0:00:15 > 0:00:18This creature is a wonder of life.
0:00:22 > 0:00:24A voracious predator,
0:00:24 > 0:00:27this male has lived underwater for nearly five months,
0:00:27 > 0:00:32feeding, growing, preparing for this moment.
0:00:37 > 0:00:38He's about to undertake
0:00:38 > 0:00:41one of the most remarkable transformations
0:00:41 > 0:00:43in the natural world.
0:00:45 > 0:00:50From aquatic predator... to master of the air.
0:01:15 > 0:01:17The brief adult life of a dragonfly
0:01:17 > 0:01:19is amongst the most energetic in nature.
0:01:28 > 0:01:32Dragonflies are the most remarkable animals.
0:01:32 > 0:01:36You can see their incredible agility in flight
0:01:36 > 0:01:41just watching them skim across the surface of this pond.
0:01:41 > 0:01:43They can pull two and a half G in a turn,
0:01:43 > 0:01:45and they can fly at 15 mph,
0:01:45 > 0:01:48which is fast for something that big.
0:01:51 > 0:01:54They've been around on Earth since before the time of the dinosaurs,
0:01:54 > 0:01:59and in that time they've been fine-tuned by natural selection
0:01:59 > 0:02:04to do what they do - which is to catch their prey on the wing.
0:02:18 > 0:02:23So, dragonflies are beautiful pieces of engineering.
0:02:23 > 0:02:26They're intricate, complex machines.
0:02:26 > 0:02:29But is that all they are?
0:02:31 > 0:02:36Because once their brief lives are over, their vitality will be gone.
0:02:41 > 0:02:44And this raises deep questions.
0:02:48 > 0:02:51What is it that makes something alive?
0:02:55 > 0:02:59And how did life begin in the first place?
0:03:01 > 0:03:05So, what is the difference between the living and the dead?
0:03:05 > 0:03:07What is life?
0:03:41 > 0:03:45I've come to one of the most isolated regions of the Philippines
0:03:45 > 0:03:48to visit the remote hilltop town of Sagada.
0:03:50 > 0:03:54It's a two-day drive from the capital, Manila,
0:03:54 > 0:03:56over some of the country's roughest roads
0:03:56 > 0:04:00that wind their way 1,500 metres up into the hills.
0:04:17 > 0:04:18This is a place
0:04:18 > 0:04:22where the traditional belief is that mountain spirits give us life
0:04:22 > 0:04:26and that our souls return to the mountain when we die...
0:04:30 > 0:04:34..and where the people who live here still imagine that
0:04:34 > 0:04:37the spirits of the dead walk among the living.
0:04:50 > 0:04:54Tonight is November 1st, and here in Sagada -
0:04:54 > 0:04:58in fact across the Philippines - that means it's the Day of the Dead.
0:04:58 > 0:05:02That's the day when people come to this graveyard on a hillside
0:05:02 > 0:05:06and, well, celebrate the lives of their relatives.
0:05:16 > 0:05:20The people light fires to honour and warm the departed,
0:05:20 > 0:05:23inviting their souls to commune with them.
0:05:42 > 0:05:45Now, not matter how unscientific it sounds,
0:05:45 > 0:05:51this idea that there's some kind of soul or spirit or animating force
0:05:51 > 0:05:56that makes us what we are and that persists after our death is common.
0:05:56 > 0:05:58Virtually every culture, every religion,
0:05:58 > 0:06:00has that deeply-held belief.
0:06:02 > 0:06:06And there's a reason for that - because it feels right.
0:06:06 > 0:06:10I mean, just think about it. It's hard to accept that when you die
0:06:10 > 0:06:14you will just stop existing and that you are, your life,
0:06:14 > 0:06:18the essence of you, is just really something
0:06:18 > 0:06:22that emerges from an inanimate bag of stuff.
0:06:55 > 0:06:57Don't get too close.
0:07:01 > 0:07:03You can see that these people feel
0:07:03 > 0:07:06not only do they come to celebrate the lives of their relatives,
0:07:06 > 0:07:09but they're coming in some sense to communicate with them.
0:07:09 > 0:07:12Their relatives, even though their physical bodies have died,
0:07:12 > 0:07:15are still in some sense here.
0:07:17 > 0:07:20When you think about it, that's not so easy to dismiss.
0:07:20 > 0:07:25If we are to state that science can explain everything about us,
0:07:25 > 0:07:29then it's incumbent on science to answer the question,
0:07:29 > 0:07:33what is it that animates living things?
0:07:33 > 0:07:37What is the difference between a piece of rock
0:07:37 > 0:07:40that's carved into a gravestone and me?
0:07:49 > 0:07:53For millennia, some form of spirituality has been evoked
0:07:53 > 0:07:58to explain what it means to be alive, and how life began.
0:08:03 > 0:08:05It's only recently
0:08:05 > 0:08:10that science has begun to answer these deepest of questions.
0:08:32 > 0:08:33In February 1943,
0:08:33 > 0:08:37the physicist Erwin Schrodinger gave a series of lectures in Dublin.
0:08:37 > 0:08:40Now, Schrodinger is almost certainly most famous
0:08:40 > 0:08:43for being one of the founders of quantum theory.
0:08:43 > 0:08:46But in these lectures, which he wrote up in this little book,
0:08:46 > 0:08:50he asked a very different question - What Is Life?
0:08:50 > 0:08:56And right up front, on page one, he says precisely what it isn't.
0:08:56 > 0:08:59It isn't something mystical, says Schrodinger.
0:08:59 > 0:09:03There isn't some magical spark that animates life.
0:09:03 > 0:09:05Life is a process.
0:09:05 > 0:09:07It's the interaction between matter and energy
0:09:07 > 0:09:11described by the laws of physics and chemistry.
0:09:11 > 0:09:12The same laws that describe
0:09:12 > 0:09:15the falling of the rain or the shining of the stars.
0:09:23 > 0:09:25So, the question is,
0:09:25 > 0:09:30how is that this magnificent complexity that we call life
0:09:30 > 0:09:34could have assembled itself on the surface of a planet
0:09:34 > 0:09:36which itself formed
0:09:36 > 0:09:41from nothing more than a collapsing cloud of gas and dust?
