0:00:05 > 0:00:08'Humans are an incredible species.'
0:00:08 > 0:00:11We've found ways to talk to each other on opposite sides of the world.
0:00:11 > 0:00:14We've discovered cures for terrible diseases.
0:00:14 > 0:00:18And some of us have even left this planet to explore space.
0:00:18 > 0:00:21But there's still so much left to find out.
0:00:21 > 0:00:25I'm Greg Foot. Ever since I was a kid, I've been into science.
0:00:25 > 0:00:29I've always been asking questions, and taking things apart to understand how they work.
0:00:29 > 0:00:31I was the kid trawling through the rock pools
0:00:31 > 0:00:35and the one that tried to turn his bike into an aeroplane.
0:00:35 > 0:00:38I even went on to do a science degree.
0:00:38 > 0:00:40'And I'm still asking questions.'
0:00:40 > 0:00:41- This is gonna hurt, right?- Yeah.
0:00:41 > 0:00:44'And I reckon a lot of you are, too.'
0:00:44 > 0:00:47And that's what this series is all about.
0:00:47 > 0:00:50Getting to the bottom of all those questions that never get properly answered,
0:00:50 > 0:00:52to reveal the Secrets of Everything.
0:01:00 > 0:01:03'On this, the final episode of The Secrets of Everything,
0:01:03 > 0:01:06'it's a battle for survival.
0:01:06 > 0:01:08'I lose my mind trying to dig to Australia.'
0:01:08 > 0:01:11- HE LAUGHS - My brain doesn't work!
0:01:11 > 0:01:14'I take a dip in deadly quicksand.'
0:01:14 > 0:01:16OK, that's not going to work.
0:01:16 > 0:01:20'And stuff myself with artery-clogging fast food.'
0:01:20 > 0:01:25- HE SIGHS - OK, that was over 1,000 calories, just for breakfast.
0:01:25 > 0:01:29'But first, the secrets of life and death.'
0:01:29 > 0:01:35So, I know that my heart is just flesh and blood like the rest of me.
0:01:35 > 0:01:37But I still attach emotions to it.
0:01:37 > 0:01:41I definitely say that I've been heartbroken before.
0:01:41 > 0:01:44But what I want to know is, if a girl was to hurt me badly enough,
0:01:44 > 0:01:47could I die of a broken heart?
0:01:47 > 0:01:51# You, and your heart
0:01:51 > 0:01:54# Should they feel so far apart? #
0:01:54 > 0:01:59'To see if this is possible, I first need to find myself a heart.'
0:01:59 > 0:02:03'To help me is Home Office pathologist Dr Stewart Hamilton.'
0:02:03 > 0:02:05- Hi, Stewart.- Hi.
0:02:05 > 0:02:07'And a recently deceased pig.'
0:02:07 > 0:02:13'It was destined for the butcher's but, like scientists have done for centuries before us,
0:02:13 > 0:02:16'we're going to use it for research purposes.'
0:02:16 > 0:02:18So, a pig is a good match for a human, right?
0:02:18 > 0:02:21Yeah, physically very similar, physiologically very similar.
0:02:21 > 0:02:25And the heart, to all intents and purposes, nearly identical to a human one.
0:02:25 > 0:02:29Brilliant. Well, first things first, we need to expose it.
0:02:32 > 0:02:37So, right bang in the middle of the chest, there is the heart.
0:02:39 > 0:02:42- Ooh, it's heavy.- It is. - It's a lot heavier than I thought.
0:02:42 > 0:02:48- So, although this is a pig's heart, this is the closest we can get to a human heart?- Yeah.
0:02:48 > 0:02:50I take it you've seen a few human hearts in your time?
0:02:50 > 0:02:53Erm, probably only about 2,500!
0:02:53 > 0:02:56Ha! So yeah, quite a few.
0:02:56 > 0:02:58I'm not sure if someone gave it to me I'd be able to tell the difference.
0:02:58 > 0:03:02- Really? They're that similar? - That similar.- Oh, right!
0:03:02 > 0:03:06That does not look anything like you get on a Valentine's Day card.
