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These are the user uploaded subtitles that are being translated: 1 00:00:02,133 --> 00:00:05,367 Freeman: WE ALL FLOAT ALONG THE RIVER OF TIME. 2 00:00:05,367 --> 00:00:08,133 BUT DOES THAT RIVER HAVE A SOURCE? 3 00:00:09,400 --> 00:00:11,400 HOW WAS TIME UNLEASHED? 4 00:00:11,400 --> 00:00:16,667 SOME BELIEVE TIME FLOWS SMOOTHLY AND ETERNALLY. 5 00:00:16,667 --> 00:00:20,300 OTHERS SAY IT DOESN'T FLOW AT ALL -- 6 00:00:20,300 --> 00:00:23,667 IT POPS INTO EXISTENCE EVERY FRACTION OF A SECOND. 7 00:00:25,733 --> 00:00:28,967 THE FINEST MINDS IN PHYSICS CAN'T AGREE. 8 00:00:28,967 --> 00:00:32,033 BUT NEW EXPERIMENTS MAY HOLD THE ANSWER 9 00:00:32,033 --> 00:00:38,233 TO THE GREATEST UNSOLVED MYSTERY IN THE HISTORY OF THE UNIVERSE. 10 00:00:38,233 --> 00:00:39,333 THE MYSTERY... 11 00:00:39,333 --> 00:00:43,133 OF WHEN TIME BEGAN. 12 00:00:46,867 --> 00:00:48,433 SPACE... 13 00:00:48,433 --> 00:00:49,800 TIME... 14 00:00:49,800 --> 00:00:51,333 LIFE ITSELF. 15 00:00:53,833 --> 00:00:59,333 THE SECRETS OF THE COSMOS LIE THROUGH THE WORMHOLE. 16 00:00:59,333 --> 00:01:02,400 -- Captions by VITAC -- www.vitac.com 17 00:01:02,400 --> 00:01:05,433 CAPTIONS PAID FOR BY DISCOVERY COMMUNICATIONS 18 00:01:12,200 --> 00:01:14,767 WHEN WERE YOU BORN? 19 00:01:14,767 --> 00:01:16,867 SOUNDS LIKE A SIMPLE QUESTION. 20 00:01:16,867 --> 00:01:20,133 YOU JUST SAY A CERTAIN YEAR, A MONTH, AND DAY. 21 00:01:20,133 --> 00:01:23,733 BUT AROUND THE WORLD, WE RECKON TIME DIFFERENTLY. 22 00:01:23,733 --> 00:01:26,833 IN SAUDI ARABIA, IT'S THE 15th CENTURY. 23 00:01:26,833 --> 00:01:29,633 IN ISRAEL, IT'S THE 58th. 24 00:01:29,633 --> 00:01:33,433 AND WE LIVE IN 24 DIFFERENT TIME ZONES. 25 00:01:33,433 --> 00:01:37,433 WE ALL MEASURE TIME RELATIVE TO SOME STARTING POINT -- 26 00:01:37,433 --> 00:01:39,200 A POINT WE HAVE CHOSEN. 27 00:01:39,200 --> 00:01:42,567 BUT IF WE REALLY WANT TO KNOW WHAT TIME IT IS, 28 00:01:42,567 --> 00:01:47,233 WE NEED TO KNOW WHEN THE COSMIC CLOCK STARTED TO TICK. 29 00:01:47,233 --> 00:01:51,067 DID TIME BEGIN WHEN THE UNIVERSE BEGAN? 30 00:01:51,067 --> 00:01:55,767 OR DID IT START SOME OTHER WAY? 31 00:01:55,767 --> 00:01:57,733 [ BIRDS CHIRPING ] 32 00:01:57,733 --> 00:02:00,200 ONCE, I WAS IN A BIKE RACE. 33 00:02:00,200 --> 00:02:04,067 I WANTED TO IMPRESS SOME FRIENDS WITH MY TERRIFIC SPEED. 34 00:02:06,067 --> 00:02:10,300 SO I GAVE IT EVERYTHING I HAD. 35 00:02:10,300 --> 00:02:16,133 IT WAS A CLOSE RACE -- SO CLOSE, I THOUGHT IT WAS A TIE. 36 00:02:16,133 --> 00:02:19,867 ONE KID SAID MY OPPONENT WAS QUICKEST. 37 00:02:19,867 --> 00:02:22,933 BUT ANOTHER SAID I WAS FASTER. 38 00:02:22,933 --> 00:02:27,067 SO, WHOSE PERCEPTION OF TIME WAS CORRECT? 39 00:02:27,067 --> 00:02:32,667 IN A WAY, WE WERE ALL RIGHT. 40 00:02:32,667 --> 00:02:36,667 TIME IS A MEASURE OF CHANGE. 41 00:02:36,667 --> 00:02:39,200 [ CLOCK TICKING ] 42 00:02:39,200 --> 00:02:42,333 BUT HOW DO WE KNOW THINGS CHANGE? 43 00:02:42,333 --> 00:02:45,233 WE RELY ON WHAT OUR SENSES TELL US, 44 00:02:45,233 --> 00:02:48,600 AND PRIMARILY, WE RELY ON WHAT WE CAN SEE. 45 00:02:48,600 --> 00:02:51,667 WE RELY ON LIGHT. 46 00:02:51,667 --> 00:02:53,667 IN THE VACUUM OF SPACE, 47 00:02:53,667 --> 00:02:58,867 LIGHT TRAVELS AT A FIXED SPEED OF 186,000 MILES PER SECOND. 48 00:02:58,867 --> 00:03:04,900 THIS IS ACCEPTED AS AN ABSOLUTE TRUTH OF THE UNIVERSE. 49 00:03:04,900 --> 00:03:09,200 AND THAT, SAYS COSMOLOGIST JANNA LEVIN, 50 00:03:09,200 --> 00:03:13,333 GIVES LIGHT A UNIQUE RELATIONSHIP TO TIME. 51 00:03:13,333 --> 00:03:15,733 Levin: IT'S ACTUALLY COMPLETELY REMARKABLE 52 00:03:15,733 --> 00:03:17,967 THAT THE SPEED OF LIGHT IS AN ABSOLUTE. 53 00:03:17,967 --> 00:03:20,133 IT'S NEVER FASTER. IT'S NEVER SLOWER. 54 00:03:20,133 --> 00:03:22,533 TO UNDERSTAND THE RELATIVITY OF TIME, 55 00:03:22,533 --> 00:03:24,500 WE REALLY NEED TO UNDERSTAND LIGHT, 56 00:03:24,500 --> 00:03:26,933 AND ONCE WE START THINKING ABOUT THE NATURE OF LIGHT, 57 00:03:26,933 --> 00:03:30,233 ALL OF OUR FAMILIAR INTUITIONS ARE TURNED ON THEIR HEADS. 58 00:03:30,233 --> 00:03:34,200 Freeman: IF THE SPEED OF LIGHT IS CONSTANT, 59 00:03:34,200 --> 00:03:37,733 THEN TIME AND SPACE MUST SHIFT AND DISTORT 60 00:03:37,733 --> 00:03:42,200 DEPENDING ON YOUR PARTICULAR POINT OF VIEW. 61 00:03:42,200 --> 00:03:45,667 Levin: EINSTEIN HAD THIS VERY PROFOUND INSIGHT 62 00:03:45,667 --> 00:03:48,667 WHEN HE STARTED TO THINK ABOUT SOMETHING AS SIMPLE AS LIGHT, 63 00:03:48,667 --> 00:03:53,100 AND HE REALIZED THAT IF LIGHT WAS GOING TO BE THE SAME 64 00:03:53,100 --> 00:03:55,500 FOR EVERYBODY IN THE UNIVERSE 65 00:03:55,500 --> 00:03:57,500 REGARDLESS OF HOW FAST THEY WERE MOVING 66 00:03:57,500 --> 00:03:59,200 OR WHERE THEY WERE IN THE UNIVERSE, 67 00:03:59,200 --> 00:04:01,133 THEN SPACE AND TIME HAD TO BE DIFFERENT 68 00:04:01,133 --> 00:04:03,400 FOR DIFFERENT OBSERVERS. 69 00:04:03,400 --> 00:04:06,133 Freeman: THIS MEANS TIME IS VERY PERSONAL. 70 00:04:06,133 --> 00:04:10,833 IT DEPENDS ON WHERE YOU ARE AND HOW FAST YOU ARE MOVING. 71 00:04:10,833 --> 00:04:13,867 AND THE WAY YOU SEE YOUR MOVEMENT THROUGH TIME 72 00:04:13,867 --> 00:04:18,233 MAY NOT BE THE WAY OTHERS SEE YOUR MOVEMENT THROUGH TIME. 73 00:04:22,333 --> 00:04:26,100 SAY, FOR INSTANCE, JANNA HAS A DOPPELGANGER 74 00:04:26,100 --> 00:04:29,400 THAT RIDES THE SUBWAYS AND TAXIS OF NEW YORK. 75 00:04:29,400 --> 00:04:30,633 [ HORN HONKS ] 76 00:04:30,633 --> 00:04:34,400 IF JANNA'S DOPPELGANGER GETS IN A CAB 77 00:04:34,400 --> 00:04:36,933 AND THAT CAB TRAVELS AT INCREDIBLE SPEEDS... 78 00:04:36,933 --> 00:04:38,400 [ TIRES SQUEALING ] 79 00:04:40,233 --> 00:04:43,333 ...TIME WILL FLOW DIFFERENTLY FOR EACH WOMAN. 80 00:04:43,333 --> 00:04:46,767 Levin: IF SHE FLIES PAST ME IN A TAXI, 81 00:04:46,767 --> 00:04:50,433 IT WILL APPEAR TO ME THAT HER TIME IS RUNNING SLOWER. 82 00:04:50,433 --> 00:04:54,333 FROM MY DOPPELGANGER'S POINT OF VIEW, THE STREET WITH ME ON IT, 83 00:04:54,333 --> 00:04:56,733 WE'RE FLYING PAST HER IN THE OPPOSITE DIRECTION, 84 00:04:56,733 --> 00:04:58,900 AND AS FAR AS SHE'S CONCERNED, HER TIME IS NORMAL. 85 00:04:58,900 --> 00:05:02,167 IT'S MY TIME THAT'S RUNNING SLOW. 86 00:05:02,167 --> 00:05:06,700 Freeman: TO UNDERSTAND WHY THIS HAPPENS, 87 00:05:06,700 --> 00:05:10,467 IMAGINE JANNA TURNS ON A DOUBLE-SIDED LASER 88 00:05:10,467 --> 00:05:14,467 WHOSE PULSING BEAMS BOUNCE OFF THE SIDEWALK BELOW HER 89 00:05:14,467 --> 00:05:16,367 AND THE BALCONY ABOVE HER HEAD. 90 00:05:16,367 --> 00:05:19,533 THE PULSES FORM A LIGHT CLOCK. 91 00:05:19,533 --> 00:05:23,400 EACH BOUNCE OF THE LASER BEAM IS ONE TICK. 92 00:05:23,400 --> 00:05:26,133 JANNA SEES THE LIGHT GO STRAIGHT UP AND DOWN, 93 00:05:26,133 --> 00:05:31,733 BUT HER CAB-RIDING DOUBLE SEES SOMETHING QUITE DIFFERENT. 