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00:01Welcome to a new and very strange world of nature.
00:06It's being taken over by the weird subatomic particles of quantum physics.
00:23As a physicist, I've spent my working life studying how these particles behave in the laboratory.
00:32But now I'm heading out into the natural world.
00:36I'm on a mission to prove that quantum physics can solve the greatest mysteries in biology.
00:43This is a real adventure for me.
00:46I'm very much out of my comfort zone trying to apply the very careful ideas I'm familiar with in a
00:52physics laboratory to the messy world of living things.
00:58I believe that quantum physics could hold many of life's secrets.
01:04That deep in the cells of animals, particles glide through walls like ghosts.
01:13That when plants capture sunlight, their cells are invaded by shimmering waves that can be everywhere at the same time.
01:24And that even our human senses are tuning in to strange quantum vibrations.
01:32In the fantastic world of quantum biology, life is a game of chance, played by quantum rules.
01:46This is what I hope to convince you of, to show you that quantum mechanics is essential in explaining many
01:53of the important processes in life.
01:54And potentially, that quantum mechanics may even underpin the very existence of life itself.
02:17My quest begins with one of the most majestic sights in nature.
02:28Every winter, barnacle geese arrive right on cue at the same Scottish river.
02:36The end of an epic 2,000-mile voyage from Svalbard, high above the Arctic Circle.
02:45Of course, many birds head south for winter, then back home for summer.
02:52But for decades, exactly how birds navigated with such accuracy was one of the greatest mysteries in biology.
03:02So the most recent discovery has caused a sensation.
03:09In the past few years, one species of bird has helped create a scientific revolution.
03:15I was one of many physicists who were shocked to discover that it navigates using one of the strangest tricks
03:21in the whole of science.
03:22It utilizes a quirk of quantum mechanics, one that bamboozled even the greatest of physicists, from Richard Feynman to Albert
03:31Einstein himself.
03:32So you might be surprised to discover the identity of this mysterious creature.
03:38Say hello to the quantum robin.
03:48This is the European robin.
03:53Every year, she migrates from northern Europe to the tip of Spain and back.
04:04In this laboratory in the woods, biologist Henrik Moritzsen is trying to solve the mystery of how she does it.
04:13But he's found himself in my world, the strange world of quantum mechanics.
04:23Quantum mechanics describes the very weird behavior of subatomic particles.
04:33Down in this realm of the very small, we have to abandon common sense and intuition.
04:41Instead, this is a world where objects can spread out like waves.
04:46Quantum particles can be in many places at once and send each other mysterious communications.
04:52I set out to understand how the bird finds its way, but it just turned out that the data more
05:01and more pointed towards this as the only explanation that could bring all the different results together.
05:10Henrik's investigating a long-standing theory that robins navigate by the Earth's magnetic field.
05:19His laboratory is an ingenious magnetic birdcage, and these plastic cones, lined with scratch-sensitive paper, provide the key measurements.
05:36Henrik's artificial magnetic field is like the Earth's, except that he can point it in any direction he likes.
05:47Inside their cones, the robins always respond to the field, leaving scratches in a single direction.
05:57The big mystery is how.
06:01The Earth's magnetic field is incredibly weak, far too weak for any living creature to detect.
06:09But Henrik has found an intriguing clue, by giving the quantum robin a mask.
06:15We have a little leather hood, similar to what you put on a falcon, you know, but just for a
06:20robin.
06:20And you have then a hole in front of one eye, or a hole in front of the other eye.
06:24But what we can see is that if you cover up the right eye, you turn off the magnetic compass
06:30processing in the left part of the brain.
06:32If you cover up this eye, you turn the compass off in this part of the brain.
06:38The robin's magnetic compass seems to be in her eyes.
06:46I can show you what's going on using my own eye.
06:49Now, we use our eyes for vision, but we also have a second light-detecting mechanism.
06:54If I shine this torch into my eye, you can see that my pupil closes down.
07:01It's basically a defense mechanism to protect my eyes.
07:05My eye is responding to particles of light, or photons.
07:11The energy provided by the photons is clearly enough to activate chemical reactions.
07:17After all, that's what controls my eye muscles.
07:22Light must be causing similar chemical reactions in the robin's eyes.
07:28In fact, it's the power supply for a unique form of magnetic compass.
07:35Inside her cells.
07:38In the weird world of subatomic particles.
07:44A place where only quantum physics can explain what's going on.
