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00:00We inhabit a cosmos of undiscovered dimensions and paradoxical realities.
00:13We live on one level of perception.
00:22But there are others.
00:30Every once in a while, a searcher happens upon the doorway to one of these other levels.
00:45One of them discovered a paradox about reality that proved to be so profound we have yet to understand how it could be possible.
01:00The universe, or perhaps should we say, universes, have never been the same.
01:12The universe, or perhaps should we say, universes, have never been the same.
01:42The universe, or perhaps not虚شر, have never been the same.
01:58¶¶
02:28Nature writes her most intimate secrets in light.
02:45The light from our star that powers all life on this world.
02:50The light that plants eat to make sugar.
02:54The light that is the yardstick of the universe,
02:56stitching diamonds into the fabric of space and time.
03:00The imprisoned light that defines black holes.
03:04The absence of light that prevents us from knowing
03:07what dark matter and dark energy are.
03:10Seeing the light usually refers to a religious epiphany.
03:14But no one is more light-obsessed than astronomers.
03:18And as soon as they began studying light,
03:20it challenged even the very best of them.
03:23Take Isaac Newton, for example.
03:44He was so desperate to understand the nature of light and colors,
03:56he was willing to stick needles in his eyes.
03:59No, I mean literally.
04:04Newton was only in his mid-twenties,
04:06but he had already laid the foundations of a new branch of mathematics
04:10called calculus and he was conducting a series of experiments
04:14that led him to conclude that color was an aspect of light.
04:20Newton wanted to find out which of the things we see
04:23are properties of light and which are caused by our nerves.
04:26Was color hiding inside the light?
04:30Or was it in our eyes?
04:32Newton carefully noted that if he conducted the experiment
04:58in a room filled with light, even with his eyes shut,
05:02some light would pass through his eyelids
05:04and he would see a great broad, bluish circle.
05:09May not sound like much of a result considering the pain,
05:12but it was with simple homemade experiments such as this one
05:15that Isaac Newton became the first person to explain rainbows
05:19and how white light hides a whole palette of colors inside itself.
05:25Most people thought of the events Newton studied
05:27as being just the way things were.
05:31The way an apple falls.
05:33The way a ray of light shines through a window.
05:36Newton's greatness stemmed from his questioning
05:39of the why and how of ordinary things.
05:44Newton asked, what was light made of?
05:47If you could break light apart into its tiniest components,
05:51what would you see?
05:52Newton noticed that light moved in straight lines.
05:56How else to explain the edges of shadows?
05:59Or the straightness of the inspiring rays of sunlight
06:03that poke through a cloud?
06:05Or the darkness that resulted from a total solar eclipse?
06:08From these observations,
06:18Newton reasoned that light must consist
06:20of a stream of particles,
06:23or corpuscles, as he called them.
06:25That a ray of light was like a stream of bullets
06:28striking the retina of the eye.
06:30But there was one man over in Holland
06:38who vigorously disagreed with Newton's particle theory of light.
06:43Christian Huygens shared Isaac Newton's insatiable curiosity.
06:48When it came to changing the world,
06:50he was no slouch himself.
06:53Despite a lifelong struggle with depression,
06:56he managed to get a lot done.
06:58While looking through a telescope
07:02that he designed and built himself,
07:05he discovered Saturn's moon, Titan.
07:25Huygens invented the pendulum clock.
07:28He worked out the mathematical formulas
07:31necessary to create a pendulum
07:33with an arc that would accurately and consistently
07:36measure out uniform increments of time.
07:40Huygens sketched a prototype for a new machine
07:43that he thought might have some promise.
07:46It was what he called a magic lantern.
07:49A few hundred years would pass
07:50before it evolved into a working motion picture projector.
07:54But back in the 17th century,
07:56Christian Huygens already had an idea for a movie,
07:59possibly influenced by his gloomy disposition.
08:02Huygens, like Newton,
08:08also invented his own new branch of mathematics,
08:13a predictive theory of the outcomes of games of chance.
08:16probability theory of the outcomes of games of chance.
08:21probability theory,
08:21a way to call heads
08:22or tails.
08:28And like Newton, Christian Huygens had his own theory of light.
08:30He didn't think light consisted of particles like bullets firing along a single path.
08:34And like Newton, Christian Huygens saw light as a wave spreading out in all directions.
