1 00:00:01,750 --> 00:00:05,510 Welcome to a new and very strange world of nature. 2 00:00:07,910 --> 00:00:12,070 It's been taken over by the weird subatomic particles of 3 00:00:12,070 --> 00:00:13,590 quantum physics. 4 00:00:16,790 --> 00:00:20,750 CHURCH BELL RINGS 5 00:00:23,950 --> 00:00:27,190 As a physicist, I've spent my working life studying 6 00:00:27,190 --> 00:00:29,630 how these particles behave in the laboratory. 7 00:00:32,950 --> 00:00:36,910 But now I'm heading out into the natural world. 8 00:00:36,910 --> 00:00:40,470 I'm on a mission to prove that quantum physics can solve 9 00:00:40,470 --> 00:00:43,870 the greatest mysteries in biology. 10 00:00:43,870 --> 00:00:46,270 This is a real adventure for me. 11 00:00:46,270 --> 00:00:49,750 I'm very much out of my comfort zone trying to apply 12 00:00:49,750 --> 00:00:54,390 the very careful ideas I'm familiar with in a physics laboratory 13 00:00:54,390 --> 00:00:56,750 to the messy world of living things. 14 00:00:59,110 --> 00:01:03,910 I believe that quantum physics could hold many of life's secrets. 15 00:01:05,750 --> 00:01:07,830 That deep in the cells of animals, 16 00:01:07,830 --> 00:01:11,750 particles glide through walls like ghosts. 17 00:01:14,110 --> 00:01:16,270 That when plants capture sunlight... 18 00:01:18,190 --> 00:01:21,230 ..their cells are invaded by shimmering waves 19 00:01:21,230 --> 00:01:23,430 that can be everywhere at the same time. 20 00:01:25,270 --> 00:01:27,510 And that even our human senses 21 00:01:27,510 --> 00:01:30,750 are tuning in to strange quantum vibrations. 22 00:01:32,990 --> 00:01:36,950 In the fantastic world of quantum biology, 23 00:01:36,950 --> 00:01:40,590 life is a game of chance, 24 00:01:40,590 --> 00:01:43,270 played by quantum rules. 25 00:01:47,070 --> 00:01:49,030 This is what I hope to convince you of, 26 00:01:49,030 --> 00:01:52,990 to show you that quantum mechanics is essential in explaining 27 00:01:52,990 --> 00:01:57,190 many of the important processes in life, and potentially, that 28 00:01:57,190 --> 00:02:01,830 quantum mechanics may even underpin the very existence of life itself. 29 00:02:17,910 --> 00:02:21,710 My quest begins with one of the most majestic sights in nature. 30 00:02:23,470 --> 00:02:25,030 Migration. 31 00:02:28,870 --> 00:02:32,390 Every winter, barnacle geese arrive right on cue 32 00:02:32,390 --> 00:02:34,390 at the same Scottish river. 33 00:02:37,190 --> 00:02:41,350 The end of an epic 2,000-mile voyage from Svalbard, 34 00:02:41,350 --> 00:02:43,190 high above the Arctic Circle. 35 00:02:46,510 --> 00:02:48,950 Of course, many birds head south for winter 36 00:02:48,950 --> 00:02:50,550 then back home for summer. 37 00:02:53,710 --> 00:02:58,070 But for decades, exactly how birds navigated with such accuracy 38 00:02:58,070 --> 00:03:00,550 was one of the greatest mysteries in biology. 39 00:03:03,310 --> 00:03:06,630 So the most recent discovery has caused a sensation. 40 00:03:09,310 --> 00:03:10,910 In the past few years, 41 00:03:10,910 --> 00:03:15,470 one species of bird has helped create a scientific revolution. 42 00:03:15,470 --> 00:03:18,790 I was one of many physicists who was shocked to discover that it 43 00:03:18,790 --> 00:03:23,630 navigates using one of the strangest tricks in the whole of science. 44 00:03:23,630 --> 00:03:26,350 It utilises a quirk of quantum mechanics, 45 00:03:26,350 --> 00:03:29,350 one that bamboozled even the greatest of physicists, 46 00:03:29,350 --> 00:03:33,350 from Richard Feynman to Albert Einstein himself. 47 00:03:33,350 --> 00:03:36,510 So you might be surprised to discover the identity of this 48 00:03:36,510 --> 00:03:38,630 mysterious creature. 49 00:03:38,630 --> 00:03:40,950 Say hello to the Quantum Robin. 50 00:03:49,270 --> 00:03:51,190 This is the European robin. 51 00:03:53,510 --> 00:03:56,550 Every year, she migrates from northern Europe 52 00:03:56,550 --> 00:03:58,470 to the tip of Spain and back. 53 00:04:05,150 --> 00:04:07,430 In this laboratory in the woods, 54 00:04:07,430 --> 00:04:10,830 biologist Henrik Mouritsen is trying to solve the mystery 55 00:04:10,830 --> 00:04:12,550 of how she does it. 56 00:04:14,350 --> 00:04:16,710 But he's found himself in MY world, 57 00:04:16,710 --> 00:04:19,550 the strange world of quantum mechanics. 58 00:04:24,630 --> 00:04:28,390 Quantum mechanics describes the very weird behaviour of 59 00:04:28,390 --> 00:04:29,870 subatomic particles. 60 00:04:34,590 --> 00:04:36,990 Down in this realm of the very small, 61 00:04:36,990 --> 00:04:39,950 we have to abandon common sense and intuition. 62 00:04:41,910 --> 00:04:46,950 Instead, this is a world where objects can spread out like waves. 63 00:04:46,950 --> 00:04:49,910 Quantum particles can be in many places at once 64 00:04:49,910 --> 00:04:53,870 and send each other mysterious communications. 65 00:04:53,870 --> 00:04:57,110 I set out to understand how the bird finds its way, 66 00:04:57,110 --> 00:05:00,390 but it just turned out that the data 67 00:05:00,390 --> 00:05:03,750 more and more pointed towards this as 68 00:05:03,750 --> 00:05:08,430 the only explanation that could bring all the different results together. 69 00:05:10,790 --> 00:05:14,830 Henrik's investigating a longstanding theory - 70 00:05:14,830 --> 00:05:18,110 that robins navigate by the Earth's magnetic field. 71 00:05:19,910 --> 00:05:23,670 His laboratory is an ingenious magnetic birdcage. 72 00:05:25,150 --> 00:05:29,190 And these plastic cones lined with scratch-sensitive paper 73 00:05:29,190 --> 00:05:30,910 provide the key measurements. 74 00:05:36,190 --> 00:05:40,750 Henrik's artificial magnetic field is like the Earth's, except that 75 00:05:40,750 --> 00:05:43,230 HE can point it in any direction he likes. 76 00:05:47,750 --> 00:05:51,990 Inside their cones, the robins always respond to the field, 77 00:05:51,990 --> 00:05:54,430 leaving scratches in a single direction. 78 00:05:58,150 --> 00:06:00,550 The big mystery is HOW. 79 00:06:02,230 --> 00:06:05,190 The Earth's magnetic field is incredibly weak, 80 00:06:05,190 --> 00:06:08,550 far too weak for any living creature to detect. 81 00:06:09,670 --> 00:06:12,910 But Henrik has found an intriguing clue 82 00:06:12,910 --> 00:06:15,950 by giving the Quantum Robin a mask. 83 00:06:15,950 --> 00:06:19,190 We have a little leather hood similar to what you put on a falcon, 84 00:06:19,190 --> 00:06:20,990 you know, but just for a robin, 85 00:06:20,990 --> 00:06:23,270 and you have then a hole in front of one eye 86 00:06:23,270 --> 00:06:25,230 or a hole in front of the other eye. 87 00:06:25,230 --> 00:06:29,030 And what we can see is that if you cover up the right eye, you turn off 88 00:06:29,030 --> 00:06:32,550 their magnetic compass processing in the left part of the brain. 89 00:06:32,550 --> 00:06:33,990 If you cover up this eye, 90 00:06:33,990 --> 00:06:37,030 you turn the compass off in this part of the brain. 91 00:06:39,230 --> 00:06:43,190 The robin's magnetic compass seems to be in her eyes. 92 00:06:47,190 --> 00:06:49,870 I can show you what's going on using my own eye. 93 00:06:49,870 --> 00:06:51,950 Now, we use our eyes for vision, 94 00:06:51,950 --> 00:06:55,270 but we also have a second light-detecting mechanism. 95 00:06:55,270 --> 00:06:58,750 If I shine this torch into my eye, 96 00:06:58,750 --> 00:07:01,870 you can see that my pupil closes down. 97 00:07:01,870 --> 00:07:04,870 It's basically a defence mechanism to protect my eyes. 98 00:07:06,590 --> 00:07:10,430 My eye is responding to particles of light - or photons. 99 00:07:12,030 --> 00:07:14,390 The energy provided by the photons 100 00:07:14,390 --> 00:07:17,710 is clearly enough to activate chemical reactions. 101 00:07:17,710 --> 00:07:20,350 After all, that's what controls my eye muscles. 102 00:07:22,430 --> 00:07:25,590 Light must be causing similar chemical reactions 103 00:07:25,590 --> 00:07:27,230 in the robin's eyes. 104 00:07:29,390 --> 00:07:34,270 In fact, it's the power supply for a unique form of magnetic compass... 105 00:07:35,550 --> 00:07:37,550 ..inside her cells... 106 00:07:39,590 --> 00:07:42,550 ..in the weird world of subatomic particles... 