07:54To see why, imagine the chemical reactions in the robin's eye taking place in mountains and valleys of energy.
08:03To get a reaction to start, you have to push molecules to the top of a mountain.
08:10Thanks to Henrik's experiments, we now know that light does most of the hard work.
08:17But when it reaches the very peak, the molecule becomes incredibly sensitive to the slightest touch.
08:28The key point here is that the robin's chemical compass is now balanced on an energy peak between two valleys.
08:35Going one way produces one set of chemical products, the other a different set.
08:41Now, even a tiny change in the Earth's magnetic field can tip the molecule over the top.
08:47But the way this happens defies common sense.
08:51The final piece of the puzzle depends on one of the truly mind-boggling ideas in physics.
08:57But don't worry if you find it hard to understand.
09:00Even Albert Einstein called it spooky.
09:05The idea is called quantum entanglement.
09:08It involves particles that seem to communicate faster than the speed of light.
09:15In 1935, Einstein published a famous paper arguing that it was impossible.
09:22But Einstein was wrong.
09:25In recent years, extremely delicate experiments have shown that subatomic particles really are entangled.
09:32in the world.
09:33It means they can subtly and instantaneously influence each other across space.
09:40And now, it seems the same thing is going on inside the robin's eye.
09:47When a photon enters the robin's eye, it creates what's called an entangled pair of electrons.
09:55Here's how it works.
09:57Each electron has two possible states.
10:00For simplicity, I'm choosing to call them red and green.
10:03Now, here's the weird thing.
10:06Until I measure it, it's neither one nor the other.
10:09But both at the same time.
10:14Think of the electrons like spinning disks.
10:18They are simultaneously red and green.
10:22But by firing a dart, I can force the first electron to be one or the other.
10:31So far, it's just a game of chance.
10:34I don't know what I'll get until I try it.
10:41So I know my first electron is red.
10:43Suppose I now measure the second electron.
10:46You'd think I'd have a 50-50 chance of getting red or green.
10:50After all, that's what you'd expect in the normal, everyday world.
10:54But you'd be wrong.
10:58In quantum entanglement, the electrons are mysteriously linked.
11:07For example, if I get red on the first,
11:10I always get red on the second.
11:16It's not a game of chance anymore.
11:20It's as if the first electron is telling the second one what to do.
11:27That's why Einstein called it spooky.
11:31The electrons seem to know that they should both have the same color,
11:35no matter how far apart they are.
11:39The really important part is that the two electrons needn't be the same color.
11:46They can be entangled in a different way,
11:49so that if the first electron is red,
11:53the second one is always green.
12:00It seems that this mysterious connection is the ultimate secret of the quantum robin's compass.
12:10Because the direction of the Earth's magnetic field can influence the outcome.
12:16Near the equator, they may be more likely to be red-red.
12:21But near the pole, they may be more likely to be red-green.
12:25And that's the vital factor that finally tips the balance of the robin's chemical compass.
12:33Tiny variations in the Earth's magnetic field change the way electrons in the robin's eye are entangled.
12:39And that's just enough to trigger her compass.
12:44Now, finally, we can see how something as weak as the Earth's magnetic field can tip that balance one way
12:52or the other.
12:58If the message changes, the chemical reaction tips a different way,
13:05changing the robin's compass reading.
13:09Suddenly, it looks like it's a fundamentally quantum mechanical phenomenon in birds.
13:15It would be one of the first, if not the first, in biology.
13:21Biologists better get used to the weirdness of physics.
13:25The robin is navigating by spooky quantum entanglement.
13:33To see subtle quantum effects, even in a controlled, austere environment of a physics lab, is really difficult.
13:40And yet, here's the robin doing it with ease.
13:43These experiments are real and verifiable.
13:46And yet, even though I'm seeing them with my own eyes, I still find it hard to believe.
14:00Bird navigation has brought physics and nature together as the science of quantum biology.
14:08There's a whole new world to explore.
14:12But its pioneers have found that it doesn't just affect birds.
14:17It affects every single one of us.
14:21Because the latest experiments say you're doing quantum physics right now.
14:27And believe it or not, you're doing it with your nose.
14:36Hello, Jim. Hello. Hello, little girl.
14:42Our sense of smell is remarkable, and quite different from our other senses of sight and hearing.
14:48Among the thousands of scents that we can recognise, many of them may well trigger very powerful memories and emotions.
14:54It's as though our sense of smell is wired directly to our inner consciousness.
