0:00:02 > 0:00:05This programme contains strong language
0:00:05 > 0:00:08Humans are an incredible species.
0:00:08 > 0:00:10We've found ways to talk to each other
0:00:10 > 0:00:11on 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 > 0:00:27I've always been asking questions
0:00:27 > 0:00:29and 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 > 0:00:37I even went on to do a science degree.
0:00:38 > 0:00:40And I'm still asking questions.
0:00:40 > 0:00:42- This will hurt right?- Yeah.
0:00:42 > 0:00:44And I reckon a lot of you are, too.
0:00:44 > 0:00:46And that's what this series is all about -
0:00:46 > 0:00:48getting to the bottom of all those questions
0:00:48 > 0:00:50that never get properly answered,
0:00:50 > 0:00:52to reveal the secrets of everything.
0:00:59 > 0:01:01This time on The Secrets of Everything.
0:01:01 > 0:01:03Ahhhh!
0:01:04 > 0:01:06We'll discover how good swearing is at helping with pain.
0:01:06 > 0:01:09- BLEEP, BLEEP.- It's going.
0:01:09 > 0:01:13Doc and I have a go at creating heaven on earth.
0:01:13 > 0:01:16Watch out. Watch out for the flash now. There it is.
0:01:16 > 0:01:19What's going on in there is a bit like what's going on in a star.
0:01:19 > 0:01:22And I get to embrace hypothermia.
0:01:22 > 0:01:25Three, two, one.
0:01:27 > 0:01:29SCREAMS LOUDLY
0:01:29 > 0:01:32The things I have to do for science.
0:01:34 > 0:01:37But first, getting the drop
0:01:37 > 0:01:38on one of our favourite urban legends.
0:01:45 > 0:01:48So, you're at the top of the Empire State Building
0:01:48 > 0:01:51and you see someone pull a penny out of their pocket.
0:01:51 > 0:01:54Then you realise that they're going to throw the penny over the top.
0:01:54 > 0:01:58What you're witnessing is a potential homicide
0:01:58 > 0:02:00because we all know that if you throw a penny
0:02:00 > 0:02:01off a tall enough building,
0:02:01 > 0:02:04if it hits someone down there, it's going to kill them.
0:02:04 > 0:02:08We all know it, but is it true?
0:02:09 > 0:02:12To find out, I need a tall building,
0:02:12 > 0:02:14some pennies and my mate Andy to throw them.
0:02:16 > 0:02:21We'll start from the second floor, about 20 metres up.
0:02:21 > 0:02:23To be a bigger target, I'm going to lie down.
0:02:25 > 0:02:26Oh, man, this is so going to hurt.
0:02:28 > 0:02:30Ow!
0:02:30 > 0:02:32Ah!
0:02:32 > 0:02:34LAUGHS
0:02:35 > 0:02:37Look at that.
0:02:37 > 0:02:41- That's from two stories up. - You've just been spanked by the Queen.
0:02:41 > 0:02:44Using a high-speed camera
0:02:44 > 0:02:48and a metre rule we can work out how fast the penny is dropping.
0:02:48 > 0:02:50Right, so that's 25 miles an hour.
0:02:50 > 0:02:52The further it falls
0:02:52 > 0:02:54the faster it goes, the harder it hits.
0:02:57 > 0:03:01The Empire State Building is far taller than this tower block
0:03:01 > 0:03:03so will a penny fall fast enough to test the legend?
0:03:05 > 0:03:10Well, at some point no matter how far it falls, it stops speeding up.
0:03:10 > 0:03:13You'd think that the further the coin falls
0:03:13 > 0:03:15the faster and faster it gets,
0:03:15 > 0:03:18as gravity accelerates it down to the ground.
0:03:18 > 0:03:21But gravity isn't the only force that's acting on the coin.
0:03:23 > 0:03:25It's counter-acted by air resistance or drag,
0:03:25 > 0:03:29which is what you feel when you put your hand out of the window as you're driving along
0:03:29 > 0:03:32and the faster you go, the harder it is.
0:03:32 > 0:03:34So, it's exactly the same for the penny.
0:03:34 > 0:03:37As it gets faster and faster, it gets harder to push through the air
0:03:37 > 0:03:41and it's the drag that slows it down.
0:03:43 > 0:03:45Eventually drag equals gravity
0:03:45 > 0:03:47and the penny can't fall any faster.