0:03:06 > 0:03:09No, there's nothing terribly emotional about it.
0:03:09 > 0:03:13'Your heart isn't there to win a beauty contest. It's a muscle with a job to do.
0:03:13 > 0:03:17Blood packed with oxygen from the lungs is delivered to your heart
0:03:17 > 0:03:18through the pulmonary vein
0:03:18 > 0:03:21before being fired out to the body through the aorta.
0:03:21 > 0:03:27Round and round, all day and all night, driven by about 2.5 billion heartbeats in an average lifetime.
0:03:29 > 0:03:34The heart, in reality, is simply a pump.
0:03:34 > 0:03:36It's there to pump blood round your body, and keep you working.
0:03:36 > 0:03:39No different to the pump on your central heating system.
0:03:39 > 0:03:43And, just like a water pump, it can go wrong.
0:03:43 > 0:03:47Put yourself on a diet of lard and fags, if you want to experience it for yourself.
0:03:50 > 0:03:55But there is a kind of heart problem you can't do anything about.
0:03:55 > 0:03:57If my girlfriend was to dump me tomorrow,
0:03:57 > 0:03:59I'd obviously be really upset.
0:03:59 > 0:04:02But could that break my heart in the same way?
0:04:02 > 0:04:06- Well, actually, yes, it could. - Really?
0:04:06 > 0:04:12There are two possibilities. One is that, in somebody who already has a degree of heart disease,
0:04:12 > 0:04:15that stress can tip the heart over the edge.
0:04:15 > 0:04:16But even somebody with a healthy heart,
0:04:16 > 0:04:21when you get stressed, you release a load of adrenaline into your body.
0:04:21 > 0:04:23Your heart rate goes up, your blood pressure goes up.
0:04:23 > 0:04:27And there is actually a condition, which is known as takotsubo cardiomyopathy,
0:04:27 > 0:04:30which is not easy to say twice!
0:04:30 > 0:04:32But most people would call it "broken heart syndrome"
0:04:32 > 0:04:36where that adrenaline actually stuns the muscle fibres in the heart
0:04:36 > 0:04:38and stops them working.
0:04:38 > 0:04:41WOMAN SCREAMS
0:04:41 > 0:04:46It's more common in older ladies, but it can happen to anyone.
0:04:46 > 0:04:48And, in the most extreme cases, it can kill you.
0:04:48 > 0:04:51- HE SIGHS - That's amazing. That's amazing.
0:04:51 > 0:04:54So, if you don't want to die of a broken heart,
0:04:54 > 0:04:59a little light exercise and the occasional bunch of flowers could go a long, long, long way.
0:04:59 > 0:05:04# Come back and mend my broken heart... #
0:05:25 > 0:05:29When I was a kid, I knew quicksand was fatal.
0:05:29 > 0:05:33I knew it was a killer because I'd seen it suck people to their deaths in films.
0:05:33 > 0:05:38But if you found yourself in quicksand, would it really be the end?
0:05:38 > 0:05:40Depends how quick the quicksand is.
0:05:40 > 0:05:44I'm sure you're supposed to stand still, because struggling makes it worse.
0:05:44 > 0:05:46Try and keep moving. Stand still, get your phone out,
0:05:46 > 0:05:48call your mum or 999, and then that's it.
0:05:48 > 0:05:52# I'm in the quicksand!
0:05:52 > 0:05:54# I'm in the quicksand! #
0:05:58 > 0:06:01'Before I get sucked into this one,
0:06:01 > 0:06:03'I want to find out just how quicksand works.
0:06:03 > 0:06:10'To do that, I'm going to need a trough full of custard powder. Obviously!
0:06:10 > 0:06:13'Most liquids, as we all know, tend to be runny
0:06:13 > 0:06:16'and they normally stay that way unless the temperature changes.'
0:06:16 > 0:06:23But other liquids, like quicksand or bizarrely custard, corn flour, behave in a much weirder way.
0:06:23 > 0:06:27When I dip my toe in, it completely vanishes, it behaves like a liquid.