14:59It's also different in another way.
15:01The other senses of sight and hearing rely on us detecting waves, light and sound.
15:06But our sense of smell involves detecting particles, chemical molecules.
15:13Recently, scientists have begun to realise that when it comes to our sense of smell, something very mysterious is going
15:20on.
15:26For decades, biologists thought they knew exactly how our noses sniffed out different chemicals.
15:35But physicists like Jenny Brooks think there could be a new ingredient in the mix.
15:41And it smells like quantum mechanics.
15:46A lot of people speak of the sense of smell and off-action and the science of olfaction as being
15:51a problem that's been solved and we know all about it.
15:53And we do know a lot about it. We know about the ingredients. We know about the equipment that we
15:58use to smell.
15:59But I would argue that there's a little bit more to understand.
16:05To understand more, I need someone to help me with a smell test.
16:11And Jem is going to sniff him out.
16:19Every human being gives off a cocktail of chemicals.
16:25Jem's nose could detect a single gram of it dissolved over an entire city.
16:35So she has no trouble finding the man I'm looking for.
16:44Meet Colin the gardener. A man who's used to smelling the flowers.
16:51Right then Colin, I'm going to put your sniffing skills to the test.
16:54Cool. I've got a selection of chemicals here and I want you to tell me what they remind you of.
17:01Okay.
17:02I'll start you off easily.
17:05Oh, that's...
17:07Like a minty...
17:09minty vapor rub.
17:10It is, yeah.
17:11Sort of thing like that.
17:13Menthol.
17:14But it's that essence.
17:18Right, here's the next one.
17:20Ah.
17:21You should be able to recognise this one.
17:24That's baking with my daughter.
17:27Icing sugar.
17:29Vanilla?
17:29Vanilla, yeah.
17:34When our noses detect a chemical, they fire a nerve signal to our brains.
17:42But different chemicals create different sensations.
17:50The standard explanation for this is to do with the shape of the molecules.
17:58The conventional theory that goes back to the 1950s says that the scent molecule has a particular shape
18:04that allows it to fit in to the receptor molecules in our nose.
18:13If it has the right shape, it's like a hand in a glove or a key in a lock.
18:18In fact, it's called the lock and key mechanism.
18:20With the wrong shape, it won't fit into the receptor.
18:23But with the right shape, it fits into the receptor, triggering that unique smell sensation.
18:33Different receptors are wired to different parts of our brains.
18:39So, when a menthol molecule locks into its specific receptor, it triggers that minty, fresh sensation.
18:48But the lock and key theory has always had a problem.
18:53And Colin's next test will show you why.
18:56Okay, how about this one?
19:00Quite strong smell.
19:02Oh, that's...
19:04Yeah.
19:05What does it remind you of? What does it conjure up? What memories?
19:08I think Christmas.
19:10Christmas cake.
19:11Yeah. Marzipan.
19:13Yeah, that's it.
19:14Almonds.
19:15Yeah.
19:18Colin identified the smell of marzipan, or almonds.
19:22In fact, it's due to a scent molecule called benzaldehyde.
19:26What I didn't give him to smell was this other chemical, cyanide.
19:31Both benzaldehyde and cyanide have the same smell.
19:34They both smell of almonds.
19:35But these molecules are both very different shapes.
19:38So, the lock and key mechanism, as an explanation for how we smell, can't be the whole story.
19:47So, why would two molecules with different shapes smell the same?
19:54Quantum biology has a head-spinning explanation.
20:00It says our noses aren't smelling chemical molecules.
20:07They're listening to them.
20:12It's not just the shape of a scent molecule that matters.
20:16Let's take a closer look at this model of a cyanide molecule.
20:19The white ball here is a hydrogen atom.
20:22And the grey sticks are the bonds that hold it together with the carbon and nitrogen.
20:27But the reality isn't as simple as that.
20:30I can give you a better sense of what's going on if we look at this larger white ball.
20:35You see, atoms don't just sit still.
20:38The bonds that hold them together are like vibrating strings.
20:41And that gives us a whole new way of thinking about smell.
20:49The bizarre new quantum theory of smell is all about vibrating bonds.
21:02Chemical molecules are playing music for our noses.
21:07Imagine a receptor molecule in my nose is like my guitar.
21:12Before it can make a sound, a scent molecule has to enter my nose.
21:16And when that scent molecule is in place, its chemical bonds provide the strings.
21:23And it's ready to be played.