0:09:46 > 0:09:50To Schrodinger, the answer had to lie in the way living things process
0:09:50 > 0:09:56one of the universe's most elusive properties - energy.
0:10:17 > 0:10:21Energy is a concept that's central to physics,
0:10:21 > 0:10:23but because it's a word we use every day
0:10:23 > 0:10:25its meaning has got a bit woolly.
0:10:25 > 0:10:27I mean, it's easy to say what it is in a sense.
0:10:27 > 0:10:31Obviously this river has got energy because over decades and centuries
0:10:31 > 0:10:34it's cut this valley through solid rock.
0:10:36 > 0:10:39But while this description sounds simple,
0:10:39 > 0:10:43in reality things are a little more complicated.
0:10:43 > 0:10:45For me, the best definition is that
0:10:45 > 0:10:48it's the length of the space time four vector and time direction,
0:10:48 > 0:10:50but that's not very enlightening, I'll grant you that.
0:10:55 > 0:10:57Over the years,
0:10:57 > 0:11:01the nature of energy has proved notoriously difficult to pin down.
0:11:01 > 0:11:05Not least because it has the seemingly magical property
0:11:05 > 0:11:07that it never runs out.
0:11:07 > 0:11:10It only ever changes from one form to another.
0:11:15 > 0:11:17Take the water in that waterfall.
0:11:17 > 0:11:19At the top of the waterfall,
0:11:19 > 0:11:22it's got something called gravitational potential energy,
0:11:22 > 0:11:24which is the energy it possesses
0:11:24 > 0:11:26due to its height above the Earth's surface.
0:11:26 > 0:11:31See, if I scoop some water out of the river into this beaker,
0:11:31 > 0:11:35then I'd have to do work to carry it up to the top of the waterfall.
0:11:35 > 0:11:38I'd have to expend energy to get it up there.
0:11:38 > 0:11:42So it would have that energy as gravitational potential.
0:11:42 > 0:11:44I can even do the sums for you.
0:11:44 > 0:11:46Half a litre of water has a mass of half a kilogram,
0:11:46 > 0:11:49multiply by the height, that's about five metres,
0:11:49 > 0:11:53the acceleration due to gravity's about ten metres per second squared.
0:11:53 > 0:11:57So that's half times five times ten is 25 joules.
0:11:57 > 0:12:00So I'd have to put in 25 joules
0:12:00 > 0:12:04to carry this water to the top of the waterfall.
0:12:04 > 0:12:07Then if I emptied it over the top of the waterfall,
0:12:07 > 0:12:10then all that gravitational potential energy
0:12:10 > 0:12:13would be transformed into other types of energy.
0:12:15 > 0:12:18Its sound, which is pressure waves in the air.
0:12:18 > 0:12:22There's the energy of the waves in the river. And there's heat.
0:12:22 > 0:12:24So it'll be a bit hotter down there
0:12:24 > 0:12:26because the water's cascading into the pool
0:12:26 > 0:12:28at the foot of the waterfall.
0:12:28 > 0:12:31Buy the key thing is energy is conserved,
0:12:31 > 0:12:33it's not created or destroyed.
0:12:36 > 0:12:37So, because energy is conserved,
0:12:37 > 0:12:40if I were to add up all the energy in the water waves,
0:12:40 > 0:12:43all the energy in the sound waves,
0:12:43 > 0:12:46all the heat energy at the bottom of the pool,
0:12:46 > 0:12:49then I would find that it would be precisely equal
0:12:49 > 0:12:53to the gravitational potential energy at the top of the falls.
0:12:58 > 0:13:02What's true for the waterfall is true for everything in the universe.
0:13:04 > 0:13:06It's a fundamental law of nature,
0:13:06 > 0:13:10known as the first law of thermodynamics.
0:13:10 > 0:13:14And the fact that energy is neither created nor destroyed
0:13:14 > 0:13:17has a profound implication.
0:13:18 > 0:13:21It means energy is eternal.
0:13:26 > 0:13:28The energy that's here now has always been here,
0:13:28 > 0:13:31and the story of the evolution of the universe
0:13:31 > 0:13:35is just the story of the transformation of that energy
0:13:35 > 0:13:37from one form to another,
0:13:37 > 0:13:39from the origin of the first galaxies
0:13:39 > 0:13:41to the ignition of the first stars
0:13:41 > 0:13:43and the formation of the first planets.
0:13:50 > 0:13:54Every single joule of energy in the universe today
0:13:54 > 0:13:59was present at the Big Bang, 13.7 billion years ago.
0:14:02 > 0:14:06Potential energy held in primordial clouds of gas and dust
0:14:06 > 0:14:09was transformed into kinetic energy
0:14:09 > 0:14:13as they collapsed to form stars and planetary systems,
0:14:13 > 0:14:15just like our own solar system.
0:14:23 > 0:14:25In the Sun,
0:14:25 > 0:14:29heat from the collapse initiated fusion reactions at its core.
0:14:34 > 0:14:37Hydrogen became helium.
0:14:37 > 0:14:41Nuclear-binding energy was released, heating the surface of the Sun,
0:14:41 > 0:14:46producing the light that began to bathe the young Earth.
0:14:53 > 0:14:57And at some point in that story, around four billion years ago,
0:14:57 > 0:15:03that transformation of energy led to the origin of life on Earth.
0:15:21 > 0:15:27Around 350 kilometres south of Sagada, this is Lake Taal.
0:15:33 > 0:15:36Despite its sleepy, languid appearance,
0:15:36 > 0:15:41this landscape has been violently transformed by energy.
0:16:06 > 0:16:07When I think of a volcano,
0:16:07 > 0:16:10I usually think of a pointy, fiery mountain
0:16:10 > 0:16:12with a little crater in the top.
0:16:12 > 0:16:14Probably a bit like that one.
0:16:14 > 0:16:19But actually this entire lake is the flooded crater of a giant volcano.
0:16:19 > 0:16:23It began erupting only about 140,000 years ago,
0:16:23 > 0:16:30and in that time it's blown 120 billion cubic metres of ash and rock
0:16:30 > 0:16:33into the Earth's atmosphere.