107 00:07:45,550 --> 00:07:48,230 ..a place where only quantum physics 108 00:07:48,230 --> 00:07:50,190 can explain what's going on. 109 00:07:55,350 --> 00:07:59,350 To see why, imagine the chemical reactions in the robin's eye 110 00:07:59,350 --> 00:08:02,390 taking place in mountains and valleys of energy. 111 00:08:04,190 --> 00:08:05,790 To get a reaction to start, 112 00:08:05,790 --> 00:08:08,870 you have to push molecules to the top of a mountain. 113 00:08:10,350 --> 00:08:12,230 Thanks to Henrik's experiments, 114 00:08:12,230 --> 00:08:15,590 we now know that light does most of the hard work. 115 00:08:18,270 --> 00:08:20,630 But when it reaches the very peak, 116 00:08:20,630 --> 00:08:24,550 the molecule becomes incredibly sensitive to the slightest touch. 117 00:08:28,590 --> 00:08:32,470 The key point here is that the robin's chemical compass is now 118 00:08:32,470 --> 00:08:36,230 balanced on an energy peak between two valleys. 119 00:08:36,230 --> 00:08:38,950 Going one way produces one set of chemical products - 120 00:08:38,950 --> 00:08:40,630 the other, a different set. 121 00:08:41,950 --> 00:08:46,510 Now, even a tiny change in the Earth's magnetic field can tip the 122 00:08:46,510 --> 00:08:52,150 molecule over the top, but the way this happens defies common sense. 123 00:08:52,150 --> 00:08:53,910 The final piece of the puzzle 124 00:08:53,910 --> 00:08:55,590 depends on one of the truly 125 00:08:55,590 --> 00:08:57,590 mind-boggling ideas in physics. 126 00:08:57,590 --> 00:08:59,270 But don't worry if you find it 127 00:08:59,270 --> 00:09:00,590 hard to understand - 128 00:09:00,590 --> 00:09:02,270 even Albert Einstein 129 00:09:02,270 --> 00:09:03,910 called it "spooky". 130 00:09:05,950 --> 00:09:09,710 The idea is called quantum entanglement. 131 00:09:09,710 --> 00:09:12,630 It involves particles that seem to communicate faster 132 00:09:12,630 --> 00:09:14,430 than the speed of light. 133 00:09:16,110 --> 00:09:19,910 In 1935, Einstein published a famous paper 134 00:09:19,910 --> 00:09:21,910 arguing that it was impossible. 135 00:09:22,990 --> 00:09:25,150 But Einstein was wrong. 136 00:09:26,270 --> 00:09:30,190 In recent years, extremely delicate experiments have shown that 137 00:09:30,190 --> 00:09:33,630 subatomic particles really are entangled. 138 00:09:33,630 --> 00:09:35,390 It means they can subtly 139 00:09:35,390 --> 00:09:38,910 and instantaneously influence each other across space. 140 00:09:40,710 --> 00:09:45,150 And now it seems the same thing is going on inside the robin's eye. 141 00:09:48,030 --> 00:09:50,670 When a photon enters the robin's eye, 142 00:09:50,670 --> 00:09:54,590 it creates what's called an entangled pair of electrons. 143 00:09:56,310 --> 00:10:00,670 Here's how it works. Each electron has two possible states. 144 00:10:00,670 --> 00:10:04,790 For simplicity, I'm choosing to call them Red and Green. 145 00:10:04,790 --> 00:10:06,590 Now, here's the weird thing. 146 00:10:06,590 --> 00:10:09,830 Until I measure it, it's neither one nor the other, 147 00:10:09,830 --> 00:10:11,950 but both at the same time. 148 00:10:14,910 --> 00:10:17,670 Think of the electrons like spinning discs. 149 00:10:18,950 --> 00:10:22,270 They're simultaneously red AND green. 150 00:10:22,270 --> 00:10:24,150 But by firing a dart... 151 00:10:26,030 --> 00:10:28,990 ..I can force the first electron to be one or the other. 152 00:10:31,470 --> 00:10:33,710 So far, it's just a game of chance. 153 00:10:34,830 --> 00:10:37,590 I don't know what I'll get until I try it. 154 00:10:41,590 --> 00:10:44,350 So I know my first electron is red. 155 00:10:44,350 --> 00:10:47,110 Suppose I now measure the second electron. 156 00:10:47,110 --> 00:10:50,950 You'd think I'd have a 50/50 chance of getting red or green. 157 00:10:50,950 --> 00:10:54,590 After all, that's what you'd expect in the normal, everyday world. 158 00:10:54,590 --> 00:10:55,630 But you'd be wrong. 159 00:10:59,110 --> 00:11:03,150 In quantum entanglement, the electrons are mysteriously linked. 160 00:11:07,590 --> 00:11:10,270 For example, if I get red on the first... 161 00:11:11,350 --> 00:11:13,870 ..I ALWAYS get red on the second. 162 00:11:16,710 --> 00:11:18,790 It's not a game of chance any more. 163 00:11:21,070 --> 00:11:24,790 It's as if the first electron is telling the second one what to do. 164 00:11:28,550 --> 00:11:30,590 That's why Einstein called it spooky. 165 00:11:32,030 --> 00:11:36,070 The electrons seem to know that they should both have the same colour, 166 00:11:36,070 --> 00:11:37,950 no matter how far apart they are. 167 00:11:39,750 --> 00:11:42,390 The really important part is that 168 00:11:42,390 --> 00:11:45,830 the two electrons needn't be the same colour. 169 00:11:47,470 --> 00:11:49,870 They can be entangled in a different way, 170 00:11:49,870 --> 00:11:51,990 so that if the first electron is red... 171 00:11:53,990 --> 00:11:56,150 ..the second one is always green. 172 00:12:01,790 --> 00:12:05,350 It seems that this mysterious connection is the ultimate secret 173 00:12:05,350 --> 00:12:07,870 of the Quantum Robin's compass... 174 00:12:11,150 --> 00:12:14,310 ..because the direction of the Earth's magnetic field 175 00:12:14,310 --> 00:12:16,030 can influence the outcome. 176 00:12:17,350 --> 00:12:21,790 Near the equator, they may be more likely to be red-red. 177 00:12:21,790 --> 00:12:26,430 But near the Pole, they may be more likely to be red-green. 178 00:12:26,430 --> 00:12:29,710 And that's the vital factor that finally tips the balance of 179 00:12:29,710 --> 00:12:32,150 the robin's chemical compass. 180 00:12:33,630 --> 00:12:37,790 Tiny variations in the Earth's magnetic field change the way 181 00:12:37,790 --> 00:12:40,870 electrons in the robin's eye are entangled, 182 00:12:40,870 --> 00:12:44,070 and that's just enough to trigger her compass. 183 00:12:45,390 --> 00:12:48,830 Now, finally, we can see how something as weak as the Earth's 184 00:12:48,830 --> 00:12:53,030 magnetic field can tip that balance one way or the other. 185 00:12:59,150 --> 00:13:01,030 If the message changes, 186 00:13:01,030 --> 00:13:03,550 the chemical reaction tips a different way... 187 00:13:05,670 --> 00:13:07,990 ..changing the robin's compass reading. 188 00:13:09,950 --> 00:13:14,070 Suddenly it looks like it's a fundamentally quantum mechanical 189 00:13:14,070 --> 00:13:16,270 phenomenon in birds. 190 00:13:16,270 --> 00:13:20,030 It would be one of the first, if not THE first, in biology. 191 00:13:21,830 --> 00:13:24,710 Biologists better get used to the weirdness of physics. 192 00:13:26,390 --> 00:13:30,150 The robin is navigating by "spooky" quantum entanglement. 193 00:13:33,870 --> 00:13:35,670 To see subtle quantum effects, 194 00:13:35,670 --> 00:13:39,150 even in a controlled, austere environment of a physics lab, 195 00:13:39,150 --> 00:13:40,470 is really difficult. 196 00:13:40,470 --> 00:13:42,870 And yet here's the robin doing it with ease. 197 00:13:44,310 --> 00:13:48,350 These experiments are real and verifiable, and yet even though 198 00:13:48,350 --> 00:13:52,110 I'm seeing them with my own eyes, I still find it hard to believe. 199 00:14:00,750 --> 00:14:02,950 Bird navigation has brought physics 200 00:14:02,950 --> 00:14:06,870 and nature together as the science of quantum biology. 201 00:14:09,230 --> 00:14:11,470 There's a whole new world to explore. 202 00:14:13,110 --> 00:14:16,550 But its pioneers have found that it doesn't just affect birds. 203 00:14:18,110 --> 00:14:20,390 It affects every single one of us. 204 00:14:22,030 --> 00:14:24,310 Because the latest experiments say 205 00:14:24,310 --> 00:14:26,710 you're doing quantum physics right now. 206 00:14:28,150 --> 00:14:31,070 And believe it or not, you're doing it with your nose. 207 00:14:37,110 --> 00:14:38,630 Hello, Jem! 208 00:14:38,630 --> 00:14:39,990 Hello. 209 00:14:39,990 --> 00:14:42,710 Hello, little girl! Hello... 210 00:14:42,710 --> 00:14:45,070 Our sense of smell is remarkable, 211 00:14:45,070 --> 00:14:48,470 and quite different from our other senses of sight and hearing. 212 00:14:48,470 --> 00:14:51,390 Among the thousands of scents that we can recognise, 213 00:14:51,390 --> 00:14:55,310 many of them may well trigger very powerful memories and emotions. 