21:26The receptor molecules contain quantum particles, electrons.
21:32As they leap from one atom to another, they vibrate the bonds of the scent molecule.
21:38Like my fingers plucking a guitar string.
21:44What's remarkable about this theory is that it tells us our sense of smell is about the vibrations of molecules.
21:51Or wave-like behaviour.
21:53And not so much about the shape of a particular scent molecule.
21:56Our sense of smell may be much more like our sense of hearing.
22:05A particular molecule, say that of grass, will vibrate at a particular frequency.
22:17But a different molecule, say that of mint, will vibrate at a different frequency.
22:35This would explain why cyanide smells like almonds.
22:41The two molecules have different shapes.
22:44But their chemical bonds just happen to vibrate at the same frequency.
22:51The quantum vibration in the odorant is almost literally like a particle of sound.
22:58So, yeah, we're saying that the process of smell could be exactly like an acoustic resonance event.
23:04It could be very analogous to hearing and seeing, actually.
23:10But can we really be listening with our noses?
23:15A bizarre theory needs a bizarre experiment to test it.
23:20Here's how it works.
23:23This molecule has a musky aroma, like perfume.
23:28But if the theory is right, then I should be able to change its smell by changing its vibrations.
23:36The musky molecule contains lots of hydrogen atoms like this bonded to carbon atoms.
23:42But what if I were to replace all these atoms with a different form of hydrogen called deuterium?
23:49Now, it won't change the shape of the molecule, but it will change the way it vibrates.
23:55And here's why.
23:56Deuterium is twice as heavy as normal hydrogen, and so it vibrates more slowly.
24:04Now, different vibrations mean different smells.
24:07So if I were to make a new form of this chemical, all packed with deuterium atoms instead of normal
24:13hydrogen,
24:14it should smell different.
24:18Quantum biologists found a unique way to carry out this experiment.
24:26A smell comparison using the most sensitive noses they could find.
24:33Fruit flies.
24:36First, the flies were trained to avoid the modified version of the musky molecule.
24:43To be honest, I haven't got a clue how you go about training a fruit fly.
24:47But apparently you can.
24:51In the laboratory, the flies had to pass through a kind of maze.
24:59They were then given a choice.
25:05Go right for the nice musky smell.
25:07Or left for the nasty, modified version.
25:19They could definitely smell the difference.
25:25They always preferred the original and turned right.
25:37The fruit fly experiment gives hard evidence that quantum smell theory really works.
25:46But ultimately, it works in harmony with the lock and key theory.
25:52First, the scent molecule fits into the receptor.
25:56Then, those molecular vibrations take over.
26:04Incredible as it seems, flies, humans and dogs may be smelling the sound of quantum biology.
26:15Our sense of smell is fascinating and mysterious as it is.
26:19But to think that when I encounter a particular scent and that sets off a whole wave of memories and
26:26emotions in my mind,
26:28that it's underpinned, that it's triggered by quantum mechanics, I think makes it even more remarkable.
26:46The mysterious influence of quantum physics reaches into every corner of the natural world.
26:57In fact, it inhabits the walls of every living cell on Earth.
27:06Because the latest experiments suggest a magical solution to one of the greatest mysteries of nature.
27:16The miracle of metamorphosis.
27:28The transformation of a tadpole into a frog has never been fully explained.
27:35In little more than six weeks, the tadpole breaks down, then reassembles in its adult form.
27:42But the big mystery is how it happens so fast.
27:47When you think about it, there's nothing more extraordinary than a tadpole turning into a frog.
27:53Take its tail, for example.
27:55Over a period of several weeks, it gets reabsorbed into the body.
27:59And the proteins and fibres that make up the flesh get recycled to form the frog's new limbs.
28:06But for this to happen, trillions and trillions of chemical reactions work together,
28:11breaking molecules, forming new ones in a carefully orchestrated dance.
28:16But the fibres that hold flesh together are very, very strong.
28:21They're a bit like these ropes holding my raft together.
28:24In order to dismantle the raft, I'd have to undo these very tight knots.
28:30You can think of it like this.
28:34A tadpole is held together by long ropes of proteins, knotted together by chemical bonds.
28:42The bonds are so strong that they should last for years, much longer than the tadpole's entire lifespan.
28:50So how can it turn into a frog in just a few weeks?
28:55The explanation involves one of the most important molecules of life.
29:01Tiny widgets in all our cells called enzymes.
29:06The enzymes are the actual machinery of the cell.