0:16:33 > 0:16:38This crater is 30 kilometres across and in places 150 metres deep.
0:16:38 > 0:16:41That's a cube of rock
0:16:41 > 0:16:46five kilometres by five kilometres by five kilometres
0:16:46 > 0:16:48just blown away.
0:16:53 > 0:16:56It's a big volcano.
0:17:04 > 0:17:07Taal Lake is testament to the immense power
0:17:07 > 0:17:11locked within the Earth at the time of its formation.
0:17:20 > 0:17:23Since the lake was created,
0:17:23 > 0:17:26a series of further eruptions formed the island in the centre.
0:17:28 > 0:17:30And at its heart
0:17:30 > 0:17:34is a place where you can glimpse the turmoil of the inner Earth,
0:17:34 > 0:17:38where energy from the core still bubbles up to the surface...
0:17:42 > 0:17:46..producing conditions similar to those that may have provided
0:17:46 > 0:17:49the very first spark of life.
0:18:02 > 0:18:06The water in this lake is different from drinking water
0:18:06 > 0:18:08in a very interesting way.
0:18:08 > 0:18:13See, if I test this bottle of water with this,
0:18:13 > 0:18:17which is called universal indicator paper,
0:18:17 > 0:18:20then you see immediately that it goes green.
0:18:20 > 0:18:23And that means that it's completely neutral.
0:18:23 > 0:18:25It's called PH7 in the jargon.
0:18:25 > 0:18:29But then look what happens when I test the water from the lake.
0:18:32 > 0:18:35Now the indicator paper stays orange.
0:18:35 > 0:18:38In fact, it might have gone a bit more orange.
0:18:38 > 0:18:41So that means that this is acid. It's about PH3.
0:18:45 > 0:18:47At the most basic level,
0:18:47 > 0:18:50the energy trapped inside the Earth is melting rocks.
0:18:50 > 0:18:53And when you melt rock like this you produce gases.
0:18:53 > 0:18:55A lot of carbon dioxide,
0:18:55 > 0:18:59and in this case of this volcano, a lot of sulphur dioxide.
0:18:59 > 0:19:02Now, sulphur dioxide dissolves in water
0:19:02 > 0:19:05and you get H2SO4, sulphuric acid.
0:19:10 > 0:19:14Now, what I mean when I say that water is acidic?
0:19:17 > 0:19:21Well, water is H2O - hydrogen and oxygen bonded together.
0:19:21 > 0:19:25But actually when it's liquid it's a bit more complicated than that.
0:19:25 > 0:19:28It's actually a sea of ions.
0:19:28 > 0:19:31So H-plus ions, that's just single protons.
0:19:31 > 0:19:35And OH-minus ions, that's oxygen and hydrogen bonded together,
0:19:35 > 0:19:37all floating around.
0:19:37 > 0:19:40Now, when something's neutral, when the PH is seven,
0:19:40 > 0:19:43that means that the concentrations of those ions
0:19:43 > 0:19:46are perfectly balanced.
0:19:46 > 0:19:48When you make water acidic,
0:19:48 > 0:19:52then you change the concentration of those ions and, to be specific,
0:19:52 > 0:19:57you increase the concentration of the H-plus ions of the protons.
0:20:01 > 0:20:06So, this process of acidification has stored the energy of the volcano
0:20:06 > 0:20:09as chemical potential energy.
0:20:13 > 0:20:18The volcano transforms heat from the inner Earth into chemical energy
0:20:18 > 0:20:22and stores it as a reservoir of protons in the lake.
0:20:25 > 0:20:27And this is the same way energy is stored
0:20:27 > 0:20:31in a simple battery or fuel cell.
0:20:34 > 0:20:37These bottles contain a weak acid
0:20:37 > 0:20:41and are connected by a semi-permeable membrane.
0:20:41 > 0:20:44Passing an electric current through them has a similar effect
0:20:44 > 0:20:48to the volcano's energy bubbling up into the lake.
0:20:48 > 0:20:52It causes protons to build up in one of the bottles.
0:20:55 > 0:20:58You can think of it, I suppose, like a waterfall,
0:20:58 > 0:21:02where the protons are up here waiting to flow down.
0:21:02 > 0:21:04All you have to do to release that energy
0:21:04 > 0:21:07and do something useful with it is complete the circuit.
0:21:07 > 0:21:11Which I can do by just connecting a motor to it.
0:21:15 > 0:21:17There you go. Look at that.
0:21:17 > 0:21:20That's the protons cascading down the waterfall
0:21:20 > 0:21:23and driving the motor around.
0:21:29 > 0:21:31It actually works!
0:21:32 > 0:21:35Quite remarkable, actually.
0:21:36 > 0:21:39Now, the fuel cell produces and exploits
0:21:39 > 0:21:44its proton gradient artificially. But there are places on Earth
0:21:44 > 0:21:48where that gradient occurs completely naturally.
0:21:48 > 0:21:50Here, for example.
0:21:50 > 0:21:52So we've got the proton reservoir over there,
0:21:52 > 0:21:55the acidic volcanic lake.
0:21:55 > 0:21:57If you look that way, there's another lake,
0:21:57 > 0:22:01and the reaction of the water with the rocks on the shore
0:22:01 > 0:22:03make that lake slightly alkaline,
0:22:03 > 0:22:06which is to say that there's a deficit of protons down there.
0:22:06 > 0:22:09So here's the waterfall,
0:22:09 > 0:22:12a reservoir of protons up there, a deficit down there.
0:22:12 > 0:22:14If you could just connect them,
0:22:14 > 0:22:17then you'd have a naturally occurring geological fuel cell.
0:22:17 > 0:22:21And it's thought that the first life on our planet
0:22:21 > 0:22:25may have exploited the energy released
0:22:25 > 0:22:28in those natural proton waterfalls.
0:22:55 > 0:22:58What do you think? It's good, isn't it?
0:23:06 > 0:23:09These are pictures from deep below the surface
0:23:09 > 0:23:13of the Atlantic Ocean, somewhere between Bermuda and the Canaries.