0:03:47 > 0:03:49It's reached its terminal velocity.
0:03:49 > 0:03:52And the way you work out that maximum speed for the coin
0:03:52 > 0:03:57is you take a formula, you plug in the density of the air, the area of the coin, the mass of the coin,
0:03:57 > 0:04:01chuck it all around and you get 67 miles per hour.
0:04:01 > 0:04:06So, a penny can't drop any faster than 67 miles per hour.
0:04:06 > 0:04:10Andy! But is that rapid enough to make it a deadly weapon?
0:04:10 > 0:04:12Reckon you'll be able to hit me from there?
0:04:12 > 0:04:14Trust me, Greg, I will hit you.
0:04:14 > 0:04:18OK. Let's do this.
0:04:18 > 0:04:20Three, two, one.
0:04:20 > 0:04:22# All right, check this out. #
0:04:24 > 0:04:25Rubbish!
0:04:27 > 0:04:29Ah!
0:04:29 > 0:04:31Close.
0:04:31 > 0:04:34Ah, this is not going to happen.
0:04:34 > 0:04:38But there is another way of getting this penny on target.
0:04:38 > 0:04:40And fast.
0:04:40 > 0:04:42Ah!
0:04:42 > 0:04:44- Did that one hurt? - Ahhhh!- Did I get your belly button?
0:04:44 > 0:04:46Yeah.
0:04:51 > 0:04:53Ah!
0:04:58 > 0:05:00Ah!
0:05:02 > 0:05:04Oh, it's instant, look. It's instant!
0:05:04 > 0:05:07It hurts, it's going to bruise
0:05:07 > 0:05:09but it's not going to kill me.
0:05:09 > 0:05:11It's just not fast enough.
0:05:11 > 0:05:14So, your highest - 49 miles an hour.
0:05:14 > 0:05:16- Oh.- It's just not up to scratch.
0:05:16 > 0:05:19- Terminal velocity, we need to get it right up there.- How can we do that?
0:05:19 > 0:05:22- I have got a plan.- What's the plan?
0:05:23 > 0:05:25Meet Andrew Savill,
0:05:25 > 0:05:29licensed armourer and supplier of real and fake guns for TV and movies.
0:05:29 > 0:05:32He's rigged up an air rifle to fire a penny.
0:05:32 > 0:05:35- This is amazing.- And we've come to this firing range
0:05:35 > 0:05:38to see if that will succeed where Andy's arm failed?
0:05:40 > 0:05:42Let's fire it. Let's see what this thing can do.
0:05:42 > 0:05:45- So, you shoot through that do you? - We do, yeah.
0:05:45 > 0:05:48- And that's going to tell us the speed.- It will do.- That's cool.
0:05:49 > 0:05:53- Ready?- Three, two, one.
0:05:53 > 0:05:56- What's it say? - That's 97 feet per second.
0:05:57 > 0:06:0197 feet per second is about 67 miles an hour,
0:06:01 > 0:06:04as fast as a falling penny can get.
0:06:04 > 0:06:07- Time to shoot me. - Andy, you know what you're doing?
0:06:07 > 0:06:08- Yes, is it not cocked?- No.
0:06:08 > 0:06:12Andrew the armourer is not happy with shooting my head.
0:06:12 > 0:06:16- Left cheek?- So he's insisting my ass gets it instead.
0:06:16 > 0:06:18Dude, your aim had better be good.
0:06:18 > 0:06:19- Great(!)- Are you ready?
0:06:19 > 0:06:21Here we go.
0:06:21 > 0:06:22Three...
0:06:22 > 0:06:25two, one...
0:06:26 > 0:06:27Ah!
0:06:27 > 0:06:30Yep, this really hurt, but the thing is
0:06:30 > 0:06:32it didn't even break the skin.
0:06:32 > 0:06:35The mighty penny isn't looking very deadly at all.
0:06:35 > 0:06:36At least that shows
0:06:36 > 0:06:38that, er...
0:06:38 > 0:06:42you can't get killed if a penny drops off the Empire State Building
0:06:42 > 0:06:47and it's going at a max speed of terminal velocity.
0:06:48 > 0:06:51I don't know why your arse would be pointing upwards though!
0:06:52 > 0:06:55Oh!