94 00:05:31,733 --> 00:05:33,500 Levin: FROM THE PERSPECTIVE OF THE CAB, 95 00:05:33,500 --> 00:05:37,333 THE LIGHT APPEARS TO TAKE A LONG DIAGONAL 96 00:05:37,333 --> 00:05:41,933 AND SO SEEMS AS THOUGH MY CLOCK IS TAKING TOO LONG TO TICK. 97 00:05:41,933 --> 00:05:44,400 SO IT SEEMS LIKE MY TIME IS RUNNING SLOW. 98 00:05:44,400 --> 00:05:48,500 Freeman: IF JANNA'S DOPPELGANGER TURNS ON THE LASER IN THE TAXI, 99 00:05:48,500 --> 00:05:51,900 SHE WILL SEE THE BEAM HITTING THE CEILING AND FLOOR 100 00:05:51,900 --> 00:05:54,067 RIGHT ABOVE AND BELOW HER. 101 00:05:54,067 --> 00:05:59,400 BUT THE JANNA ON THE STREET SEES THE BEAM MOVE DIAGONALLY. 102 00:05:59,400 --> 00:06:05,067 BECAUSE THE BEAM HAS LONGER TO TRAVEL, ITS TICK LOOKS SLOWER. 103 00:06:05,067 --> 00:06:06,800 FROM MY PERSPECTIVE ON THE STREET, 104 00:06:06,800 --> 00:06:08,200 IF I'M LOOKING INTO THE TAXI, 105 00:06:08,200 --> 00:06:10,967 I SEE THEIR LIGHT TAKE A LONG DIAGONAL, 106 00:06:10,967 --> 00:06:14,633 AND SO I THINK IT'S TAKING THEIR CLOCK TOO LONG TO TICK. 107 00:06:14,633 --> 00:06:17,500 FROM MY PERSPECTIVE, THEIR CLOCKS ARE RUNNING SLOW. 108 00:06:17,500 --> 00:06:18,767 [ WHIRRING ] 109 00:06:18,767 --> 00:06:23,467 Freeman: THE EFFECT INCREASES THE FASTER YOU GO. 110 00:06:23,467 --> 00:06:26,367 IF THE CAB APPROACHES THE SPEED OF LIGHT, 111 00:06:26,367 --> 00:06:28,700 THE SPEED LIMIT OF THE UNIVERSE, 112 00:06:28,700 --> 00:06:33,133 TIME OUTSIDE THE CAB APPEARS TO STAND STILL. 113 00:06:33,133 --> 00:06:36,300 IF THAT TAXI WAS TO FLY BY AT THE SPEED OF LIGHT, 114 00:06:36,300 --> 00:06:39,067 IT WOULD LOOK LIKE MY CLOCK WAS NEVER GOING TO TICK, 115 00:06:39,067 --> 00:06:42,633 LIKE MY TIME HAD STOOD STILL, LIKE TIME WAS FROZEN. 116 00:06:42,633 --> 00:06:45,867 Freeman: SO, WHICH OBSERVER IS CORRECT? 117 00:06:45,867 --> 00:06:48,533 THE JANNA WHO'S STANDING STILL? 118 00:06:48,533 --> 00:06:50,400 OR THE JANNA IN MOTION? 119 00:06:50,400 --> 00:06:53,533 Levin: MY DOPPELGANGER AND I JUST FUNDAMENTALLY DISAGREE 120 00:06:53,533 --> 00:06:54,867 ON THE PASSAGE OF TIME, 121 00:06:54,867 --> 00:06:56,133 AND IT'S TRUE. 122 00:06:56,133 --> 00:06:59,067 WE'RE BOTH RIGHT -- TIME IS RELATIVE. 123 00:06:59,067 --> 00:07:05,200 Freeman: RELATIVITY MEANS THAT THERE CAN BE NO SINGLE UNIVERSAL TIME. 124 00:07:05,200 --> 00:07:09,567 HOWEVER, THERE WAS ONE MOMENT WHEN ALL PERSPECTIVES ON TIME 125 00:07:09,567 --> 00:07:11,867 MUST HAVE BEEN THE SAME -- 126 00:07:11,867 --> 00:07:16,433 A MOMENT WHEN EVERYTHING EXISTED IN ONE SINGLE PLACE... 127 00:07:16,433 --> 00:07:18,733 THE BIG BANG. 128 00:07:18,733 --> 00:07:21,933 Levin: ONE OF THE HARDEST THINGS TO GRASP ABOUT THE IDEA 129 00:07:21,933 --> 00:07:24,733 OF THE BIG BANG AND THE CREATION OF THE UNIVERSE 130 00:07:24,733 --> 00:07:30,233 IS THE IDEA THAT TIME ITSELF MAY HAVE BEGUN IN THAT BIG EVENT, 131 00:07:30,233 --> 00:07:36,100 THAT SPACE WAS CREATED IN THE BIG BANG AND TIME BEGAN TO TICK. 132 00:07:36,100 --> 00:07:40,333 BEFORE OUR BIG BANG, THERE MIGHT NOT HAVE BEEN SPACE OR TIME. 133 00:07:40,333 --> 00:07:44,100 Freeman: JANNA BELIEVES THE BIG BANG WAS PROBABLY 134 00:07:44,100 --> 00:07:48,267 WHEN ALL THE VARIOUS TIME STREAMS IN THE UNIVERSE BEGAN 135 00:07:48,267 --> 00:07:51,867 AND THAT, SINCE THEN, TIME HAS PASSED DIFFERENTLY 136 00:07:51,867 --> 00:07:57,267 IN DIFFERENT PLACES DEPENDING ON HOW THOSE PLACES HAVE MOVED. 137 00:07:57,267 --> 00:08:00,067 BUT COULD WE CREATE PLACES IN OUR UNIVERSE 138 00:08:00,067 --> 00:08:06,267 WHERE TIME CAN APPEAR TO STOP AND THEN BEGIN AGAIN? 139 00:08:06,267 --> 00:08:09,133 IF WE COULD HIDE AN EVENT FROM LIGHT, 140 00:08:09,133 --> 00:08:11,767 COULD WE ALSO HIDE IT FROM TIME? 141 00:08:14,067 --> 00:08:16,067 THESE ARE QUESTIONS 142 00:08:16,067 --> 00:08:19,867 PROFESSOR ALEX GAETA ASKED HIMSELF. 143 00:08:19,867 --> 00:08:22,067 A FORMER COMPETITION-TENNIS PLAYER, 144 00:08:22,067 --> 00:08:24,733 ALEX IS A PHYSICIST AT CORNELL UNIVERSITY 145 00:08:24,733 --> 00:08:29,133 SPECIALIZING IN ULTRA-FAST OPTICS. 146 00:08:29,133 --> 00:08:31,633 THIS TECHNOLOGY IS USUALLY USED 147 00:08:31,633 --> 00:08:34,567 FOR HIGH-SPEED DATA TRANSMISSION. 148 00:08:34,567 --> 00:08:36,467 BUT AFTER READING A PAPER 149 00:08:36,467 --> 00:08:39,600 WRITTEN BY THEORISTS AT IMPERIAL COLLEGE, 150 00:08:39,600 --> 00:08:43,967 HE REALIZED IT COULD ALSO CREATE A GAP IN TIME. 151 00:08:43,967 --> 00:08:46,333 Gaeta: YOU KNOW, LIGHT IS AN ELECTROMAGNETIC DISTURBANCE. 152 00:08:46,333 --> 00:08:48,067 THE MINUTE THINGS START CHANGING, 153 00:08:48,067 --> 00:08:50,167 THAT'S AN INDICATION THAT TIME IS PASSING. 154 00:08:50,167 --> 00:08:52,733 SO ALL THESE CHANGES THAT ARE OCCURRING 155 00:08:52,733 --> 00:08:55,067 ARE CREATING ALL THESE ELECTROMAGNETIC DISTURBANCES 156 00:08:55,067 --> 00:08:59,500 THAT WE CAN DETECT AND MEASURE AS PASSAGE OF TIME. 157 00:08:59,500 --> 00:09:01,600 WHAT WE'VE FIGURED OUT IS A WAY 158 00:09:01,600 --> 00:09:04,667 OF ESSENTIALLY TURNING OFF THE LIGHTS, 159 00:09:04,667 --> 00:09:07,767 TURNING THEM BACK ON WITHOUT, YOU KNOW, 160 00:09:07,767 --> 00:09:11,100 YOU SENSING THAT THEY'VE EVER ACTUALLY BEEN TURNED OFF. 161 00:09:15,100 --> 00:09:17,833 Freeman: WHAT WOULD HAPPEN IF YOU TURNED OFF 162 00:09:17,833 --> 00:09:19,233 THE LIGHT SHINING ON TIME 163 00:09:19,233 --> 00:09:21,633 LONG ENOUGH TO HIDE AN EVENT? 164 00:09:21,633 --> 00:09:27,567 SAY, FOR INSTANCE, ALEX IS IN A CLOSE GAME WITH HIS SON, MAX. 165 00:09:27,567 --> 00:09:31,400 HE'S COMING UP TO MATCH POINT, AND HE WANTS TO WIN. 166 00:09:31,400 --> 00:09:35,700 IF ALEX COULD CREATE A HOLE IN TIME, 167 00:09:35,700 --> 00:09:37,867 NO ONE COULD SEE HIM DO THIS... 168 00:09:41,600 --> 00:09:47,733 TO OBSERVERS, INCLUDING HIS SON, ALEX WINS THE SET WITHOUT PAUSE. 169 00:09:47,733 --> 00:09:48,900 [ REWINDING ] 170 00:09:50,100 --> 00:09:53,900 RIGHT NOW, THIS IS IMPOSSIBLE. 171 00:09:53,900 --> 00:09:57,367 BUT ALL GREAT THINGS START SMALL. 172 00:10:00,167 --> 00:10:05,500 THIS IS THE KEY COMPONENT OF ALEX'S EXPERIMENT -- 173 00:10:05,500 --> 00:10:07,267 THE SPLIT-TIME LENS. 174 00:10:07,267 --> 00:10:08,367 [ MACHINERY BEEPS ] 175 00:10:08,367 --> 00:10:11,033 IT FOCUSES LIGHT SIGNALS AND TIME 176 00:10:11,033 --> 00:10:14,400 THE WAY A GLASS LENS FOCUSES LIGHT IN SPACE. 177 00:10:14,400 --> 00:10:18,033 IN A VACUUM, THE SPEED OF LIGHT IS CONSTANT, 178 00:10:18,033 --> 00:10:22,667 BUT THAT SPEED CHANGES WHEN LIGHT PASSES THROUGH A MATERIAL 179 00:10:22,667 --> 00:10:25,867 OR WHEN IT RUNS INTO ANOTHER LIGHT BEAM. 180 00:10:25,867 --> 00:10:30,267 ALEX'S SPLIT-TIME LENS USES BOTH TRICKS. 181 00:10:30,267 --> 00:10:34,400 ALEX SHOOTS A LASER INTO A BEAM OF LIGHT, 182 00:10:34,400 --> 00:10:37,133 SLOWING IT EVER SO SLIGHTLY. 183 00:10:37,133 --> 00:10:40,233 THE BEAM THEN PASSES THROUGH A GLASS FIBER 184 00:10:40,233 --> 00:10:42,400 WHERE IT SPLITS INTO TWO PARTS, 185 00:10:42,400 --> 00:10:44,733 EACH WITH A DIFFERENT WAVELENGTH. 186 00:10:44,733 --> 00:10:48,833 THE LOWER WAVELENGTH PULLS AHEAD OF THE HIGHER WAVELENGTH, 187 00:10:48,833 --> 00:10:51,500 LEAVING A GAP OF ABSOLUTE DARKNESS. 188 00:10:51,500 --> 00:10:55,433 ANYTHING WITHIN THAT GAP IS IMPOSSIBLE TO OBSERVE 189 00:10:55,433 --> 00:10:57,800 SINCE THERE IS NO LIGHT THERE. 