214 00:14:55,310 --> 00:14:57,190 It's as though our sense of smell is 215 00:14:57,190 --> 00:14:59,590 wired directly to our inner consciousness. 216 00:14:59,590 --> 00:15:01,630 It's also different in another way. 217 00:15:01,630 --> 00:15:05,590 The other senses of sight and hearing rely on us detecting waves - 218 00:15:05,590 --> 00:15:07,150 light and sound. 219 00:15:07,150 --> 00:15:10,590 But our sense of smell involves detecting particles - 220 00:15:10,590 --> 00:15:11,750 chemical molecules. 221 00:15:13,870 --> 00:15:17,310 Recently, scientists have begun to realise that when it comes to 222 00:15:17,310 --> 00:15:21,550 our sense of smell, something very mysterious is going on. 223 00:15:21,550 --> 00:15:23,070 GUNSHOT 224 00:15:27,670 --> 00:15:32,030 For decades, biologists thought they knew exactly how our noses 225 00:15:32,030 --> 00:15:34,070 sniffed out different chemicals. 226 00:15:36,670 --> 00:15:39,870 But physicists like Jenny Brookes think there could be a new 227 00:15:39,870 --> 00:15:41,230 ingredient in the mix. 228 00:15:42,550 --> 00:15:46,350 And it smells like quantum mechanics. 229 00:15:46,350 --> 00:15:49,110 A lot of people speak of the sense of smell and olfaction, 230 00:15:49,110 --> 00:15:52,630 and the science of olfaction as being a problem that's been solved 231 00:15:52,630 --> 00:15:55,310 and we know all about it - and we do know a lot about it. 232 00:15:55,310 --> 00:15:57,110 We know about the ingredients, 233 00:15:57,110 --> 00:15:59,790 we know about the equipment that we use to smell. 234 00:15:59,790 --> 00:16:03,230 But I would argue that there's a little bit more to understand. 235 00:16:05,830 --> 00:16:09,590 To understand more, I need someone to help me with a smell test. 236 00:16:12,590 --> 00:16:14,350 And Jem is going to sniff him out. 237 00:16:19,830 --> 00:16:22,710 Every human being gives off a cocktail of chemicals. 238 00:16:25,550 --> 00:16:28,470 Jem's nose could detect a single gram of it 239 00:16:28,470 --> 00:16:31,190 dissolved over an entire city. 240 00:16:35,310 --> 00:16:37,950 So she has no trouble finding the man I'm looking for. 241 00:16:44,830 --> 00:16:49,030 Meet Colin the gardener, a man who's used to smelling the flowers. 242 00:16:51,350 --> 00:16:54,950 Right, then, Colin, I'm going to put your sniffing skills to the test. 243 00:16:54,950 --> 00:16:58,630 Cool. I've got a selection of chemicals here, 244 00:16:58,630 --> 00:17:01,070 and I want you to tell me what they remind you of. 245 00:17:01,070 --> 00:17:02,070 OK. 246 00:17:03,110 --> 00:17:04,630 I'll start you off easily. 247 00:17:04,630 --> 00:17:05,790 COLIN SNIFFS 248 00:17:05,790 --> 00:17:07,710 Oh, that's... 249 00:17:07,710 --> 00:17:11,070 ..like a minty, minty vapour rub... It is, yeah. ..sort of thing. 250 00:17:11,070 --> 00:17:13,510 Yeah, this is... Something what you'd rub... 251 00:17:13,510 --> 00:17:16,710 This is men...menthol. Menthol. Yeah. But it's that essence. 252 00:17:18,470 --> 00:17:20,030 Right, here's the next one. 253 00:17:21,550 --> 00:17:24,030 Ah. You should be able to recognise this one. 254 00:17:25,030 --> 00:17:27,110 That's baking with my daughter. 255 00:17:27,110 --> 00:17:29,510 Mm-hm. Erm, icing sugar sort of thing... 256 00:17:29,510 --> 00:17:31,190 Vanilla. Vanilla, yeah. 257 00:17:35,310 --> 00:17:37,670 When our noses detect a chemical, 258 00:17:37,670 --> 00:17:40,150 they fire a nerve signal to our brains. 259 00:17:43,390 --> 00:17:46,550 But different chemicals create different sensations. 260 00:17:50,590 --> 00:17:53,190 The standard explanation for this is to do with 261 00:17:53,190 --> 00:17:54,910 the shape of the molecules. 262 00:17:58,590 --> 00:18:01,630 The conventional theory that goes back to the 1950s 263 00:18:01,630 --> 00:18:05,870 says that the scent molecule has a particular shape that allows it 264 00:18:05,870 --> 00:18:09,030 to fit in to the receptor molecules in our nose. 265 00:18:13,710 --> 00:18:16,670 If it has the right shape, it's like a hand in a glove, 266 00:18:16,670 --> 00:18:20,950 or a key in a lock. In fact, it's called the lock and key mechanism. 267 00:18:20,950 --> 00:18:24,390 With the wrong shape, it won't fit into the receptor. 268 00:18:24,390 --> 00:18:27,310 But with the right shape, it fits into the receptor, 269 00:18:27,310 --> 00:18:30,230 triggering that unique smell sensation. 270 00:18:33,510 --> 00:18:37,470 Different receptors are wired to different parts of our brains. 271 00:18:39,630 --> 00:18:43,590 So, when a menthol molecule locks into its specific receptor, 272 00:18:43,590 --> 00:18:46,070 it triggers that minty fresh sensation. 273 00:18:49,510 --> 00:18:52,390 But the lock and key theory has always had a problem... 274 00:18:53,750 --> 00:18:56,710 ..and Colin's next test will show you why. 275 00:18:56,710 --> 00:18:58,950 OK, how about... 276 00:18:58,950 --> 00:19:00,550 this one? 277 00:19:00,550 --> 00:19:02,310 Quite a strong smell. 278 00:19:02,310 --> 00:19:04,470 Oh, that's... 279 00:19:04,470 --> 00:19:07,390 Yeah. What does it remind you of? What does it conjure up? 280 00:19:07,390 --> 00:19:09,030 What memories? 281 00:19:09,030 --> 00:19:10,670 I think Christmas. 282 00:19:10,670 --> 00:19:13,870 Christmas cake. Yeah. Marzipan. 283 00:19:13,870 --> 00:19:16,150 Marz...marz...yeah, that's it, yeah. 284 00:19:16,150 --> 00:19:18,350 Almonds. Very, yeah. 285 00:19:18,350 --> 00:19:22,630 Colin identified the smell of marzipan or almonds. 286 00:19:22,630 --> 00:19:27,150 In fact, it's due to a scent molecule called benzaldehyde. 287 00:19:27,150 --> 00:19:31,950 What I didn't give him to smell was this other chemical - cyanide. 288 00:19:31,950 --> 00:19:34,630 Both benzaldehyde and cyanide have the same smell, 289 00:19:34,630 --> 00:19:36,270 they both smell of almonds, 290 00:19:36,270 --> 00:19:39,310 but these molecules are both very different shapes, 291 00:19:39,310 --> 00:19:41,390 so the lock and key mechanism, 292 00:19:41,390 --> 00:19:44,870 as an explanation for how we smell, can't be the whole story. 293 00:19:48,190 --> 00:19:52,510 So why would two molecules with different shapes smell the same? 294 00:19:54,550 --> 00:19:57,590 Quantum biology has a head-spinning explanation. 295 00:20:01,270 --> 00:20:04,510 It says our noses aren't smelling chemical molecules... 296 00:20:08,030 --> 00:20:09,670 ..they're LISTENING to them. 297 00:20:13,150 --> 00:20:16,790 It's not just the shape of a scent molecule that matters. 298 00:20:16,790 --> 00:20:20,310 Let's take a closer look at this model of a cyanide molecule. 299 00:20:20,310 --> 00:20:22,670 The white ball here is a hydrogen atom, 300 00:20:22,670 --> 00:20:26,230 and the grey sticks are the bonds that hold it together 301 00:20:26,230 --> 00:20:28,230 with the carbon and nitrogen. 302 00:20:28,230 --> 00:20:30,310 But the reality isn't as simple as that. 303 00:20:30,310 --> 00:20:32,590 I can give you a better sense of what's going on 304 00:20:32,590 --> 00:20:35,390 if we look at this larger white ball. 305 00:20:35,390 --> 00:20:38,430 You see, atoms don't just sit still. 306 00:20:38,430 --> 00:20:42,870 The bonds that hold them together are like vibrating strings, 307 00:20:42,870 --> 00:20:46,510 and that gives us a whole new way of thinking about smell. 308 00:20:49,790 --> 00:20:55,190 The bizarre new quantum theory of smell is all about vibrating bonds. 309 00:20:56,950 --> 00:20:58,910 HE PLAYS HARMONICS ON GUITAR 310 00:21:03,030 --> 00:21:06,670 Chemical molecules are playing music for our noses. 311 00:21:08,430 --> 00:21:13,070 Imagine a receptor molecule in my nose is like my guitar. 312 00:21:13,070 --> 00:21:17,230 Before it can make a sound, a scent molecule has to enter my nose, 313 00:21:17,230 --> 00:21:21,190 and when that scent molecule is in place, its chemical bonds 314 00:21:21,190 --> 00:21:25,390 provide the strings, and it's ready to be played. 315 00:21:27,150 --> 00:21:30,310 The receptor molecules contain quantum particles - 316 00:21:30,310 --> 00:21:31,550 electrons. 317 00:21:32,990 --> 00:21:36,710 As they leap from one atom to another, they vibrate the bonds of 318 00:21:36,710 --> 00:21:38,870 the scent molecule, 319 00:21:38,870 --> 00:21:41,670 like my fingers plucking a guitar string. 