1 00:00:00,346 --> 00:00:01,493 Does a universe without ears 2 00:00:01,905 --> 00:00:02,813 Need sound 3 00:00:03,466 --> 00:00:05,352 A tree falls in a forest 4 00:00:05,426 --> 00:00:06,753 With no one around 5 00:00:06,865 --> 00:00:07,253 So tell me 6 00:00:07,586 --> 00:00:08,733 Did it make a sound 7 00:00:09,346 --> 00:00:11,753 This question has puzzled philosophers for three centuries 8 00:00:11,785 --> 00:00:13,632 And still has no standard answer today 9 00:00:13,986 --> 00:00:15,544 But today I want to tell you 10 00:00:15,545 --> 00:00:17,832 Why this question has gone unanswered for three centuries 11 00:00:17,865 --> 00:00:19,344 Is not that it is too difficult 12 00:00:19,346 --> 00:00:21,625 It is that those asking and answering it 13 00:00:21,626 --> 00:00:24,099 Are simply not on the same wavelength 14 00:00:24,253 --> 00:00:24,599 Hello 15 00:00:24,733 --> 00:00:25,160 Everyone 16 00:00:25,373 --> 00:00:26,340 I am Leo Wang 17 00:00:26,692 --> 00:00:29,340 A physicist would find this question baffling 18 00:00:29,612 --> 00:00:30,280 The tree fell 19 00:00:30,612 --> 00:00:31,320 And struck the ground 20 00:00:31,652 --> 00:00:33,131 Compressing air molecules 21 00:00:33,133 --> 00:00:35,500 Into alternating bands of compression and rarefaction 22 00:00:35,652 --> 00:00:39,100 Spreading outward at about 344 meters per second 23 00:00:39,453 --> 00:00:42,420 This happens whether anyone is there or not 24 00:00:42,652 --> 00:00:43,280 Whether you are present 25 00:00:43,493 --> 00:00:44,939 The air still gets compressed 26 00:00:45,253 --> 00:00:46,399 So a physicist would say 27 00:00:46,732 --> 00:00:47,932 Of course there is sound 28 00:00:47,933 --> 00:00:48,839 What is there to argue about 29 00:00:49,937 --> 00:00:51,244 But a philosopher would ask 30 00:00:51,537 --> 00:00:52,184 Wait 31 00:00:52,257 --> 00:00:54,004 What exactly do you mean by sound 32 00:00:54,497 --> 00:00:57,045 The shoving motion of molecules in the air 33 00:00:57,617 --> 00:00:59,684 Or the buzzing sensation inside your ears 34 00:01:00,177 --> 00:01:01,976 If sound is just air vibration 35 00:01:01,978 --> 00:01:05,245 Then two rocks colliding in space make no sound 36 00:01:05,697 --> 00:01:07,424 But if you were on a space station 37 00:01:07,458 --> 00:01:08,784 Watching through a window 38 00:01:08,858 --> 00:01:10,617 As two meteors collided 39 00:01:10,617 --> 00:01:12,004 Would you not instinctively feel 40 00:01:12,218 --> 00:01:13,284 That there should be a sound 41 00:01:13,738 --> 00:01:14,084 You see 42 00:01:14,458 --> 00:01:15,705 This is not mere wordplay 43 00:01:15,897 --> 00:01:18,864 It hides a profound question about the nature of the universe 44 00:01:19,773 --> 00:01:22,419 Let me first break sound down completely 45 00:01:22,773 --> 00:01:23,919 At the physical level 46 00:01:24,253 --> 00:01:25,539 An object vibrates 47 00:01:25,572 --> 00:01:28,860 Creating periodic pressure changes in the surrounding medium 48 00:01:28,932 --> 00:01:31,940 Those pressure changes travel outward as waves 49 00:01:32,053 --> 00:01:33,220 Those are sound waves 50 00:01:33,493 --> 00:01:34,440 Sound waves have frequency 51 00:01:34,693 --> 00:01:35,571 Amplitude 52 00:01:35,572 --> 00:01:36,199 And waveform 53 00:01:36,613 --> 00:01:38,539 All measurable physical quantities 54 00:01:38,693 --> 00:01:42,619 A seismograph can record infrasound below human hearing 55 00:01:42,693 --> 00:01:46,339 An ultrasound device can detect vibrations at tens of thousands of hertz 56 00:01:46,533 --> 00:01:49,500 These waves truly exist in the physical world 57 00:01:49,572 --> 00:01:51,059 Without anyone needing to hear them 58 00:01:51,847 --> 00:01:52,234 But 59 00:01:52,567 --> 00:01:54,014 When you say sound 60 00:01:54,127 --> 00:01:56,014 That is usually not what you mean 61 00:01:56,327 --> 00:01:58,214 You mean high and low pitch 62 00:01:58,526 --> 