09:03It was already known in that time that sound must travel as a wave.
09:10How?
09:11Because a voice could be heard around a door when it was slightly ajar.
09:15So sound must travel around the door as water would.
09:20Like a wave.
09:21Huygens thought that light moved the same way sounded, spreading out as waves.
09:38So, which genius was right?
09:56so which genius was right the answer to that question of whether light was a particle or a
10:12wave would prove to be complicated now enter Thomas Young the man who exposed the enigma
10:22at the heart of light and unraveled the fabric of the cosmos that we thought we knew
10:31come with me to one of the greatest mysteries in the history of science it's a story about a man
10:39who could do just about anything and Thomas Young did for 1500 years no one had been able to decipher
10:48Egyptian hieroglyphics by identifying six major sounds that the hieroglyphics represented he was
10:56able to decrypt six of the symbols which led to the complete translation of the ancient Egyptian
11:04language by others he was the first to chart the family tree of the Indo-European languages as a
11:13physician he identified a deformity in the shape of the eye the defective vision he named astigmatism
11:27but it was Young's design of an experiment that sent physics down the rabbit hole we still live in it
11:34looks simple right how could three sheets of cardboard set such a catastrophe in motion a
11:40green glass shade like this one will only allow the green light through so that only a single color
11:48or frequency of light will pass through the slits why was that important because he assumed that the
11:55many overlapping colors would result in the same light waves that Huygens imagined called an interference
12:01pattern he forced that single color of light to travel through two separate slits to see what kind of
12:09pattern the light would make on that last piece of cardboard if light was a particle you'd expect to
12:15see two distinct clumps of light in the opposite wall where the individual particles of light ended up after
12:21they passed through the slits but that's not what happened instead a completely unexpected pattern the one that two waves would make when they overlapped or interfered with each other
12:40that's why they're called an interference pattern Young had demonstrated that light was actually a wave that Newton the greatest genius in the history of science was half wrong that light was not a particle as he had confidently proclaimed
12:59there's a reason that arguments from authority hold little weight in science
13:06there's a reason that arguments from authority hold little weight in science
13:10nature and nature only settles the argument and she has so many tricks up her sleeve only a fool would ever consider our understanding of nature complete
13:18Newton had missed something fundamental surprising but we haven't gotten to the really disturbing part yet
13:37Thomas Young left a time bomb with a long fuse one that took a hundred years to burn down before it exploded it wasn't until the end of the 19th century that science developed the necessary tools to find an opening to a hidden universe a realm of deeper mystery you can hear the discoverer's astonishment in his own
14:07account
14:37would be too small to have been detected by any means then known to science
14:44that voice that particular organization of sound waves frozen in time nearly a hundred years ago belongs to JJ Thompson he's remembering his discovery of the electron in his cathode ray experiment he had heated up a metal electrode until it spit out an electron
15:05and another and another and another
15:12for the first time an elementary particle of the atom was made visible
15:19science was breaking into nature's vault where she had kept her most closely held secrets
15:24and that's when things got really crazy if even the smallest units of matter atoms say had even smaller components such as an electron then could the same thing be true of light
15:39scientists and their never-ending fascination with light set out to devise ways of isolating smaller and smaller units of it
15:46it proved to be the passageway through the looking glass
15:51it was the crossing of a threshold into a wonderland where the known rules of physics do not apply
15:58for the first time they were able to isolate the tiniest unit of light a single photon
16:05and to perform Young's double slit experiment on a whole new level
16:13tracing its precise path either through the right slit or the left slit
16:20we'll pull over to the side of the road for the best possible view of which slit
16:25the right or the left the photon passes through to get to the far wall
16:30left slit right slit another right slit left slit
16:36if we watched them all day long the pattern would be random about half would go through either slit
16:48wait a second
16:50where are the waves?
16:52where's Young's interference pattern?