0:23:13 > 0:23:16And it's a place known as the Lost City.
0:23:16 > 0:23:18You can see why.
0:23:18 > 0:23:23Look at these huge towers of rock, some of them 50-60 metres high,
0:23:23 > 0:23:27reaching up from the floor of the Atlantic and into the ocean.
0:23:27 > 0:23:30It's what's known as a hydrothermal vent system.
0:23:30 > 0:23:34So these things are formed by hot water and minerals and gases
0:23:34 > 0:23:37rising up from deep within the Earth.
0:23:37 > 0:23:40But the reason it's thought that life on Earth may have begun
0:23:40 > 0:23:43in such structures is because
0:23:43 > 0:23:46these are a very unique kind of hydrothermal vent
0:23:46 > 0:23:48called an alkaline vent.
0:23:48 > 0:23:51And, about four billion years ago, when life on Earth began,
0:23:51 > 0:23:55seawater would have been mildly acidic.
0:23:55 > 0:24:00So, here is that proton gradient, that source of energy for life.
0:24:00 > 0:24:04You've got a reservoir of protons in the acidic seawater
0:24:04 > 0:24:08and a deficit of protons around the vents.
0:24:13 > 0:24:16And the vents don't just provide an energy source.
0:24:16 > 0:24:20They're also rich in the raw materials life needs.
0:24:23 > 0:24:26Hydrogen gas, carbon dioxide
0:24:26 > 0:24:31and minerals containing iron, nickel and sulphur.
0:24:33 > 0:24:34But there's more than that.
0:24:34 > 0:24:39See, these vents are porous - there are little chambers inside them -
0:24:39 > 0:24:42and they can act to concentrate organic molecules.
0:24:47 > 0:24:50You've got everything inside these vents.
0:24:50 > 0:24:54You've got concentrated building blocks of life
0:24:54 > 0:24:56trapped inside the rock.
0:24:58 > 0:25:00And you've got that proton gradient,
0:25:00 > 0:25:06you've got that waterfall that provides the energy for life.
0:25:06 > 0:25:10So this could be where your distant ancestors come from.
0:25:10 > 0:25:17And places like these could be the places where life on Earth began.
0:25:21 > 0:25:25The first living things might have started out
0:25:25 > 0:25:27as part of the rock that created them.
0:25:33 > 0:25:36Simple organisms that exploited energy
0:25:36 > 0:25:40from the naturally-occurring proton gradients in the vents.
0:25:45 > 0:25:47And we think this because
0:25:47 > 0:25:52living things still get their energy using proton gradients today.
0:26:04 > 0:26:07Deep within ourselves,
0:26:07 > 0:26:11the chemistry the first life exploited in the vents
0:26:11 > 0:26:15is wrapped up in structures called mitochondria -
0:26:15 > 0:26:19microscopic batteries that power the processes of life.
0:26:25 > 0:26:30This is a picture of the mitochondria
0:26:30 > 0:26:32from the little brown bat.
0:26:32 > 0:26:36This is a picture of the mitochondria from a plant.
0:26:36 > 0:26:39It's actually a member of the mustard family.
0:26:39 > 0:26:43This is a picture of the mitochondria in bread mould.
0:26:43 > 0:26:49And this of mitochondria inside a malaria parasite.
0:26:49 > 0:26:56So, the fascinating thing is that all these animals and plants,
0:26:56 > 0:27:00and in fact virtually every living thing on the planet,
0:27:00 > 0:27:05uses proton gradients to produce energy to live. Why?
0:27:05 > 0:27:08Well, the answer is probably
0:27:08 > 0:27:12because all these radically different forms of life
0:27:12 > 0:27:14share a common ancestor.
0:27:14 > 0:27:17And that common ancestor was something that lived in
0:27:17 > 0:27:22those ancient undersea vents, four billion years ago,
0:27:22 > 0:27:25where naturally-occurring proton gradients
0:27:25 > 0:27:28provided the energy for the first life.
0:27:28 > 0:27:33So, if you're looking for a universal spark of life,
0:27:33 > 0:27:35then this is it.
0:27:35 > 0:27:40The spark of life is proton gradients.
0:27:49 > 0:27:54In those four billion years, that spark has grown into a flame.
0:27:56 > 0:28:00And a few simple organisms clustered around a hydrothermal vent
0:28:00 > 0:28:05have evolved to produce all the magnificent diversity
0:28:05 > 0:28:06that covers the Earth today.
0:28:32 > 0:28:35Today, life on Earth is so diverse,
0:28:35 > 0:28:39it covers so much of the planet that you can find places like this lake,
0:28:39 > 0:28:43where it's effectively its own sealed ecosystem.
0:28:43 > 0:28:46It's saltwater, it's connected to the sea,
0:28:46 > 0:28:49but it's only connected through small channels through the rock.
0:28:49 > 0:28:54So that means that the marine life in here is effectively isolated.
0:29:06 > 0:29:08This is the Golden Jellyfish,
0:29:08 > 0:29:15a unique sub-species only found in this one lake on this one island,
0:29:15 > 0:29:18in the tiny Micronesian Republic of Palau.
0:29:22 > 0:29:24They used to live like most jellyfish,
0:29:24 > 0:29:29cruising the open ocean, catching tiny creatures, zooplankton,
0:29:29 > 0:29:32in their long tentacles.
0:29:33 > 0:29:37But today their tentacles have all but disappeared
0:29:37 > 0:29:39because the Golden Jellyfish
0:29:39 > 0:29:43have evolved to do something that very few other animals can do.
0:29:58 > 0:30:01It really is incredible.
0:30:01 > 0:30:05There are, I want to say millions of jellyfish,
0:30:05 > 0:30:06as far as you can see,
0:30:06 > 0:30:10all the way down till the light vanishes there are jellyfish.
0:30:10 > 0:30:14And you can see they've congregated in the sun.
0:30:14 > 0:30:16If you go over there to where the lake's in shade,
0:30:16 > 0:30:17there are just none.
0:30:17 > 0:30:20They're in this pool of light, beneath the sun.
0:30:20 > 0:30:22There are millions of them.