00:01:59,973 Bright and dark timbre 63 00:02:00,487 --> 00:02:03,166 That sensation when fingernails scrape a blackboard 64 00:02:03,166 --> 00:02:05,333 And your whole body breaks into goosebumps 65 00:02:06,086 --> 00:02:09,214 Close your eyes and imagine that sound 66 00:02:09,687 --> 00:02:12,213 The instant a fingernail scratches across the board 67 00:02:12,687 --> 00:02:14,474 Did your shoulders tense up 68 00:02:15,287 --> 00:02:17,414 That thing making your whole body uncomfortable 69 00:02:17,647 --> 00:02:19,613 Is not inside the air molecules 70 00:02:19,926 --> 00:02:22,486 Air molecules do not know what a high note is 71 00:02:22,486 --> 00:02:23,533 Or a low note 72 00:02:23,766 --> 00:02:25,773 Much less what drives someone crazy 73 00:02:26,166 --> 00:02:28,974 They are merely being pushed back and forth 74 00:02:29,726 --> 00:02:32,565 Vibrations between 20 and 20000 hertz 75 00:02:32,567 --> 00:02:35,373 Are converted into electrical signals by your cochlea 76 00:02:35,446 --> 00:02:38,893 And sent along the auditory nerve to the auditory cortex 77 00:02:38,967 --> 00:02:41,454 Only after extremely complex processing 78 00:02:41,486 --> 00:02:44,373 Do you experience something called sound 79 00:02:45,453 --> 00:02:49,380 And that processing is stranger than you imagine 80 00:02:49,812 --> 00:02:52,259 Your brain is not a faithful mirror 81 00:02:52,372 --> 00:02:54,940 It is an intensely active creator 82 00:02:55,213 --> 00:02:59,500 A 2016 study published in PNAS found 83 00:02:59,733 --> 00:03:02,299 That the brain processes sequences of sound 84 00:03:02,372 --> 00:03:04,699 Essentially as a prediction machine 85 00:03:04,893 --> 00:03:08,780 Your brain does not passively wait for sound waves and translate them 86 00:03:08,852 --> 00:03:12,979 It actively predicts what sound will come next 87 00:03:13,132 --> 00:03:17,019 Then uses the incoming signal to correct that prediction 88 00:03:17,293 --> 00:03:19,091 When you hear a familiar melody 89 00:03:19,092 --> 00:03:20,620 And one note is suddenly wrong 90 00:03:20,692 --> 00:03:22,651 That instinctive discomfort 91 00:03:22,652 --> 00:03:24,820 Is your reaction to a broken prediction 92 00:03:25,493 --> 00:03:26,160 In other words 93 00:03:26,412 --> 00:03:27,612 The sound you hear 94 00:03:27,613 --> 00:03:31,381 Is largely filled in by your brain 95 00:03:31,494 --> 00:03:33,661 That is why the same recording 96 00:03:33,734 --> 00:03:35,140 Sounds heavenly to one person 97 00:03:35,253 --> 00:03:36,700 And like noise to another 98 00:03:36,973 --> 00:03:38,461 With vibrations at the same frequency 99 00:03:38,494 --> 00:03:41,980 A bat hears a completely different world from you 100 00:03:42,253 --> 00:03:43,820 Dogs can hear ultrasound 101 00:03:43,894 --> 00:03:46,221 Snakes can sense vibrations through the ground 102 00:03:46,334 --> 00:03:48,941 Whales can receive low frequency signals 103 00:03:48,973 --> 00:03:50,980 From companions hundreds of kilometers away 104 00:03:51,174 --> 00:03:55,168 Every species lives in its own universe of sound 105 00:03:55,361 --> 00:03:56,389 The German biologist 106 00:03:56,722 --> 00:03:58,920 Jakob von Uexkull 107 00:03:58,922 --> 00:04:01,200 Proposed a concept over a century ago 108 00:04:01,202 --> 00:04:02,408 Called the Umwelt 109 00:04:02,841 --> 00:04:06,848 He said every organism is enclosed in its own perceptual bubble 110 00:04:07,042 --> 00:04:10,209 The boundaries of its world are the boundaries of its senses 111 00:04:10,521 --> 00:04:13,149 The entire universe of a tick contains only three signals 112 00:04:13,762 --> 00:04:18,209 The smell of butyric acid a temperature of 37 degrees and the touch of hair 113 00:04:18,561 --> 00:04:19,509 For a tick 114 00:04:19,882 --> 00:04:21,689 Sound simply does not exist 115 00:04:22,081 --> 00:04:22,788 And what about us 116 00:04:23,322 --> 00:04:26,249 We assume the human version