0:06:27 > 0:06:31But when I kick it, it behaves like a solid.
0:06:31 > 0:06:36So I'm going to try to walk on water. Well, custard.
0:06:38 > 0:06:39Yes!
0:06:39 > 0:06:42'Although it might look like a miracle,
0:06:42 > 0:06:45'I'm able to walk on the custard
0:06:45 > 0:06:49'because it belongs to a weird bunch of liquids called non-Newtonian fluids.'
0:06:52 > 0:06:54'Unlike normal liquids,
0:06:54 > 0:06:57they get thicker or thinner under pressure.
0:06:59 > 0:07:02'Quicksand is another one of these bizarre fluids.
0:07:02 > 0:07:06'It's just a mixture of sand, water and clay
0:07:06 > 0:07:08'and it looks quite solid on the surface.
0:07:08 > 0:07:11'But, step on to it, and you're in trouble.'
0:07:13 > 0:07:15The first thing that happens...
0:07:15 > 0:07:19- HE LAUGHS - ..is it turns really liquidy.
0:07:20 > 0:07:27And I sink in. And then, straight after, the quicksand separates into two layers.
0:07:27 > 0:07:31At the top, it's more watery.
0:07:31 > 0:07:36But below that, down where my foot is, it's a lot more sandy.
0:07:36 > 0:07:41'The quicksand has behaved just as weirdly as the custard, but in the opposite way.
0:07:41 > 0:07:45'Under the pressure of my foot, it gets runnier.
0:07:45 > 0:07:49'And then, as I sink down, it feels like it's grabbing my leg like a vice.'
0:07:49 > 0:07:53And it's that that is stopping me pulling it out.
0:07:53 > 0:07:58'So if I was fully submerged in its grip, would anyone be strong enough to pull me out?'
0:07:59 > 0:08:02This one requires my stunt double!
0:08:03 > 0:08:07# I love ya, you dummy! #
0:08:07 > 0:08:08Ugh.
0:08:08 > 0:08:13- Right, I think we're going to need muscle for this. Right, are you ready?- OK.
0:08:13 > 0:08:16One, two, three. Argh!
0:08:20 > 0:08:24Ugh. No, no. I don't think we can do that.
0:08:24 > 0:08:27I think we need reinforcements.
0:08:27 > 0:08:30'This lorry has some serious power.
0:08:30 > 0:08:33'It's normally used for lifting 10-ton skips,
0:08:33 > 0:08:36'so hopefully it's got enough oomph to get our dummy unstuck.'
0:08:46 > 0:08:49Ooh! Head's off! Argh!
0:08:49 > 0:08:52I think we're free. Come on, last bit. Yes.
0:08:52 > 0:08:54That took a skip lorry to pull him out.
0:08:54 > 0:09:00Scientists have actually calculated it can take the same force you need to lift a small car.
0:09:00 > 0:09:05'Seeing as the chances of having a skip lorry to hand if you're stuck in quicksand are quite low,
0:09:05 > 0:09:08'I'm now going to see whether there's any technique I can use
0:09:08 > 0:09:10'to wrestle myself free from its clutches.'
0:09:10 > 0:09:14Whoa! OK. This is kind of scary.
0:09:14 > 0:09:16You feel like it's sucking you in.
0:09:16 > 0:09:19There's just nothing underneath my feet, there's no firm platform.
0:09:19 > 0:09:21Argh!
0:09:21 > 0:09:23I've gotta find a way to get out.
0:09:23 > 0:09:28'In fact, because of the strange behaviour of quicksand under pressure,
0:09:28 > 0:09:30'flailing around is not a good idea.
0:09:30 > 0:09:34'You'll waste precious energy, and it makes it more runny.'
0:09:36 > 0:09:37OK, that's not going to work.
0:09:37 > 0:09:41'But even though it looks like I'm in real trouble,
0:09:41 > 0:09:44'there's no way I'm ever going to sink further than my waist.'
0:09:44 > 0:09:46HE LAUGHS
0:09:46 > 0:09:51'And that's because my body is less dense than quicksand, so I'm actually floating in it.