29:09They're actually the little machines inside cells that do the chemical transformations that are involved in everyday life.
29:17They're absolutely crucial.
29:19And the reason they're so crucial is because what they're able to do is to accelerate chemical reactions by enormous
29:27amounts.
29:28Let me show you just how quickly enzymes get to work.
29:33Inside this bottle is a substance called hydrogen peroxide.
29:37You're probably most familiar with it as the chemical used to bleach hair.
29:41In fact, I obtained this sample from my local hairdressers.
29:46Hydrogen peroxide is also produced in the body and it's the job of the liver to get rid of it.
29:52Now the way it does that is using an enzyme which breaks down hydrogen peroxide into water and oxygen.
29:59Now to show you just how quickly this enzyme works, I'm going to do a quick demonstration.
30:03I've got some liver here which I've chopped up in order to release the enzyme.
30:12Now watch what happens when I add this liver mixture containing the enzyme to the hydrogen peroxide.
30:18Watch how quickly the oxygen is released.
30:37Just a hundred grams of liver fired my rocket nearly 20 feet.
30:45Liver enzymes make the breakdown of hydrogen peroxide incredibly efficient.
30:50It happens a trillion times faster.
30:53That's a million, million times faster than it would otherwise.
30:58In metamorphosis, it's enzymes that dismantle the tadpole's tail.
31:05And that means breaking down an incredibly tough protein called collagen.
31:12Collagen is one of the most important proteins for the biological world.
31:16It's the protein which actually gives that resilience, that elasticity to tendons, to cartilage, and of course to our skin
31:25as well.
31:26And in the tail of the tadpole, it provides the kind of scaffold, right, that supports that structure.
31:33Now, when the tadpole is transformed into the frog, what you need to do is to essentially have an enzyme,
31:40collagenase, which will literally snip the collagen down into small pieces and thereby take that scaffold apart.
31:51But how do enzymes break chemical bonds apart so incredibly fast?
31:58Let me show you why it's a problem only quantum biology can solve.
32:05Think of it this way.
32:07All these different parts of the knot are like subatomic particles, electrons, protons, that hold the different parts of the
32:15molecule together.
32:16Now, to untie the knot, enzymes have to move protons about.
32:21But as you can see, this takes quite a bit of effort and a lot of time if there are
32:27many, many knots to unpick.
32:30Physicists have a fancy way of saying put in effort to get something done.
32:34They say you have to overcome an energy barrier.
32:44OK, here's my energy barrier.
32:49And here's my proton.
32:52To break a bond apart, it needs enough energy to get over the barrier.
32:59The trouble is, when we work out how long this would take, it's much too slow to break down a
33:06tadpole's tail.
33:09But this is where protons turn into ghosts.
33:15I wouldn't blame you for thinking that this is an idea that a clever theoretician has come up with, that
33:21it's just mere speculation, something that we have no proof of.
33:25But we do. It takes place all the time.
33:31In the quantum world, protons don't have to go over barriers.
33:39They can tunnel straight through.
33:45Tunnelling strikes at the very heart of what is most strange about quantum mechanics.
33:50It's like nothing we see in our everyday world.
33:53A quantum particle can tunnel from one place to another, even if it has to pass through an impenetrable barrier.
34:00They're not solid objects like balls in our everyday world.
34:06They have spread out, fuzzy, wave-like behaviour that allows them to leak through an energy barrier.
34:13A particle can disappear on one side of the barrier and instantaneously reappear on the other.
34:21In nuclear physics, this effect is a proven fact.
34:26Without quantum tunnelling, the sun simply wouldn't shine.
34:34But I never thought I'd see it...
34:37..in a tadpole.
34:39It's hard to stress just how weird this process is.
34:43It's as though I would approach a solid brick wall and, like a phantom, disappear from one side and reappear
34:50on the other.
34:55The most important advantage of tunnelling is its speed.
35:01It happens incredibly quickly.
35:04Much faster than if protons go over the barrier.
35:09As a nuclear physicist, quantum tunnelling is my bread and butter.
35:13Subatomic particles like protons do it all the time.
35:17But what has this got to do with biology?
35:25The answer is that without quantum ghosts, the metamorphosis of a tadpole would be impossible.
35:33Remember, chemical bonds are basically knots.
35:39Tunnelling unties them fast.
35:43Have a look at these two knots.
35:45Now, on the face of it, they look identical.
35:48But there's a subtle difference.