320 00:21:41,670 --> 00:21:43,430 GUITAR NOTE CHIMES 321 00:21:44,710 --> 00:21:47,630 What's remarkable about this theory is that it tells us 322 00:21:47,630 --> 00:21:51,670 our sense of smell is about the vibrations of molecules, 323 00:21:51,670 --> 00:21:53,230 or wave-like behaviour, 324 00:21:53,230 --> 00:21:57,630 and not so much about the shape of a particular scent molecule. 325 00:21:57,630 --> 00:22:01,350 Our sense of smell may be much more like our sense of hearing. 326 00:22:02,390 --> 00:22:04,390 HE PLUCKS HIGH NOTE 327 00:22:05,710 --> 00:22:08,550 A particular molecule, say that of grass, 328 00:22:08,550 --> 00:22:11,470 will vibrate at a particular frequency. 329 00:22:11,470 --> 00:22:13,470 HE PLUCKS LOW NOTE 330 00:22:17,670 --> 00:22:20,550 But a different molecule, say, that of mint, 331 00:22:20,550 --> 00:22:23,390 will vibrate at a different frequency. 332 00:22:23,390 --> 00:22:25,390 HE PLUCKS MID-RANGE NOTE 333 00:22:29,990 --> 00:22:31,710 PLUCKED NOTE REVERBERATES 334 00:22:33,990 --> 00:22:35,430 HIGHER NOTE REVERBERATES 335 00:22:36,670 --> 00:22:40,310 This would explain why cyanide smells like almonds. 336 00:22:42,030 --> 00:22:45,070 The two molecules have different shapes, 337 00:22:45,070 --> 00:22:48,830 but their chemical bonds just happen to vibrate 338 00:22:48,830 --> 00:22:50,430 at the same frequency. 339 00:22:52,430 --> 00:22:55,590 The constant vibration in the odorant is almost 340 00:22:55,590 --> 00:22:58,030 literally like a particle of sound. 341 00:22:58,030 --> 00:23:01,190 So, yeah, we're saying that the process of smell could be 342 00:23:01,190 --> 00:23:04,510 exactly like an acoustic resonance event, 343 00:23:04,510 --> 00:23:09,590 it could be very analogous to, erm, hearing and seeing, actually. 344 00:23:10,990 --> 00:23:13,830 But can we really be listening with our noses? 345 00:23:15,990 --> 00:23:19,270 A bizarre theory needs a bizarre experiment to test it. 346 00:23:21,270 --> 00:23:22,470 Here's how it works. 347 00:23:24,470 --> 00:23:27,830 This molecule has a musky aroma, like perfume. 348 00:23:29,590 --> 00:23:31,310 But if the theory is right, 349 00:23:31,310 --> 00:23:36,670 then I should be able to change its smell by changing its vibrations. 350 00:23:36,670 --> 00:23:39,030 The musky molecule contains 351 00:23:39,030 --> 00:23:41,870 lots of hydrogen atoms like this 352 00:23:41,870 --> 00:23:45,870 bonded to carbon atoms, but what if I were to replace all these atoms 353 00:23:45,870 --> 00:23:50,510 with a different form of hydrogen called deuterium? 354 00:23:50,510 --> 00:23:53,110 Now, it won't change the shape of the molecule, 355 00:23:53,110 --> 00:23:56,070 but it will change the way it vibrates. 356 00:23:56,070 --> 00:24:00,630 And here's why - deuterium is twice as heavy as normal hydrogen, 357 00:24:00,630 --> 00:24:04,510 and so it vibrates more slowly. 358 00:24:04,510 --> 00:24:07,790 Now, different vibrations mean different smells, 359 00:24:07,790 --> 00:24:10,750 so if I were to make a new form of this chemical, 360 00:24:10,750 --> 00:24:14,350 all packed with deuterium atoms instead of normal hydrogen, 361 00:24:14,350 --> 00:24:16,310 it should smell different. 362 00:24:19,190 --> 00:24:23,310 Quantum biologists found a unique way to carry out this experiment. 363 00:24:26,710 --> 00:24:28,390 A smell comparison, 364 00:24:28,390 --> 00:24:32,150 using the most sensitive noses they could find. 365 00:24:33,230 --> 00:24:34,510 INSECTS BUZZ 366 00:24:34,510 --> 00:24:35,910 Fruit flies. 367 00:24:37,110 --> 00:24:40,390 First, the flies were trained to avoid the modified version 368 00:24:40,390 --> 00:24:42,150 of the musky molecule. 369 00:24:43,510 --> 00:24:44,590 To be honest, 370 00:24:44,590 --> 00:24:48,390 I haven't got a clue how you go about training a fruit fly, 371 00:24:48,390 --> 00:24:50,070 but apparently you can. 372 00:24:52,190 --> 00:24:56,790 In the laboratory, the flies had to pass through a kind of maze. 373 00:24:59,910 --> 00:25:01,790 They were then given a choice. 374 00:25:05,510 --> 00:25:08,590 Go right for the nice, musky smell, 375 00:25:08,590 --> 00:25:12,790 or left, for the nasty, modified version. 376 00:25:12,790 --> 00:25:16,470 HE STRUMS GENTLY 377 00:25:19,990 --> 00:25:22,430 They could definitely smell the difference. 378 00:25:25,950 --> 00:25:29,510 They always preferred the original and turned right. 379 00:25:37,910 --> 00:25:41,070 The fruit fly experiment gives hard evidence 380 00:25:41,070 --> 00:25:43,550 that quantum smell theory really works. 381 00:25:46,510 --> 00:25:50,710 But ultimately, it works in harmony with the lock and key theory. 382 00:25:52,470 --> 00:25:56,310 First, the scent molecule fits into the receptor... 383 00:25:57,550 --> 00:26:00,630 ..then those molecular vibrations take over. 384 00:26:04,030 --> 00:26:07,590 Incredible as it seems, flies, humans 385 00:26:07,590 --> 00:26:11,830 and dogs may be smelling the sound of quantum biology. 386 00:26:15,910 --> 00:26:19,550 Our sense of smell is fascinating and mysterious as it is, 387 00:26:19,550 --> 00:26:23,390 but to think that when I encounter a particular scent 388 00:26:23,390 --> 00:26:26,830 and that sets off a whole wave of memories 389 00:26:26,830 --> 00:26:30,670 and emotions in my mind, that it's underpinned, 390 00:26:30,670 --> 00:26:33,110 that it's triggered by quantum mechanics, 391 00:26:33,110 --> 00:26:35,830 I think makes it even more remarkable. 392 00:26:35,830 --> 00:26:38,950 CROWS CAW 393 00:26:47,710 --> 00:26:51,630 The mysterious influence of quantum physics 394 00:26:51,630 --> 00:26:53,590 reaches into every corner of the natural world. 395 00:26:58,230 --> 00:27:00,750 In fact, it inhabits the walls 396 00:27:00,750 --> 00:27:03,270 of every living cell on Earth. 397 00:27:06,950 --> 00:27:10,550 Because the latest experiments suggest a magical solution 398 00:27:10,550 --> 00:27:13,110 to one of the greatest mysteries of nature. 399 00:27:17,350 --> 00:27:20,230 The miracle of metamorphosis. 400 00:27:29,470 --> 00:27:32,950 The transformation of a tadpole into a frog 401 00:27:32,950 --> 00:27:35,830 has never been fully explained. 402 00:27:35,830 --> 00:27:39,710 In little more than six weeks, the tadpole breaks down, 403 00:27:39,710 --> 00:27:43,190 then reassembles in its adult form. 404 00:27:43,190 --> 00:27:47,910 But the big mystery is how it happens so fast. 405 00:27:47,910 --> 00:27:50,670 When you think about it, there's nothing more extraordinary 406 00:27:50,670 --> 00:27:53,310 than a tadpole turning into a frog. 407 00:27:53,310 --> 00:27:55,510 Take its tail, for example. 408 00:27:55,510 --> 00:27:59,430 Over a period of several weeks, it gets reabsorbed into the body 409 00:27:59,430 --> 00:28:03,230 and the proteins and fibres that make up the flesh 410 00:28:03,230 --> 00:28:06,870 get recycled to form the frog's new limbs. 411 00:28:06,870 --> 00:28:08,750 But for this to happen, 412 00:28:08,750 --> 00:28:11,950 trillions and trillions of chemical reactions work together, 413 00:28:11,950 --> 00:28:17,110 breaking molecules, forming new ones in a carefully orchestrated dance. 414 00:28:17,110 --> 00:28:21,190 But the fibres that hold flesh together are very, very strong. 415 00:28:21,190 --> 00:28:24,910 They're a bit like these ropes holding my raft together. 416 00:28:24,910 --> 00:28:29,990 In order to dismantle the raft, I'd have to undo these very tight knots. 417 00:28:31,510 --> 00:28:33,430 You could think of it like this... 418 00:28:34,790 --> 00:28:38,710 ..a tadpole is held together by long robes of proteins 419 00:28:38,710 --> 00:28:41,190 knotted together by chemical bonds. 420 00:28:43,110 --> 00:28:46,990 The bonds are so strong that they should last for years, 421 00:28:46,990 --> 00:28:50,830 much longer than the tadpole's entire life span. 422 00:28:50,830 --> 00:28:56,310 So how can it turn into a frog in just a few weeks? 423 00:28:56,310 --> 00:29:00,230 The explanation involves one of the most important molecules of life. 424 00:29:01,790 --> 00:29:06,390 Tiny widgets in all our cells called enzymes. 