0:07:13 > 0:07:16If you look up at the stars on a clear night,
0:07:16 > 0:07:19what you're actually looking at is where we came from
0:07:19 > 0:07:23because all the elements in us and pretty much all the elements
0:07:23 > 0:07:27on the whole of the earth, were made up there, in the stars.
0:07:27 > 0:07:30So, what actually is a star?
0:07:30 > 0:07:35And is it possible to create a new one here on Earth?
0:07:35 > 0:07:37# Lying in the grass
0:07:37 > 0:07:41# Watching the stars come out... #
0:07:42 > 0:07:45If there's anyone I know who can help me build a star,
0:07:45 > 0:07:49it's a man who is a chemist, a practical engineer,
0:07:49 > 0:07:51meteorologist and...
0:07:52 > 0:07:55..Polish musician?
0:07:56 > 0:07:58He is Dr Zbigniew Szydlo.
0:08:00 > 0:08:01I just call him Doc.
0:08:01 > 0:08:04- All right, Doc. So, the challenge this time...- Yep.
0:08:04 > 0:08:06- ..is, I want to build a star. - A star?
0:08:06 > 0:08:08That's absolutely amazing.
0:08:08 > 0:08:09How do you plan to do that, my dear boy?
0:08:09 > 0:08:12Well, we need to... I was hoping that you,
0:08:12 > 0:08:15- being the source of everything chemical...- Yup.
0:08:15 > 0:08:17..would be able to give me a chemical reaction
0:08:17 > 0:08:19that's as close to what we see in a star as possible.
0:08:19 > 0:08:21Eh, ah. I don't know whether it'll work,
0:08:21 > 0:08:22but we can try getting close to one.
0:08:22 > 0:08:25Stars are basically huge, hot fireballs.
0:08:25 > 0:08:27So, first up, something hot.
0:08:27 > 0:08:30- I'm going to do something called a thermite reaction.- OK.
0:08:30 > 0:08:32Which is when you react iron oxide,
0:08:32 > 0:08:35which is basically rust, with aluminium powder.
0:08:35 > 0:08:38Now, aluminium has a huge affinity for oxygen
0:08:38 > 0:08:42and it actually rips the oxygen away from the iron oxide,
0:08:42 > 0:08:44leaving iron behind.
0:08:44 > 0:08:47And, as it does so, it releases an amazing amount of heat energy,
0:08:47 > 0:08:48which is what we're going to see.
0:08:48 > 0:08:51So, this is going to be our hot, unstoppable reaction.
0:08:51 > 0:08:54That's our unstoppable chemical reaction.
0:08:54 > 0:08:56Now, what we do, is we pour it in there, very, very carefully.
0:08:56 > 0:08:59- That's it, spot on. - Deeper?- No, that's fine.
0:08:59 > 0:09:02- So, I think we're all set to go so now.- Good.
0:09:02 > 0:09:04So, you're going to get an initial, little bit of smoke,
0:09:04 > 0:09:06then a blinding flash,
0:09:06 > 0:09:10a massive puff of white smoke and then, your star will be born.
0:09:10 > 0:09:13Doc kick-starts the reaction with more chemicals
0:09:13 > 0:09:15and special ingredients.
0:09:15 > 0:09:17- Fingers crossed, there she goes. - Blinding flash.
0:09:17 > 0:09:20- There we go.- Oh.- Watch out, watch out for the flash now.
0:09:20 > 0:09:23Blinding flash. Watch out. Stop there. The top's gone.
0:09:23 > 0:09:26- There it is.- Aw, that's the top of the beaker.
0:09:26 > 0:09:28The top's gone, but there's our cloud of white smoke.
0:09:28 > 0:09:31Right, let's have a quick look. Absolutely. Watch out.
0:09:31 > 0:09:35- It's still bubbling away.- Go again in a minute.- Yeah, that's OK.
0:09:35 > 0:09:36- Let's quickly have a look at that.- Whoa.
0:09:36 > 0:09:39Just look at that. Whole beaker's vaporised.
0:09:39 > 0:09:41Is that just molten glass?
0:09:41 > 0:09:44Molten glass, molten aluminium oxide
0:09:44 > 0:09:47and molten iron, right at the bottom there, sir.
0:09:47 > 0:09:51What's going on there is a bit like what's going on inside a star.
0:09:51 > 0:09:53The chemical reaction is changing those chemicals
0:09:53 > 0:09:57and then releasing heat and light energy.