35:51This knot has the two short ends of the rope on the same side.
35:56Whereas this one has the two short ends on opposite sides.
36:00Now, you think that wouldn't make a difference.
36:03But it does.
36:05You see, this knot is very hard to break.
36:10Whereas this one is easy.
36:16Quantum tunnelling turns strong knots into weak ones.
36:25So, in a tadpole, the entire collagen scaffold breaks apart easily.
36:31And finally, other enzymes rebuild it in the shape of a frog.
36:40The quantum tunnelling of particles is one of those weird features of the subatomic world
36:45that a physicist like me is very familiar with.
36:48After all, it's responsible for radioactive decay.
36:52And it goes on inside the sun.
36:53It's the reason why the sun and all stars shine.
36:57But to discover that it's going on inside every cell of every living organism on the planet,
37:03because every cell contains enzymes,
37:05now that I find truly amazing.
37:11Quantum biology casts its spell over every living creature.
37:18We've seen that birds, mammals, insects and amphibians
37:22are governed by the strangest laws in science.
37:27But the most dramatic recent breakthrough
37:30concerns the single vital process on which all these forms of life depend.
37:37the conversion of air and sunlight into plants.
37:47This fine specimen is a Larix decidua, or European larch.
37:52It's about 100 feet high.
37:54And right at this moment, passing just this side of the planet Venus,
37:58is a bullet with this tree's name on it.
38:03The bullet is a photon,
38:05nearing the end of its long journey from the sun.
38:12Its ultimate destiny is to kick-start a series of chemical reactions
38:16that underpins all life on Earth.
38:22Photosynthesis.
38:23Every second of every day, 16,000 tons of new plant life are created on Earth.
38:30And for me, it's incredible to think that our existence on this planet depends on what happens in the next
38:37trillionth of a second.
38:49The crucial first stage of photosynthesis is the capture of energy from the sun.
38:56It's nearly 100% efficient, vastly superior to any human technology.
39:04But the way that every plant on Earth achieves this is one of the great puzzles in biology.
39:11When it turned out that quantum weirdness might hold the answer, physicists could hardly believe it.
39:19It was like a revelation.
39:21It was very exciting.
39:23Because I was used to work on problems that were quite abstract.
39:27Experiments.
39:28I'm a theoretician, but I always related my theory to experiments that were very clean in the lab.
39:33Things that you can control.
39:34But now finding out that the things that I knew can help me to understand better how nature works,
39:40really, I don't know, scientifically, it was like a new inspiration to my life as a scientist.
39:47So I really, I would say, I fell in love with this field.
39:54Textbook Biology says the colour of green plants comes from chlorophyll molecules.
40:00Inside the living cells, they absorb light from the sun.
40:07This energy is then transferred incredibly quickly to the food-making factory at the heart of the cell.
40:17The entire event takes just a millionth of a millionth of a second.
40:22When the photon hits the cell, it knocks an electron out of the middle of a chlorophyll molecule.
40:28This creates a tiny packet of energy called an exciton.
40:33The exciton then bounces its way through a forest of chlorophyll molecules until it reaches what's called the reaction centre.
40:41Now that's where its energy is used to drive chemical processes that create the all-important biomolecules of life.
40:49The problem is, the exciton needs to find its way to the reaction centre in the first place.
41:00Textbook Biology can't explain how the exciton does this.
41:07Because, of course, it doesn't know where it's going.
41:13It just bounces around like a pinball in a process called a random walk.
41:22Sooner or later, it'll pass through every single part of the cell.
41:29But this isn't the most efficient way to get around.
41:36Because when the exciton eventually does reach the reaction centre, it's by pure chance.
41:48If the exciton just blindly and randomly hops between the chlorophyll molecules, it would take too long to reach the
41:55reaction centre and would have lost its energy as waste heat.
41:59But it doesn't. Something very different must be going on.
42:05The vital clue comes from recent experiments that stunned the world of science.
42:13Chemists fired lasers at plant cells to simulate the capture of light from the sun.
42:21They confirmed the exciton wasn't bouncing along a haphazard route through the cell.
42:28This original understanding didn't explain what we were observing in the lab.
42:32So the mystery realized, OK, so then what is the explanation for what we are observing in the lab?
42:40The solution is that plants obey the most famous law in all of quantum mechanics.
42:49The uncertainty principle.
42:54It says you can never be certain that the exciton is in one specific place.