alone deserves the name sound 117 00:04:26,442 --> 00:04:27,649 As if the whole universe 118 00:04:27,682 --> 00:04:29,761 Should follow our cochlea 119 00:04:29,762 --> 00:04:31,189 To define what counts as sound 120 00:04:31,481 --> 00:04:32,408 And what does not 121 00:04:33,421 --> 00:04:34,580 More than three centuries ago 122 00:04:34,582 --> 00:04:37,188 A British philosopher had already seen this problem 123 00:04:37,621 --> 00:04:38,709 John Locke 124 00:04:38,741 --> 00:04:41,029 He divided the qualities of objects into two kinds 125 00:04:41,181 --> 00:04:42,428 The first were primary qualities 126 00:04:42,462 --> 00:04:44,741 Qualities an object possesses whether anyone observes it 127 00:04:44,741 --> 00:04:46,368 Real qualities of the object itself 128 00:04:46,702 --> 00:04:47,748 Such as shape 129 00:04:47,822 --> 00:04:48,248 Size 130 00:04:48,621 --> 00:04:49,008 Mass 131 00:04:49,342 --> 00:04:50,469 And state of motion 132 00:04:50,662 --> 00:04:52,308 The other kind he called secondary qualities 133 00:04:52,342 --> 00:04:54,909 Qualities that arise only when an object 134 00:04:54,981 --> 00:04:56,128 Interacts with a perceiver 135 00:04:56,462 --> 00:04:57,549 Such as color 136 00:04:57,582 --> 00:04:58,008 Sound 137 00:04:58,381 --> 00:04:58,808 Smell 138 00:04:59,101 --> 00:04:59,529 Taste 139 00:04:59,702 --> 00:05:01,145 And temperature 140 00:05:01,618 --> 00:05:02,804 What did Locke mean 141 00:05:03,258 --> 00:05:05,784 He meant the shape of an apple belongs to the apple 142 00:05:05,857 --> 00:05:06,816 Even when you do not look at it 143 00:05:06,818 --> 00:05:07,984 It remains round 144 00:05:08,217 --> 00:05:10,825 But the redness of the apple does not belong to it 145 00:05:11,058 --> 00:05:15,265 Redness arises when light reflects from the apple into your eyes 146 00:05:15,378 --> 00:05:17,385 And the retina converts it into signals 147 00:05:17,457 --> 00:05:18,904 Which the brain then processes 148 00:05:18,938 --> 00:05:20,784 Only then do you experience redness 149 00:05:21,258 --> 00:05:24,904 If no eyes had ever appeared anywhere in the universe 150 00:05:24,938 --> 00:05:27,224 Then red would never have existed 151 00:05:27,537 --> 00:05:29,736 The apple surface does reflect 152 00:05:29,738 --> 00:05:32,065 Electromagnetic waves around 700 nanometers long 153 00:05:32,217 --> 00:05:34,945 But a 700 nanometer wave is not red 154 00:05:35,258 --> 00:05:37,940 Red is a label your brain attaches 155 00:05:38,414 --> 00:05:39,580 Sound works the same way 156 00:05:39,974 --> 00:05:40,561 The tree fell 157 00:05:40,734 --> 00:05:41,933 The air vibrated 158 00:05:41,933 --> 00:05:43,380 But vibration is not sound 159 00:05:43,654 --> 00:05:47,421 Sound is your auditory system and brain translating vibration 160 00:05:47,774 --> 00:05:51,253 If no creature with ears had ever appeared in the universe 161 00:05:51,253 --> 00:05:53,500 Then sound would never have existed 162 00:05:53,693 --> 00:05:57,301 The physical world would contain only moving particles and traveling waves 163 00:05:57,414 --> 00:05:58,541 But no pitch 164 00:05:58,573 --> 00:05:59,241 No timbre 165 00:05:59,493 --> 00:06:00,493 No melody 166 00:06:00,493 --> 00:06:01,500 No noise 167 00:06:01,573 --> 00:06:04,356 And no song that could move anyone to tears 168 00:06:04,829 --> 00:06:06,476 But Locke only went halfway 169 00:06:06,628 --> 00:06:09,476 He preserved shape mass and other primary qualities 170 00:06:09,628 --> 00:06:11,315 And regarded them as objective 171 00:06:11,349 --> 00:06:12,875 Independent of any observer 172 00:06:13,229 --> 00:06:15,916 Then someone even more radical came along 173 00:06:16,349 --> 00:06:17,255 George Berkeley 174 00:06:17,709 --> 00:06:18,947 An Irish philosopher 175 00:06:18,948 --> 00:06:20,195 Who later became a bishop 176 00:06:20,508 --> 00:06:23,236 He pushed Lockes logic all the way to its conclusion 