190 00:10:57,800 --> 00:11:00,433 THE LIGHT THEN PASSES THROUGH ANOTHER TIME LENS 191 00:11:00,433 --> 00:11:04,233 THAT RE-UNIFIES THE BEAM WITH NO VISIBLE CHANGE. 192 00:11:08,833 --> 00:11:11,067 USING THIS DEVICE, 193 00:11:11,067 --> 00:11:16,500 ALEX HAS CREATED GAPS THAT LAST ALMOST A BILLIONTH OF A SECOND. 194 00:11:16,500 --> 00:11:18,400 THAT MAY NOT SOUND LIKE MUCH, 195 00:11:18,400 --> 00:11:21,800 BUT IN THE WORLD OF HIGH-SPEED INFORMATION TRANSFER, 196 00:11:21,800 --> 00:11:23,400 IT'S SIGNIFICANT. 197 00:11:23,400 --> 00:11:25,467 Gaeta: LET'S SAY YOU HAVE A DATA STREAM 198 00:11:25,467 --> 00:11:27,633 AND YOU DON'T WANT TO INTERRUPT IT AT ALL 199 00:11:27,633 --> 00:11:29,600 BUT YOU WANT TO PUT SOME INFORMATION 200 00:11:29,600 --> 00:11:30,733 INTO THAT DATA STREAM 201 00:11:30,733 --> 00:11:31,833 AND THEN TAKE IT OUT. 202 00:11:31,833 --> 00:11:33,933 SO, BY CREATING THIS GAP, 203 00:11:33,933 --> 00:11:37,067 YOU CAN CREATE THE GAP, NOT DISTURB THE LIGHT STREAM, 204 00:11:37,067 --> 00:11:39,467 INSERT A LITTLE BIT OF DATA, TRANSMIT IT, 205 00:11:39,467 --> 00:11:42,300 AND THEN LATER ON, PULL OUT THAT DATA 206 00:11:42,300 --> 00:11:45,533 AND THEN PUT THE DATA STREAM BACK TOGETHER. 207 00:11:45,533 --> 00:11:50,100 Freeman: AND THAT INFORMATION WOULD BE HIDDEN FROM THE PASSAGE OF TIME. 208 00:11:51,833 --> 00:11:57,200 TODAY, CREATING A LIGHT GAP THAT LASTS FOR ONE SECOND 209 00:11:57,200 --> 00:12:02,333 WOULD REQUIRE A MACHINE 186,000 MILES LONG. 210 00:12:02,333 --> 00:12:06,933 SO ALEX WILL HAVE TO WIN HIS TENNIS MATCHES THE HARD WAY. 211 00:12:06,933 --> 00:12:10,733 BUT THE TECHNOLOGY IS RAPIDLY EVOLVING. 212 00:12:10,733 --> 00:12:13,233 IN PRINCIPLE, THERE HAVE BEEN DEMONSTRATIONS 213 00:12:13,233 --> 00:12:16,300 WHERE THEY CAN SLOW DOWN LIGHT BY FACTORS OF 10 TO THE 7th, 214 00:12:16,300 --> 00:12:17,867 10 TO THE 8th. 215 00:12:17,867 --> 00:12:19,467 IN THE NEAR FUTURE, IT COULD BE EVEN MORE. 216 00:12:19,467 --> 00:12:21,867 YOU COULD ESSENTIALLY ALMOST STOP LIGHT, 217 00:12:21,867 --> 00:12:25,067 STORE LIGHT FOR RELATIVELY LONG PERIODS OF TIME, SECONDS, 218 00:12:25,067 --> 00:12:28,700 AND THEN ESSENTIALLY RELEASE IT TO TRAVEL, AGAIN, 219 00:12:28,700 --> 00:12:30,600 BACK AT THE SPEED OF LIGHT. 220 00:12:30,600 --> 00:12:34,967 ALEX AND JANNA'S WORK EXPLORES THE DEEP CONNECTION 221 00:12:34,967 --> 00:12:38,900 BETWEEN OBSERVERS, LIGHT, AND THE PASSAGE OF TIME. 222 00:12:38,900 --> 00:12:41,133 IT BEGS THE QUESTION, 223 00:12:41,133 --> 00:12:44,933 DOES TIME EXIST IF THERE IS NO ONE AROUND TO SEE IT? 224 00:12:44,933 --> 00:12:48,300 ONE SCIENTIST SAYS NO -- 225 00:12:48,300 --> 00:12:52,567 TIME BEGAN MUCH LATER THAN WE THINK. 226 00:12:59,800 --> 00:13:02,633 HOW OFTEN HAVE YOU WOKEN UP IN A DARKENED ROOM 227 00:13:02,633 --> 00:13:06,333 AND HAD NO IDEA WHAT TIME IT WAS? 228 00:13:06,333 --> 00:13:12,200 HAVE YOU BEEN OUT FOR MINUTES OR HOURS? 229 00:13:12,200 --> 00:13:17,433 WHEN YOU ARE SLEEPING, YOU HAVE NO SENSE THAT TIME IS PASSING. 230 00:13:17,433 --> 00:13:21,600 PERHAPS THE COSMOS EXPERIENCES TIME IN THE SAME WAY. 231 00:13:21,600 --> 00:13:24,767 THE BIG BANG WAS THE MOMENT OUR UNIVERSE WAS BORN, 232 00:13:24,767 --> 00:13:29,867 BUT WHAT IF IT DIDN'T WAKE UP RIGHT AWAY? 233 00:13:29,867 --> 00:13:35,400 COULD THERE HAVE BEEN A TIME WHEN THE UNIVERSE HAD NO TIME? 234 00:13:39,267 --> 00:13:42,667 PROFESSOR LARRY SCHULMAN IS A LITTLE OUT OF PLACE 235 00:13:42,667 --> 00:13:44,133 IN DRESDEN, GERMANY. 236 00:13:44,133 --> 00:13:47,700 HIS HOME BASE IS NEW YORK'S CLARKSON UNIVERSITY, 237 00:13:47,700 --> 00:13:51,100 WHICH OFTEN SITS UNDER A STATIC SHEET OF ICE. 238 00:13:51,100 --> 00:13:53,067 NOT SO DIFFERENT, LARRY SAYS, 239 00:13:53,067 --> 00:13:55,667 FROM THE STATE OF THE EARLY UNIVERSE, 240 00:13:55,667 --> 00:13:59,767 WHEN, HE CLAIMS, TIME DID NOT EXIST. 241 00:14:02,900 --> 00:14:05,900 LARRY EXPLORES THE BEHAVIOR OF SYSTEMS 242 00:14:05,900 --> 00:14:08,200 COMPOSED OF LARGE NUMBERS OF PARTICLES 243 00:14:08,200 --> 00:14:11,867 SUCH AS THE WATER IN THIS FOUNTAIN OR THE UNIVERSE. 244 00:14:11,867 --> 00:14:15,067 STATISTICAL MECHANICS CAN ALSO TELL US ABOUT 245 00:14:15,067 --> 00:14:17,600 THE RELATIONSHIP OF LIGHT TO TIME. 246 00:14:17,600 --> 00:14:19,067 [ BELL TOLLS ] 247 00:14:19,067 --> 00:14:21,267 LIGHT CARRIES INFORMATION ABOUT EVENTS. 248 00:14:21,267 --> 00:14:25,833 WE USE IT TO DETERMINE WHAT IS HAPPENING NOW. 249 00:14:25,833 --> 00:14:28,067 BUT BECAUSE LIGHT HAS A SPEED LIMIT, 250 00:14:28,067 --> 00:14:33,467 EVERYTHING WE SEE ACTUALLY TOOK PLACE IN THE PAST. 251 00:14:33,467 --> 00:14:36,667 Schulman: THE TIME IT WOULD TAKE, FOR EXAMPLE, FROM THE SUN 252 00:14:36,667 --> 00:14:39,267 IS ABOUT 8 MINUTES BECAUSE IT'S 93 MILLION MILES, 253 00:14:39,267 --> 00:14:42,433 AND YOU FIGURE WITH A VELOCITY OF 186,000 MILES PER SECOND, 254 00:14:42,433 --> 00:14:44,600 THAT'S HOW LONG THE LIGHT WOULD TAKE. 255 00:14:44,600 --> 00:14:47,633 SO, IF THE SUN WERE TO EXPLODE, FOR EXAMPLE, 256 00:14:47,633 --> 00:14:49,133 YOU WOULD NOT KNOW ABOUT IT 257 00:14:49,133 --> 00:14:53,200 UNTIL EIGHT MINUTES AFTER THE EVENT. 258 00:14:53,200 --> 00:14:55,833 Freeman: THE LIGHT OF THE MOST DISTANT PARTS OF THE UNIVERSE 259 00:14:55,833 --> 00:15:00,533 HAS BEEN TRAVELING TOWARD US FOR 13.8 BILLION YEARS. 260 00:15:00,533 --> 00:15:04,500 THIS IS WHEN THE UNIVERSE BEGAN IN THE BIG BANG. 261 00:15:08,900 --> 00:15:10,700 THE EARLY UNIVERSE WAS NOTHING 262 00:15:10,700 --> 00:15:12,867 BUT A FIELD OF CHARGED PARTICLES, 263 00:15:12,867 --> 00:15:16,367 A DENSE, HOT CLOUD OF PLASMA. 264 00:15:16,367 --> 00:15:18,733 PHOTONS, PARTICLES OF LIGHT, 265 00:15:18,733 --> 00:15:22,900 COULD NOT TRAVEL VERY FAR IN THIS SOUP. 266 00:15:22,900 --> 00:15:27,200 THEN ABOUT 380,000 YEARS INTO THE LIFE OF THE UNIVERSE, 267 00:15:27,200 --> 00:15:31,600 THERE WAS A SUDDEN CHANGE CALLED RECOMBINATION. 268 00:15:31,600 --> 00:15:35,067 THIS IS WHEN ATOMS BEGAN TO FORM. 269 00:15:35,067 --> 00:15:36,467 Schulman: PRIOR TO RECOMBINATION, 270 00:15:36,467 --> 00:15:37,867 IF AN ELECTRON AND A PROTON 271 00:15:37,867 --> 00:15:40,467 WOULD APPROACH AND BIND TEMPORARILY, 272 00:15:40,467 --> 00:15:43,233 THEY WOULD BE WHACKED BY A PHOTON COMING ALONG 273 00:15:43,233 --> 00:15:44,533 AND BE KNOCKED APART. 274 00:15:44,533 --> 00:15:47,067 RECOMBINATION IS A PROCESS 275 00:15:47,067 --> 00:15:49,200 IN WHICH THE ELECTRONS AND THE PROTONS, 276 00:15:49,200 --> 00:15:50,633 WHICH WERE PREVIOUSLY LOOSE 277 00:15:50,633 --> 00:15:53,067 AND SEPARATED FROM EACH OTHER IN THE PLASMA, 278 00:15:53,067 --> 00:15:56,733 FINALLY CAN GET TOGETHER. 279 00:15:56,733 --> 00:16:01,567 Freeman: IT'S A BIT LIKE HOCKEY. 280 00:16:01,567 --> 00:16:05,833 IF YOU IMAGINE THE HOCKEY PUCK IS A PHOTON. 281 00:16:05,833 --> 00:16:11,733 THIS IS THE RIVER ELBE, AND SOMETIMES IT FREEZES OVER. 282 00:16:11,733 --> 00:16:13,500 SUPPOSING I WOULD WAIT FOR THAT 283 00:16:13,500 --> 00:16:15,767 AND GO OUT THERE WITH MY HOCKEY PUCK, 284 00:16:15,767 --> 00:16:18,833 I COULD KNOCK IT TO THE BANK WITH NO PROBLEM. 