0:09:52 > 0:09:55'Quicksand's reputation as a killer isn't because you drown in it,
0:09:55 > 0:09:59'it's because, if you're stuck in it and the tide comes in, you're a goner.'
0:10:01 > 0:10:03'But there is a way to get out,
0:10:03 > 0:10:08'and that's by spreading your weight and making very small movements upwards.'
0:10:08 > 0:10:11Yeah! Come on, that's it, last bit.
0:10:11 > 0:10:14'I still need a bit of help, though.'
0:10:14 > 0:10:17- Oh my!- You all right?- Oh! Oh!
0:10:17 > 0:10:21Right, who's next?
0:10:21 > 0:10:23- No?- Not today!
0:10:51 > 0:10:53Right, check this out. It's a beautiful demonstration
0:10:53 > 0:10:59of one of the simplest ideas in science, that hot air rises.
0:10:59 > 0:11:01That flame's heating up all the air inside.
0:11:01 > 0:11:05It's less dense than the cold air around it.
0:11:05 > 0:11:08Up it goes.
0:11:10 > 0:11:16So why then are mountains, the highest places on the Earth, freezing cold?
0:11:16 > 0:11:20# Ain't no mountain high enough
0:11:20 > 0:11:25# Nothing can keep me, Keep me from you. #
0:11:25 > 0:11:28If there's anybody who can help me get to the bottom of this one,
0:11:28 > 0:11:31it's a man who's a chemist,
0:11:31 > 0:11:35practical engineer, meteorologist and...
0:11:37 > 0:11:39..Polish musician?
0:11:39 > 0:11:43He is Dr Zbigniew Szydlo. I just call him Doc.
0:11:46 > 0:11:47All right, Doc?
0:11:47 > 0:11:51Great to see you! Fridge sorted. See you in a few minutes then, OK?
0:11:55 > 0:12:00OK, so I'm down here, literally a couple of metres above sea level.
0:12:00 > 0:12:02Doc is up at the top of the hill.
0:12:02 > 0:12:04It's 17C down here.
0:12:04 > 0:12:07I'm going to bike up to meet him and see what happens to the temperature.
0:12:13 > 0:12:18# So we go out to the hill We lie down. #
0:12:18 > 0:12:22'You'd think that the higher you get, the warmer it should become,
0:12:22 > 0:12:24what with all that warm air floating upwards.'
0:12:24 > 0:12:27Right, I'm now at 130 metres above sea level.
0:12:27 > 0:12:32The weather hasn't really changed, but the temperature is now creeping down.
0:12:32 > 0:12:35We've just touched 16 degrees.
0:12:35 > 0:12:38OK. Onwards to the top.
0:12:39 > 0:12:45'But surely, if you climb up a mountain, you're getting nearer to the sun?'
0:12:45 > 0:12:50'The problem is, temperatures actually drop by about one degree every 100 metres you climb.'
0:12:50 > 0:12:52It just doesn't seem to make sense, but it's true.
0:12:52 > 0:12:58And, to find out why it happens, I need to investigate a fundamental force of nature.
0:12:58 > 0:13:00Talking of which, there's Doc.
0:13:02 > 0:13:07- Hi, Doc.- Oh, you're here, brilliant! - Hello, matey.- Can you give us a hand with this then?
0:13:07 > 0:13:10OK, let's go then. Are you all ready? No, grab with the other side.
0:13:10 > 0:13:13Up from underneath. One, two, three, lift. Brilliant!
0:13:13 > 0:13:15- Where we going?- We're going in here.
0:13:17 > 0:13:18Right, drop this down here.
0:13:18 > 0:13:22Right, Doc. Your challenge is to make a mountain out of a fridge.
0:13:22 > 0:13:24- Brilliant.- Doc.- Yeah?- Keep cool!
0:13:25 > 0:13:28'Doc's an expert at dismantling things.
0:13:28 > 0:13:31'But if you're not, it's obviously not a good idea to try this at home.
0:13:33 > 0:13:35'While he's doing that,
0:13:35 > 0:13:40'I'm going to use this tyre to investigate how pressure can effect temperature.'