16:58this is where the weird begins
17:01I cannot explain to you what you're about to see
17:04that's because no one on earth understands it yet
17:07if you can't live with that
17:10then you're not going to be happy with what lies up ahead
17:13on the smallest possible scale that we've ever discovered
17:17the quantum universe
17:19the mere act of observation changes reality
17:23ok photons, keep on coming
17:26but this time we promise not to look
17:29we promise not to look
17:32you're not going to believe this
17:33but we can change the pattern on the far wall
17:36simply by not watching
17:38which slit the photons pass through
17:40I know it sounds crazy
17:42but in every trial ever conducted
17:44the outcome depends on whether or not
17:47the experiment was observed
17:49so the reason we didn't get the interference pattern earlier
18:10wasn't because we chopped up the light into single photons
18:13it was because we were observing
18:16which slit the photons passed through
18:19but how could a photon know
18:22if someone is watching
18:24a photon doesn't have eyes
18:26a photon doesn't have a brain
18:28how could it know it was being watched
18:31you might reasonably conclude
18:34that a single photon is such a tiny thing
18:36that it's very hard to see without using complex technology
18:41this machinery does violence to the delicate photon
18:45it changes it
18:47but that doesn't explain
18:48why photons behave like particles when we're watching
18:51but waves when we're not
18:53if light is fundamentally a particle
18:56then it should never create a wave pattern
18:58whether we're observing it or not
19:01and how can individual photons
19:03know where to take their places
19:05so that as a group
19:06they create the interference patterns of waves
19:10this is a maddening conundrum
19:12at the heart of quantum physics
19:15Isaac Newton and Christian Huygens
19:19were both equally right
19:21and equally wrong
19:24light is both a wave and a particle
19:27and neither
19:29until we make an observation
19:32the photon exists in a state of uncertainty
19:36governed by laws of probability
19:38and when we do observe it
19:40it becomes something completely different
19:43we would be lost in the quantum universe
19:48without Christian Huygens
19:50his probability theory provides
19:52even now
19:53the only key we have
19:55to grasping the laws of quantum reality
19:57every particle is at the mercy of random chance
20:01and shifting probabilities
20:03thinking about it
20:05is like looking at an optical illusion
20:07you can only grab hold of it
20:09for moments at a time
20:10before it pops back into something else
20:18in the quantum universe
20:20there's an undiscovered frontier
20:22where the laws of our world
20:24give way to the ones that apply
20:26on the tiniest scale we know
20:28they're divorced from our everyday experience
20:31how can you think about a world
20:34that has different rules than ours
20:36it's not easy
20:38that's why I want to take you to this place
20:40where it's not only possible to make such a leap
20:43it's mandatory
20:45it's a world very much like our own
20:48except in one respect
21:02it just happens to be missing
21:04a spatial dimension
21:05the third one
21:12in order to venture into the quantum cosmos
21:15we have to be able to imagine another dimension
21:18that's very hard to do
21:20it's much easier to wrap your mind around a world
21:23that's missing one of the three dimensions
21:25that we take for granted
21:27the beings of the world we're about to enter
21:29have only two
21:31this world was first imagined
21:33by a man named Edwin Abbott
21:36everyone
21:37and everything here
21:38and everyone they know and love
21:40is flat
21:42their houses are flat
21:44some are squares
21:46others are triangles
21:48some have more complex shapes
21:50say octagons
21:52but all are completely flat
21:55they scurry about on foot
21:57or in little vehicles
21:59in and out of their flat buildings
22:01busy with their flat lives
22:03everyone on this world
22:05has width and length
22:07but no height whatsoever
22:10these flat worlders
22:11know about left right
22:13and forward back
22:14but have no hint
22:16not an inkling
22:17about up down
22:19except for one tiny group
22:21the mathematicians
22:23who imagine something more
22:25the mathematicians dream of a world in three dimensions
22:31but it's too hard for most of the flat worlders to think about
22:35the mathematician says
22:37listen it's really very easy
22:40we all know left right
22:42we all know forward back
22:44so let's just imagine another dimension
22:46at right angles to the other two
22:48but the flat worlders say
22:50what are you talking about
22:52at right angles to the other two
22:54everybody knows that there can only be two dimensions
22:57go ahead wise guy
22:59show us that third dimension
23:01where is it?
23:02so the mathematician draws a picture
23:06poor teacher
23:16nobody listens to mathematicians
23:23every creature on flat world
23:25sees its fellows as merely short lines
23:28which are the nearest sides of their oblong bodies
23:32but the insides of a flat worlder
23:34are forever mysterious
23:36unless exposed by some terrible accident
23:39or autopsy
23:40and then one day
23:43we came along
23:49hello
23:50how are you?