285 00:16:18,833 --> 00:16:22,467 Freeman: BUT THE UNIVERSE JUST AFTER THE BIG BANG WAS FULL OF OBSTACLES. 286 00:16:22,467 --> 00:16:27,167 Schulman: NOW SUPPOSE THAT SURROUNDING ME WERE A BUNCH OF GOALIES 287 00:16:27,167 --> 00:16:28,667 NOT PROTECTING A GOAL, 288 00:16:28,667 --> 00:16:31,867 BUT JUST MAKING SURE THAT MY HOCKEY PUCK DIDN'T PASS THEM. 289 00:16:31,867 --> 00:16:34,233 SO ALL THESE GOALIES ARE STANDING AROUND, 290 00:16:34,233 --> 00:16:37,167 AND EVERY TIME I HIT THE PUCK, ONE OF THEM STOPS IT. 291 00:16:37,167 --> 00:16:39,067 THIS PUCK IS NOT GONNA GET THROUGH. 292 00:16:39,067 --> 00:16:43,067 Freeman: THIS, LARRY SAYS, IS THE EARLY UNIVERSE. 293 00:16:43,067 --> 00:16:46,933 PHOTON PUCKS COULDN'T GET PAST THE ELECTRON AND PROTON GOALIES, 294 00:16:46,933 --> 00:16:50,467 SO LIGHT DIDN'T FLOW. 295 00:16:50,467 --> 00:16:54,067 Schulman: ON THE OTHER HAND, THESE GOALIES ARE A LITTLE BIT UNUSUAL, 296 00:16:54,067 --> 00:16:56,067 AND THEY ALTERNATE BOY, GIRL, BOY, GIRL, 297 00:16:56,067 --> 00:16:58,900 BUT AT FIRST, THEY DIDN'T KNOW THAT BECAUSE OF THEIR BIG MASKS. 298 00:16:58,900 --> 00:17:01,367 AFTER A WHILE, ONE OF THEM REMOVES THE MASK, 299 00:17:01,367 --> 00:17:03,467 AND THE GUY NEXT TO HER SAYS, "OH." 300 00:17:03,467 --> 00:17:04,733 HMM. 301 00:17:04,733 --> 00:17:07,167 THEN THE PUCK CAN GET RIGHT THROUGH. 302 00:17:07,167 --> 00:17:09,667 ONCE THE PHOTONS COULD ESCAPE EASILY, 303 00:17:09,667 --> 00:17:11,733 THE WORLD CHANGED DRAMATICALLY. 304 00:17:11,733 --> 00:17:13,233 [ CHUCKLES ] 305 00:17:14,633 --> 00:17:19,133 IN THE EARLY UNIVERSE, PHOTONS COULD NEVER MOVE FREELY, 306 00:17:19,133 --> 00:17:21,600 AND THERE WAS NO WAY TO MEASURE CHANGE. 307 00:17:21,600 --> 00:17:26,467 LARRY ARGUES, THAT MEANS TIME DID NOT EXIST. 308 00:17:26,467 --> 00:17:29,100 ONLY AFTER RECOMBINATION, 309 00:17:29,100 --> 00:17:32,367 WHEN THE UNIVERSE COOLED AND ATOMS FORMED, 310 00:17:32,367 --> 00:17:35,300 DID LIGHT BEGIN TO MOVE AROUND FREELY. 311 00:17:35,300 --> 00:17:41,233 THAT, SAYS LARRY, IS WHEN THE UNIVERSE'S CLOCK BEGAN TO TICK. 312 00:17:41,233 --> 00:17:44,900 THE VERY EARLIEST POINT, THERE'S NEVER EVEN A TIME. 313 00:17:44,900 --> 00:17:47,267 BUT EVENTUALLY, THERE WAS SOMETHING CALLED TIME, 314 00:17:47,267 --> 00:17:50,733 WHICH WAS KEEPING TRACK OF THE WAY THINGS CHANGED. 315 00:17:50,733 --> 00:17:52,067 [ BELL RINGS ] 316 00:17:52,067 --> 00:17:54,967 THIS COULD EXPLAIN THE BIRTH OF TIME IN OUR UNIVERSE. 317 00:17:56,600 --> 00:18:03,200 BUT IF OUR UNIVERSE ENDS, WILL TIME DIE WITH IT? 318 00:18:03,200 --> 00:18:07,933 THIS PHYSICIST THINKS TIME IS TRULY FUNDAMENTAL -- 319 00:18:07,933 --> 00:18:09,867 TIME IS ALWAYS HERE. 320 00:18:09,867 --> 00:18:12,567 IT IS SPACE THAT COMES AND GOES. 321 00:18:16,067 --> 00:18:21,067 TIME MOVES FORWARD, NEVER BACKWARD. 322 00:18:21,067 --> 00:18:26,100 PHYSICISTS SAY THAT IS BECAUSE ENERGY ALWAYS DISSIPATES. 323 00:18:27,933 --> 00:18:30,300 IF YOU WIND TIME BACK FAR ENOUGH, 324 00:18:30,300 --> 00:18:35,533 YOU WOULD SEE THE ENTIRE ENERGY OF THE UNIVERSE COMING TOGETHER. 325 00:18:35,533 --> 00:18:40,700 AT THE BIG BANG, EVERYTHING IS FOCUSED ON A SINGLE POINT. 326 00:18:40,700 --> 00:18:44,933 YOU CAN'T WIND TIME BACK ANY MORE THAN THIS. 327 00:18:44,933 --> 00:18:47,200 OR CAN YOU? 328 00:18:47,200 --> 00:18:51,100 PHYSICIST SEAN CARROLL 329 00:18:51,100 --> 00:18:53,567 OF THE CALIFORNIA INSTITUTE OF TECHNOLOGY 330 00:18:53,567 --> 00:18:56,767 HAS SPENT MUCH OF HIS CAREER CONTEMPLATING TIME. 331 00:18:56,767 --> 00:19:00,767 THOUGH THE ORIGIN OF TIME IS A MYSTERY, 332 00:19:00,767 --> 00:19:03,067 SEAN IS CERTAIN OF ONE THING -- 333 00:19:03,067 --> 00:19:07,833 IN OUR UNIVERSE, TIME HAS A DIRECTION, 334 00:19:07,833 --> 00:19:11,400 AN ARROW THAT RUNS THROUGH EVERYTHING. 335 00:19:11,400 --> 00:19:17,300 TIME IS A MEASURE OF CHANGE IN THE UNIVERSE. 336 00:19:17,300 --> 00:19:19,467 IF NOTHING WERE CHANGING IN THE WORLD, 337 00:19:19,467 --> 00:19:21,700 THERE'D BE NO WAY OF KNOWING THAT TIME WAS PASSING. 338 00:19:21,700 --> 00:19:23,800 EVERYTHING WOULD BE THE SAME AT EVERY SINGLE MOMENT. 339 00:19:23,800 --> 00:19:24,933 THERE'D BE NO CLOCKS. 340 00:19:24,933 --> 00:19:27,067 TIME ITSELF WOULD BASICALLY HAVE NO MEANING. 341 00:19:27,067 --> 00:19:28,567 [ ARROW WHOOSHES ] 342 00:19:31,133 --> 00:19:34,667 Freeman: AS LONG AS SOMETHING IS CHANGING, NO MATTER HOW SMALL, 343 00:19:34,667 --> 00:19:37,233 TIME IS FLOWING. 344 00:19:37,233 --> 00:19:42,100 AND OUR UNIVERSE IS IN A CONSTANT STATE OF CHANGE. 345 00:19:42,100 --> 00:19:44,067 AT THE DAWN OF THE UNIVERSE, 346 00:19:44,067 --> 00:19:48,900 AN ENORMOUS AMOUNT OF ENERGY WAS COMPRESSED INTO A SINGLE POINT. 347 00:19:48,900 --> 00:19:50,867 THEN CAME THE BIG BANG. 348 00:19:52,233 --> 00:19:55,333 SINCE THEN, WITH EVERY PASSING SECOND, 349 00:19:55,333 --> 00:19:58,867 THAT ENERGY HAS BECOME MORE AND MORE SPREAD OUT. 350 00:19:58,867 --> 00:20:03,900 THE MEASURE OF THAT SPREADING OF ENERGY IS CALLED ENTROPY. 351 00:20:03,900 --> 00:20:08,767 SEAN BELIEVES THE FORWARD MOVEMENT OF TIME, TIME'S ARROW, 352 00:20:08,767 --> 00:20:13,667 IS THE STEADY MOVEMENT FROM LOW ENTROPY TO HIGH ENTROPY. 353 00:20:13,667 --> 00:20:17,933 BUT WHAT SET TIME'S ARROW IN MOTION? 354 00:20:17,933 --> 00:20:19,733 Carroll: THE PUZZLE THAT WE HAVE 355 00:20:19,733 --> 00:20:21,600 IS THAT ENTROPY TENDS TO INCREASE, 356 00:20:21,600 --> 00:20:24,567 BUT OUR BIG BANG WAS A CONDITION OF VERY, VERY LOW ENTROPY, 357 00:20:24,567 --> 00:20:27,000 SO HOW DID IT GET THAT WAY? 358 00:20:27,000 --> 00:20:28,833 WHERE COULD IT HAVE COME FROM? 359 00:20:28,833 --> 00:20:33,467 EVERYTHING WE KNOW IN PHYSICS IS THINGS INCREASING IN ENTROPY. 360 00:20:33,467 --> 00:20:35,100 SO IF YOU GO BACK TO THE BIG BANG, 361 00:20:35,100 --> 00:20:38,633 THERE WAS NO LOWER ENTROPY PLACE IT COULD'VE COME FROM. 362 00:20:38,633 --> 00:20:41,467 Freeman: SEAN SUSPECTS THE ANSWER 363 00:20:41,467 --> 00:20:46,133 IS THAT OUR UNIVERSE IS THE CHILD OF ANOTHER UNIVERSE. 364 00:20:46,133 --> 00:20:48,967 BUT WHAT WAS THAT UNIVERSE LIKE? 365 00:20:48,967 --> 00:20:51,233 MAYBE LIKE THIS... 366 00:20:51,233 --> 00:20:53,533 IMAGINE A UNIVERSE THAT'S IN EQUILIBRIUM. 367 00:20:53,533 --> 00:20:56,233 IT'S IN A HIGH-ENTROPY STATE. IT'S EMPTIED OUT. 368 00:20:56,233 --> 00:20:57,800 IT'S JUST SITTING THERE QUIETLY, 369 00:20:57,800 --> 00:20:59,600 MUCH LIKE THE WATER IN THIS TANK. 370 00:20:59,600 --> 00:21:02,633 YOU DON'T SEE ANY MOTION. 371 00:21:02,633 --> 00:21:04,967 Freeman: NOW IMAGINE IN THIS UNIVERSE 372 00:21:04,967 --> 00:21:07,200 WHERE ALL THE ENERGY IS DISSIPATED, 373 00:21:07,200 --> 00:21:11,767 SUDDENLY AN AREA OF DENSE ENERGY POPS INTO EXISTENCE, 374 00:21:11,767 --> 00:21:15,900 MUCH LIKE THIS BAG OF EFFERVESCENT TABLETS. 375 00:21:15,900 --> 00:21:18,767 Carroll: THE SELTZER STARTS SMALL AND DENSE AND LOW ENTROPY 376 00:21:18,767 --> 00:21:22,333 JUST LIKE OUR UNIVERSE DID NEAR THE BIG BANG, 377 00:21:22,333 --> 00:21:25,533 BUT THEN WE EXPANDED AND COOLED, GALAXIES FORMED, 378 00:21:25,533 --> 00:21:29,633 AND THE ARROW OF TIME PROGRESSES FROM PAST TO FUTURE. 