0:09:57 > 0:10:01Doc, I think we've run out of reactant.
0:10:01 > 0:10:04And that's the problem. To fuel a star, even a medium-sized one,
0:10:04 > 0:10:07like our sun, would mean harnessing all the energy
0:10:07 > 0:10:12from 600 million tonnes of hydrogen, every second.
0:10:12 > 0:10:14# Take me into the fight
0:10:14 > 0:10:18# And I'm an easy brother... #
0:10:18 > 0:10:22But that's not to say that I can't try to make a tiny star
0:10:22 > 0:10:23here on Earth.
0:10:23 > 0:10:29Stars aren't actually made out of iron oxide, aluminium and spit.
0:10:29 > 0:10:31They're mainly something called plasma.
0:10:31 > 0:10:36The same stuff as lightning and the Northern Lights.
0:10:36 > 0:10:39And that we can make by using Doc's microwave
0:10:39 > 0:10:43in a way that I've going to tell you not to try at home.
0:10:43 > 0:10:46I'm going to capture my hot gas in a jar,
0:10:46 > 0:10:49but I need to make sure air can get up into it as well.
0:10:52 > 0:10:54Whoa, there it is.
0:10:57 > 0:10:59Now, that is pretty cool. What's happening?
0:10:59 > 0:11:04Well, the energy from the microwave is breaking down that flame,
0:11:04 > 0:11:05that hot gas.
0:11:05 > 0:11:09It's ripping the electrons away from the molecules of the gas
0:11:09 > 0:11:12and that's leaving charged particles called ions.
0:11:12 > 0:11:15And that ionised gas is plasma.
0:11:15 > 0:11:18You're looking at a very tiny star.
0:11:18 > 0:11:21So, you can make a star on Earth.
0:11:21 > 0:11:23Kind of. But it's only ever going to be tiny
0:11:23 > 0:11:27because you just can't get enough fuel to make anything bigger,
0:11:27 > 0:11:28like the Sun.
0:11:28 > 0:11:31But still pretty cool to think that you can make a micro star
0:11:31 > 0:11:32in your microwave.
0:11:53 > 0:11:57We all do it, but does swearing actually help us when we get hurt?
0:11:57 > 0:11:59Or is it just an excuse to mouth off?
0:11:59 > 0:12:01Just a little, little bit, it does help.
0:12:01 > 0:12:05I swear religiously and it helps a lot.
0:12:05 > 0:12:08It makes you feel better for a second, definitely.
0:12:08 > 0:12:11Actually help relieve pain? I don't think so.
0:12:11 > 0:12:13It's the first thing that comes to the end of the tongue.
0:12:13 > 0:12:15# Takes my pain away... #
0:12:17 > 0:12:21This is Ella. She's normally quite sweet,
0:12:21 > 0:12:24but, today, she's going to inflict pain.
0:12:24 > 0:12:27- Hello, Ella.- Hi.- So, thanks for helping me out with this.
0:12:27 > 0:12:32So, what I need you to do, is use this hammer to hit my finger.
0:12:32 > 0:12:34That's brilliant.
0:12:34 > 0:12:37If you can start the stopwatch, as you hit me,
0:12:37 > 0:12:39- and then we'll see how long the pain lasts for.- OK.
0:12:39 > 0:12:43Go on then. To begin with, I'm going to try not to swear.
0:12:43 > 0:12:45Come on.
0:12:46 > 0:12:49Ah! Banana, banana, banana, banana.
0:12:49 > 0:12:52Banana, banana, banana, banana,
0:12:52 > 0:12:54banana, banana, banana.
0:12:54 > 0:12:57Yeah, I can feel it. Banana, banana. Ah!
0:12:57 > 0:13:00Banana, banana, banana.
0:13:00 > 0:13:02You really whacked that.
0:13:02 > 0:13:06Banana, banana, banana.
0:13:07 > 0:13:11OK, it's gone. It's gone, it's gone.
0:13:11 > 0:13:13- This time I'm going to swear. - Right.- Yes!
0:13:13 > 0:13:16And we'll see if that means I can get over the pain
0:13:16 > 0:13:19- in a shorter period of time.- OK.
0:13:19 > 0:13:20Phhhw.
0:13:21 > 0:13:23Come on.
0:13:23 > 0:13:25Come on.
0:13:25 > 0:13:27Ah! BEEP.