0:30:22 > 0:30:25Beautifully elegant things just floating around.
0:30:27 > 0:30:30I'm not being unduly hyperbolic, it's quite remarkable.
0:30:33 > 0:30:36MAKES MUFFLED NOISE
0:30:54 > 0:30:58This lake is home to over 20 million jellyfish.
0:31:02 > 0:31:05Whose success comes down to a remarkable adaptation.
0:31:08 > 0:31:12Their bodies play host to thousands of other organisms -
0:31:12 > 0:31:17photosynthetic algae that harvest energy directly from sunlight.
0:31:26 > 0:31:29The jellyfish engulf the algae as juveniles,
0:31:29 > 0:31:35and by adulthood algal cells make up around 10% of their biomass.
0:31:37 > 0:31:41Grouped into clusters of up to 200 individuals,
0:31:41 > 0:31:44they live inside the jellyfish's own cells.
0:31:50 > 0:31:53The Golden Jellyfish uses algae
0:31:53 > 0:31:56to get most of its energy from photosynthesis.
0:32:10 > 0:32:13They go to the surface and gently... Wow, there's one there.
0:32:13 > 0:32:15They're gently turning.
0:32:15 > 0:32:18The reason they do that is to give all their algae
0:32:18 > 0:32:21an equal dose of sunlight.
0:32:23 > 0:32:25So they're quite democratic creatures,
0:32:25 > 0:32:29just making sure they get as much food as they can.
0:32:29 > 0:32:34They just come up you, jellying around, photosynthesising.
0:32:41 > 0:32:43They tell me they don't sting.
0:32:43 > 0:32:46But I'm sure I've got a tingling from it.
0:32:51 > 0:32:53And it's not just their anatomy
0:32:53 > 0:32:55that's adapted to harvest solar energy.
0:32:57 > 0:32:59Every morning as the sun rises,
0:32:59 > 0:33:02the jellyfish begin to swim towards the east.
0:33:07 > 0:33:12As the sun tracks across the sky, they move back again towards the west,
0:33:12 > 0:33:13where they spend their night.
0:33:19 > 0:33:24So the jellyfish have this beautiful, intimate
0:33:24 > 0:33:28and complex relationship with the position of the sun in the sky.
0:33:32 > 0:33:35As sunlight is captured by their algae,
0:33:35 > 0:33:38it's converted into chemical energy.
0:33:40 > 0:33:44Energy they use to combine simple molecules,
0:33:44 > 0:33:48water and carbon dioxide, to produce are far more complex one.
0:33:50 > 0:33:51Glucose.
0:33:52 > 0:33:57Once absorbed by the jellyfish, glucose and other molecules
0:33:57 > 0:34:00not only power their daily voyage across the lake,
0:34:00 > 0:34:04they provide the basic building blocks the jellyfish
0:34:04 > 0:34:08use to grow the elegant and complex structures of their bodies.
0:34:18 > 0:34:22So the jellyfish, through their symbiotic algae,
0:34:22 > 0:34:27absorb the light, the energy from the sun, and they use it to live,
0:34:27 > 0:34:29to power their processes of life.
0:34:29 > 0:34:32And that's true, directly or indirectly,
0:34:32 > 0:34:36for every form of life on the surface of our planet.
0:34:36 > 0:34:39But things are a little bit more interesting than that,
0:34:39 > 0:34:43because energy is neither created nor destroyed.
0:34:43 > 0:34:48So life doesn't eat it somehow, it doesn't use it up,
0:34:48 > 0:34:50it doesn't remove it from the universe.
0:34:50 > 0:34:51So what does it do?
0:34:56 > 0:34:59To understand how energy sustains life,
0:34:59 > 0:35:04you have to understand exactly what happens to it as the cosmos evolves.
0:35:11 > 0:35:14POWERFUL EXPLOSION BOOMS
0:35:14 > 0:35:16In the first instance after the Big Bang
0:35:16 > 0:35:19there was nothing in the universe but energy.
0:35:26 > 0:35:30As it changed from one form to another, galaxies, stars
0:35:30 > 0:35:32and planets were born.
0:35:37 > 0:35:42But while the total amount of energy in the universe stays constant,
0:35:42 > 0:35:46with every single transformation something does change.
0:35:48 > 0:35:52The energy itself becomes less and less useful.
0:35:52 > 0:35:54It becomes ever more disordered.
0:35:58 > 0:36:02And you can see this process in action as energy from the sun
0:36:02 > 0:36:04hits the surface of the Earth.
0:36:08 > 0:36:10So think about think about this sand on the beach,
0:36:10 > 0:36:13it's been under the glare of the sun all day,
0:36:13 > 0:36:16it's been absorbing its light which has been heating it up,
0:36:16 > 0:36:19and now that the sun is dipping below the horizon,
0:36:19 > 0:36:21then the sand is still hot to the touch
0:36:21 > 0:36:26because it's re-radiating all the energy that it absorbed as heat
0:36:26 > 0:36:29back into the universe.
0:36:29 > 0:36:33The key word there is "all". All the energy.
0:36:33 > 0:36:36If it didn't do that then it'd just gradually heat up
0:36:36 > 0:36:37day after day after day,
0:36:37 > 0:36:40and eventually, I suppose, the whole beach would melt.
0:36:40 > 0:36:42So what's changed?
0:36:42 > 0:36:46Well, it's the quality of the energy, if you like.
0:36:46 > 0:36:48Think about it.
0:36:48 > 0:36:52If as much energy is coming back off this sand now as it absorbed from the sun,
0:36:52 > 0:36:54then it should be giving me a suntan.
0:36:54 > 0:36:58I should need sun cream if I sit looking at this beach all night.
0:36:58 > 0:36:59And obviously I don't.
0:36:59 > 0:37:04The difference is that this energy is of a lower quality.
0:37:04 > 0:37:06It can do less.
0:37:06 > 0:37:10It's heat, which is a very low quality of energy indeed.
0:37:10 > 0:37:13So what the sand's done is take highly ordered,
0:37:13 > 0:37:15high quality energy from the sun
0:37:15 > 0:37:21and convert it to an equal amount of low quality disordered energy.