177 00:06:23,589 --> 00:06:25,036 He said wait a moment 178 00:06:25,108 --> 00:06:27,455 What makes you think shape is objective 179 00:06:27,988 --> 00:06:29,276 You see a circle 180 00:06:29,428 --> 00:06:31,676 Because light enters your eyes 181 00:06:31,789 --> 00:06:34,075 And forms a pattern on the retina 182 00:06:34,108 --> 00:06:36,515 Then your brain tells you it is round 183 00:06:36,748 --> 00:06:38,308 You touch a sphere 184 00:06:38,308 --> 00:06:41,075 Because sensory nerves send signals to your brain 185 00:06:41,269 --> 00:06:42,748 Everything you perceive 186 00:06:42,748 --> 00:06:44,835 Whether color or shape 187 00:06:44,868 --> 00:06:46,796 Whether sound or mass 188 00:06:46,868 --> 00:06:49,116 Is entirely an experience within consciousness 189 00:06:49,308 --> 00:06:52,995 You never directly encounter anything outside consciousness 190 00:06:54,029 --> 00:06:56,315 So how do you know that when you are not looking 191 00:06:56,349 --> 00:06:57,616 The apple is still round 192 00:06:58,257 --> 00:06:59,603 In 1710 Berkeley 193 00:07:00,016 --> 00:07:01,543 Wrote in his famous book 194 00:07:01,576 --> 00:07:03,884 A proposition that shook Western philosophy 195 00:07:04,336 --> 00:07:06,184 To be is to be perceived 196 00:07:06,497 --> 00:07:07,903 Although the famous question 197 00:07:07,976 --> 00:07:09,783 About a tree falling in a forest 198 00:07:09,937 --> 00:07:11,824 Was not posed by Berkeley himself 199 00:07:11,896 --> 00:07:14,423 It perfectly captures his central intuition 200 00:07:14,656 --> 00:07:16,495 If no one is there to perceive it 201 00:07:16,497 --> 00:07:18,244 How can you claim that tree exists 202 00:07:18,696 --> 00:07:20,324 Or that it made a sound 203 00:07:20,937 --> 00:07:22,295 If Berkeley is right 204 00:07:22,297 --> 00:07:24,903 Then the issue goes far beyond sound 205 00:07:25,656 --> 00:07:28,295 It is not only color smell and taste 206 00:07:28,297 --> 00:07:29,816 Those so called secondary qualities 207 00:07:29,817 --> 00:07:31,983 That disappear without an observer 208 00:07:32,136 --> 00:07:35,136 Even shape size position and motion 209 00:07:35,136 --> 00:07:36,004 Things we consider 210 00:07:36,297 --> 00:07:37,975 Solid objective realities 211 00:07:37,976 --> 00:07:40,504 Would all depend on someone perceiving them 212 00:07:40,737 --> 00:07:43,415 Then in a universe with no sentient beings 213 00:07:43,417 --> 00:07:45,129 What exactly would remain 214 00:07:45,702 --> 00:07:48,348 Let me approach this from a modern angle 215 00:07:48,502 --> 00:07:52,709 Donald Hoffman a cognitive scientist at UC Irvine 216 00:07:52,781 --> 00:07:55,949 Built a model using mathematics and evolutionary game theory 217 00:07:56,101 --> 00:07:58,089 And reached an extremely counterintuitive conclusion 218 00:07:58,622 --> 00:08:01,668 Natural selection does not favor seeing the truth 219 00:08:01,742 --> 00:08:03,988 It only favors seeing what is useful 220 00:08:04,302 --> 00:08:05,589 His model shows 221 00:08:05,622 --> 00:08:08,380 That organisms perceiving objective reality more accurately 222 00:08:08,382 --> 00:08:10,988 Are actually eliminated in evolutionary competition 223 00:08:11,141 --> 00:08:12,021 The survivors 224 00:08:12,021 --> 00:08:15,015 Are organisms that build useful interfaces 225 00:08:15,368 --> 00:08:17,454 Hoffman offers a brilliant analogy 226 00:08:17,887 --> 00:08:21,094 Your computer desktop has a blue folder icon 227 00:08:21,368 --> 00:08:24,635 You do not think that blue square is the file itself 228 00:08:25,288 --> 00:08:29,414 The file really exists as a series of electromagnetic states on a drive 229 00:08:29,647 --> 00:08:32,974 But the operating system shows you a small blue square 230 00:08:33,248 --> 00:08:36,935 Because you can use the file without seeing those circuit signals 231 00:08:37,207 --> 00:08:39,814 Your sensory system does exactly this 232 