0:13:33 > 0:13:37BEEP, BEEP, BEEP.
0:13:37 > 0:13:38It's going.
0:13:39 > 0:13:43OK, it's getting better. BEEP, BEEP, BEEP.
0:13:43 > 0:13:44BEEP.
0:13:44 > 0:13:46BEEP.
0:13:46 > 0:13:47BEEP.
0:13:47 > 0:13:50OK, it's gone. Yeah, it's gone.
0:13:50 > 0:13:53- How was that?- That was 56 seconds.
0:13:53 > 0:13:55Oh, good. You know what?
0:13:55 > 0:13:58It did feel like the pain was less when I swore,
0:13:58 > 0:14:00but it is so subjective
0:14:00 > 0:14:03and using a hammer isn't particularly scientific.
0:14:03 > 0:14:05- So, I think we need to try something else.- Yeah.
0:14:05 > 0:14:06And we need lots of people.
0:14:08 > 0:14:10I've assembled a group of victims
0:14:10 > 0:14:12and devised a new way of causing them pain
0:14:12 > 0:14:16with a bucket of ice water.
0:14:16 > 0:14:20Right, so what I need you guys to do is to put your hand
0:14:20 > 0:14:24into the bucket of ice and hold it in there for as long as you can,
0:14:24 > 0:14:28until you can't stand the pain, but you're not allowed to swear.
0:14:28 > 0:14:31If you do want to shout out, just yell banana.
0:14:31 > 0:14:33OK? Right.
0:14:33 > 0:14:35Three.
0:14:35 > 0:14:36Two.
0:14:36 > 0:14:38One.
0:14:39 > 0:14:41OK, that's pretty cold.
0:14:42 > 0:14:47The freezing water cools the skin right down and it's painful.
0:14:47 > 0:14:49Ahhh, banana, banana.
0:14:49 > 0:14:52I think I've lost a finger. Banana.
0:14:52 > 0:14:53Ah!
0:14:56 > 0:14:57Right, your turn.
0:14:59 > 0:15:01Banana.
0:15:06 > 0:15:08Yeah, that's cold. Banana.
0:15:14 > 0:15:16This time, you can swear, say whatever you like,
0:15:16 > 0:15:17just yell it out there.
0:15:19 > 0:15:21BEEP.
0:15:21 > 0:15:24BEEP. Ah!
0:15:24 > 0:15:27BEEP, BEEP, BEEP, BEEP.
0:15:27 > 0:15:30Ah! BEEP.
0:15:32 > 0:15:37Scientists think that swearing can work as a genuine painkiller.
0:15:37 > 0:15:39BEEP.
0:15:39 > 0:15:43It increases the heart rate and activates parts of the brain.
0:15:43 > 0:15:45BEEP, BEEP, BEEP.
0:15:45 > 0:15:48Releasing chemicals called endorphins.
0:15:48 > 0:15:51And they can help you tolerate the pain.
0:15:51 > 0:15:53It's part of the fight or flight response
0:15:53 > 0:15:58and that helps us survive dangerous situations.
0:15:59 > 0:16:02OK, guys, so, when we swore,
0:16:02 > 0:16:06on average, we lasted one minute and 30 seconds longer.
0:16:06 > 0:16:10- Oh, great.- Great.- Which is good stuff. That's amazing.
0:16:10 > 0:16:13Swearing, used in the right context, has the ability
0:16:13 > 0:16:15to reduce the pain that we feel.
0:16:15 > 0:16:17Whether that's a quick hit from a hammer,
0:16:17 > 0:16:19or a sustained amount of pain by sticking your hand
0:16:19 > 0:16:22in loads of icy water. BEEP.
0:16:22 > 0:16:26Saying that, though, the more you use it, the less effective it is.
0:16:26 > 0:16:29So, keep all those BEEP, BEEP and BEEP to yourself
0:16:29 > 0:16:31until you really need them.
0:16:51 > 0:16:55Here's Professor Logic. How do you do, professor?
0:16:55 > 0:17:01Professor Logic is a busy man. So much to see, so much to learn,
0:17:01 > 0:17:02so much to measure.
0:17:07 > 0:17:11Today, Professor Logic is working on his spaceship.
0:17:11 > 0:17:15He's trying to make it go a bit quicker.
0:17:15 > 0:17:18Just exactly how fast are you intending to go, professor?