379 00:21:29,633 --> 00:21:32,467 LIKEWISE, THE SELTZER FIZZES AND BECOMES HIGHER ENTROPY 380 00:21:32,467 --> 00:21:35,367 AS IT MIXES WITH THE WATER AROUND IT. 381 00:21:35,367 --> 00:21:37,700 AND EVENTUALLY, JUST LIKE OUR UNIVERSE 382 00:21:37,700 --> 00:21:39,367 WILL COME BACK TO EQUILIBRIUM 383 00:21:39,367 --> 00:21:41,433 AND THE ARROW OF TIME WILL CEASE, 384 00:21:41,433 --> 00:21:43,067 THE SELTZER REACHES EQUILIBRIUM 385 00:21:43,067 --> 00:21:44,967 BY MIXING WITH THE WATER AROUND IT, 386 00:21:44,967 --> 00:21:47,767 AND WE'RE BACK TO A STATE THAT DOESN'T CHANGE ANYMORE, 387 00:21:47,767 --> 00:21:50,500 A STATE WITHOUT ANY ARROW OF TIME. 388 00:21:50,500 --> 00:21:53,533 Freeman: BUT HOW COULD A DEAD UNIVERSE, 389 00:21:53,533 --> 00:21:56,700 ONE WITH NO LIFE, STARS, OR SOLID MATTER, 390 00:21:56,700 --> 00:22:01,967 GIVE BIRTH TO ANOTHER UNIVERSE? 391 00:22:01,967 --> 00:22:05,900 ACCORDING TO QUANTUM PHYSICS, EVEN AN EMPTY VOID 392 00:22:05,900 --> 00:22:09,567 WILL EXPERIENCE TINY FLUCTUATIONS OF ENERGY. 393 00:22:09,567 --> 00:22:13,267 THIS MEANS THAT EVERY ONCE IN A WHILE, 394 00:22:13,267 --> 00:22:16,600 SOMETHING CAN POP OUT OF NOTHING. 395 00:22:16,600 --> 00:22:20,067 THINK ABOUT THE ATOMIC NUCLEUS OF A RADIOACTIVE ELEMENT. 396 00:22:20,067 --> 00:22:22,433 IT JUST SITS THERE. YOU LOOK AT IT. 397 00:22:22,433 --> 00:22:24,833 IT'S NOT CHANGING AS YOU LOOK AT IT, 398 00:22:24,833 --> 00:22:28,200 BUT THERE IS A POSSIBILITY EVERY SECOND THAT IT WILL DECAY, 399 00:22:28,200 --> 00:22:30,500 THAT IT WILL SPIT OUT A NEW PARTICLE. 400 00:22:30,500 --> 00:22:32,967 WHAT WE'RE SAYING IS THAT SPACE-TIME ITSELF 401 00:22:32,967 --> 00:22:35,367 CAN BE RADIOACTIVE JUST LIKE THAT NUCLEUS, 402 00:22:35,367 --> 00:22:38,267 EXCEPT INSTEAD OF SPITTING OUT A NEW PARTICLE, 403 00:22:38,267 --> 00:22:41,567 IT CAN SPIT OUT AN ENTIRELY NEW UNIVERSE. 404 00:22:41,567 --> 00:22:48,533 Freeman: NEW UNIVERSES MAY CONSTANTLY BE POPPING INTO EXISTENCE. 405 00:22:48,533 --> 00:22:52,433 [ POPCORN POPS ] 406 00:22:52,433 --> 00:22:56,367 A RANDOM QUANTUM FLUCTUATION IN AN ANCIENT UNIVERSE -- 407 00:22:56,367 --> 00:22:59,667 A UNIVERSE SO OLD, TIME FELL APART -- 408 00:22:59,667 --> 00:23:04,733 MIGHT EVEN HAVE GIVEN BIRTH TO OUR UNIVERSE. 409 00:23:04,733 --> 00:23:07,433 THIS PROCESS OF STARTING WITH NO ARROW OF TIME, 410 00:23:07,433 --> 00:23:10,100 BUDDING OFF A NEW UNIVERSE, HAVING AN ARROW, 411 00:23:10,100 --> 00:23:12,300 AND THE ARROW ONLY LASTS FOR A LITTLE WHILE 412 00:23:12,300 --> 00:23:14,133 AS THAT UNIVERSE EXPANDS AND COOLS, 413 00:23:14,133 --> 00:23:16,667 BUT ONCE IT REACHES EQUILIBRIUM, THE ARROW STOPS -- 414 00:23:16,667 --> 00:23:19,067 THIS COULD HAPPEN MANY, MANY, MANY, MANY TIMES. 415 00:23:19,067 --> 00:23:20,233 LET'S PUT IT THAT WAY -- 416 00:23:20,233 --> 00:23:22,067 MAYBE AN INFINITE NUMBER OF TIMES, 417 00:23:22,067 --> 00:23:24,367 BUT CERTAINLY A VERY, VERY LARGE NUMBER, 418 00:23:24,367 --> 00:23:27,067 SO IT'S POSSIBLE THAT THE UNIVERSE WE CAME FROM 419 00:23:27,067 --> 00:23:29,867 WAS NOWHERE NEAR THE FIRST. 420 00:23:29,867 --> 00:23:36,600 OUR BIG BANG MIGHT NOT HAVE BEEN THE BEGINNING. 421 00:23:36,600 --> 00:23:41,767 OUR COSMOS' TIME COULD HAVE ANCESTORS THAT PREDATED IT 422 00:23:41,767 --> 00:23:46,133 AND DESCENDENTS AFTER THIS UNIVERSE IS GONE. 423 00:23:46,133 --> 00:23:50,267 BUT THERE MAY BE AN EVEN DEEPER TRUTH ABOUT TIME, 424 00:23:50,267 --> 00:23:52,567 A TRUTH WE WILL NEVER LEARN 425 00:23:52,567 --> 00:23:57,667 UNTIL WE ACCEPT THAT IT DOESN'T REALLY EXIST. 426 00:24:06,367 --> 00:24:09,300 [ WATCH TICKING ] 427 00:24:09,300 --> 00:24:11,933 WHAT WOULD WE DO WITHOUT TIME? 428 00:24:11,933 --> 00:24:16,367 HOW COULD WE KEEP TRACK OF THE EVENTS IN OUR LIVES 429 00:24:16,367 --> 00:24:21,067 WITHOUT THE STEADY PULSE OF MINUTES, DAYS, AND YEARS? 430 00:24:21,067 --> 00:24:25,500 BUT IT MAY BE THAT NONE OF THAT IS REAL. 431 00:24:25,500 --> 00:24:28,933 IT MAY BE THAT TIME 432 00:24:28,933 --> 00:24:31,333 IS NOTHING MORE THAN A MIRAGE. [ TICKING STOPS ] 433 00:24:38,133 --> 00:24:39,933 THIS IS THE BELIEF 434 00:24:39,933 --> 00:24:44,133 HELD BY THEORETICAL PHYSICIST CARLO ROVELLI. 435 00:24:44,133 --> 00:24:46,367 AS A STUDENT IN HIS NATIVE ITALY, 436 00:24:46,367 --> 00:24:48,333 CARLO WAS ON THE BARRICADES, 437 00:24:48,333 --> 00:24:51,767 FIGHTING AGAINST THE RESURGENT FASCIST MOVEMENT. 438 00:24:51,767 --> 00:24:54,133 Rovelli: I WAS YOUNG IN THE '70s, 439 00:24:54,133 --> 00:24:57,533 AND THERE WAS THE BIG DREAM OF CHANGING THE WORLD. 440 00:24:57,533 --> 00:25:00,300 WE FAILED. WE DIDN'T CHANGE THE WORLD. 441 00:25:00,300 --> 00:25:02,933 AND SO I THINK I MOVED INTO SCIENCE 442 00:25:02,933 --> 00:25:05,767 BECAUSE I THOUGHT IT WAS ANOTHER WAY OF CHANGING THE WORLD, 443 00:25:05,767 --> 00:25:08,067 AND PERHAPS I COULD BE MORE SUCCESSFUL THERE. 444 00:25:08,067 --> 00:25:13,067 CARLO LEAVES THE CENTRE DE PHYSIQUE THéORIQUE DE LUMINY, 445 00:25:13,067 --> 00:25:15,767 A THINK TANK IN THE SOUTH OF FRANCE. 446 00:25:15,767 --> 00:25:19,367 BUT HE'S STILL BREAKING THE RULES. 447 00:25:19,367 --> 00:25:23,267 AS THE LEADING VOICE OF THE THEORY OF THERMAL TIME, 448 00:25:23,267 --> 00:25:26,933 HE IS RAISING THE BANNER FOR A PARADIGM SHIFT 449 00:25:26,933 --> 00:25:28,800 IN FUNDAMENTAL PHYSICS. 450 00:25:28,800 --> 00:25:30,200 IN A NUTSHELL, 451 00:25:30,200 --> 00:25:34,900 THERMAL TIME PROPOSES THAT TIME DOES NOT EXIST -- 452 00:25:34,900 --> 00:25:38,600 AT LEAST NOT AT THE FUNDAMENTAL LEVEL OF REALITY. 453 00:25:38,600 --> 00:25:41,300 Rovelli: THE IDEA THAT THERE'S NO TIME ON THE FUNDAMENTAL LEVEL 454 00:25:41,300 --> 00:25:42,700 IS NOT SO COMPLICATED AFTER ALL. 455 00:25:42,700 --> 00:25:44,467 LET ME GIVE YOU AN EXAMPLE. 456 00:25:44,467 --> 00:25:46,700 IMAGINE THAT YOU DESCRIBE SOMETHING HAPPENING IN TIME, 457 00:25:46,700 --> 00:25:49,067 LIKE THIS IS OSCILLATING IN TIME. 458 00:25:49,067 --> 00:25:50,067 WHAT DO WE MEAN? 459 00:25:50,067 --> 00:25:51,467 WE MEAN THAT THERE IS SOMETHING 460 00:25:51,467 --> 00:25:52,933 THAT MOVES WITH RESPECT TO TIME. 461 00:25:52,933 --> 00:25:54,067 BUT WHAT IS TIME? 462 00:25:54,067 --> 00:25:56,800 TIME IS THE POSITION OF THE HAND. 463 00:25:56,800 --> 00:25:59,200 SO WHAT WE ARE REALLY OBSERVING HERE, 464 00:25:59,200 --> 00:26:02,600 WHAT WE'RE REALLY DOING HERE IS COMPARING THIS MOVEMENT 465 00:26:02,600 --> 00:26:04,867 WITH THE MOVEMENT OF THE HANDS OF THE CLOCK. 466 00:26:04,867 --> 00:26:07,867 SO WE DESCRIBE HOW THE HAND'S CHANGING TIME, 467 00:26:07,867 --> 00:26:10,933 BUT WHAT WE REALLY SEE IS JUST HOW THIS ANGLE 468 00:26:10,933 --> 00:26:13,100 CHANGES WITH RESPECT TO THIS ANGLE. 469 00:26:13,100 --> 00:26:16,167 SO, DO WITHOUT TIME MEANS JUST TO DESCRIBE THE WORLD 470 00:26:16,167 --> 00:26:19,067 IN TERMS OF THE WAY THE VARIOUS VARIABLES CHANGE 471 00:26:19,067 --> 00:26:20,667 WITH RESPECT TO ONE ANOTHER 472 00:26:20,667 --> 00:26:24,400 WITHOUT EVER HAVING TO BRINGING THIS UNOBSERVABLE TIME 473 00:26:24,400 --> 00:26:25,933 INTO THE PICTURE. 