425 00:29:06,390 --> 00:29:09,830 The enzymes are the actual machinery of the cell. 426 00:29:09,830 --> 00:29:13,990 They are actually the little machines inside cells 427 00:29:13,990 --> 00:29:17,950 that do the chemical transformations that are involved in everyday life. 428 00:29:17,950 --> 00:29:19,950 They are absolutely crucial. 429 00:29:19,950 --> 00:29:23,510 And the reason they're so crucial is because what they are able to do 430 00:29:23,510 --> 00:29:28,950 is to accelerate chemical reactions by enormous amounts. 431 00:29:28,950 --> 00:29:32,590 Let me show you just how quickly enzymes get to work. 432 00:29:34,310 --> 00:29:38,230 Inside this bottle is a substance called hydrogen peroxide. 433 00:29:38,230 --> 00:29:40,310 You're probably most familiar with it 434 00:29:40,310 --> 00:29:41,910 as the chemical used to bleach hair. 435 00:29:41,910 --> 00:29:44,230 In fact, I obtained this sample 436 00:29:44,230 --> 00:29:46,350 from my local hairdressers. 437 00:29:46,350 --> 00:29:49,110 Hydrogen peroxide is also produced in the body, 438 00:29:49,110 --> 00:29:52,190 and it's the job of the liver to get rid of it. 439 00:29:52,190 --> 00:29:54,430 The way it does that is using an enzyme 440 00:29:54,430 --> 00:29:59,470 which breaks down hydrogen peroxide into water and oxygen. 441 00:29:59,470 --> 00:30:02,670 Now, to show you just how quickly this enzyme works, 442 00:30:02,670 --> 00:30:04,710 I'm going to do a quick demonstration. 443 00:30:04,710 --> 00:30:07,270 I've got some liver here which I've chopped up 444 00:30:07,270 --> 00:30:09,630 in order to release the enzyme. 445 00:30:12,030 --> 00:30:15,550 Now, watch what happens when I add this liver mixture 446 00:30:15,550 --> 00:30:19,030 containing the enzyme to the hydrogen peroxide. 447 00:30:19,030 --> 00:30:21,590 Watch how quickly the oxygen is released. 448 00:30:33,750 --> 00:30:35,990 CROWS CAW 449 00:30:37,470 --> 00:30:42,510 Just 100 grams of liver fired my rocket nearly 20 feet. 450 00:30:46,230 --> 00:30:49,350 Liver enzymes make the breakdown of hydrogen peroxide 451 00:30:49,350 --> 00:30:51,030 incredibly efficient. 452 00:30:51,030 --> 00:30:53,670 It happens a trillion times faster. 453 00:30:53,670 --> 00:30:57,430 That's a million, million times faster than it would otherwise. 454 00:30:59,590 --> 00:31:01,990 In metamorphosis, it's enzymes 455 00:31:01,990 --> 00:31:04,590 that dismantle the tadpole's tail. 456 00:31:05,950 --> 00:31:07,750 And that means breaking down 457 00:31:07,750 --> 00:31:09,630 an incredibly tough protein 458 00:31:09,630 --> 00:31:10,950 called collagen. 459 00:31:12,670 --> 00:31:17,270 Collagen is one of the most important proteins in the biological world. 460 00:31:17,270 --> 00:31:21,470 It's the protein which actually gives that resilience, that elasticity 461 00:31:21,470 --> 00:31:23,990 to tendons, to cartilage, 462 00:31:23,990 --> 00:31:27,230 and of course to our skin, as well. 463 00:31:27,230 --> 00:31:31,150 And in the tail of the tadpole, it provides the kind of scaffold 464 00:31:31,150 --> 00:31:34,350 that supports that structure. 465 00:31:34,350 --> 00:31:37,390 Now, when the tadpole is transformed into the frog, 466 00:31:37,390 --> 00:31:40,710 what you need to do is to essentially have an enzyme, 467 00:31:40,710 --> 00:31:44,150 collagenase, which will literally snip the collagen down 468 00:31:44,150 --> 00:31:47,950 into small pieces and thereby take that scaffold apart. 469 00:31:52,070 --> 00:31:56,870 But how do enzymes break chemical bonds apart so incredibly fast? 470 00:31:59,110 --> 00:32:04,070 Let me show you why it's a problem only quantum biology can solve. 471 00:32:06,230 --> 00:32:10,190 Think of it this way, all these different parts of the knot 472 00:32:10,190 --> 00:32:13,790 are like subatomic particles - electrons, protons - 473 00:32:13,790 --> 00:32:16,670 that hold the different parts of the molecule together. 474 00:32:16,670 --> 00:32:22,270 Now, to untie the knot, enzymes have to move protons about. 475 00:32:22,270 --> 00:32:25,950 But as you can see, this takes quite a bit of effort 476 00:32:25,950 --> 00:32:29,590 and a lot of time if there are many knots to unpick. 477 00:32:30,830 --> 00:32:33,030 Physicists have a fancy way of saying 478 00:32:33,030 --> 00:32:35,390 "put in effort to get something done". 479 00:32:35,390 --> 00:32:38,710 They say you have to overcome an energy barrier. 480 00:32:45,430 --> 00:32:47,670 OK, here's my energy barrier. 481 00:32:49,910 --> 00:32:51,790 And here's my proton. 482 00:32:53,590 --> 00:32:55,190 To break a bond apart, 483 00:32:55,190 --> 00:32:58,310 it needs enough energy to get over the barrier. 484 00:33:00,110 --> 00:33:03,630 The trouble is, when we work out how long this would take, 485 00:33:03,630 --> 00:33:06,510 it's much too slow to break down a tadpole's tale. 486 00:33:09,470 --> 00:33:13,030 But this is where protons turn into ghosts. 487 00:33:16,310 --> 00:33:19,150 I wouldn't blame you for thinking that this is an idea 488 00:33:19,150 --> 00:33:21,750 that a clever theoretician has come up with, 489 00:33:21,750 --> 00:33:26,470 that it's just mere speculation - something that we have no proof of. 490 00:33:26,470 --> 00:33:29,550 But we do. It takes place all the time. 491 00:33:31,710 --> 00:33:33,510 In the quantum world, 492 00:33:33,510 --> 00:33:36,630 protons don't have to go over barriers. 493 00:33:39,830 --> 00:33:41,910 They can tunnel... 494 00:33:41,910 --> 00:33:43,470 straight through. 495 00:33:45,470 --> 00:33:48,430 Tunnelling strikes at the very heart of what is most strange 496 00:33:48,430 --> 00:33:50,390 about quantum mechanics. 497 00:33:50,390 --> 00:33:53,430 It's like nothing we see in our everyday world. 498 00:33:53,430 --> 00:33:56,990 A quantum particle can tunnel from one place to another 499 00:33:56,990 --> 00:34:00,670 even if it has to pass through an impenetrable barrier. 500 00:34:00,670 --> 00:34:06,270 They are not solid objects like balls in our everyday world. 501 00:34:06,270 --> 00:34:09,070 They have spread out, fuzzy, 502 00:34:09,070 --> 00:34:13,790 wavelike behaviour that allows them to leak through an energy barrier. 503 00:34:13,790 --> 00:34:16,950 A particle can disappear on one side of the barrier 504 00:34:16,950 --> 00:34:20,190 and instantaneously reappear on the other. 505 00:34:22,190 --> 00:34:25,550 In nuclear physics, this effect is a proven fact. 506 00:34:27,310 --> 00:34:31,430 Without quantum tunnelling, the Sun simply wouldn't shine. 507 00:34:33,910 --> 00:34:36,070 But I never thought I'd see it... 508 00:34:38,350 --> 00:34:40,310 ..in a tadpole. 509 00:34:40,310 --> 00:34:44,070 It's hard to stress just how weird this process is. 510 00:34:44,070 --> 00:34:47,270 It's as though I would approach a solid brick wall and, 511 00:34:47,270 --> 00:34:51,990 like a phantom, disappear from one side and reappear on the other. 512 00:34:56,030 --> 00:34:59,470 The most important advantage of tunnelling is its speed. 513 00:35:01,990 --> 00:35:04,670 It happens incredibly quickly - 514 00:35:04,670 --> 00:35:07,630 much faster than if protons go OVER the barrier. 515 00:35:10,070 --> 00:35:13,750 As a nuclear physicist, quantum tunnelling is my bread and butter. 516 00:35:13,750 --> 00:35:17,470 Subatomic particles like protons do it all the time. 517 00:35:17,470 --> 00:35:20,190 But what has this got to do with biology? 518 00:35:26,230 --> 00:35:29,310 The answer is that without quantum ghosts, 519 00:35:29,310 --> 00:35:32,390 the metamorphosis of a tadpole would be impossible. 520 00:35:34,150 --> 00:35:37,430 Remember, chemical bonds are basically knots. 521 00:35:39,590 --> 00:35:43,470 Tunnelling unties them - fast. 522 00:35:43,470 --> 00:35:45,870 Have a look at these two knots. 523 00:35:45,870 --> 00:35:48,830 Now, on the face of it they look identical, 524 00:35:48,830 --> 00:35:51,470 but there's a subtle difference. 525 00:35:51,470 --> 00:35:54,030 This knot has the two short ends 526 00:35:54,030 --> 00:35:56,230 of the rope on the same side. 527 00:35:56,230 --> 00:35:57,910 Whereas this one 528 00:35:57,910 --> 00:36:00,070 has the two short ends on opposite sides. 