23:52hi, i'm a visitor from the third dimension
23:56hello
23:58i feel sorry for the little guy
24:01to him
24:03it appears that my greeting
24:04is emanating
24:05from his own flat body
24:07an alien voice from within
24:09that's because nothing
24:11can come from above
24:12there is no above
24:13in this world
24:14a three dimensional creature like me
24:16can only exist on flat world
24:19where my feet
24:20touch the surface of the plane
24:22sorry little guy
24:27i know how weird this must be for you
24:30don't worry
24:32don't worry
24:33you're on a perfectly safe trip
24:35to a third dimension
24:37nothing's gonna harm you
24:39but this is your chance
24:41to see a whole new perspective
24:43on where you live
24:44at first
24:46at first
24:47our flat worlder can make no sense of what is happening
24:49it is utterly outside the realm of flat world experience
24:52but eventually
24:54he realizes that he's viewing flat world from a totally new vantage point
24:58above
24:59now he can see into closed rooms
25:02he can see into his flat fellows
25:05this unprecedented three dimensional view of his two dimensional universe is devastating
25:12traveling to another dimension provides as an incidental benefit a kind of x-ray vision
25:17just as the flat world houses can have no roofs
25:21their inhabitants can have no sky
25:23because that sky could only exist in a third dimension
25:28little guys suffered enough
25:30better put him down
25:32from the point of view of its spouse
25:36this flat worlder has distressingly disappeared
25:39then unaccountably materialized
25:41from out of nowhere
25:43it's easier to imagine the universe in fewer dimensions than our comfort zone of three
26:12a zero dimensional universe
26:15it's just a point
26:16a dot with no dimension at all
26:19or a one dimensional universe
26:22where everyone is a line segment
26:25or the two dimensional flat world
26:29or 3-D where we all live
26:35we can laugh at the cluelessness of two worlds
26:41the cluelessness of two dimensional creatures
26:43unable to imagine a three dimensional world
26:46but when it comes to quantum reality
26:49that inability resembles the problems we have
26:53the best we can do for now
26:55is to imagine this three dimensional cube
26:58as a four dimensional hypercube
27:00we're living in our own flat world
27:05just like the 19th century writer Edwin Abbott
27:08in his book Flatland was trying
27:10it's the rarest of events
27:21when a searcher happens on a hole in the curtain
27:25that hides the matrix
27:26it was not until Isaac Newton
27:31that we began to understand the motions of the worlds
27:36the variety of living things always astonished us
27:41but Charles Darwin discovered how time and the environment
27:45sculpted these forms including us
27:48from life's first living cell
27:52we had no idea that the quantum universe even existed
27:55until Albert Einstein revealed it
27:58the mysterious laws of this paradoxical cosmos
28:02deeply disturbed him
28:03and we have yet to understand them ourselves
28:06at its heart was a relationship
28:11that seemed to violate the speed of light
28:13the backbone of modern physics
28:16and reality itself
28:18that blue photon
28:23a quantum packet of light
28:25will divide into two
28:26splitting its energy
28:29and emerging as a pair of red photons
28:32these new red photons
28:35are married in the most profound physical sense
28:38or as quantum physicists say
28:40entangled
28:41and no matter how far they wander from each other
28:46in space and in time
28:48the bond between them will endure
28:52it's a little like Plato's ancient Greek explanation of love
28:56a single being splits into two
28:59and separates
29:01for the rest of their existence
29:03each remains the one and only soulmate of the other
29:06exquisitely attuned to the inner life of its partner
29:10even if they are separated from each other
29:12by a whole universe
29:15observe the spin of one photon
29:18and you will instantly know the spin of its entangled partner
29:21it's not something special about these particular photons
29:24as far as we know
29:26it's the rule
29:28this kind of long distance relationship
29:31has been going on for the whole history of the universe
29:34two photons born in the early universe
29:41nearly 14 billion years ago
29:44separate and head in opposite directions
29:47they could end up tens of billions of light years apart
29:52and yet
29:53over all that time and across all that space
29:56the bond between them endures
29:59what is it about a photon or an electron
30:02or any other elementary particle
30:04once entangled
30:05that makes them capable of such lasting fidelity
30:08and to me an even stranger fact
30:11is that all it takes to sever that awesome commitment
30:14is the simple act of measurement
30:16all I have to do
30:19is measure the spin of one of them
30:22how can it be
30:23that only one seemingly innocuous act
30:26by a third party
30:27can forever sever such a deep and enduring bond
30:31there she is
30:42half of our cosmic couple
30:44somewhere at this very moment
30:48many billions of light years away from us
30:51her soulmate
30:52is suddenly feeling something different
30:54the thrill is gone
30:56the bond has been broken
31:00they are no longer entangled with each other
31:06our simple act of observing one of them
31:09has ruined a marriage
31:11that has lasted since the beginning of time
31:14but how could that be?