0:37:28 > 0:37:30This descent into disorder
0:37:30 > 0:37:33is happening across the entire universe.
0:37:45 > 0:37:51As time passes, every single joule of energy is converted into heat.
0:37:54 > 0:37:59The universe gradually cools towards absolute zero.
0:37:59 > 0:38:04Until with no ordered energy left, the cosmos grinds to a halt
0:38:04 > 0:38:08and every structure in it decays away.
0:38:19 > 0:38:24Yet whilst the universe is dying, everywhere you look life goes on.
0:38:26 > 0:38:30It's a deep paradox that Schroedinger was well aware of
0:38:30 > 0:38:33when he wrote his book in 1943.
0:38:36 > 0:38:38"How can it be," writes Schroedinger,
0:38:38 > 0:38:41"That the living organism avoids decay?"
0:38:41 > 0:38:46In other words, how can it be that life seems to continue to build
0:38:46 > 0:38:48increasingly complex structures
0:38:48 > 0:38:54when the rest of the universe is falling to bits, is decaying away?
0:38:54 > 0:39:00Now, that's a paradox, because the universe is falling to bits,
0:39:00 > 0:39:03it is tending towards disorder.
0:39:03 > 0:39:06That is enshrined in a law of physics called
0:39:06 > 0:39:09the Second Law Of Thermodynamics.
0:39:09 > 0:39:12And I think most physicists believe that it's the one
0:39:12 > 0:39:16law of physics that will never be broken.
0:39:31 > 0:39:36The key to understanding how life obeys the laws of thermodynamics
0:39:36 > 0:39:38is to look at both the energy it takes in
0:39:38 > 0:39:41and the energy it gives out.
0:39:46 > 0:39:50This is a thermal camera, so hot things show up as red,
0:39:50 > 0:39:52and cold things show up as blue.
0:39:52 > 0:39:54COCKEREL CROWS
0:39:54 > 0:39:57So what you're seeing here is that the chicken is hotter
0:39:57 > 0:39:59than its surroundings.
0:39:59 > 0:40:02Now, heat is a highly disordered form of energy,
0:40:02 > 0:40:09so the chicken is radiating disorder out into the wider universe.
0:40:12 > 0:40:15By converting chemical energy into heat,
0:40:15 > 0:40:20life transforms energy from an ordered to a disordered form,
0:40:20 > 0:40:25in exactly the same way as every other process in the universe.
0:40:29 > 0:40:31COCKEREL CROWS
0:40:33 > 0:40:35In fact, every single human being
0:40:35 > 0:40:40can generate 6,000 times more heat per kilogram than the sun.
0:40:44 > 0:40:48And it's by converting so much energy from one form to another
0:40:48 > 0:40:54that life is able to hang on to a tiny amount of order for itself.
0:40:54 > 0:40:59Just enough to resist the inevitable decay of the universe.
0:40:59 > 0:41:02COCKEREL CROWS
0:41:02 > 0:41:04So it's no accident that living things are hot
0:41:04 > 0:41:07and export heat to their surroundings.
0:41:07 > 0:41:11Because it's an essential part of being alive.
0:41:11 > 0:41:15Living things borrow order from the wider universe,
0:41:15 > 0:41:18and then they export it again as disorder.
0:41:18 > 0:41:20But it's not precisely in balance.
0:41:20 > 0:41:23They have to export more disorder
0:41:23 > 0:41:25than the amount of order they import.
0:41:25 > 0:41:28That is the content of the Second Law Of Thermodynamics.
0:41:28 > 0:41:31And living things have to obey the Second Law
0:41:31 > 0:41:36because they're physical structures, they obey the laws of physics.
0:41:41 > 0:41:46Just by being alive, we too are part of the process of energy
0:41:46 > 0:41:50transformation that drives the evolution of the universe.
0:41:54 > 0:41:59We take sunlight that has its origins at the very start of time,
0:41:59 > 0:42:04and transform it into heat that will last for eternity.
0:42:09 > 0:42:11So, far from being a paradox,
0:42:11 > 0:42:16living things can be explained by the laws of physics.
0:42:16 > 0:42:20The very same laws that describe the falling of the rain
0:42:20 > 0:42:21and the shining of the stars.
0:42:44 > 0:42:48The dragonfly draws its energy from proton gradients,
0:42:48 > 0:42:52the fundamental chemistry that powers life.
0:42:56 > 0:42:59But the real miracles are the structures
0:42:59 > 0:43:01they build with that energy.
0:43:06 > 0:43:08Borrowing order to generate cells.
0:43:10 > 0:43:13Arranging those cells into tissues.
0:43:15 > 0:43:19And those tissues into the intricate architecture of their bodies.
0:43:23 > 0:43:26So we've developed a quite detailed understanding
0:43:26 > 0:43:31of the underlying machinery that powers these dragonflies,
0:43:31 > 0:43:33and indeed all life on Earth.
0:43:33 > 0:43:36And whilst we don't have all the answers, it is certainly safe to say
0:43:36 > 0:43:38that there's no mysticism required.
0:43:38 > 0:43:41You don't need some kind of magical flame
0:43:41 > 0:43:43to animate these little machines.
0:43:43 > 0:43:47They operate according to the laws of physics,
0:43:47 > 0:43:49and I think they're no less magical for that.
0:43:54 > 0:43:59Yet the dragonfly will only maintain this delicate balancing act for so long.
0:44:01 > 0:44:04Because all living things share the same fate.
0:44:09 > 0:44:11Each individual will die.
0:44:14 > 0:44:17But life itself endures.
0:44:18 > 0:44:22DRAGONFLIES BUZZ
0:44:25 > 0:44:28This is because there's something that separates life
0:44:28 > 0:44:31from every other process in the universe.
0:44:36 > 0:44:40BOAT ENGINE CHUGS
0:44:42 > 0:44:46WILD ANIMAL ROARS
0:44:46 > 0:44:50MONKEYS CHATTER
0:44:52 > 0:44:54This is the Malaysian state of Sabah,
0:44:54 > 0:44:57on the northern tip of the island of Borneo.
0:44:59 > 0:45:03It's one of the most bio-diverse places on the planet.