0:17:20 > 0:17:23You're aiming for close to the speed of light.
0:17:25 > 0:17:28Ah. you're going to be doing a spot of time travelling.
0:17:28 > 0:17:32Time to say goodbye to your friends and neighbours.
0:17:32 > 0:17:35Really, professor, you're old enough to be her father.
0:17:43 > 0:17:46Professor Logic, what on Earth are you up to?
0:17:50 > 0:17:54I see. You think that because the theory of relativity
0:17:54 > 0:17:58says that time slows down as you approach the speed of light,
0:17:58 > 0:18:02that, when you get back to Earth, you'll be younger.
0:18:04 > 0:18:06So, that's what this is all about.
0:18:13 > 0:18:16# You can tell by the way I use my walk
0:18:16 > 0:18:19# I'm a woman's man No time to talk... #
0:18:19 > 0:18:22Oh, dear, professor, you've made a mistake.
0:18:22 > 0:18:25You haven't got younger, everyone else has got older.
0:18:25 > 0:18:29While you've been travelling at approaching the speed of light,
0:18:29 > 0:18:33you're time slowed down relative to everyone else's.
0:18:33 > 0:18:35Two months for you, a lifetime for them.
0:18:35 > 0:18:39I'm afraid that's relativity for you, Professor Logic.
0:18:56 > 0:19:00We've all heard rumours of the bizarre and unexplained
0:19:00 > 0:19:03and there's one in particular that I'm really interested in.
0:19:03 > 0:19:07Every now and again, someone finds a burnt human body,
0:19:07 > 0:19:12but the hands arms and legs are left untouched, so is the room.
0:19:12 > 0:19:18It's claimed to be spontaneous human combustion, but is it possible?
0:19:18 > 0:19:21Could I simply burst into flames?
0:19:23 > 0:19:26# Hot as the flames... #
0:19:28 > 0:19:30To get to the bottom of this gruesome phenomenon,
0:19:30 > 0:19:34I'm going to recreate a typical case.
0:19:36 > 0:19:38This container makes a good living room
0:19:38 > 0:19:43and this recently deceased pig is our human substitute.
0:19:43 > 0:19:45It was destined for the butchers,
0:19:45 > 0:19:47but, like scientists have done for centuries,
0:19:47 > 0:19:49we're going to use it for research
0:19:49 > 0:19:52because its physiology, size and skin are all very similar to ours.
0:19:52 > 0:19:54Right, we've got to make this more human-like,
0:19:54 > 0:19:57so we need to wrap it up in some clothes.
0:19:57 > 0:19:59Pig in a blanket.
0:19:59 > 0:20:03The first thing to know about spontaneous combustion
0:20:03 > 0:20:06is that the victims are usually found near to a source of ignition,
0:20:06 > 0:20:09like a gas fire or a smouldering ashtray.
0:20:09 > 0:20:12So, we can knock spontaneous on the head straight away.
0:20:12 > 0:20:15But there's still a lot of weirdness to investigate,
0:20:15 > 0:20:18like, why is it only the torso gets burnt?
0:20:18 > 0:20:21And why is the room left untouched?
0:20:21 > 0:20:26So, here goes. Some typical, un-spontaneous combustion.
0:20:26 > 0:20:30Normally, if you were...fell asleep with a cigarette,
0:20:30 > 0:20:32the cigarette would just drop onto whatever you're wearing
0:20:32 > 0:20:35- and then it would go. So, we'll try it?- Yeah.
0:20:35 > 0:20:38Let's see if that will take on the cotton blanket?
0:20:40 > 0:20:44- Well, it's starting to go, isn't it? - Yeah, looks like.
0:20:45 > 0:20:48- So, that's the cigarette pretty much gone.- Yeah.
0:20:48 > 0:20:52It's burnt through the cotton, we're pretty much down to flesh.
0:20:54 > 0:20:58Now, normally, you'd simply wake up and put yourself out.
0:20:58 > 0:21:01But, if you were already dead or otherwise incapacitated,
0:21:01 > 0:21:03you'd continue to burn.
0:21:03 > 0:21:05This could take many hours,
0:21:05 > 0:21:08so we're speeding things up to the point where the body catches fire.
0:21:09 > 0:21:12# Darling
0:21:12 > 0:21:15# There's fire in the house tonight... #
0:21:17 > 0:21:19So, it's been what? An hour and a half now?