529 00:36:01,150 --> 00:36:05,470 Now, you'd think that wouldn't make a difference, but it does. 530 00:36:05,470 --> 00:36:06,910 You see, THIS knot... 531 00:36:08,390 --> 00:36:10,190 ..is very hard to break, 532 00:36:10,190 --> 00:36:11,630 whereas THIS one... 533 00:36:13,150 --> 00:36:14,070 ..is easy. 534 00:36:16,270 --> 00:36:17,710 Quantum tunnelling... 535 00:36:20,390 --> 00:36:23,350 ..turns strong knots into weak ones. 536 00:36:25,870 --> 00:36:27,470 So in a tadpole, 537 00:36:27,470 --> 00:36:31,590 the entire collagen scaffold breaks apart easily. 538 00:36:31,590 --> 00:36:36,950 And finally, other enzymes rebuild it in the shape of a frog. 539 00:36:41,470 --> 00:36:45,070 The quantum tunnelling of particles is one of those weird features 540 00:36:45,070 --> 00:36:46,470 of the subatomic world 541 00:36:46,470 --> 00:36:49,190 that a physicist like me is very familiar with. 542 00:36:49,190 --> 00:36:52,310 After all, it's responsible for radioactive decay 543 00:36:52,310 --> 00:36:54,190 and it goes on inside the Sun. 544 00:36:54,190 --> 00:36:57,510 It's the reason why the Sun and all stars shine. 545 00:36:57,510 --> 00:37:01,390 But to discover this going on inside every cell of every 546 00:37:01,390 --> 00:37:05,590 living organism on the planet, because every cell contains enzymes, 547 00:37:05,590 --> 00:37:08,270 now, THAT I find truly amazing. 548 00:37:12,150 --> 00:37:16,190 Quantum biology casts its spell over every living creature. 549 00:37:18,430 --> 00:37:21,830 We've seen that birds, mammals, insects 550 00:37:21,830 --> 00:37:27,030 and amphibians are governed by the strangest laws in science. 551 00:37:28,550 --> 00:37:31,470 But the most dramatic recent breakthrough concerns 552 00:37:31,470 --> 00:37:35,910 the single vital process on which all these forms of life depend. 553 00:37:37,670 --> 00:37:41,110 The conversion of air and sunlight 554 00:37:41,110 --> 00:37:42,390 into plants. 555 00:37:47,790 --> 00:37:52,990 This fine specimen is a Larix decidua, or European larch. 556 00:37:52,990 --> 00:37:56,070 It's about 100 feet high and right at this moment, 557 00:37:56,070 --> 00:37:58,710 passing just this side of the planet Venus, 558 00:37:58,710 --> 00:38:01,070 is a bullet with this tree's name on it. 559 00:38:03,790 --> 00:38:05,430 The bullet is a photon 560 00:38:05,430 --> 00:38:08,790 nearing the end of its long journey from the Sun. 561 00:38:12,830 --> 00:38:15,510 Its ultimate destiny is to kick-start 562 00:38:15,510 --> 00:38:20,270 a series of chemical reactions that underpins all life on Earth... 563 00:38:21,470 --> 00:38:23,950 ..photosynthesis. 564 00:38:23,950 --> 00:38:25,990 Every second of every day, 565 00:38:25,990 --> 00:38:30,750 16,000 tonnes of new plant life are created on Earth. 566 00:38:30,750 --> 00:38:33,590 And for me, it's incredible to think that our existence 567 00:38:33,590 --> 00:38:36,710 on this planet depends on what happens 568 00:38:36,710 --> 00:38:39,310 in the next trillionth of a second. 569 00:38:50,230 --> 00:38:53,110 The crucial first stage of photosynthesis 570 00:38:53,110 --> 00:38:55,070 is the capture of energy from the Sun. 571 00:38:57,150 --> 00:38:59,310 It's nearly 100% efficient, 572 00:38:59,310 --> 00:39:02,430 vastly superior to any human technology. 573 00:39:05,430 --> 00:39:08,510 But the way that every plant on Earth achieves this 574 00:39:08,510 --> 00:39:10,750 is one of the great puzzles in biology. 575 00:39:11,910 --> 00:39:15,430 When it turned out that quantum weirdness might hold the answer, 576 00:39:15,430 --> 00:39:17,510 physicists could hardly believe it. 577 00:39:20,230 --> 00:39:21,750 It was like a revelation. 578 00:39:21,750 --> 00:39:23,590 It was very exciting, because I was 579 00:39:23,590 --> 00:39:25,350 used to working on problems 580 00:39:25,350 --> 00:39:27,910 that were quite abstract experiments. 581 00:39:27,910 --> 00:39:31,590 I am a theoretician, but I always related my theory 582 00:39:31,590 --> 00:39:33,670 to experiments that were very clean in the lab, 583 00:39:33,670 --> 00:39:35,150 things that you can control. 584 00:39:35,150 --> 00:39:38,190 But now, finding out that the things that I knew can help me 585 00:39:38,190 --> 00:39:40,990 to understand better how nature works, 586 00:39:40,990 --> 00:39:45,070 really, scientifically, it was like a... 587 00:39:45,070 --> 00:39:46,630 a new inspiration to my life, 588 00:39:46,630 --> 00:39:51,070 so I would say I fell in love with this field. 589 00:39:54,390 --> 00:39:57,990 Textbook biology says the colour of green plants 590 00:39:57,990 --> 00:40:00,070 comes from chlorophyll molecules. 591 00:40:01,350 --> 00:40:05,270 Inside the living cells, they absorb light from the Sun. 592 00:40:07,950 --> 00:40:11,150 This energy is then transferred incredibly quickly 593 00:40:11,150 --> 00:40:14,110 to the food-making factory at the heart of the cell. 594 00:40:17,790 --> 00:40:19,630 The entire event takes 595 00:40:19,630 --> 00:40:22,830 just a millionth of a millionth of a second. 596 00:40:22,830 --> 00:40:25,150 When the photon hits the cell, 597 00:40:25,150 --> 00:40:29,350 it knocks an electron out of the middle of a chlorophyll molecule. 598 00:40:29,350 --> 00:40:33,590 This creates a tiny packet of energy called an exciton. 599 00:40:33,590 --> 00:40:35,430 The exciton then bounces its way 600 00:40:35,430 --> 00:40:38,190 through a forest of chlorophyll molecules 601 00:40:38,190 --> 00:40:41,670 until it reaches what is called the reaction centre. 602 00:40:41,670 --> 00:40:45,430 Now, that is where its energy is used to drive chemical processes 603 00:40:45,430 --> 00:40:49,630 that create the all-important biomolecules of life. 604 00:40:49,630 --> 00:40:53,230 The problem is, the exciton needs to find its way to the reaction centre 605 00:40:53,230 --> 00:40:55,150 in the first place. 606 00:41:00,990 --> 00:41:04,910 Textbook biology can't explain how the exciton does this. 607 00:41:08,230 --> 00:41:11,150 Because, of course, it doesn't know where it's going. 608 00:41:13,870 --> 00:41:16,310 It just bounces around like a pinball 609 00:41:16,310 --> 00:41:18,910 in a process called a random walk. 610 00:41:23,390 --> 00:41:24,630 Sooner or later, 611 00:41:24,630 --> 00:41:27,430 it will pass through every single part of the cell. 612 00:41:30,390 --> 00:41:33,470 But this isn't the most efficient way to get around. 613 00:41:37,110 --> 00:41:40,710 Because when the exciton eventually does reach the reaction centre... 614 00:41:42,110 --> 00:41:43,590 ..it's by pure chance. 615 00:41:49,190 --> 00:41:51,670 If the exciton just blindly and randomly 616 00:41:51,670 --> 00:41:54,230 hops between the chlorophyll molecules, 617 00:41:54,230 --> 00:41:57,150 it would take too long to reach the reaction centre 618 00:41:57,150 --> 00:42:00,430 and would have lost its energy as waste heat. 619 00:42:00,430 --> 00:42:03,830 But it doesn't. Something very different must be going on. 620 00:42:05,710 --> 00:42:09,190 The vital clue comes from recent experiments 621 00:42:09,190 --> 00:42:11,110 that stunned the world of science. 622 00:42:13,990 --> 00:42:17,390 Chemists fired lasers at plant cells 623 00:42:17,390 --> 00:42:19,630 to simulate the capture of light from the Sun. 624 00:42:22,470 --> 00:42:26,030 They confirmed the exciton wasn't bouncing along a haphazard route 625 00:42:26,030 --> 00:42:27,310 through the cell. 626 00:42:28,550 --> 00:42:31,190 This original understanding didn't explain what 627 00:42:31,190 --> 00:42:32,830 we were observing in the lab. 628 00:42:32,830 --> 00:42:34,990 So the mystery lies in, OK, 629 00:42:34,990 --> 00:42:38,710 so then, what is the explanation for what we are observing in the lab? 630 00:42:41,150 --> 00:42:44,670 The solution is that plants obey the most famous law 631 00:42:44,670 --> 00:42:47,110 in all of quantum mechanics... 632 00:42:49,390 --> 00:42:51,390 ..the uncertainty principle. 633 00:42:54,830 --> 00:42:56,830 It says it you can never be certain 634 00:42:56,830 --> 00:43:00,310 that the exciton is in one specific place. 