0:45:03 > 0:45:05INSECT BUZZES
0:45:05 > 0:45:08Home to 15,000 plant species...
0:45:10 > 0:45:12..3,000 species of tree...
0:45:14 > 0:45:16..420 species of bird...
0:45:19 > 0:45:22..and 222 species of mammals.
0:45:23 > 0:45:27- Including those. - ELEPHANTS ROAR LOUDLY
0:45:31 > 0:45:34Borneo's rainforests contain trees that are thought to live
0:45:34 > 0:45:36for more than 1,000 years.
0:45:41 > 0:45:45But the forest itself has existed for tens of millions of years.
0:45:51 > 0:45:56The reason it persists is because each generation of animal and plant
0:45:56 > 0:46:01passes the information to recreate itself on to the next generation.
0:46:03 > 0:46:04And that's possible
0:46:04 > 0:46:09because of a molecule found in every cell of every living thing.
0:46:11 > 0:46:14A molecule called DNA.
0:46:25 > 0:46:32Now, all I need to isolate my DNA is some washing up liquid,
0:46:32 > 0:46:38a bit of salt, and the chemist's best friend, vodka.
0:46:38 > 0:46:42Now, to get a sample of DNA I can just use myself.
0:46:42 > 0:46:47If I just swill my tongue around on the edge of my cheek,
0:46:47 > 0:46:50I'll dislodge some cheek cells into my saliva.
0:46:51 > 0:46:53DOG BARKS OUTSIDE
0:46:55 > 0:46:57LAUGHS
0:46:57 > 0:46:59I missed the test tube.
0:46:59 > 0:47:01There we are. A physicist doing an experiment.
0:47:05 > 0:47:06STIFLES LAUGHTER
0:47:07 > 0:47:12Then I add a bit of washing up liquid.
0:47:12 > 0:47:17Now, what this will do is it will break open those cheek cells
0:47:17 > 0:47:21and it will also degrade the membrane that surrounds
0:47:21 > 0:47:25the cell nucleus that contains the DNA.
0:47:25 > 0:47:30Salt will encourage the molecules to clump together.
0:47:31 > 0:47:35DNA is insoluble in alcohol.
0:47:35 > 0:47:42So you should get a layer of alcohol
0:47:42 > 0:47:44with DNA molecules precipitated out.
0:47:49 > 0:47:54Yeah. There, can you see?
0:47:54 > 0:47:57Those strands of white.
0:47:57 > 0:48:03And so in that cloudy, almost innocuous looking solid
0:48:03 > 0:48:08are all the instructions needed to build a human being.
0:48:12 > 0:48:17So that is what makes life unique.
0:48:27 > 0:48:31Only living things have the ability to encode
0:48:31 > 0:48:33and transmit information in this way.
0:48:36 > 0:48:40And the consequences of that profoundly affect
0:48:40 > 0:48:43our understanding of what it is to be alive.
0:48:44 > 0:48:48This rainforest is part of the Sepilok Forest Reserve,
0:48:48 > 0:48:53and in here somewhere are some of our closest genetic relatives.
0:49:06 > 0:49:08Shh-shh.
0:49:11 > 0:49:13There, there, can you see?
0:49:20 > 0:49:25Orang-utans are highly specialised for a life lived in the forest canopy.
0:49:26 > 0:49:30Their arms are twice as long as their legs.
0:49:30 > 0:49:33And all four limbs are incredibly flexible.
0:49:33 > 0:49:38Each one ending in a hand whose curved bones
0:49:38 > 0:49:41are perfectly adapted for gripping branches.
0:49:44 > 0:49:48These adaptations are encoded in information
0:49:48 > 0:49:50passed down in their DNA.
0:49:55 > 0:49:56LAUGHS GENTLY
0:49:56 > 0:49:57He's got a hat on.
0:50:00 > 0:50:02He has actually just put a hat on.
0:50:16 > 0:50:20This is the orang-utan's genetic code.
0:50:20 > 0:50:22It was published in 2011,
0:50:22 > 0:50:27and there are over three billion letters in it.
0:50:27 > 0:50:29If flip through it...
0:50:32 > 0:50:33..look at that.
0:50:35 > 0:50:39Now, it's composed of only four letters, A, C, T and G,
0:50:39 > 0:50:41which are known as bases.
0:50:41 > 0:50:44They're chemical compounds. They're molecules.
0:50:44 > 0:50:48And the way it works is beautifully simple.
0:50:48 > 0:50:51They're grouped into threes, called codons,
0:50:51 > 0:50:56and some of them just tell the code reader, if you like,
0:50:56 > 0:50:59how to start, or where to start and when...
0:50:59 > 0:51:01and when it's going to stop.
0:51:03 > 0:51:05LAUGHS
0:51:07 > 0:51:08He's fast.
0:51:11 > 0:51:14So you'd have a start and a stop.
0:51:14 > 0:51:19In between, each group of three codes for a particular amino acid.
0:51:21 > 0:51:24Now, amino acids are the building blocks of proteins,
0:51:24 > 0:51:29which are the building blocks of all living things.
0:51:29 > 0:51:32So you would just read along,
0:51:32 > 0:51:35you'd find, start, stop, and then
0:51:35 > 0:51:38you'd go along in threes, build amino acid, build amino acid,
0:51:38 > 0:51:40build amino acid, build amino acid,
0:51:40 > 0:51:42stitch those together into a protein,
0:51:42 > 0:51:44and if you keep doing that,
0:51:44 > 0:51:48eventually you'll come out with one of those.
0:51:52 > 0:51:57It's not that simple of course. But the basics are there.
0:51:59 > 0:52:04This code, written in there, are the instructions to make him.
0:52:13 > 0:52:16To faithfully reproduce those instructions
0:52:16 > 0:52:18for generation after generation,
0:52:18 > 0:52:21the orang-utans and, and indeed all life on Earth,
0:52:21 > 0:52:24rely on a remarkable property of DNA.
0:52:25 > 0:52:29Its incredible stability and resistance to change.
0:52:34 > 0:52:38Every time a cell divides, its DNA must be copied.
0:52:38 > 0:52:42And the genetic code is highly resistant to copying errors.
