There they remain, not doing much until, that is, just before the pupal stage, when they spring into action.
Using this mush for nutrients, they grow and multiply, developing into new structures.
So, by the end of the pupal stage, the imaginal discs that were once in the legs of the caterpillar, have developed into the legs of the butterfly.
You end up with something like this! Actually, it happens more like this.
Depending on the species, the pupal stage can last from a few weeks to ten years! Eventually, a butterfly emerges, attractive and ready to mate, fulfilling its reproductive function.
So, Matt, most damage to a caterpillar won't carry through to the butterfly.
Amazingly, most cells get completely mushed up and their contents reused.
lf a caterpillar damages the few structures that survive the pupal stage, they can remain damaged in the butterfly.
lf it damages that innermost skin layer, the butterfly may have scar tissue.
lf the imaginal discs are damaged or removed, the butterfly might not even develop certain structures.
And that's how scientists figured out how metamorphosis works.
Thank you, Yan.
Here's a Yanism that you might like.
- OK.
- Being an aeronautical engineer.
What l want you to do is imagine you've got airport A.
And down here you've got airport B.
- Yeah.
- Right.
Here is my aeroplane.
lmagine there's no wind and this is going at a constant speed.
lt takes off from airport A, goes to B and back again, a round trip.
lmagine that journey.
Hold it in your mind.
This is the same journey, but there is a wind blowing from A to B.
The plane goes at the same speed relative to the air.
So, A with the wind, to B, then back against the wind, to A.
My question for you, which journey is going to take longer or are they going to be the same? l think this is really tricky.
Have a think about this at home.
l like this.
An aircraft's engine power only dictates the speed it can go relative to the wind.
So if it keeps the same power on, it's going to get faster this way and slower that way.
This is a really good test of either your logical deduction or algebra.
Have a little go at this at home.
Get a pen and paper and see if you can work it out.
lt's tricky.
Now, back in January, l got the chance to visit Hawaii and the awesome observatories at the top of Mauna Kea.
Hawaii is stunning.
The island chain erupted out of the ocean as a result of volcanic activity.
So l grabbed the chance to get up close and personal with the might of Mother Nature.
There's incredible heat coming off this.
Lots of water vapour and sulphur dioxide.
lt hits your eyes.
'On the southern coast of Hawaii's Big lsland, 'the volcano Kilauea constantly spews lava into the Pacific Ocean.
'lt's the most active volcano in the world.
'Since 1953, it's erupted 33 times 'and it's been non-stop for the last 18 years.
' lt's so hot! Streams of 1 ,000 degree Oelsius lava pouring into the sea.
This is Kilauea in all her glory.
'The lava from this volcano isn't the only threat here.
'Along the coast, unstable volcanic rock can crash into the ocean, 'causing another destructive force of nature, the tsunami.
'Small tsunamis like those caused by landslides 'happen at least twice a year across the globe.
'Much larger ones can occur every 15 years, 'caused by huge earthquakes at the bottom of the sea.
' Ordinary waves like these are created by the wind.
Even though they look tame, they've got the power to knock me over.
But add an earthquake and you're talking about a wave with a different kind of power altogether.
'How exactly are tsunamis different from ordinary waves? 'Surprisingly, it's not about their size.
'lt's how fast and how far apart they are.
' Here's an ordinary wave.
The distance between each crest, or the wavelength, is usually 100 to 200 metres.
When an earthquake occurs, the sea floor is deformed.
That displaces the body of water above.
As this water attempts to regain equilibrium, you get your tsunami wave.
The distance between each crest increases to anything up to 300 miles.
'Out in the deep ocean, a tsunami wave is only a metre or so high, 'but it can travel up to 600 miles an hour and hit land peak first 'or trough first, which looks like a sudden low tide.
' As the wave approaches the shore and the water depth decreases, the speed of the wave decreases, but that energy has to go somewhere, so the height of the wave begins to increase to 30 metres or more.
The wave moves inland up to one or two miles and takes everything in its path.
Sometimes, the second wave up to two hours away can be even more powerful than the first.
'Hawaii has been hit by at least 50 tsunamis since records began.
'After 159 people were killed in 1946, 'the islands established a tsunami warning centre, 'one of three in the world.
'After the tsunami of Boxing Day 2004, 'it took on a truly international role.
' These are seismometers all over the Earth.
Up here, this is seismometers that have actually seen something.
We have one dot in Southern Oalifornia.
lf there were a big earthquake, we would see a bunch of white dots.
Then, as the energy spreads out across the Earth, you would see all of these dots light up.
You've got 7.
8 on the Richter scale, what happens next? My pager goes off, so l come running in and look at this screen.
Wow, ok.
Each of these tracers would suddenly show something.
We tell people when the tsunami's going to arrive.
- How do you calculate that? - We know where the earthquake is.
We know how fast a tsunami travels cos that depends on water depth.
So we can compute when it's going to arrive at various places.
The tsunami's in one hour, two hours, three hours.
There's Hawaii.
lt takes 15 hours to get to Hawaii.
'These predictions are aided by pressure sensors in the Pacific 'which allow the force of a tsunami to be tracked.
'38 buoys across the ocean pick up signals from sensors on the sea bed 'and relay them back by satellite to Hawaii.
'The centre issues warnings not just to Hawaiians, - 'but to people all over the world.
' - A magnitude 8.
8 moment.
'With every tsunami, whatever the size, Gerard collects new data 'to make their predictions even more accurate 'the next time a big tsunami hits.
' The size of the 2004 earthquake, a magnitude 9.
2 or 9.
3 earthquake, a real monster, the chances of that happening again are very good.
ln all probability, it will be in the Pacific for the simple reason that the Pacific has most earthquakes.
For the Pacific, the 2004 tsunami was actually a godsend, because it reminded us of the hazard and we realised we're not ready.
So there was an immediate scramble and the system was greatly improved.
We've got to the point where we think we're ready.
Liz, l'd love to know, when you were in that boat, did the sea actually feel hot? We leant over the side and it was like a hot bath, really nice.
Except the fumes were something else.
We were inhaling some of it so got out of there sharpish.
- lt did look a bit close.
- lt was! We were lucky.
Kilauea hadn't been flowing into the sea for six months.
We thought we were never going to get it.
5am we get the call.
''You are the luckiest people alive! Get on a boat and get some shots.
'' What l didn't understand was the infrastructure behind the early warning system.
That bit of Hawaii looking out for so much of the planet! You've got Gerard with his pager.
He's our primary source of contact.
He's got a back-up to the pager and a back-up to the back-up and lots of people in the centre.
- That's only going to get better.
- Absolutely.
That's it for this week.
- Say goodbye, boys.
- Bye.
Bye.