635 00:43:02,790 --> 00:43:06,270 Instead, it behaves like a quantum wave, 636 00:43:06,270 --> 00:43:08,870 smearing itself out across the cell. 637 00:43:13,550 --> 00:43:17,030 The exciton doesn't simply move from A to B. 638 00:43:19,510 --> 00:43:22,030 In a bizarre but very real sense, 639 00:43:22,030 --> 00:43:26,870 it's heading in every direction at the same time. 640 00:43:26,870 --> 00:43:29,350 It's spreading itself out as a wave 641 00:43:29,350 --> 00:43:33,150 so that it can explore all possible routes simultaneously. 642 00:43:33,150 --> 00:43:34,830 This strikes at the very heart 643 00:43:34,830 --> 00:43:37,230 of what's so strange about quantum mechanics. 644 00:43:37,230 --> 00:43:41,230 The exciton wave isn't just going this way or that way, 645 00:43:41,230 --> 00:43:44,510 it's following all paths at the same time. 646 00:43:44,510 --> 00:43:47,430 That's what gives it such incredible efficiency. 647 00:44:00,750 --> 00:44:01,870 The beauty of it is... 648 00:44:04,070 --> 00:44:06,470 ..if the exciton is trying every route 649 00:44:06,470 --> 00:44:08,430 to the reaction centre at once... 650 00:44:10,190 --> 00:44:13,950 ..it's bound to find the fastest possible way to deliver its energy. 651 00:44:17,750 --> 00:44:21,190 It's hard to express how incredible this discovery seems 652 00:44:21,190 --> 00:44:22,750 to physicists like me. 653 00:44:23,950 --> 00:44:27,350 Biological cells are full of the random jiggling 654 00:44:27,350 --> 00:44:29,510 of billions of atoms and molecules. 655 00:44:31,510 --> 00:44:34,710 But somehow, excitons maintain their form 656 00:44:34,710 --> 00:44:39,310 as beautiful, perfect quantum waves, 657 00:44:39,310 --> 00:44:44,030 transporting the energy that guarantees life on Earth. 658 00:44:47,910 --> 00:44:52,350 It opened a whole new scientific path for me. 659 00:44:52,350 --> 00:44:54,430 And I really enjoy the fact that 660 00:44:54,430 --> 00:44:57,550 to be able to understand fully what is happening there or in the plants, 661 00:44:57,550 --> 00:44:59,390 you have to interact with scientists 662 00:44:59,390 --> 00:45:02,070 that have completely different approaches 663 00:45:02,070 --> 00:45:04,990 like biologists and chemists. 664 00:45:04,990 --> 00:45:07,150 But we all have to come together 665 00:45:07,150 --> 00:45:09,710 to actually understand what is the relevant of this, 666 00:45:09,710 --> 00:45:11,430 the relevance of this. 667 00:45:11,430 --> 00:45:14,110 So, for me, this is one of the most exciting parts of this field. 668 00:45:17,430 --> 00:45:21,030 Real scientific experiments leave no doubt. 669 00:45:22,790 --> 00:45:25,950 The strange hand of quantum mechanics has shaped 670 00:45:25,950 --> 00:45:27,590 the entire living world. 671 00:45:30,270 --> 00:45:34,510 It's not a surprise that you should find quantum tricks being used 672 00:45:34,510 --> 00:45:36,510 in biological systems. 673 00:45:36,510 --> 00:45:38,510 The reason is, because they're better. 674 00:45:43,270 --> 00:45:45,590 Quantum entanglement is normally seen 675 00:45:45,590 --> 00:45:48,710 in the tightly-controlled conditions of the physics lab. 676 00:45:50,070 --> 00:45:52,150 But now, we know that robins use it 677 00:45:52,150 --> 00:45:54,590 to navigate with extraordinary precision. 678 00:45:59,190 --> 00:46:02,830 Quantum vibrations mean our noses LISTEN to chemicals... 679 00:46:04,350 --> 00:46:07,030 ..enhancing our perception of the world around us. 680 00:46:11,430 --> 00:46:14,710 The living cells of all animals depend on protons 681 00:46:14,710 --> 00:46:17,710 that vanish and reappear like ghosts... 682 00:46:20,150 --> 00:46:22,910 ..speeding up the vital processes of life. 683 00:46:28,630 --> 00:46:31,310 And photosynthesis reveals the big picture. 684 00:46:33,390 --> 00:46:34,750 A shimmering world 685 00:46:34,750 --> 00:46:38,870 where quantum waves capture the Sun's energy in an instant. 686 00:46:40,870 --> 00:46:43,310 Sometimes, people say, "Ah, but physicists have been 687 00:46:43,310 --> 00:46:45,590 "looking for this for decades". 688 00:46:45,590 --> 00:46:48,430 Well, biology has had millions of years. 689 00:46:49,590 --> 00:46:52,910 The ultramodern science of quantum mechanics 690 00:46:52,910 --> 00:46:54,870 is an ancient fact of life. 691 00:46:57,190 --> 00:46:59,030 For the end of my journey, 692 00:46:59,030 --> 00:47:01,750 I want to take these ideas to their logical conclusion. 693 00:47:01,750 --> 00:47:03,190 Of course, as a scientist, 694 00:47:03,190 --> 00:47:07,830 any speculations I have have to be backed up by careful experiments. 695 00:47:07,830 --> 00:47:10,990 So I want to concoct a thought experiment that helps me 696 00:47:10,990 --> 00:47:15,270 to answer the biggest biological question I can think of. 697 00:47:15,270 --> 00:47:18,470 Does quantum physics play any role 698 00:47:18,470 --> 00:47:20,990 in the mechanism of evolution itself? 699 00:47:27,030 --> 00:47:30,750 In 1859, Charles Darwin stunned the world 700 00:47:30,750 --> 00:47:33,910 with his Theory Of Evolution By Natural Selection. 701 00:47:35,390 --> 00:47:37,710 He went on to explain the differences 702 00:47:37,710 --> 00:47:39,670 between humans and other apes. 703 00:47:41,630 --> 00:47:45,190 150 years later, there's no doubt that Darwin's theory 704 00:47:45,190 --> 00:47:46,870 accounts for every living organism 705 00:47:46,870 --> 00:47:48,990 on land and sea. 706 00:47:51,550 --> 00:47:53,750 But I'd like to explore the latest, 707 00:47:53,750 --> 00:47:57,190 extraordinary interpretation of his ideas. 708 00:47:57,190 --> 00:47:59,190 STIRRING STRINGS 709 00:48:02,270 --> 00:48:06,670 Could there be a quantum theory of evolution? 710 00:48:06,670 --> 00:48:11,550 MUSIC: Adagio of Spartacus and Phrygia from Spartacus Suite No.2 by Aram Khachaturian 711 00:48:33,630 --> 00:48:38,270 Can quantum evolution explain how the snail got its shell? 712 00:48:41,670 --> 00:48:44,190 The snails I'm used to seeing in my back garden 713 00:48:44,190 --> 00:48:47,150 tend to have rather bland, boring shells. 714 00:48:47,150 --> 00:48:49,230 So have a look at this beauty. 715 00:48:50,670 --> 00:48:53,870 The patterns on its shell very perfectly match 716 00:48:53,870 --> 00:48:55,950 the lines on the stem. 717 00:48:58,590 --> 00:49:02,190 It's called a banded snail. Cepaea nemoralis. 718 00:49:03,470 --> 00:49:06,230 And the pattern isn't there by accident. 719 00:49:10,350 --> 00:49:11,910 Come and have a look at this. 720 00:49:15,710 --> 00:49:17,750 Less well adapted snails 721 00:49:17,750 --> 00:49:20,430 are more likely to be found here. 722 00:49:20,430 --> 00:49:23,830 This stone is called a thrush's anvil. 723 00:49:23,830 --> 00:49:26,390 The song thrush is the snail's main predator. 724 00:49:26,390 --> 00:49:27,670 It catches the snail 725 00:49:27,670 --> 00:49:30,670 and smashes its shell against the stone to get to the snail. 726 00:49:30,670 --> 00:49:32,150 Now, what I can see here 727 00:49:32,150 --> 00:49:35,270 is that there aren't many banded snail shells, 728 00:49:35,270 --> 00:49:38,830 suggesting that its colours camouflage it very well, 729 00:49:38,830 --> 00:49:40,110 hiding it from the bird. 730 00:49:43,910 --> 00:49:45,550 Darwin's theory says 731 00:49:45,550 --> 00:49:49,550 that evolution depends on variation within a species. 732 00:49:52,030 --> 00:49:56,030 Snails with camouflage are more likely to survive and reproduce... 733 00:49:58,550 --> 00:50:01,270 ..passing on their shells to the next generation 734 00:50:01,270 --> 00:50:05,190 so that the species as a whole becomes better adapted. 735 00:50:08,030 --> 00:50:12,030 So, variation - the random differences between snails - 736 00:50:12,030 --> 00:50:14,910 is the driving force behind their evolution. 737 00:50:17,030 --> 00:50:20,750 Now, all species evolve and adapt to their environment. 738 00:50:20,750 --> 00:50:22,870 But the question I'd like to explore is 739 00:50:22,870 --> 00:50:25,790 whether quantum mechanics plays a role in this. 740 00:50:29,910 --> 00:50:31,510 The only way to find out 741 00:50:31,510 --> 00:50:33,750 is by scientific experiments. 742 00:50:36,030 --> 00:50:39,910 So, my adventures in quantum biology finally bring me home. 743 00:50:42,030 --> 00:50:44,030 To the University of Surrey. 744 00:50:46,630 --> 00:50:48,150 Here, in the laboratories, 745 00:50:48,150 --> 00:50:52,550 I'm planning a new analysis of the most celebrated molecule in science. 