43:02Instead, it behaves like a quantum wave, smearing itself out across the cell.
43:13The exciton doesn't simply move from A to B.
43:19In a bizarre but very real sense, it's heading in every direction at the same time.
43:25It's spreading itself out as a wave so that it can explore all possible routes simultaneously.
43:32This strikes at the very heart of what's so strange about quantum mechanics.
43:36The exciton wave isn't just going this way or that way.
43:40It's following all paths at the same time.
43:44That's what gives it such incredible efficiency.
43:59The beauty of it is, if the exciton is trying every route to the reaction center at once,
44:09it's bound to find the fastest possible way to deliver its energy.
44:16It's hard to express how incredible this discovery seems to physicists like me.
44:23Biological cells are full of the random jiggling of billions of atoms and molecules.
44:30But somehow excitons maintain their form as beautiful, perfect quantum waves.
44:39It's transporting the energy that guarantees life on Earth.
44:47It opened a whole new scientific path for me.
44:51And I really enjoy the fact that to be able to understand fully what is happening there or in the
44:56plants,
44:57you have to interact with scientists that have completely different approaches like biologists and chemists.
45:04But we all have to come together to actually understand what is the relevance of this.
45:10So, for me, this is one of the most exciting parts of this field.
45:16Real scientific experiments leave no doubt.
45:21The strange hand of quantum mechanics has shaped the entire living world.
45:29It's not a surprise that you should find quantum tricks being used in biological systems.
45:35The reason is because they're better.
45:42Quantum entanglement is normally seen in the tightly controlled conditions of the physics lab.
45:49But now we know that robins use it to navigate with extraordinary precision.
45:58Quantum vibrations mean our noses listen to chemicals, enhancing our perception of the world around us.
46:10The living cells of all animals depend on protons that vanish and reappear like ghosts.
46:28And photosynthesis reveals the big picture.
46:32A shimmering world where quantum waves capture the sun's energy in an instant.
46:40Sometimes people say, ah, but physicists have been looking for this for decades.
46:44Well, biology has had millions of years.
46:49The ultra-modern science of quantum mechanics is an ancient fact of life.
46:57For the end of my journey, I want to take these ideas to their logical conclusion.
47:01Of course, as a scientist, any speculations I have have to be backed up by careful experiments.
47:07So I want to concoct a thought experiment that helps me to answer the biggest biological question I can think
47:14of.
47:14Does quantum physics play any role in the mechanism of evolution itself?
47:26In 1859, Charles Darwin stunned the world with his theory of evolution by natural selection.
47:34He went on to explain the differences between humans and other apes.
47:41150 years later, there's no doubt that Darwin's theory accounts for every living organism on land and sea.
47:50But I'd like to explore the latest extraordinary interpretation of his ideas.
48:01Could there be a quantum theory of evolution?
48:32Can quantum evolution
48:35explain how the snail got its shell. The snails I'm used to seeing in my back
48:43garden tend to have rather bland, boring shells. So have a look at this beauty. The
48:50patterns on its shell very perfectly match the lines on the stem. It's called
48:58a banded snail, Sapir nemoralis, and the pattern isn't there by accident.
49:09Come and have a look at this.
49:15Less well-adapted snails are more likely to be found here.
49:19This stone is called a thrush's anvil. The song thrush is the snail's main predator.
49:25It catches a snail and smashes its shell against the stone to get to the snail.
49:31Now, what I can see here is that there aren't many banded snail shells, suggesting that its
49:36colours camouflage it very well, hiding it from the bird.
49:44Darwin's theory says that evolution depends on variation within a species.
49:51Snails with camouflage are more likely to survive and reproduce.
49:58Passing on their shells to the next generation, so that the species as a whole becomes better adapted.
50:07So variation, the random differences between snails, is the driving force behind their evolution.
50:15Now, all species evolve and adapt to their environment. But the question I'd like to explore
50:22is whether quantum mechanics plays a role in this.
50:29The only way to find out is by scientific experiments.
50:35So my adventures in quantum biology finally bring me home.
50:41To the University of Surrey.
50:46Here in the laboratories, I'm planning a new analysis of the most celebrated molecule in science.
50:57Deoxyribonucleic acid, or DNA.
51:02Its double helix holds the genetic code for every living organism.
51:09It's a remarkable fact that Darwin himself had no idea what created variation in the species.
51:17The structure of DNA wasn't discovered until 1953 by Francis Crick and James Watson.