31:16and that's not the only crazy thing about this
31:19how could one photon
31:21a cosmos away from its partner
31:23send a breakup message
31:25across the universe
31:27and have the other photon receive it instantaneously
31:31faster than the speed of light
31:33could possibly carry such a message between them?
31:42these are two of the greatest unanswered questions in science
31:46so don't worry if they bother you
31:49these questions haunted a mind as great as Einstein's
31:52for the rest of his life
31:55there's nothing more intriguing to a scientist
31:58than a paradox
32:00if light
32:01the fastest thing there can be
32:03has a cosmic speed limit
32:04then it would be impossible for one photon
32:07to communicate with another
32:09instantly across such vastness
32:12Einstein found it almost unbearable
32:14to live in this kind of universe
32:16where what he called
32:17spooky action at a distance was possible
32:20remember those particles in the double slit experiment?
32:34taking either the left or the right slit?
32:37those choices amounted to nothing more than random chance
32:41but even random chance must follow certain rules
32:44that's the basis for Huygens probability theory
32:47and for calculating the odds
32:49and flipping a coin
32:51or throwing dice
32:53when Einstein applied probability theory
32:55to the problem of entangled photons
32:58he was deeply disturbed
33:00if these photons
33:01could brazenly violate the speed of light
33:04then the universe
33:05and all of creation
33:07was nothing more than a casino
33:09where the laws of nature can be broken
33:12Einstein dealt with his discomfort
33:15by clinging to the idea
33:17that the dice
33:18was somehow loaded
33:19in a way we didn't yet understand
33:22we had passed this way before
33:24more than a hundred thousand years ago
33:27our ancestors
33:28domesticated fire
33:30they didn't know what fire was
33:32but they used it anyway
33:34to build a civilization
33:36and so it was with quantum physics
33:39we didn't need to understand it
33:41to exploit its countless practical applications
33:44scientific and technological
33:46much as our ancestors used fire
33:49without understanding how it worked
33:51we lived with this mystery for decades
33:54we have entered a territory
33:57beyond the reach of classical physics
33:59where the elementary particles
34:01that make up everything
34:03including us
34:04respond to events they can't possibly know about
34:07in the outlaw casino of the quantum universe
34:12there is no objective reality
34:16and that's where we're headed next
34:22we are made of atoms
34:34the bizarre quantum universe is inside us
34:38tugged on by undiscovered moons
34:41performing its impossible magic on every level of life and experience
34:45what is this?
34:48a smattering of stars?
34:50or something else?
34:52we are sending an image made of light to your eyes
34:56it's arriving at your retina at this very moment
34:59the cells in your retina are changing chemically right now
35:03because we are stimulating some of them with photons
35:06your retina stores these changes for a fraction of a second
35:10now it's erasing them in readiness for the next barrage of photons
35:15your retina doesn't detect all of them
35:18it can't
35:19it picks up on only a small percentage of photons that come your way
35:23it's impossible to predict which particular cell in your retina
35:28will catch a photon
35:30even when it comes to something as vital as our vision
35:33all we have is our probabilities
35:38now we're shooting many more photons at you
35:42more like half a million
35:44what are you looking at?
35:46the surface of some planet orbiting another star?
35:49we need still more of those photons to know for sure
35:52say a couple of million or more
35:55only when we send all of those photons your way
35:59tens of millions of them
36:01does reality begin to take shape
36:03over time probabilities become likelihoods
36:08and eventually likelihoods become certainties
36:12but is there really any such thing as certainty?
36:16if everything even our own vision is governed by probabilities
36:21can there be any absolute reality?
36:24is there any hope of rescuing our classical idea of reality
36:31in the quantum universe?