00:08:40,048 --> 00:08:43,814 You need not read photon wavelengths to distinguish red from green 233 00:08:43,967 --> 00:08:47,135 Because vision translates wavelength into color 234 00:08:47,928 --> 00:08:50,455 You need not measure the frequency of air vibrations 235 00:08:50,528 --> 00:08:52,615 To distinguish high notes from low ones 236 00:08:52,888 --> 00:08:55,975 Because hearing translates frequency into pitch 237 00:08:56,288 --> 00:08:57,294 But pay attention 238 00:08:57,367 --> 00:09:00,135 The translation and the original are two different things 239 00:09:00,487 --> 00:09:02,126 The world you experience 240 00:09:02,127 --> 00:09:04,934 And the world that truly exists may be related 241 00:09:05,048 --> 00:09:06,774 As indirectly as a desktop icon 242 00:09:06,808 --> 00:09:10,347 And the electromagnetic states on a hard drive 243 00:09:10,900 --> 00:09:11,766 What does this mean 244 00:09:12,220 --> 00:09:15,626 It means sound is not something inherently present in the universe 245 00:09:16,260 --> 00:09:18,126 Sound is a coding scheme invented by the consciousness 246 00:09:18,419 --> 00:09:19,427 Of sentient beings for survival 247 00:09:19,459 --> 00:09:21,947 A coding scheme they invented 248 00:09:22,620 --> 00:09:23,327 You might say 249 00:09:23,659 --> 00:09:24,307 All right 250 00:09:24,380 --> 00:09:27,386 Even if sound and color are codes we invented 251 00:09:27,500 --> 00:09:30,567 The physical processes producing them must be real 252 00:09:31,100 --> 00:09:33,006 Air vibrations must still exist 253 00:09:33,500 --> 00:09:35,766 Atoms and molecules must exist objectively 254 00:09:36,462 --> 00:09:37,179 Fine 255 00:09:37,179 --> 00:09:40,099 Then let us push the question one level deeper 256 00:09:40,372 --> 00:09:43,499 Quantum mechanics tells us something deeply strange 257 00:09:43,772 --> 00:09:45,051 In the microscopic world 258 00:09:45,052 --> 00:09:47,099 Before a particle is measured 259 00:09:47,211 --> 00:09:49,379 It has no definite position or momentum 260 00:09:49,731 --> 00:09:52,258 It exists in a superposition of all possible states 261 00:09:52,611 --> 00:09:54,499 Only when you measure it 262 00:09:54,652 --> 00:09:57,739 Does it collapse from superposition into a definite value 263 00:09:58,211 --> 00:10:01,975 This is the famous measurement problem in quantum mechanics 264 00:10:02,568 --> 00:10:06,056 Now follow me back through the chain of reasoning 265 00:10:06,609 --> 00:10:08,655 Sound does not exist objectively 266 00:10:08,769 --> 00:10:10,375 It depends on someone hearing it 267 00:10:10,808 --> 00:10:12,807 Color does not exist objectively 268 00:10:12,808 --> 00:10:14,456 It depends on someone seeing it 269 00:10:14,969 --> 00:10:18,816 But the vibration of air molecules should be objective 270 00:10:19,048 --> 00:10:19,796 The problem is 271 00:10:20,288 --> 00:10:22,456 Molecules are made of atoms 272 00:10:22,568 --> 00:10:25,375 And atoms are made of more fundamental particles 273 00:10:25,489 --> 00:10:27,368 Yet those most fundamental particles 274 00:10:27,369 --> 00:10:28,515 Before they are observed 275 00:10:28,928 --> 00:10:30,855 Do not occupy definite states either 276 00:10:31,168 --> 00:10:32,456 So here is the question 277 00:10:33,369 --> 00:10:36,207 If even the particles making up air vibrations 278 00:10:36,208 --> 00:10:39,336 Need observation to possess definite physical properties 279 00:10:39,369 --> 00:10:41,567 Then does air vibration itself 280 00:10:41,568 --> 00:10:43,648 Without any observer present 281 00:10:43,648 --> 00:10:45,115 Actually count as existing 282 00:10:45,928 --> 00:10:48,416 I am not saying air vibration is unreal 283 00:10:48,808 --> 00:10:49,316 I am saying 284 00:10:49,688 --> 00:10:51,816 Perhaps we need to rethink 285 00:10:51,928 --> 00:10:55,456 What objective existence really means 286 00:10:56,009 --> 00:11:00,056 Perhaps objective