51:22The most famous feature of DNA is, of course, its beautiful double helix structure.
51:28But that's just scaffolding. The real genetic secret lies in between.
51:36The four different coloured molecules are called bases.
51:41The colour code on one side, say blue, red, blue, forms a gene that parents pass on to their offspring.
51:51A gene is a bit like a jigsaw puzzle. It fits together like this.
51:57A full strand of the double helix forms a coloured pattern.
52:03But the other strand always pairs up the same way.
52:10A blue base always goes with yellow, and green always goes with red.
52:17Because only those colours have the right shape to fit together.
52:22What Crick and Watson realised was that this provides a mechanism for passing on the genetic code.
52:30When cells reproduce, the two strands of DNA separate, ready to be copied.
52:38But red still goes with green.
52:42And yellow still goes with blue.
52:46So, bit by bit, the cell creates two new strands.
52:51Two perfect copies of the entire genetic code.
52:57So far, there's no genetic variation.
53:00This new copy is identical to the original.
53:03But here's the interesting bit.
53:05During the copying process, something very important can happen.
53:09Sometimes mistakes creep in.
53:17So, we're going to look at these two bases here.
53:22The two prongs that hold them together are subatomic particles.
53:28They're protons.
53:29They're basically the bonds between the strands of DNA.
53:32These protons can jump across to the other side.
53:38If the strands split when the protons have jumped across, they find themselves in the wrong position.
53:47Now, this red base will no longer bind to a green base.
53:53Instead, it has to bond to a yellow base.
53:59Slotting this back in, we see that now this copy is no longer identical to the original,
54:05because I have a yellow base here instead of a green one.
54:09We've brought in a genetic mutation.
54:13Jumping protons would change the snail's DNA.
54:18It could make a new gene for camouflage shells.
54:22The question is, how do protons jump?
54:28It's my belief that quantum spookiness can take over.
54:33Now, for these mutations to take place, the protons have to overcome an energy barrier.
54:39And if you remember what happened with enzymes, well, you can probably guess what's coming next.
54:49Protons can behave as if barriers don't exist.
54:58But does this ghostly effect really happen?
55:06My colleagues in biology are already looking for the very first evidence of quantum mutations.
55:14Biologists didn't really even know about quantum mechanics.
55:17So when you tell them that, you know, particles can be in two places at once,
55:21they kind of say, well, not in my cells they can't.
55:24Our experiment involves samples of bacteria.
55:29The first sample is prepared in normal water, containing hydrogen nuclei, or protons.
55:37When the bacteria reproduce, we simply count the mutations.
55:42But if our theory is correct, then we should be able to change the rate at which mutations occur.
55:50Remember how we tested the quantum theory of smell?
55:53What if I replace the proton with its big brother, the deuteron?
55:58This is the nucleus of an atom of deuterium.
56:01Now, crucially, a deuteron is twice as heavy as a proton.
56:04And this should influence how easy it is for the deuteron to quantum tunnel.
56:10Quantum mechanics is full of surprises.
56:14Protons tunnel easily.
56:19Deuterons don't.
56:26These heavier particles are much more likely to bounce straight back.
56:33So the second sample of bacteria is prepared in heavy water, which is full of deuterons.
56:41Our theory says you should get far fewer mutations.
56:46And so far, the results are extremely encouraging.
56:50The preliminary experiments that we've done gives us a hint that the mutation rate is indeed
56:56depressed in deuterated water. We find that it is lowered. So my hunch is that we're right.
57:02But we'll have to wait a little while before we're sure.
57:09Final proof lies in the future.
57:12Even if we're right, quantum tunneling is a rare form of mutation.
57:18But our results promise hard evidence for a new explanation of one of the most fundamental
57:24processes of life.
57:27Even the merest possibility of a new quantum mechanism for evolution itself is tremendously exciting.
57:34In fact, the story of quantum biology is only just beginning.
57:39What the frog, the robin, the fruit fly and the tree have shown us is that real quantum effects are
57:46going on in nature all the time.
57:48And if there's anything we've learned from the history of quantum mechanics, it's this.
57:53We can never be certain where new discoveries will take us next.
58:06Quantum biology is a revolution in science.
58:10But it's time I got back to the physics department.
58:33Higher than the tallest building.
58:35Higher than the biggest plane.
58:37James May goes to the edge of space.
58:39That's available now on BBC iPlayer.
58:41Next here on BBC4, though, we're uncovering the truth about meteors with Horizon.
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