746 00:50:56,430 --> 00:51:00,230 Deoxyribonucleic acid, or DNA. 747 00:51:03,310 --> 00:51:08,110 Its double helix holds the genetic code for every living organism. 748 00:51:10,630 --> 00:51:14,310 It's a remarkable fact that Darwin himself had no idea 749 00:51:14,310 --> 00:51:17,470 what created variation in the species. 750 00:51:17,470 --> 00:51:21,030 The structure of DNA wasn't discovered until 1953 751 00:51:21,030 --> 00:51:23,830 by Francis Crick and James Watson. 752 00:51:23,830 --> 00:51:26,750 The most famous feature of DNA is of course 753 00:51:26,750 --> 00:51:29,470 its beautiful double helix structure. 754 00:51:29,470 --> 00:51:31,150 But that's just scaffolding. 755 00:51:31,150 --> 00:51:34,070 The real genetic secret lies in between. 756 00:51:37,310 --> 00:51:40,950 The four different-coloured molecules are called bases. 757 00:51:42,630 --> 00:51:46,790 The colour code on one side - say blue, red, blue - 758 00:51:46,790 --> 00:51:51,230 forms a gene that parents pass on to their offspring. 759 00:51:51,230 --> 00:51:54,270 A gene is a bit like a jigsaw puzzle. 760 00:51:54,270 --> 00:51:56,230 It fits together like this. 761 00:51:58,070 --> 00:52:02,510 A full strand of the double helix forms a coloured pattern. 762 00:52:04,590 --> 00:52:07,670 But the other strand always pairs up the same way. 763 00:52:10,910 --> 00:52:13,630 A blue base always goes with yellow 764 00:52:13,630 --> 00:52:16,990 and green always goes with red. 765 00:52:18,510 --> 00:52:22,950 Because only those colours have the right shape to fit together. 766 00:52:22,950 --> 00:52:26,430 What Crick and Watson realised was that this provides 767 00:52:26,430 --> 00:52:29,430 a mechanism for passing on the genetic code. 768 00:52:30,830 --> 00:52:34,910 When cells reproduce, the two strands of DNA separate, 769 00:52:34,910 --> 00:52:36,430 ready to be copied. 770 00:52:38,670 --> 00:52:40,990 But red still goes with green... 771 00:52:43,350 --> 00:52:45,470 ..and yellow still goes with blue. 772 00:52:47,070 --> 00:52:48,710 So bit by bit, 773 00:52:48,710 --> 00:52:50,910 the cell creates two new strands. 774 00:52:52,630 --> 00:52:56,310 Two perfect copies of the entire genetic code. 775 00:52:57,670 --> 00:53:00,430 So far, there's no genetic variation. 776 00:53:00,430 --> 00:53:03,950 This new copy is identical to the original. 777 00:53:03,950 --> 00:53:05,750 But here's the interesting bit. 778 00:53:05,750 --> 00:53:09,950 During the copying process, something very important can happen. 779 00:53:09,950 --> 00:53:11,910 Sometimes, mistakes creep in. 780 00:53:14,990 --> 00:53:16,950 They're called mutations. 781 00:53:18,390 --> 00:53:21,670 Let's have a look at these two bases here. 782 00:53:23,430 --> 00:53:28,110 The two prongs that hold them together are subatomic particles. 783 00:53:28,110 --> 00:53:29,550 They're protons. 784 00:53:29,550 --> 00:53:33,390 They're basically the bonds between the strands of DNA. 785 00:53:33,390 --> 00:53:37,030 These protons can jump across to the other side. 786 00:53:38,990 --> 00:53:42,990 If the strands split when the protons have jumped across, 787 00:53:42,990 --> 00:53:45,670 they find themselves in the wrong position. 788 00:53:47,750 --> 00:53:53,310 Now, this red base will no longer bind to a green base. 789 00:53:53,310 --> 00:53:57,790 Instead, it has to bond to a yellow base. 790 00:53:58,990 --> 00:54:00,670 Slotting this back in, 791 00:54:01,870 --> 00:54:05,590 we see that now this copy is no longer identical to the original 792 00:54:05,590 --> 00:54:09,550 because I have a yellow base here instead of a green one. 793 00:54:09,550 --> 00:54:12,430 We've brought in a genetic mutation. 794 00:54:14,070 --> 00:54:17,310 Jumping protons would change the snail's DNA. 795 00:54:18,950 --> 00:54:21,790 It could make a new gene for camouflaged shells. 796 00:54:23,430 --> 00:54:26,230 The question is, how do protons jump? 797 00:54:29,110 --> 00:54:32,510 It's my belief that quantum's spookiness can take over. 798 00:54:34,190 --> 00:54:36,630 Now, for these mutations to take place, 799 00:54:36,630 --> 00:54:40,350 the protons have to overcome an energy barrier. 800 00:54:40,350 --> 00:54:42,790 And if you remember what happened with enzymes, 801 00:54:42,790 --> 00:54:45,990 well, you can probably guess what's coming next. 802 00:54:49,470 --> 00:54:52,990 Protons can behave as if barriers don't exist. 803 00:54:55,110 --> 00:54:57,710 They tunnel straight through. 804 00:54:59,070 --> 00:55:01,830 But does this ghostly effect really happen? 805 00:55:06,150 --> 00:55:08,910 My colleagues in biology are already looking 806 00:55:08,910 --> 00:55:11,990 for the very first evidence of quantum mutations. 807 00:55:14,990 --> 00:55:17,870 Biologists didn't really even know about quantum mechanics, 808 00:55:17,870 --> 00:55:21,710 so when you tell them that particles can be in two places at once, 809 00:55:21,710 --> 00:55:23,950 they kind of say, "Well, not in my cells, they can't!" 810 00:55:25,470 --> 00:55:28,470 Our experiment involves samples of bacteria. 811 00:55:29,870 --> 00:55:32,670 The first sample is prepared in normal water, 812 00:55:32,670 --> 00:55:35,790 containing hydrogen nuclei, or protons. 813 00:55:37,550 --> 00:55:41,950 When the bacteria reproduce, we simply count the mutations. 814 00:55:43,430 --> 00:55:45,230 But if our theory is correct, 815 00:55:45,230 --> 00:55:48,910 then we should be able to change the rate at which mutations occur. 816 00:55:50,510 --> 00:55:53,990 Remember how we tested the quantum theory of smell? 817 00:55:53,990 --> 00:55:58,630 What if I replaced the proton with its big brother, the deuteron? 818 00:55:58,630 --> 00:56:01,710 This is the nucleus of an atom of deuterium. 819 00:56:01,710 --> 00:56:05,470 Now, crucially, a deuteron is twice as heavy as a proton 820 00:56:05,470 --> 00:56:08,390 and this should influence how easy it is for 821 00:56:08,390 --> 00:56:10,190 the deuteron to quantum tunnel. 822 00:56:11,310 --> 00:56:13,670 Quantum mechanics is full of surprises. 823 00:56:15,070 --> 00:56:16,910 Protons tunnel easily. 824 00:56:19,070 --> 00:56:21,430 Deuterons...don't. 825 00:56:26,950 --> 00:56:30,910 These heavier particles are much more likely to bounce straight back. 826 00:56:34,150 --> 00:56:38,350 So the second sample of bacteria is prepared in heavy water, 827 00:56:38,350 --> 00:56:40,150 which is full of deuterons. 828 00:56:41,950 --> 00:56:45,510 Our theory says you should get far fewer mutations. 829 00:56:47,230 --> 00:56:50,910 And, so far, the results are extremely encouraging. 830 00:56:50,910 --> 00:56:54,950 The preliminary experiments that we've done gives us a hint 831 00:56:54,950 --> 00:56:58,510 that the mutation rate is indeed depressed in deuterated water. 832 00:56:58,510 --> 00:57:03,190 We find that it is lower. So my hunch is that we're right, 833 00:57:03,190 --> 00:57:07,110 but we'll have to wait a little while before we're sure. 834 00:57:09,510 --> 00:57:11,230 Final proof lies in the future. 835 00:57:12,790 --> 00:57:14,310 Even if we're right, 836 00:57:14,310 --> 00:57:17,230 quantum tunnelling is a rare form of mutation. 837 00:57:19,470 --> 00:57:22,190 But our results promise hard evidence 838 00:57:22,190 --> 00:57:26,350 for a new explanation of one of the most fundamental processes of life. 839 00:57:28,470 --> 00:57:32,150 Even the merest possibility of a new quantum mechanism 840 00:57:32,150 --> 00:57:35,590 for evolution itself is tremendously exciting. 841 00:57:35,590 --> 00:57:40,070 In fact, the story of quantum biology is only just beginning. 842 00:57:40,070 --> 00:57:44,310 What the frog, the robin, the fruit fly and the tree have shown us 843 00:57:44,310 --> 00:57:48,990 is that real quantum effects are going on in nature all the time. 844 00:57:48,990 --> 00:57:50,910 And if there's anything we've learnt 845 00:57:50,910 --> 00:57:53,470 from the history of quantum mechanics, it's this - 846 00:57:53,470 --> 00:57:57,550 we can never be certain where new discoveries will take us next. 847 00:58:06,870 --> 00:58:10,430 Quantum biology is a revolution in science. 848 00:58:11,550 --> 00:58:14,430 But it's time I got back to the physics department.