474 00:26:29,600 --> 00:26:33,967 Freeman: ISAAC NEWTON INTRODUCED THE IDEA OF A VARIABLE, "T" FOR "TIME," 475 00:26:33,967 --> 00:26:38,233 TO DESCRIBE HOW OBJECTS MOVE. 476 00:26:38,233 --> 00:26:40,833 BUT QUANTUM PHYSICS TREATS TIME DIFFERENTLY 477 00:26:40,833 --> 00:26:43,333 THAN NEWTON'S CLASSICAL SYSTEM. 478 00:26:43,333 --> 00:26:45,767 IN FACT, AT THE PLANCK SCALE, 479 00:26:45,767 --> 00:26:48,467 THE SMALLEST UNIT OF THE PHYSICAL WORLD, 480 00:26:48,467 --> 00:26:52,300 TIME VARIABLES SIMPLY DON'T WORK. 481 00:26:52,300 --> 00:26:55,533 CARLO THINKS THE ONLY WAY TO RESOLVE THIS CONTRADICTION 482 00:26:55,533 --> 00:27:00,300 IS TO GO BACK BEFORE NEWTON AND GET RID OF THE VARIABLE "T." 483 00:27:00,300 --> 00:27:04,467 HE HAS COMPLETELY REFORMULATED QUANTUM THEORY 484 00:27:04,467 --> 00:27:06,700 WITHOUT THE USE OF TIME. 485 00:27:06,700 --> 00:27:10,167 BUT THAT'S JUST THE BEGINNING. 486 00:27:10,167 --> 00:27:12,967 THE INTERESTING PART IS ACTUALLY THE SECOND PART 487 00:27:12,967 --> 00:27:14,633 BECAUSE IF WE ACCEPT THE IDEA 488 00:27:14,633 --> 00:27:17,300 THAT THERE'S NO TIME ON THE FUNDAMENTAL LEVEL, 489 00:27:17,300 --> 00:27:19,467 NEVERTHELESS WE DO EXPERIENCE TIME. 490 00:27:19,467 --> 00:27:22,067 TIME PASSES FOR US, RIGHT? WE LIVE IN TIME. 491 00:27:22,067 --> 00:27:25,767 SO WHERE DOES THIS TIME EXPERIENCE COME FROM? 492 00:27:27,667 --> 00:27:29,267 [ ENGINE TURNS OVER ] 493 00:27:29,267 --> 00:27:31,067 [ ENGINE REVVING ] 494 00:27:31,067 --> 00:27:35,167 Freeman: THE ANSWER, CARLO THINKS, IS HEAT. 495 00:27:35,167 --> 00:27:37,400 WHEN YOU ADD HEAT TO MATTER, 496 00:27:37,400 --> 00:27:40,867 IRREVERSIBLE PROCESSES BEGIN TO TAKE PLACE, 497 00:27:40,867 --> 00:27:43,700 EVENTS THAT CAN'T BE UNDONE. 498 00:27:43,700 --> 00:27:47,600 THINGS BEGIN TO CHANGE IN TIME. 499 00:27:47,600 --> 00:27:51,867 Rovelli: SO, EVERY TIME THERE IS SOME LACK OF REVERSIBILITY IN TIME, 500 00:27:51,867 --> 00:27:52,967 THERE'S HEAT. 501 00:27:52,967 --> 00:27:55,533 SO TIME IS TIED TO HEAT, 502 00:27:55,533 --> 00:27:59,067 AND I THINK THAT THE KEY IDEA IS NOT THAT HEAT COMES FROM TIME, 503 00:27:59,067 --> 00:28:01,067 BUT IS THAT TIME COMES FROM HEAT. 504 00:28:01,067 --> 00:28:02,600 AND HEAT IS THERMODYNAMICS, 505 00:28:02,600 --> 00:28:07,233 AND WE HAVE UNDERSTOOD THAT THERMODYNAMIC IS STATISTICS. 506 00:28:07,233 --> 00:28:10,367 SO TIME IS TIED TO STATISTICS. 507 00:28:10,367 --> 00:28:12,933 Freeman: WE DON'T KNOW THE FINE DETAILS OF NATURE. 508 00:28:12,933 --> 00:28:16,100 WE ONLY UNDERSTAND THE AVERAGE. 509 00:28:16,100 --> 00:28:21,767 WE HAVE ONLY A STATISTICAL KNOWLEDGE. 510 00:28:21,767 --> 00:28:25,333 SAY CARLO HAS AN OVEN. 511 00:28:25,333 --> 00:28:28,967 TO MEASURE ALL THE QUANTUM INTERACTIONS INSIDE THE OVEN, 512 00:28:28,967 --> 00:28:31,933 HE WOULD NEED TO MAKE BILLIONS OF MEASUREMENTS. 513 00:28:31,933 --> 00:28:34,967 BUT NO ONE CAN DO THAT. 514 00:28:34,967 --> 00:28:36,900 SO, INSTEAD, HE SAYS, AAH! 515 00:28:36,900 --> 00:28:41,200 "THIS OVEN IS 450 DEGREES." 516 00:28:41,200 --> 00:28:44,467 TEMPERATURE IS AN AVERAGE OF THE ENERGIES 517 00:28:44,467 --> 00:28:46,767 IN THE COUNTLESS PARTICLES IN A SYSTEM. 518 00:28:46,767 --> 00:28:49,200 IT'S WHAT WE GET WHEN WE GIVE UP DESCRIBING 519 00:28:49,200 --> 00:28:51,400 WHAT'S HAPPENING IN THE QUANTUM WORLD, 520 00:28:51,400 --> 00:28:54,933 AND, CARLO SAYS, SO IS TIME. 521 00:28:54,933 --> 00:28:57,400 Rovelli: IF WE COULD SEE ALL THE DETAILS OF THE WORLD, 522 00:28:57,400 --> 00:28:59,533 WE WOULD SEE A TIMELESS WORLD IN SOME SENSE. 523 00:28:59,533 --> 00:29:02,967 WE WOULDN'T SEE THIS THING THAT WE FEEL AS TIME. 524 00:29:06,167 --> 00:29:08,867 Freeman: TO CARLO, 525 00:29:08,867 --> 00:29:12,933 TIME IS JUST A STATEMENT OF LIMITED INFORMATION. 526 00:29:12,933 --> 00:29:16,833 THE FUNDAMENTAL LEVEL OF THE UNIVERSE IS TIMELESS. 527 00:29:16,833 --> 00:29:19,100 BUT AT LARGER LEVELS OF REALITY, 528 00:29:19,100 --> 00:29:22,067 WHEN THE INTERACTIONS OF MATTER AND HEAT 529 00:29:22,067 --> 00:29:24,200 BEGIN TO HAVE VISIBLE EFFECTS, 530 00:29:24,200 --> 00:29:28,267 THE THING WE CALL "TIME" IS BORN. 531 00:29:28,267 --> 00:29:30,800 TIME BEGAN WHEN SOME SYSTEM, 532 00:29:30,800 --> 00:29:33,467 INSTEAD OF INTERACTING JUST WITH ITS NEIGHBOR, 533 00:29:33,467 --> 00:29:36,267 INTERACTED WITH A BIG SET OF SYSTEMS. 534 00:29:36,267 --> 00:29:38,367 SO TIME BEGAN WHEN SOME SYSTEM 535 00:29:38,367 --> 00:29:41,067 STARTED HAVING PARTIAL INFORMATION, 536 00:29:41,067 --> 00:29:43,400 NOT COMPLETE INFORMATION ABOUT ITS SURROUNDING. 537 00:29:43,400 --> 00:29:47,800 TIME BEGIN WITH OUR IGNORANCE AND GROWS WITH OUR IGNORANCE. 538 00:29:47,800 --> 00:29:50,300 Freeman: IT'S A RADICAL VIEW OF THE UNIVERSE, 539 00:29:50,300 --> 00:29:55,333 BUT CARLO HAS NEVER BEEN AFRAID TO CHALLENGE THE STATUS QUO. 540 00:29:55,333 --> 00:29:58,067 IS CARLO CORRECT? 541 00:29:58,067 --> 00:30:01,100 IS TIME REALLY JUST OUR FAILURE TO COMPREHEND 542 00:30:01,100 --> 00:30:03,800 THE DISPERSION OF HEAT? 543 00:30:03,800 --> 00:30:07,033 THIS WOMAN SAYS THERE IS ANOTHER POSSIBILITY. 544 00:30:07,033 --> 00:30:09,200 TIME IS REAL. [ CLOCK TICKING ] 545 00:30:09,200 --> 00:30:12,200 BUT IT IS BORN AND REBORN 546 00:30:12,200 --> 00:30:15,067 A TRILLION, TRILLION TIMES A SECOND. 547 00:30:21,433 --> 00:30:24,000 WHEN I MOVE FROM PLACE TO PLACE, 548 00:30:24,000 --> 00:30:28,467 MY SENSES TELL ME IT HAPPENS IN ONE CONTINUOUS SWEEP. 549 00:30:28,467 --> 00:30:32,067 BUT ACCORDING TO QUANTUM MECHANICS, ANY MOVEMENT... 550 00:30:33,500 --> 00:30:36,300 IS ACTUALLY A SERIES OF MICROSCOPIC JITTERS 551 00:30:36,300 --> 00:30:38,100 THROUGH SPACE. 552 00:30:38,100 --> 00:30:39,333 HUH? 553 00:30:39,333 --> 00:30:41,067 NO ONE HAS YET WORKED OUT 554 00:30:41,067 --> 00:30:44,867 HOW TO APPLY THE THEORY OF QUANTUM MECHANICS TO TIME, 555 00:30:44,867 --> 00:30:48,800 BUT SOME SCIENTISTS ARE GETTING VERY CLOSE. 556 00:30:48,800 --> 00:30:55,233 IF THEY SUCCEED, WE WILL HAVE TO ACCEPT A STRANGE, NEW IDEA -- 557 00:30:55,233 --> 00:30:58,533 EVERY MINUTE FRACTION OF A SECOND, 558 00:30:58,533 --> 00:31:06,333 TIME BURSTS INTO EXISTENCE OVER AND OVER. 559 00:31:06,333 --> 00:31:13,533 LIKE ALL OF US, FAY DOWKER EXPERIENCES A FLOW OF TIME. 560 00:31:13,533 --> 00:31:15,333 SHE WAS A GIRL... 561 00:31:15,333 --> 00:31:17,433 THEN A UNIVERSITY STUDENT... 562 00:31:17,433 --> 00:31:21,900 AND NOW SHE'S A PHYSICIST AT LONDON'S IMPERIAL COLLEGE. 563 00:31:21,900 --> 00:31:24,533 NOTHING IS MORE FUNDAMENTAL TO OUR EXPERIENCES 564 00:31:24,533 --> 00:31:26,767 THAN THAT WE HAVE THOSE EXPERIENCES IN TIME. 565 00:31:26,767 --> 00:31:29,067 WE ARE AWARE OF TIME PASSING. 