0:21:19 > 0:21:22- I reckon about an hour and a half. - It's still burning away.
0:21:22 > 0:21:26We seem to have a beautiful flame just centred in the middle, don't we?
0:21:26 > 0:21:28Yeah. If you look closely, you can see the skin's split
0:21:28 > 0:21:31and now the fat's rendering down. The fat's becoming liquid
0:21:31 > 0:21:34and it's actually the fat of the animal that's burning.
0:21:34 > 0:21:39And that fat is soaking into the remnants of the blanket.
0:21:39 > 0:21:41The pig's clothed body acts like an inside out candle.
0:21:41 > 0:21:46The melting fat is the wax and the blanket is the wick.
0:21:46 > 0:21:50And, like a candle, the whole thing burns with a low flame,
0:21:50 > 0:21:53so the fire is unlikely to spread to the rest of the room.
0:21:53 > 0:21:56- There you go. Fire, six hours later. - Yeah.
0:21:56 > 0:21:59You can see where that wick effect's happening, in the middle.
0:21:59 > 0:22:00I mean, this is it.
0:22:00 > 0:22:03It's a big pool of fat burrowing down with the flame.
0:22:03 > 0:22:05Exactly. And that's where it started,
0:22:05 > 0:22:07that's where the cigarette caught fire.
0:22:07 > 0:22:11- And the head and the trotters... - Still intact.- ..nothing.
0:22:11 > 0:22:14I mean, they haven't even been touched.
0:22:14 > 0:22:15And the reason?
0:22:15 > 0:22:19Bits not covered by clothing can't become part of the wick
0:22:19 > 0:22:23and they don't contain enough fat to burn by themselves.
0:22:23 > 0:22:27The mystery of the burnt torso explained.
0:22:27 > 0:22:30So, when the police go in and they find arms, legs and head
0:22:30 > 0:22:33and loads of, kind of, burnt ash in the middle,
0:22:33 > 0:22:35but the whole of the rest of the room fine,
0:22:35 > 0:22:38spontaneous human combustion.
0:22:38 > 0:22:41- Probably not so spontaneous. - That isn't so spontaneous. Yeah
0:22:43 > 0:22:47Well, at least I don't have to worry about bursting into flames anymore.
0:23:16 > 0:23:21Living here, in the UK, we all know what it feels like to be chilly.
0:23:21 > 0:23:24Being exposed to extreme cold is just bad news
0:23:24 > 0:23:26for us thin-skinned humans.
0:23:26 > 0:23:29But what does the extreme cold do to your body?
0:23:29 > 0:23:31And is it possible to survive it?
0:23:31 > 0:23:35I think I'd just move and move and dance and wiggle.
0:23:35 > 0:23:39Find a pocket-knife from somewhere, find an animal, cut it open
0:23:39 > 0:23:44and live inside that and slowly, slowly crawl my way to civilisation.
0:23:44 > 0:23:47Double jumper, five coats.
0:23:47 > 0:23:49Well, we'd get naked and hug.
0:23:49 > 0:23:52And if you're really bad, get a cup of coffee.
0:23:53 > 0:23:57# Cos you're giving me the chills... #
0:24:04 > 0:24:08It's not exactly the weather for a pool party,
0:24:08 > 0:24:10but me and my mates are up for a challenge.
0:24:10 > 0:24:12The temperature in this unheated pool
0:24:12 > 0:24:14is about 12 degrees above freezing,
0:24:14 > 0:24:16but we're prepared to take the plunge
0:24:16 > 0:24:18in the interests of scientific research.
0:24:20 > 0:24:21Right, let's get rigged up.
0:24:21 > 0:24:26Cold water robs the body of heat roughly 30 times faster than air,
0:24:26 > 0:24:29which means our bodies are in for a shock.
0:24:29 > 0:24:32I'm wearing this mask to monitor my breathing rate
0:24:32 > 0:24:33and oxygen consumption
0:24:33 > 0:24:37and the clip on my finger will tell me my heart rate.
0:24:37 > 0:24:39- Heart rate, 85.- 85.
0:24:39 > 0:24:41Time for a quick temperature check.
0:24:41 > 0:24:44- Yeah.- 36.5 degrees.
0:24:44 > 0:24:46And in we go.
0:24:46 > 0:24:50Three, two, one.