existence is not all or nothing 287 00:11:00,089 --> 00:11:02,096 But a bottomless onion 288 00:11:02,369 --> 00:11:03,607 Each time you peel away one layer 289 00:11:03,609 --> 00:11:07,488 You find another layer dependent on an observer 290 00:11:07,962 --> 00:11:09,289 Twenty five hundred years ago 291 00:11:09,322 --> 00:11:11,641 When the Buddha discussed human perception 292 00:11:11,641 --> 00:11:14,009 He offered an extraordinarily precise framework 293 00:11:14,202 --> 00:11:17,529 We devoted an entire earlier episode to this framework 294 00:11:17,641 --> 00:11:19,689 He divided the sensory world into six groups 295 00:11:19,761 --> 00:11:21,328 Eye ear nose tongue body and mind 296 00:11:21,401 --> 00:11:23,568 Corresponding to form sound smell taste touch and mental objects 297 00:11:23,801 --> 00:11:25,429 Your ears receive the object of sound 298 00:11:25,722 --> 00:11:26,889 Giving rise to auditory consciousness 299 00:11:26,962 --> 00:11:29,289 Only then comes the experience of hearing sound 300 00:11:29,521 --> 00:11:30,889 The Buddhist insight is 301 00:11:30,921 --> 00:11:34,129 Sound is not an independent thing floating through the universe 302 00:11:34,401 --> 00:11:36,448 It arises through dependent conditions 303 00:11:36,641 --> 00:11:37,948 It requires vibrations in air 304 00:11:38,281 --> 00:11:39,488 It requires the faculty of hearing 305 00:11:39,521 --> 00:11:41,169 And it requires consciousness 306 00:11:41,202 --> 00:11:43,129 All three conditions are essential 307 00:11:43,241 --> 00:11:44,348 If any one is absent 308 00:11:44,602 --> 00:11:46,459 Sound does not exist 309 00:11:46,892 --> 00:11:48,059 Think about music 310 00:11:48,451 --> 00:11:51,219 Music may be the most extreme example of this question 311 00:11:51,411 --> 00:11:53,138 A Beethoven symphony 312 00:11:53,252 --> 00:11:54,738 From the standpoint of physics 313 00:11:54,852 --> 00:11:56,531 Is merely airwaves with different frequencies 314 00:11:56,531 --> 00:11:59,459 And different amplitudes superimposed 315 00:11:59,852 --> 00:12:01,559 But what you hear is sorrow 316 00:12:01,892 --> 00:12:02,898 Grandeur 317 00:12:03,012 --> 00:12:05,459 Something that brings tears to your eyes 318 00:12:05,972 --> 00:12:07,679 Is sorrow inside those air vibrations 319 00:12:08,372 --> 00:12:09,339 Obviously not 320 00:12:09,612 --> 00:12:13,059 Sorrow is meaning your consciousness gives those vibrations 321 00:12:13,291 --> 00:12:15,819 If the universe contained no sentient beings 322 00:12:16,132 --> 00:12:17,778 There would be not only no sound 323 00:12:17,892 --> 00:12:21,618 Music itself would never have existed at all 324 00:12:22,451 --> 00:12:24,378 Beethovens Ninth Symphony 325 00:12:24,411 --> 00:12:27,299 Represents a peak of human spiritual experience 326 00:12:27,372 --> 00:12:29,251 Yet in a purely physical universe 327 00:12:29,252 --> 00:12:31,066 Not even its shadow exists 328 00:12:31,298 --> 00:12:33,625 This is almost exactly what cognitive neuroscience 329 00:12:33,658 --> 00:12:36,666 Would say twenty five hundred years later 330 00:12:37,339 --> 00:12:38,725 A study published in 2021 331 00:12:39,139 --> 00:12:40,857 In the journal Scientific Reports 332 00:12:40,859 --> 00:12:42,706 Clearly showed 333 00:12:42,938 --> 00:12:46,505 That sound awareness requires more than vibrations of the eardrum 334 00:12:46,658 --> 00:12:48,378 It requires the auditory cortex 335 00:12:48,379 --> 00:12:51,346 Working with higher attention networks 336 00:12:51,578 --> 00:12:52,666 The researchers found 337 00:12:52,739 --> 00:12:56,625 That using spatially processed sounds with patients with disorders of consciousness 338 00:12:56,658 --> 00:13:00,186 Could significantly strengthen distinct brain responses 339 00:13:00,339 --> 00:13:02,586 This shows that the level of conscious participation 340 00:13:02,619 --> 00:13:03,566 Directly determines 341 00:13:03,898 --> 00:13:06,145 Whether a sound experience occurs and what it is like 342 00:13:07,019 --> 00:13:09,225 Sound waves can reach a persons eardrum 343 00:13:09,379 --> 00:13:11,177 But if consciousness does not participate 344 00:13:11,178 --> 00:13:12,286 There is no sound there 345 00:13:12,578 --> 00:13:13,522 Only vibration 346 00:13:13,835 --> 00:13:15,922 So let us return to the original question 347 00:13:16,235 --> 00:13:17,961 If there are no sentient beings 348 00:13:18,075 --> 00:13:19,422 Would sound exist in the universe 349 00:13:19,955 --> 00:13:22,001 If you mean vibrations in air 350 00:13:22,034 --> 00:13:23,762 Then perhaps the answer is yes 351 00:13:23,835 --> 00:13:26,241 As long as a physical process produces vibration 352 00:13:26,355 --> 00:13:28,841 But air vibration is not the same as sound 353 00:13:29,075 --> 00:13:31,341 If you mean pitch timbre 354 00:13:31,715 --> 00:13:33,741 Melody harmony and noise 355 00:13:34,115 --> 00:13:35,234 That moment late at night 356 00:13:35,235 --> 00:13:37,162 When you suddenly hear a loud bang 357 00:13:37,195 --> 00:13:39,081 And your heart skips a beat 358 00:13:39,154 --> 00:13:41,322 Then the answer is absolutely not 359 00:13:41,514 --> 00:13:43,394 These things were created only when 360 00:13:43,394 --> 00:13:45,682 The first life form with hearing appeared 361 00:13:45,715 --> 00:13:46,981 At that very moment 362 00:13:47,394 --> 00:13:49,274 And when the final life form 363 00:13:49,274 --> 00:13:51,422 With hearing disappears 364 00:13:51,794 --> 00:13:53,267 They will vanish completely 365 00:13:53,700 --> 00:13:55,907 But this is not the most astonishing part 366 00:13:56,141 --> 00:13:59,187 The most astonishing part comes when you push this logic further 367 00:13:59,580 --> 00:14:01,907 If sound needs a listener to exist 368 00:14:02,141 --> 00:14:04,348 Color needs a viewer to exist 369 00:14:04,541 --> 00:14:06,628 Smell needs someone to smell it 370 00:14:06,781 --> 00:14:08,948 And temperature needs someone to feel it 371 00:14:09,100 --> 00:14:11,868 Then after removing every capacity for perception 372 00:14:11,940 --> 00:14:14,540 From a universe with no sentient beings 373 00:14:14,541 --> 00:14:15,248 What remains 374 00:14:16,060 --> 00:14:16,807 You might say 375 00:14:17,381 --> 00:14:18,547 Mathematics remains 376 00:14:19,021 --> 00:14:20,267 The laws of physics remain 377 00:14:20,700 --> 00:14:23,147 Pure structures and relationships remain 378 00:14:23,580 --> 00:14:24,900 But this touches 379 00:14:24,901 --> 00:14:27,667 The deepest puzzle in physics and the philosophy of mathematics 380 00:14:28,580 --> 00:14:31,379 Are physical laws properties of the universe itself 381 00:14:31,381 --> 00:14:34,368 Or effective codes the human mind uses to describe it 382 00:14:35,141 --> 00:14:36,448 Is mathematics discovered 383 00:14:36,700 --> 00:14:37,728 Or invented 384 00:14:38,261 --> 00:14:40,828 If all sentient beings disappeared 385 00:14:40,860 --> 00:14:42,844 Would one plus one still equal two 386 00:14:43,417 --> 00:14:45,183 Let me offer one possible way to think about it 387 00:14:45,577 --> 00:14:46,803 But first I must be clear 388 00:14:47,177 --> 00:14:48,135 This is a conjecture 389 00:14:48,136 --> 00:14:49,063 Not a conclusion 390 00:14:49,376 --> 00:14:52,543 Perhaps this sound question remains unresolved after three centuries 391 00:14:52,616 --> 00:14:54,884 Because it points toward a more fundamental truth 392 00:14:55,456 --> 00:14:57,976 The universe is not a container that existed first 393 00:14:57,976 --> 00:15:01,583 With sentient beings later appearing inside it by chance to observe 394 00:15:01,817 --> 00:15:03,495 Perhaps the universe and the observer 395 00:15:03,496 --> 00:15:05,864 Have always formed an indivisible whole 396 00:15:06,096 --> 00:15:08,463 Perhaps perception is not an accessory to the universe 397 00:15:08,496 --> 00:15:11,957 But a necessary condition for the universe to become a universe 398 00:15:12,150 --> 00:15:15,558 Late in life physicist John Wheeler drew a famous diagram 399 00:15:15,711 --> 00:15:17,318 A large capital letter U 400 00:15:17,510 --> 00:15:19,877 One end was the beginning of the universe in the Big Bang 401 00:15:20,030 --> 00:15:22,470 And the other grew a giant eye 402 00:15:22,471 --> 00:15:24,158 Looking back toward that beginning 403 00:15:24,430 --> 00:15:25,909 What he meant was 404 00:15:25,910 --> 00:15:28,837 Observers participate in creating the history of the universe 405 00:15:29,310 --> 00:15:30,350 Without observers 406 00:15:30,351 --> 00:15:33,997 The past of the universe remains in an unresolved superposition 407 00:15:34,390 --> 00:15:35,949 It is not that the universe existed first 408 00:15:35,951 --> 00:15:38,798 And one day happened to grow ears that could hear 409 00:15:39,030 --> 00:15:42,357 The ear and the universe are two sides of the same event 410 00:15:42,670 --> 00:15:44,757 Sound is not an accessory to the universe 411 00:15:44,991 --> 00:15:48,095 Sound is one way the universe becomes aware of itself 412 00:15:48,608 --> 00:15:49,715 Have you ever considered this 413 00:15:50,248 --> 00:15:52,536 You have heard countless sounds in your life 414 00:15:52,728 --> 00:15:53,195 Wind 415 00:15:53,488 --> 00:15:53,955 Rain 416 00:15:54,288 --> 00:15:55,055 Birdsong 417 00:15:55,055 --> 00:15:55,849 Music 418 00:15:55,849 --> 00:15:57,296 The voices of loved ones 419 00:15:57,408 --> 00:16:00,055 A dog barking suddenly in the stillness of night 420 00:16:00,449 --> 00:16:01,756 Yet every one of these sounds 421 00:16:02,049 --> 00:16:03,016 Without exception 422 00:16:03,049 --> 00:16:05,016 Happens entirely within your consciousness 423 00:16:05,288 --> 00:16:08,896 You have never heard a sound outside your consciousness 424 00:16:09,248 --> 00:16:12,416 Not because your consciousness is too small to hold the outer world 425 00:16:12,648 --> 00:16:14,376 But because sound itself 426 00:16:14,569 --> 00:16:17,136 Can exist only within consciousness 427 00:16:17,449 --> 00:16:19,896 Whatever lies outside consciousness is not called sound 428 00:16:20,008 --> 00:16:20,975 It is called vibration 429 00:16:21,528 --> 00:16:22,475 And vibration itself 430 00:16:22,888 --> 00:16:24,577 Is silent 431 00:16:25,051 --> 00:16:27,817 This may be what the tree falling in the forest 432 00:16:27,890 --> 00:16:30,577 Has truly been asking us for three centuries 433 00:16:31,051 --> 00:16:32,697 It is not asking a question about acoustics 434 00:16:32,850 --> 00:16:34,738 It is asking about the nature of existence 435 00:16:34,970 --> 00:16:35,638 It is asking 436 00:16:36,051 --> 00:16:38,489 If you remove every perceiver 437 00:16:38,490 --> 00:16:40,978 From the equation of the universe 438 00:16:41,010 --> 00:16:42,758 What exactly have you removed 439 00:16:43,370 --> 00:16:45,778 Perhaps you have not removed a supporting character 440 00:16:46,010 --> 00:16:48,477 Perhaps you have removed the stage itself 441 00:16:48,631 --> 00:16:49,257 What do you think 442 00:16:49,751 --> 00:16:52,278 Can a universe with no sentient beings 443 00:16:52,310 --> 00:16:53,857 Still be called a universe 444 00:16:54,430 --> 00:16:56,558 I will not answer that question today 445 00:16:56,751 --> 00:16:57,497 Because honestly 446 00:16:57,790 --> 00:16:59,717 I have not figured it out myself 447 00:17:00,111 --> 00:17:01,357 But I have an intuition 448 00:17:01,471 --> 00:17:03,030 The ultimate answer to this question 449 00:17:03,030 --> 00:17:06,359 May be directly tied to the nature of consciousness 450 00:17:07,038 --> 00:17:07,900 And this thread of consciousness 451 00:17:08,111 --> 00:17:09,594 Is one we have only begun to pull 452 00:17:09,856 --> 00:17:10,449 I am Leo Wang 453 00:17:10,728 --> 00:17:11,696 See you next time