0:52:42 > 0:52:45The little enzymes, the chemical machines that do the copying,
0:52:45 > 0:52:49on average make only one mistake in a billion letters.
0:52:49 > 0:52:53I mean, that's like copying out the Bible about 280 times
0:52:53 > 0:52:55and making just one mistake.
0:53:00 > 0:53:04That fidelity means adaptations are faithfully transmitted
0:53:04 > 0:53:06from parent to offspring.
0:53:08 > 0:53:13And so while we think of evolution as a process of constant change,
0:53:13 > 0:53:17in fact the vast majority of the code is preserved.
0:53:19 > 0:53:22So even though we're separated from the orang-utans
0:53:22 > 0:53:26by nearly 14 million years of evolution,
0:53:26 > 0:53:30what's really striking is just how similar we are.
0:53:31 > 0:53:35And those similarities are far more than skin deep.
0:53:38 > 0:53:42Orang-utans are surely one of the most human of animals.
0:53:42 > 0:53:47And they share many behavioural traits that you would
0:53:47 > 0:53:49define as being uniquely human.
0:53:51 > 0:53:54They nurture their young for eight years before they let them
0:53:54 > 0:53:56go on their own into the forest.
0:53:56 > 0:54:00In that time the infants learn which fruits are safe to eat
0:54:00 > 0:54:02and which are poisonous.
0:54:02 > 0:54:06Which branches will hold their weight and which won't.
0:54:06 > 0:54:09And they can do all that because they have a memory,
0:54:09 > 0:54:12they can remember things that happened to them in their life,
0:54:12 > 0:54:14they can learn from them,
0:54:14 > 0:54:17and they can pass them on from generation to generation.
0:54:24 > 0:54:28And that deep connection extends far beyond our closest relatives.
0:54:30 > 0:54:33Because our DNA contains the fingerprint
0:54:33 > 0:54:37of almost four billion years of evolution.
0:54:37 > 0:54:40BIRDS SING
0:54:43 > 0:54:46If I draw a tree of life for the primates,
0:54:46 > 0:54:52then we share a common ancestor with the chimps, Bonobos.
0:54:52 > 0:54:55About four to six million years ago.
0:54:55 > 0:55:01And if you compare our genetic sequences you find
0:55:01 > 0:55:07that our genes are 99% the same.
0:55:07 > 0:55:11You go back to the split with gorillas,
0:55:11 > 0:55:14about six to eight million years ago and again,
0:55:14 > 0:55:21if you compare our genes you find that they are 98.4% the same.
0:55:23 > 0:55:27Back in time again, common ancestor with our friends over there,
0:55:27 > 0:55:34the orang-utans, then our genes are 97.4% the same.
0:55:34 > 0:55:36And you could carry on all the way back in time.
0:55:36 > 0:55:40You could look for our common ancestor with a chicken,
0:55:40 > 0:55:44and you'd find that our codes are about 60% the same.
0:55:44 > 0:55:48And in fact, if you look for any animal, like him,
0:55:48 > 0:55:53a little fly, or a bacteria, something that seems superficially
0:55:53 > 0:55:57completely unrelated to us, then you'll still find sequences
0:55:57 > 0:56:01in the genetic code which are identical to sequences in my cells.
0:56:01 > 0:56:07So this tells us that all life on Earth is related,
0:56:07 > 0:56:10it's all connected through our genetic code.
0:56:20 > 0:56:23DNA is the blueprint for life.
0:56:25 > 0:56:30But its extraordinary fidelity means it also contains a story.
0:56:30 > 0:56:32And what a story it is.
0:56:35 > 0:56:39The entire history of evolution from the present day
0:56:39 > 0:56:43all the way back to the very first spark of life.
0:56:46 > 0:56:51And it tells us that we're connected, not only to every plant
0:56:51 > 0:56:58and animal alive today, but to every single thing that has ever lived.
0:57:21 > 0:57:23The question, what is life,
0:57:23 > 0:57:26is surely one of the grandest of questions.
0:57:26 > 0:57:29And we've learnt that life isn't really a thing at all.
0:57:29 > 0:57:33It's a collection of chemical processes that can harness
0:57:33 > 0:57:36a flow of energy to create local islands of order,
0:57:36 > 0:57:39like me and this forest,
0:57:39 > 0:57:42by borrowing order from the wider universe
0:57:42 > 0:57:46and then transmitting it from generation to generation
0:57:46 > 0:57:49through the elegant chemistry of DNA.
0:57:49 > 0:57:51And the origins of that chemistry
0:57:51 > 0:57:54can be traced back four billion years,
0:57:54 > 0:57:58most likely to vents in the primordial ocean.
0:57:58 > 0:58:02And, most wonderfully of all, the echoes of that history,
0:58:02 > 0:58:06stretching back for a third of the age of the universe,
0:58:06 > 0:58:11can be seen in every cell of every living thing on Earth.
0:58:11 > 0:58:15And that leads to what I think is the most exciting idea of all,
0:58:15 > 0:58:20because far from being some chance event ignited by a mystical spark,
0:58:20 > 0:58:23the emergence of life on Earth might have been
0:58:23 > 0:58:27an inevitable consequence of the laws of physics.
0:58:27 > 0:58:28And if that's true,
0:58:28 > 0:58:32then a living cosmos might be the only way our cosmos can be.
0:58:46 > 0:58:52# Just remember you're a tiny little person on a planet
0:58:52 > 0:58:55# In a universe expanding and immense
0:58:57 > 0:59:01# That life began evolving and dissolving and resolving
0:59:01 > 0:59:05# In the deep primordial oceans by the hydrothermal vents
0:59:05 > 0:59:09# Our Earth which had its birth almost five billion years ago
0:59:09 > 0:59:12# From out a collapsing cloud of gas
0:59:12 > 0:59:15# Grew life which was quite new
0:59:15 > 0:59:16# And eventually led to you
0:59:16 > 0:59:20# In only 3.5 billion years or less. #
0:59:20 > 0:59:22WHISTLING TO END OF SONG
0:59:22 > 0:59:24Subtitles by Red Bee Media Ltd