0:13:42 > 0:13:45Hopefully, when I fill this full of air, let's see what happens.
0:13:51 > 0:13:55'The green and yellow bits show where it's warmer.
0:13:55 > 0:13:58'As more and more air molecules are pumped in,
0:13:58 > 0:14:01'the energy increases, and that raises the temperature.'
0:14:02 > 0:14:04And the reverse is also true.
0:14:04 > 0:14:06If you open the valve, all that air comes flying out.
0:14:06 > 0:14:10It expands. You're losing all those energetic air molecules,
0:14:10 > 0:14:12and the temperature goes down.
0:14:12 > 0:14:15It's one of the fundamental laws of nature,
0:14:15 > 0:14:17Compress a gas and it heats up.
0:14:17 > 0:14:20Let it expand, and it cools down.
0:14:20 > 0:14:22OK? Yep.
0:14:22 > 0:14:24'And this is exactly what's happening in Doc's fridge.'
0:14:24 > 0:14:29- Right. So we're plugging her in, and see what happens?- Yeah.
0:14:30 > 0:14:35'The fridge works because the gas here in the bottom is compressed, so it's warm.
0:14:35 > 0:14:38'But, as it's allowed to expand rapidly around the ice box,
0:14:38 > 0:14:41'it cools right down to below zero,
0:14:41 > 0:14:43'cold enough to make ice.'
0:14:46 > 0:14:50'And, bizarrely, Doc's fridge works a bit like planet Earth.
0:14:51 > 0:14:55The air at the bottom of the fridge is a bit like the air at sea level.
0:14:55 > 0:14:58It's relatively warm because it's being compressed,
0:14:58 > 0:15:01this time by miles of atmosphere above it.
0:15:03 > 0:15:05Further up, there's less atmosphere,
0:15:05 > 0:15:07fewer air molecules bashing about,
0:15:07 > 0:15:11less energy and, just like Doc's ice box, it's colder.
0:15:13 > 0:15:15And that's why the top of mountains...
0:15:18 > 0:15:20..are freezing.
0:15:20 > 0:15:24- Time for an ice cream.- Yeah. Let's go to the beach. It's warmer down there.- Absolutely.
0:15:43 > 0:15:47- NARRATOR:- Here's Professor Logic. How do you do, Professor?
0:15:47 > 0:15:50Professor Logic is a busy man.
0:15:50 > 0:15:55So much to see, so much to learn, so much to measure.
0:16:00 > 0:16:03Today, Professor Logic is observing space.
0:16:05 > 0:16:09And he's rather excited because he's discovered something new.
0:16:10 > 0:16:13Ah ha!
0:16:13 > 0:16:15Er, what is it?
0:16:15 > 0:16:19I'm afraid you're going to have to help me here, Professor.
0:16:19 > 0:16:23I see. You've discovered a black hole.
0:16:23 > 0:16:25Well, that is exciting.
0:16:25 > 0:16:28Why is it called a black hole, Professor?
0:16:28 > 0:16:29Because you can't see it.
0:16:29 > 0:16:33And how do you know if you've discovered it in the first place?
0:16:39 > 0:16:44A black hole forms when a large star burns out and implodes.
0:16:44 > 0:16:49All its matter collapses into a dense point that you can't see.
0:16:49 > 0:16:51How very inconvenient, Professor.
0:16:51 > 0:16:56But, you know, it's there because its gravitational field is so strong
0:16:56 > 0:17:01that it sucks up everything around it, even light.
0:17:01 > 0:17:05Well, don't get too close, you might get sucked up yourself.
0:17:05 > 0:17:07You want to get sucked up?
0:17:07 > 0:17:12But, once you're in, doesn't something called spaghettification
0:17:12 > 0:17:14stretch you out into an enormous string of atoms,
0:17:14 > 0:17:19before crushing you into a soup of collapsed subatomic particles?
0:17:19 > 0:17:22Doesn't sound much like fun to me.
0:17:22 > 0:17:25You don't care?