0:24:50 > 0:24:53- Ah!- Ah!- Ah!- Whoa!- That's cold. - Oh, oh.
0:24:55 > 0:24:56- Ah!- Ooh.
0:24:56 > 0:25:00Oh, oh, oh.
0:25:02 > 0:25:05As soon as I hit the water, my breathing rate
0:25:05 > 0:25:07and oxygen consumption go through the roof.
0:25:07 > 0:25:10And, no surprise, we're all shivering.
0:25:10 > 0:25:13I can't control it, my muscles are just going.
0:25:13 > 0:25:15That's the body's way of keeping warm,
0:25:15 > 0:25:17but all this takes energy
0:25:17 > 0:25:22and that's bad, because if you use too much energy, you're a goner.
0:25:22 > 0:25:25On top of all this, my heart rate's shot up.
0:25:25 > 0:25:29It say's 87. More energy out of the window.
0:25:29 > 0:25:33- Andy, I want to try something on you.- Yes. What?- Pop that on your finger.
0:25:33 > 0:25:35'But nature has a way of slowing it down.'
0:25:35 > 0:25:36Get your base line reading.
0:25:36 > 0:25:39'Which saves energy.' 96.
0:25:39 > 0:25:41- 96?- 96.
0:25:41 > 0:25:45- Ready?- Andy!- What now?
0:25:45 > 0:25:46Go! Go!
0:25:49 > 0:25:5059.
0:25:50 > 0:25:52This lowering of your heart rate
0:25:52 > 0:25:55is called the mammalian diving reflex.
0:25:55 > 0:25:59All mammals do it. It's a way of burning less oxygen
0:25:59 > 0:26:01when you can't replace it by breathing,
0:26:01 > 0:26:04extending your range when you're swimming under water.
0:26:04 > 0:26:08And using less energy in the form of oxygen is also what happens
0:26:08 > 0:26:11when you body temperature drops.
0:26:11 > 0:26:14- Good.- What's that?- 35.3.
0:26:14 > 0:26:18So, before I got in, my core temperature was 36.5.
0:26:18 > 0:26:21It's now dropped to 35.3.
0:26:21 > 0:26:24- Let's get out. - LAUGHTER
0:26:24 > 0:26:29Obviously, getting out of freezing water is the very best thing to do,
0:26:29 > 0:26:32but, weirdly, the coldness we're trying to escape
0:26:32 > 0:26:34can sometimes save lives.
0:26:34 > 0:26:38The interesting thing is that, as your body cools down,
0:26:38 > 0:26:41your bodily functions start to slow down
0:26:41 > 0:26:44and your organs require less oxygen.
0:26:44 > 0:26:47As they require less oxygen, you need to breath less
0:26:47 > 0:26:49and, eventually, you get to the point
0:26:49 > 0:26:51where your body needs so little oxygen,
0:26:51 > 0:26:53you could actually survive without breathing at all.
0:26:53 > 0:26:59And this simple fact has led to an amazing medical break through.
0:26:59 > 0:27:01By chilling them to 16 degrees,
0:27:01 > 0:27:05doctors can put patients into a state of suspended animation
0:27:05 > 0:27:09and perform complex operations without the blood circulating.
0:27:09 > 0:27:12Usually, this would mean certain death, but, at these temperatures,
0:27:12 > 0:27:16the body is using almost no energy and can often survive
0:27:16 > 0:27:20for up to 40 minutes before being warmed up and resuscitated.
0:27:20 > 0:27:24So, extreme cold can do some awful things to warm-blooded mammals
0:27:24 > 0:27:29like ourselves, but, ironically, in some situations,
0:27:29 > 0:27:32losing your heat could save your life.
0:27:32 > 0:27:35There are still plenty more secrets out there.
0:27:35 > 0:27:37Next time:
0:27:37 > 0:27:40Why digging to Australia is even trickier than you thought.
0:27:42 > 0:27:44My brain doesn't work.
0:27:44 > 0:27:47Why this, plus this, plus this
0:27:47 > 0:27:50equals far more of this than you could possibly imagine.
0:27:50 > 0:27:55But I only burned 1,210 calories.
0:27:55 > 0:27:57And what about this?
0:27:57 > 0:28:00Your challenge is to make a mountain out of a fridge.
0:28:00 > 0:28:02You really couldn't make it up.
0:28:08 > 0:28:12Subtitles by Red Bee Media Ltd