566 00:31:29,067 --> 00:31:32,333 TIME SEEMS TO FLOW. 567 00:31:32,333 --> 00:31:35,333 WE CAN HARDLY MAKE SENSE OF OUR LIVES EXCEPT IN THE CONTEXT 568 00:31:35,333 --> 00:31:38,167 OF SOME FIXED PAST OF EVENTS THAT HAVE ALREADY HAPPENED 569 00:31:38,167 --> 00:31:40,200 AND THAT CAN NEVER BE CHANGED 570 00:31:40,200 --> 00:31:42,400 AND SOME OPEN FUTURE OF EVENTS 571 00:31:42,400 --> 00:31:45,367 THAT ARE FREE AND HAVEN'T HAPPENED YET 572 00:31:45,367 --> 00:31:48,067 AND SOME MYSTERIOUS AND ELUSIVE MOMENT OF NOW 573 00:31:48,067 --> 00:31:50,867 THAT APPEARS TO SEPARATE THE TWO. 574 00:31:52,700 --> 00:31:55,667 Freeman: THIS IDEA SEEMS OBVIOUS. 575 00:31:55,667 --> 00:32:00,433 BUT, ACTUALLY, IT GOES AGAINST OUR BEST SCIENTIFIC THEORY 576 00:32:00,433 --> 00:32:03,400 OF HOW THE UNIVERSE WORKS. 577 00:32:03,400 --> 00:32:05,433 THE THEORY OF RELATIVITY 578 00:32:05,433 --> 00:32:09,533 TELLS US SPACE AND TIME ARE INEXTRICABLY JOINED. 579 00:32:09,533 --> 00:32:13,500 ALL TIME THAT WILL EXIST ALREADY EXISTS 580 00:32:13,500 --> 00:32:16,533 IN A BLOCK WE CALL "SPACE-TIME." 581 00:32:16,533 --> 00:32:19,067 AS WE PASS FROM BIRTH TO DEATH, 582 00:32:19,067 --> 00:32:22,067 WE GLIMPSE OUR OWN INDIVIDUAL TRAILS 583 00:32:22,067 --> 00:32:25,600 THROUGH THIS FROZEN SPACE-TIME LANDSCAPE. 584 00:32:25,600 --> 00:32:29,933 BUT FAY BELIEVES THE UNIVERSE IS NOT A FROZEN BLOCK. 585 00:32:29,933 --> 00:32:31,900 IT IS A GROWING PILE 586 00:32:31,900 --> 00:32:36,300 MADE OF QUANTUM GRAINS OF SPACE AND TIME. 587 00:32:36,300 --> 00:32:40,633 SPACE-TIME SEEMS SMOOTH AND CONTINUOUS TO US, 588 00:32:40,633 --> 00:32:42,567 BUT THAT'S JUST BECAUSE WE'RE VERY LARGE 589 00:32:42,567 --> 00:32:45,067 AND WE SEE THINGS AT LARGE SCALES. 590 00:32:45,067 --> 00:32:49,333 SO, IF WE IMAGINE THAT A SOLID CUBE OF SOMETHING, 591 00:32:49,333 --> 00:32:50,967 SAY A SUGAR CUBE, 592 00:32:50,967 --> 00:32:54,100 REPRESENTS A PIECE OF SPACE-TIME, 593 00:32:54,100 --> 00:32:56,900 THEN FROM FAR AWAY, THAT LOOKS SOLID. 594 00:32:56,900 --> 00:32:58,533 IT LOOKS LIKE A CHUNK. 595 00:32:58,533 --> 00:33:00,600 BUT WE KNOW THAT IF YOU ZOOM IN ON IT 596 00:33:00,600 --> 00:33:03,067 AND LOOK AT ITS MORE FUNDAMENTAL STRUCTURE, 597 00:33:03,067 --> 00:33:05,133 WE SEE THAT IT BREAKS UP INTO GRAINS. 598 00:33:05,133 --> 00:33:09,067 THE IDEA WITH A GRANULAR MODEL OF SPACE-TIME IS SIMILAR. 599 00:33:09,067 --> 00:33:13,633 AT FUNDAMENTAL, TINY SCALES, IT'S GRAINY AND PARTICULATE. 600 00:33:13,633 --> 00:33:16,067 AT LARGE SCALES, IT APPEARS SMOOTH AND CONTINUOUS. 601 00:33:16,067 --> 00:33:18,567 WE DON'T NOTICE THAT GRANULARITY. 602 00:33:18,567 --> 00:33:23,733 Freeman: JUST HOW SMALL IS A GRAIN OF SPACE-TIME? 603 00:33:23,733 --> 00:33:26,900 INCONCEIVABLY SMALL. 604 00:33:26,900 --> 00:33:30,533 ROUGHLY A MILLION, TRILLION, TRILLION, TRILLIONTH 605 00:33:30,533 --> 00:33:31,900 OF A SECOND. 606 00:33:31,900 --> 00:33:34,967 THIS IS WHAT PHYSICISTS BELIEVE 607 00:33:34,967 --> 00:33:38,300 IS THE SMALLEST POSSIBLE UNIT OF MEASUREMENT. 608 00:33:38,300 --> 00:33:41,767 FAY THINKS SPACE-TIME IS BUILT 609 00:33:41,767 --> 00:33:46,600 FROM A PRODIGIOUS STACK OF THESE IMPOSSIBLY TINY GRAINS, 610 00:33:46,600 --> 00:33:50,333 WHICH SHE CALLS "SPACE-TIME ATOMS." 611 00:33:50,333 --> 00:33:53,433 Dowker: THIS MARRIES TOGETHER TWO CONCEPTS -- 612 00:33:53,433 --> 00:33:57,267 THAT SPACE-TIME IS FUNDAMENTALLY ATOMIC 613 00:33:57,267 --> 00:34:00,767 OR BITTY OR GRANULAR AT VERY TINY SCALES 614 00:34:00,767 --> 00:34:03,500 WITH THE NOTION OF CAUSALITY, 615 00:34:03,500 --> 00:34:08,367 THE FACT THAT CAUSE MUST PRECEDE EFFECT. 616 00:34:08,367 --> 00:34:10,667 SO, FOR EXAMPLE, IF I HEAR A LOUD NOISE... 617 00:34:10,667 --> 00:34:11,967 [ TIRES SCREECH, CRASH ] 618 00:34:11,967 --> 00:34:14,100 ...THEN THAT WILL STARTLE ME, 619 00:34:14,100 --> 00:34:17,400 AND I MIGHT DROP MY CUP OF COFFEE. 620 00:34:17,400 --> 00:34:20,200 SO THE CAUSE WAS THE LOUD NOISE. 621 00:34:20,200 --> 00:34:25,633 THE EFFECT WAS THE DROPPING OF MY CUP OF COFFEE. 622 00:34:25,633 --> 00:34:30,200 Freeman: IF, AS RELATIVITY INSISTS, 623 00:34:30,200 --> 00:34:34,867 ALL OF SPACE AND TIME ALREADY EXIST, 624 00:34:34,867 --> 00:34:38,733 THE COFFEE CUP WILL ALWAYS FALL, IS ALWAYS FALLING, 625 00:34:38,733 --> 00:34:41,067 HAS ALWAYS FALLEN. 626 00:34:41,067 --> 00:34:43,567 BUT IN FAY'S VIEW, 627 00:34:43,567 --> 00:34:46,633 THE UNIVERSE IS A SET OF EVENTS THAT IS FOREVER GROWING. 628 00:34:46,633 --> 00:34:48,200 [ TIRES SCREECH, CRASH ] 629 00:34:48,200 --> 00:34:51,933 WHEN WE OBSERVE THESE CONNECTED SEQUENCES OF EVENTS, 630 00:34:51,933 --> 00:34:53,967 WHAT SHE CALLS A CAUSAL SET, 631 00:34:53,967 --> 00:34:57,500 WE PERCEIVE THAT TIME IS PASSING. 632 00:34:57,500 --> 00:35:00,167 Dowker: A CAUSAL SET CAN GROW 633 00:35:00,167 --> 00:35:04,167 BY THE ACCUMULATION OF NEW SPACE-TIME ATOMS. 634 00:35:04,167 --> 00:35:08,067 AND THIS BIRTH OF NEW SPACE-TIME ATOMS 635 00:35:08,067 --> 00:35:12,867 COULD BE THE PASSAGE OF TIME AS WE KNOW IT. 636 00:35:12,867 --> 00:35:16,067 Freeman: WHAT WE EXPERIENCE AS THE PRESENT 637 00:35:16,067 --> 00:35:19,233 IS THE BIRTH OF THESE NEW SPACE-TIME ATOMS. 638 00:35:19,233 --> 00:35:21,867 THE OLD ATOMS DON'T DIE. 639 00:35:21,867 --> 00:35:26,067 THEY PILE UP INTO THE THING WE CALL "THE PAST." 640 00:35:26,067 --> 00:35:28,267 THE FUTURE HAS YET TO BE BORN. 641 00:35:28,267 --> 00:35:33,067 Dowker: ONCE A SPACE-TIME ATOM IS BORN AND EXISTS, 642 00:35:33,067 --> 00:35:35,800 IT WILL THEN FORM PART OF THE PAST. 643 00:35:35,800 --> 00:35:36,900 SO, IN THAT SENSE, 644 00:35:36,900 --> 00:35:38,700 IT ALSO REALIZES OUR SENSE 645 00:35:38,700 --> 00:35:40,333 THAT THE PAST IS FIXED, 646 00:35:40,333 --> 00:35:44,600 THAT THE PAST HAS HAPPENED, AND THAT IT CANNOT BE CHANGED. 647 00:35:46,800 --> 00:35:50,467 Freeman: TIME MAY NOT BE A CONTINUOUS RIVER, 648 00:35:50,467 --> 00:35:53,900 BUT RATHER AN ENDLESS RAIN OF EVENTS. 649 00:35:53,900 --> 00:35:57,367 SO, WHICH CONCEPT OF TIME IS CORRECT? 650 00:35:57,367 --> 00:36:00,267 ARE WE GETTING CLOSER TO THE ORIGIN OF TIME? 651 00:36:00,267 --> 00:36:03,167 WE MAY SOON KNOW. 652 00:36:03,167 --> 00:36:08,800 IN THIS LABORATORY, RESEARCHERS ARE WORKING ON A NEW EXPERIMENT 653 00:36:08,800 --> 00:36:10,667 THAT COULD FOREVER CHANGE 654 00:36:10,667 --> 00:36:13,500 OUR UNDERSTANDING OF TIME AND THE UNIVERSE. 655 00:36:18,833 --> 00:36:23,167 TIME MAY HAVE BEGUN AT THE BIG BANG. 656 00:36:23,167 --> 00:36:26,567 IT MAY HAVE ALWAYS BEEN FLOWING. 657 00:36:26,567 --> 00:36:32,400 OR IT COULD BE BORN TRILLIONS OF TIMES EVERY SECOND. 658 00:36:32,400 --> 00:36:36,067 THIS DEBATE COULD GO ON FOR DECADES. 