0:17:25 > 0:17:30You've heard that black holes might be gateways to other universes?
0:17:31 > 0:17:36And you want to meet the inhabitants of the other universes?
0:17:36 > 0:17:37I see.
0:17:39 > 0:17:41Well, goodbye, Professor.
0:17:43 > 0:17:46And, er, good luck.
0:18:15 > 0:18:20This is me suffering for science, or rather for my stomach.
0:18:20 > 0:18:24I'm burning off the weight I put on in one wild day of eating,
0:18:24 > 0:18:29trying to answer the question: Does fast food make you fat?
0:18:29 > 0:18:33It tastes good, so you kind of get greedy for more.
0:18:33 > 0:18:37Greediness makes you fat. I worked in fast food for three years.
0:18:37 > 0:18:39Everything in moderation is OK for you.
0:18:39 > 0:18:43It's so convenient, isn't it? Like, you can't be bothered to cook for yourself.
0:18:43 > 0:18:46# I think of you and lick my lips.
0:18:46 > 0:18:50# You've got the taste I can't resist Can't resist, can't resist... #
0:18:50 > 0:18:54'As a bloke, I need around 2,500 calories a day.'
0:18:54 > 0:18:57'If you're female, it's about 2,000.'
0:18:57 > 0:18:58- Morning.- Morning.
0:18:58 > 0:19:01'But today, in the interests of science,
0:19:01 > 0:19:04'I'm going to bust my limit with a Great British fry up.'
0:19:04 > 0:19:07'Not exactly fast, but it ain't short on calories.'
0:19:10 > 0:19:14- HE SIGHS - OK. That was over 1,000 calories, just for breakfast.
0:19:14 > 0:19:16'Who'd have thought it?
0:19:16 > 0:19:20'That's almost half my day's calorie allowance gone in just one meal.
0:19:22 > 0:19:25'But what exactly is a calorie?
0:19:25 > 0:19:29'Well, it's the measurement of a food's energy.
0:19:29 > 0:19:32'And, different foods have very different amounts.
0:19:32 > 0:19:37'The trouble is, it's not always obvious how different, unless you set fire to them.'
0:19:37 > 0:19:39Let's start with some fibre.
0:19:39 > 0:19:43This is just a leaf of your common iceberg lettuce.
0:19:47 > 0:19:49Whoa!
0:19:49 > 0:19:51Big flame.
0:19:51 > 0:19:53But it doesn't burn for very long.
0:19:53 > 0:19:58So there's clearly not much energy in there, the lettuce is low in calories.
0:19:58 > 0:20:01This is my weakness, salt and vinegar crisps.
0:20:04 > 0:20:06Off it goes.
0:20:07 > 0:20:09OK, this one's burning a lot longer
0:20:09 > 0:20:13and that shows it's got a lot more energy inside it.
0:20:13 > 0:20:18A crisp is, therefore, clearly much higher in calories.
0:20:18 > 0:20:20'And that's mainly down to the F word: Fat.
0:20:20 > 0:20:24'Fat is the most energy-giving foodstuff you can eat.
0:20:24 > 0:20:29'And that's why this crisp, which is about a third fat, burnt way longer than the lettuce leaf.'
0:20:33 > 0:20:36'And that's the thing with fast food.
0:20:36 > 0:20:40'Weight for weight, it tends to contain much more fat than a far less tempting meal.'
0:20:44 > 0:20:48That, plus breakfast, takes my tally to over 3,000 calories already,
0:20:48 > 0:20:50and it's only lunchtime.
0:20:51 > 0:20:54'The trouble is, it's so moreish.
0:20:54 > 0:20:59'And that's because we've evolved to crave that mouth-watering mix of fat, salt and sugar,
0:20:59 > 0:21:03'which is why we find fast food so tasty.
0:21:03 > 0:21:06'Talking of which, time for dinner.'
0:21:06 > 0:21:13So, this rounds off three meals in one day, that topped 7,000 calories.
0:21:13 > 0:21:17'That's 4,500 more than I actually need.