36:34scientists have come up with one way to preserve our traditional understanding of cause and effect
36:39called the many worlds hypothesis
36:42that's a misnomer because it can't be tested scientifically
36:46but it goes like this
36:48every probability that can happen
36:51does happen in some parallel cosmos that is foreclosed to us
36:56an infinite number of ever-branching realities unfolding at every possible juncture
37:05every probability that can happen does happen in some parallel cosmos that is foreclosed to us
37:13or is probability just an illusion itself? a phantom of our ignorance?
37:26it is if we live in a universe where every single event was already foreordained at the beginning of time
37:35what is called super determinism
37:38in a super deterministic universe
37:56the catastrophic failure of treaties
37:59a sneeze
38:00the asteroid that wiped out the dinosaurs
38:03one particular bee pollinating one particular flower
38:07you listening to me right now
38:10all of these events were set in lockstep motion
38:14at the moment the universe began
38:16when it was all no larger than a marble
38:25super determinism has an additional version
38:28it can explain the mystery of entanglement
38:32the ability of entangled particles to communicate across the vastness
38:37apparently violating the speed limit of light
38:41in a super deterministic cosmos
38:43entangled partners separated by whole galaxies
38:47don't need to hear from each other to change their spin
38:51they were always destined to do so
38:53at that precise moment
38:55and so were their partners
38:58and so was the intruder
39:00who severed their bond
39:02by observing one of them
39:04think of it
39:09all these events
39:11and trillions of others
39:13inscribed
39:16inscribed
39:17in the potential
39:18of the first moment
39:19of the universe
39:20since everything in the universe
39:22is made of those same elementary particles
39:25including us
39:26we are subject to the same laws
39:28as those that rule
39:30the quantum universe
39:32and so it is
39:33for what will happen next
39:35and what will happen
39:37and what will happen
39:38after that
39:47the good news is
39:48super determinism
39:49gives us a solution
39:50to the mystery of entanglement
39:52the bad news is
39:54it seems to rob us
39:55of all agency
39:56are we just going through the motions
39:58acting out a script
40:00that was written for us
40:01nearly 14 billion years ago
40:03all the while telling ourselves
40:06how clever we were
40:07in that argument
40:08how selfish
40:09how brave
40:10if you could only change
40:12that one little thing
40:13about yourself
40:15in a universe
40:17devoid of free will
40:19are we nothing more
40:20than deterministic robots
40:33we have found a way
40:44to hitch a ride
40:45on the uncertainties
40:46to forge technologies
40:48that would otherwise
40:49be unattainable
40:50we have built a quantum clock
40:53one that you never have to wind
40:55it will only lose a single second
40:57in the next 15 billion years
41:01a three-dimensional lattice
41:11of laser light
41:12keeps isolated atoms
41:14of the element strontium
41:15suspended in space
41:17for all we know
41:19we may be mere collections
41:21of pre-programmed particles
41:23in a deterministic universe
41:25but I say
41:28let's not live like we are
41:30besides
41:32we have no way of knowing
41:33if that's true
41:34and to think that
41:37in some sense
41:38our freedom to explore
41:40the quantum realm
41:41begins with Thomas Young
41:43remember
41:45it was Young
41:46who also found the key
41:48to decrypting the lost language
41:49of the ancient Egyptians
41:51with quantum encryption
41:59we are creating codes
42:01that vanish the moment
42:02someone tries to hack into them
42:04the key to the code
42:06can be sent via entangled photons
42:08the observer effect
42:10is our insurance policy
42:12that no spy can decipher the message
42:14without causing the entanglement
42:16to break apart
42:18rendering the message unintelligible
42:21we still don't know
42:25how a photon
42:26can be both a particle
42:27and a wave at the same time
42:29what I love about science
42:32is that it demands of us
42:34a tolerance for ambiguity
42:36it requires us to live
42:38with humility
42:39regarding our ignorance
42:40withholding judgment
42:42until the evidence comes in
42:44that needn't prevent us
42:46from using the little
42:47we do know
42:48to search for
42:49and decrypt
42:50new languages
42:51of reality
42:56in this vast cosmos
42:58we are all
42:59flat worlders
43:03science is the struggle
43:05to imagine
43:06and find
43:07above
43:09an
43:26and
43:27and
43:28and
43:30it is
43:32the
43:33the