659 00:36:36,067 --> 00:36:38,967 OR IT COULD END ANY DAY NOW. 660 00:36:38,967 --> 00:36:41,967 BECAUSE WE MAY FINALLY HAVE AN EXPERIMENT 661 00:36:41,967 --> 00:36:46,267 THAT REVEALS THE TRUE NATURE OF TIME. 662 00:36:46,267 --> 00:36:53,067 AT THE BERKELEY CAMPUS OF THE UNIVERSITY OF CALIFORNIA, 663 00:36:53,067 --> 00:36:56,867 PROFESSOR HARTMUT HAEFFNER IS BUILDING A TIME RING -- 664 00:36:56,867 --> 00:37:01,633 AN OBJECT THAT WILL ROTATE LIKE THIS DISK. 665 00:37:01,633 --> 00:37:03,733 BUT WHILE THIS METAL RING 666 00:37:03,733 --> 00:37:07,200 IS LEVITATED USING ELECTROMAGNETIC FORCE, 667 00:37:07,200 --> 00:37:11,767 A TIME RING WILL BE DRIVEN BY A JITTER IN TIME. 668 00:37:12,933 --> 00:37:15,433 IF IT WORKS, 669 00:37:15,433 --> 00:37:18,633 THIS EXPERIMENT WILL PROVE A CONTROVERSIAL THEORY -- 670 00:37:18,633 --> 00:37:23,100 THE QUANTUM FLUCTUATIONS THAT HAVE BEEN OBSERVED IN SPACE 671 00:37:23,100 --> 00:37:25,200 ALSO EXIST IN TIME. 672 00:37:25,200 --> 00:37:26,467 [ CLOCK TICKING SPORADICALLY ] 673 00:37:26,467 --> 00:37:28,667 Haeffner: WE PHYSICISTS LIKE SYMMETRIES, 674 00:37:28,667 --> 00:37:32,267 AND ONE SYMMETRY IS LIKE SPACE AND TIME. 675 00:37:32,267 --> 00:37:35,067 WE WOULD LIKE TO TREAT THEM ON THE SAME FOOTING, 676 00:37:35,067 --> 00:37:37,367 SO WHATEVER WE OBSERVE IN SPACE, 677 00:37:37,367 --> 00:37:40,233 WE THINK WE SHOULD ALSO SEE IN TIME, 678 00:37:40,233 --> 00:37:43,667 AND THIS WOULD ACTUALLY SIMPLIFY THE DESCRIPTION OF THE UNIVERSE 679 00:37:43,667 --> 00:37:45,067 OR MAKE IT MORE ELEGANT. 680 00:37:45,067 --> 00:37:50,167 Freeman: NANOTECHNOLOGIST TONGCANG LI, ALSO AT BERKELEY, 681 00:37:50,167 --> 00:37:52,867 DEVISED THE TIME-RING EXPERIMENT. 682 00:37:52,867 --> 00:37:54,500 HE APPROACHED HARTMUT, 683 00:37:54,500 --> 00:37:58,167 AN EXPERT IN TRAPPING AND STUDYING ATOMIC PARTICLES. 684 00:37:58,167 --> 00:38:01,067 BUT HARTMUT HAD HIS DOUBTS. 685 00:38:01,067 --> 00:38:03,300 Haeffner: IN THE BEGINNING, I MEAN, I WAS THINKING, 686 00:38:03,300 --> 00:38:04,400 "I MEAN, THEY ARE CRAZY. 687 00:38:04,400 --> 00:38:06,467 I MEAN, THIS IS A RIDICULOUS IDEA," 688 00:38:06,467 --> 00:38:10,767 AND THEN WE START TO TALKING, AND I REALIZED, "OH, WAIT. 689 00:38:10,767 --> 00:38:12,800 "THIS IS REALLY WEIRD, BUT THEY ARE RIGHT. 690 00:38:12,800 --> 00:38:14,200 THIS IS THE WAY IT SHOULD BE." 691 00:38:14,200 --> 00:38:17,767 Freeman: ON THIS ELECTRODE, 692 00:38:17,767 --> 00:38:21,100 INSIDE A SPACE THE WIDTH OF A HUMAN HAIR, 693 00:38:21,100 --> 00:38:25,933 HARTMUT AND HIS TEAM WILL CREATE A PERFECTLY STATIC LANDSCAPE -- 694 00:38:25,933 --> 00:38:29,733 A LANDSCAPE ISOLATED FROM OUTSIDE ENERGY. 695 00:38:29,733 --> 00:38:33,067 TO FURTHER REDUCE ENERGY IN THE SYSTEM, 696 00:38:33,067 --> 00:38:36,067 HE MUST TRAP AND COOL CALCIUM IONS 697 00:38:36,067 --> 00:38:40,833 DOWN TO A FEW BILLIONTHS OF A DEGREE ABOVE ABSOLUTE ZERO -- 698 00:38:40,833 --> 00:38:45,367 COLDER THAN ANYTHING HAS EVER BEEN COOLED BEFORE. 699 00:38:45,367 --> 00:38:50,067 THIS WILL TAKE THE IONS DOWN TO THEIR GROUND STATE -- 700 00:38:50,067 --> 00:38:52,667 THE STATE OF MINIMUM POSSIBLE ENERGY. 701 00:38:52,667 --> 00:38:58,333 ONLY THEN CAN THE EFFECTS OF SPACE BE SEPARATED FROM TIME. 702 00:38:58,333 --> 00:39:02,133 Haeffner: IMAGINE THESE BALL BEARINGS ARE CALCIUM IONS 703 00:39:02,133 --> 00:39:05,067 AND WE'RE GOING TO INJECT 100 OF THESE CALCIUM IONS 704 00:39:05,067 --> 00:39:06,900 INTO OUR VACUUM CHAMBER. 705 00:39:06,900 --> 00:39:08,600 SO, AT NORMAL TEMPERATURES, 706 00:39:08,600 --> 00:39:12,633 THESE IONS MOVE AROUND RAPIDLY IN RANDOM DIRECTIONS, 707 00:39:12,633 --> 00:39:16,433 BUT WHEN WE COOL THEM, THEY FORM THIS RING AND THEY SLOW DOWN, 708 00:39:16,433 --> 00:39:18,600 AND YOU WOULD EXPECT THAT AT SOME POINT, 709 00:39:18,600 --> 00:39:20,167 THIS RING STOPS MOVING. 710 00:39:20,167 --> 00:39:21,500 IT WOULDN'T ROTATE, 711 00:39:21,500 --> 00:39:24,600 BUT IF THIS THEORY IS CORRECT, 712 00:39:24,600 --> 00:39:28,233 THAT RING SHOULD MOVE, ROTATE, SPIN. 713 00:39:30,933 --> 00:39:34,200 Freeman: AN OBJECT AT GROUND STATE SHOULDN'T MOVE, 714 00:39:34,200 --> 00:39:39,100 BECAUSE IT NEITHER CONSUMES NOR PRODUCES ENERGY. 715 00:39:39,100 --> 00:39:45,067 BUT QUANTUM MECHANICS TELLS US ZERO DOES NOT MEAN ZERO. 716 00:39:45,067 --> 00:39:49,733 EVEN AT GROUND STATE, THERE WILL STILL BE QUANTUM FLUCTUATIONS. 717 00:39:49,733 --> 00:39:53,467 IN QUANTUM MECHANICS, THERE'S ALWAYS THIS FINITE JITTER MOTION 718 00:39:53,467 --> 00:39:54,767 IN THE GROUND STATE. 719 00:39:54,767 --> 00:39:56,167 THINGS WILL STILL MOVE, 720 00:39:56,167 --> 00:39:58,633 BUT THEY WILL MOVE IN AN UNDIRECTED WAY. 721 00:39:58,633 --> 00:40:00,367 WHAT WE ARE AFTER IS SOMETHING 722 00:40:00,367 --> 00:40:04,600 WHERE THERE IS STILL MOTION IN A PARTICULAR DIRECTION. 723 00:40:04,600 --> 00:40:07,733 IT WOULD BE DIFFERENT IN THE SENSE THAT IT'S DIRECTED. 724 00:40:07,733 --> 00:40:10,167 [ WHIRRING ] 725 00:40:10,167 --> 00:40:13,467 Freeman: FREEZING THE IONS WILL ALLOW THEM 726 00:40:13,467 --> 00:40:17,100 TO MAKE ONLY TINY, RANDOM MOVEMENTS IN SPACE -- 727 00:40:17,100 --> 00:40:19,767 TOO SMALL TO MAKE THE RING MOVE. 728 00:40:19,767 --> 00:40:24,700 BUT IF THE ION RING BEGINS TO TURN ANYWAY, 729 00:40:24,700 --> 00:40:29,133 IT WILL MEAN THERE HAS BEEN A FLUCTUATION IN TIME. 730 00:40:29,133 --> 00:40:32,433 FROM THE THEORY PERSPECTIVE, IT'S NOT AT ALL CLEAR 731 00:40:32,433 --> 00:40:35,500 WHAT IS GOING TO HAPPEN AT THESE LOW TEMPERATURES. 732 00:40:35,500 --> 00:40:38,733 THERE ARE PEOPLE WHO SAY THAT THIS RING SHOULD MOVE, 733 00:40:38,733 --> 00:40:40,467 AND OTHERS SAY IT SHOULDN'T. 734 00:40:40,467 --> 00:40:43,300 Freeman: IF THE TIME RING WORKS, 735 00:40:43,300 --> 00:40:46,100 THEN BOTH SPACE AND TIME FLUCTUATE. 736 00:40:46,100 --> 00:40:50,433 THAT MIGHT SUPPORT FAY DOWKER'S THEORY THAT SPACE-TIME 737 00:40:50,433 --> 00:40:54,767 IS CONSTANTLY GENERATING ITSELF IN QUANTUM DIPS. 738 00:40:54,767 --> 00:40:58,100 AT THE VERY LEAST, IT WILL DEMONSTRATE 739 00:40:58,100 --> 00:41:01,267 THAT SPACE AND TIME ARE INEXTRICABLY LINKED 740 00:41:01,267 --> 00:41:03,067 IN THE QUANTUM REALM. 741 00:41:03,067 --> 00:41:07,067 Haeffner: SO, WE HAVE THESE QUANTUM FLUCTUATIONS IN SPACE, 742 00:41:07,067 --> 00:41:08,833 BUT TIME WE TREAT AS SOMETHING 743 00:41:08,833 --> 00:41:11,567 WHICH YOU CAN KNOW VERY PRECISELY. 744 00:41:11,567 --> 00:41:15,067 WELL, ACTUALLY, WHAT I WOULD BE FEELING MUCH MORE HAPPY WITH 745 00:41:15,067 --> 00:41:17,867 IS IF QUANTUM MECHANICS WOULD ALSO ASSUME 746 00:41:17,867 --> 00:41:20,167 THAT TIME IS FUZZY, SO TO SPEAK, 747 00:41:20,167 --> 00:41:25,367 THAT YOU CAN'T TELL WHAT TIME IT IS EXACTLY, ONLY APPROXIMATELY, 748 00:41:25,367 --> 00:41:27,333 THAT YOU HAVE FLUCTUATIONS OF TIME. 749 00:41:27,333 --> 00:41:28,933 AND I'VE NEVER WORKED WITH SOMETHING 750 00:41:28,933 --> 00:41:30,600 WHERE TIME FLUCTUATES, SO... 751 00:41:30,600 --> 00:41:32,233 [ CHUCKLES ] 752 00:41:32,233 --> 00:41:34,967 WHEN I SEE IT, MAYBE THEN IT BECOMES NATURAL TO ME, TOO. 753 00:41:34,967 --> 00:41:36,267 [ WHIRRING ] 754 00:41:40,167 --> 00:41:44,367 IF WE FIND THE ORIGINS OF TIME, 755 00:41:44,367 --> 00:41:49,100 WE WILL ANSWER ONE OF THE DEEPEST RIDDLES OF CREATION. 756 00:41:49,100 --> 00:41:50,500 BUT WE MIGHT ALSO LEARN 757 00:41:50,500 --> 00:41:55,067 THAT TIME IS MEANINGLESS TO THE UNIVERSE -- 758 00:41:55,067 --> 00:41:57,833 TIME ONLY MATTERS TO US 759 00:41:57,833 --> 00:42:03,167 BECAUSE IT ANCHORS US BETWEEN OUR MEMORIES OF THE PAST... 760 00:42:03,167 --> 00:42:05,067 AND THE MYSTERY OF THE FUTURE. 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