0:21:17 > 0:21:21'All of this excess energy will be stored as fat,
0:21:21 > 0:21:24'over half a kilo of it if I don't burn it off.
0:21:27 > 0:21:32'Fast food might make me fat, but exercise will sort me out. Won't it?'
0:21:36 > 0:21:39Oh, man. That was two laps.
0:21:39 > 0:21:42Lasted just over two hours.
0:21:42 > 0:21:47But I only burnt 1,210 calories.
0:21:47 > 0:21:52So, fast food doesn't technically make you fat, you know.
0:21:52 > 0:21:57A calorie is a calorie. But, pound for pound, fast food contains more energy.
0:21:57 > 0:22:01And, man, does it take a lot to burn it off!
0:22:01 > 0:22:05# I want it, I need it Nothing else can beat it
0:22:05 > 0:22:08# Hot and spicy Whenever I'm in town. #
0:22:18 > 0:22:20FANFARE
0:22:20 > 0:22:23BURPS AND FARTS
0:22:36 > 0:22:39So, Australia's nice this time of year.
0:22:39 > 0:22:43Slight problem on the cashflow front, though. No money for flights.
0:22:43 > 0:22:48But, if you can't fly there, couldn't you just dig through the Earth and pop out down under?
0:22:48 > 0:22:53# So follow me down I'll show you around
0:22:53 > 0:22:57# There's a place we gotta go. #
0:23:04 > 0:23:08OK, so I'm clearly not going to win any prizes for digging.
0:23:08 > 0:23:13But, say, I had all my mates, a tunnelling machine, a digger, the full works,
0:23:13 > 0:23:15could I then get to Australia?
0:23:20 > 0:23:24'The trouble is, it's not just Tarmac and earth that stands between me and Bondi Beach.'
0:23:24 > 0:23:26There's the little matter of the Earth's core.
0:23:26 > 0:23:29And that's a problem, because it's hot.
0:23:29 > 0:23:32For every 40 metres you burrow down,
0:23:32 > 0:23:37the temperature increases by an average of one degree Celsius.
0:23:37 > 0:23:40And Australia is over 10,000 kilometres away.
0:23:40 > 0:23:44So you do the maths. You're going to be toast.
0:23:44 > 0:23:47Down there, it's the same as the temperature on the surface of the sun.
0:23:47 > 0:23:52But what if I lined my hole with a heatproof material so I didn't burn up?
0:23:52 > 0:23:54Could I get all the way to Australia then?
0:23:54 > 0:23:58Insulating a tunnel might sort out the heat problem.
0:23:58 > 0:24:02But, unfortunately, there's a small matter of air pressure to contend with.
0:24:02 > 0:24:05To find out more about this, I'm getting into this diving chamber
0:24:05 > 0:24:09with diving specialist Simon Wilson
0:24:09 > 0:24:11and an inflatable man called John.
0:24:11 > 0:24:16Now, if you can imagine it, as you go deeper and deeper down your hole into the centre of the Earth,
0:24:16 > 0:24:19there's more and more air above you.
0:24:19 > 0:24:22The more air there is, the heavier it is, the more presses down on you.
0:24:22 > 0:24:24And that increases the air pressure.
0:24:24 > 0:24:27Now, rather than actually go deeper,
0:24:27 > 0:24:30Simon is going to fill this chamber full of lots of air.
0:24:30 > 0:24:32That's going to increase the pressure artificially.
0:24:32 > 0:24:35OK. Let me know when you're good to go?
0:24:35 > 0:24:37Let's do it, then.
0:24:39 > 0:24:41Ooh, you can feel it straight away.
0:24:42 > 0:24:45Whoa! He's going already.
0:24:45 > 0:24:47Look at the state of that, look.
0:24:47 > 0:24:50All the air around him is really high pressure.
0:24:50 > 0:24:53So, it's pushing down. And it's really low pressure inside him.
0:24:53 > 0:24:55It can't do anything. Just getting squashed.
0:24:55 > 0:25:00And the reason that we're not doing that is because we've got fluid inside us
0:25:00 > 0:25:03and that kind of pushes out and balances out.
0:25:07 > 0:25:10It's getting really warm as well, really hot.
0:25:10 > 0:25:12John's completely gone.
0:25:12 > 0:25:15It's important to remember this. The air hasn't gone from John.
0:25:15 > 0:25:18It's still in there, but it's just compressed.
0:25:19 > 0:25:22- 30 metres.- 30 metres?
0:25:25 > 0:25:27SQUEAKY VOICE: Is my voice going higher?
0:25:27 > 0:25:28HE LAUGHS
0:25:28 > 0:25:32'We're now at such a high pressure, the way my vocal cavity vibrates has changed
0:25:32 > 0:25:35'and my voice comes out at a higher pitch.'
0:25:35 > 0:25:37I sound a bit like Donald Duck!
0:25:40 > 0:25:43OK. That's the chamber at the bottom, about 50 metres.
0:25:47 > 0:25:49'We're only a tiny fraction of the way to Australia.
0:25:49 > 0:25:52The equivalent of 14 kilometres, in fact.'
0:25:52 > 0:25:55- HIGH PITCHED VOICE:- I just feel a little bit...drunk.
0:25:55 > 0:25:58'And it's not just my voice that's gone weird.'
0:25:58 > 0:26:00What you're experiencing is nitrogen narcosis.
0:26:00 > 0:26:04- You're trying to make sentences. - HE LAUGHS HYSTERICALLY
0:26:04 > 0:26:06'Because of the higher pressure down here,
0:26:06 > 0:26:09'I'm breathing in much more nitrogen gas than I normally would,
0:26:09 > 0:26:12'and that really affects my nerve impulses.'
0:26:12 > 0:26:15I can't take my voice seriously!
0:26:15 > 0:26:18'I feel like I'm trashed, and I can't think straight.'
0:26:18 > 0:26:22Pick up the chalk and do these four questions, OK?
0:26:24 > 0:26:277 x 6...
0:26:27 > 0:26:307... 14...
0:26:30 > 0:26:3221... 33... Properly!
0:26:32 > 0:26:37- HE LAUGHS - 35... 42, 42.
0:26:37 > 0:26:3914, carry the 1.
0:26:39 > 0:26:411, 2...
0:26:41 > 0:26:4334.
0:26:43 > 0:26:46Write Australia backwards.
0:26:46 > 0:26:48A, U...
0:26:48 > 0:26:50A, U, S, T...
0:26:50 > 0:26:51BLEEP!
0:26:51 > 0:26:54A, U, S, T...
0:26:54 > 0:26:56No, that's not right!
0:26:56 > 0:26:58This is really embarrassing.
0:26:58 > 0:27:00Australia. Is that right?
0:27:00 > 0:27:04Our Australia cousins, it's USA Australia.
0:27:04 > 0:27:07HE LAUGHS HYSTERICALLY
0:27:07 > 0:27:09My brain doesn't work!
0:27:09 > 0:27:12'So, at the equivalent of a mere 14 kilometres underground...'
0:27:12 > 0:27:15I sound Australian in my head.
0:27:15 > 0:27:20'..the intoxicating affects of all that nitrogen would have brought my dig to Oz to a premature end.'
0:27:21 > 0:27:23'Time to go back up.'
0:27:23 > 0:27:27Come on, John. Come back to us, John!
0:27:27 > 0:27:32'And so he did. As the pressure decreased, the air in his body expanded.'
0:27:32 > 0:27:33John has recovered.
0:27:33 > 0:27:35'And restored him to his former glory.'
0:27:35 > 0:27:38Look at that.
0:27:39 > 0:27:43'And happily, I started making more sense too.'
0:27:43 > 0:27:44How are you feeling, John?
0:27:47 > 0:27:50So, what with the very high temperatures, extremely high pressures,
0:27:50 > 0:27:55I don't think me and John are going to be digging to Australia anytime soon.
0:27:55 > 0:28:00# Don't let me down, Don't let me down, don't let me down,
0:28:00 > 0:28:02# I won't... #
0:28:04 > 0:28:06Subtitles by Red Bee Media Ltd