0:01 humans consider themselves unique so
0:03 they have rooted their whole theory of
0:05 existence on their
0:07 uniqueness one is their unit of measure
0:11 but it's not every social structure we
0:14 build is only a mere sketch we have
0:17 codified our existence to bring it down
0:19 to human size to make it comprehensible
0:22 to help us forget its unfathomable scale
0:26 we created a
0:28 scale but if the universe is not
0:30 regulated by mathematical laws and
0:32 humans are not the unit of measurement
0:35 then what governs on
0:38 that time gives legitimacy to its
0:41 existence time is the only true unit of
0:44 measure it provides evidence for
0:46 Matter's
0:47 existence without time we don't
0:53 exist time is unity
1:01 [Music]
1:08 think of a river the river moves with a
1:11 smooth steady Rhythm its Waters Gliding
1:15 Over rocks and swirling into
1:17 edies from afar the river might seem
1:20 like a single Continuous Flow a ribbon
1:23 of water stretching from the heights of
1:25 the mountain to The Valleys
1:28 below but stand at the The Edge and
1:31 watch it long enough and you'll notice
1:34 the river is never the same the water
1:38 you see now is not the same water you
1:40 saw a moment
1:41 ago heraclitus once said you cannot step
1:45 into the same river twice each drop once
1:48 it passes is gone forever replaced by
1:53 new ones which in turn will also Rush by
1:56 and disappear
1:58 Downstream and yet despite this endless
2:01 change the river seems Eternal it's
2:05 always there flowing onward never
2:07 pausing never
2:09 retreating this River always moving
2:12 forward is much like how we imagine
2:15 something
2:16 else time we often picture time as a
2:20 flowing current sweeping us along in its
2:22 Relentless stream from past to
2:26 Future like the river we cannot step
2:29 into the same moment twice every instant
2:32 is new different slipping away as
2:35 quickly as it arrives yet just as the
2:38 river bends or slows so too can time
2:43 Einstein showed us that time can stretch
2:45 and contract depending on where you are
2:48 and how fast you're moving imagine
2:51 speeding down a river at Breakneck Pace
2:54 everything around you blurs while to
2:56 someone sitting still on the bank the
2:58 flow seems slow slower almost
3:02 calm time behaves in a similar way for
3:06 someone moving near the speed of light
3:08 time slows down compared to someone
3:11 standing still and there's more picture
3:15 a river that
3:16 freezes when the flow stops the water is
3:19 trapped in a single moment creating a
3:22 crystalline surface that glistens in the
3:25 sunlight in certain extreme conditions
3:28 time itself pauses
3:30 much like the still surface of an icy
3:32 River the water beneath remains
3:35 suspended caught in a moment of
3:37 Stillness in the depths of space near a
3:40 black hole time Slows To almost a
3:43 standstill the river of time which we
3:46 believe moves ever forward becomes
3:48 sluggish and nearly Frozen ens snared by
3:52 the gravity of the
3:53 cosmos we live our lives feeling Time
3:56 Rush past us like the river but if we
3:59 look closer ER we begin to see that time
4:02 isn't as straightforward as we might
4:05 think the river's flow can be bent
4:08 stopped or stretched in ways that seem
4:11 impossible at first
4:13 glance is time any different could it be
4:17 that time is in fact just an illusion
4:30 the arrow of time points in one
4:33 direction from the past to the Future
4:37 marking a clear distinction between what
4:39 has already happened and what is yet to
4:41 come this forward flow is evident in
4:44 everything around us waves crash and
4:48 recede leaves fall and Decay and energy
4:52 dissipates as processes unfold in
4:54 irreversible
4:56 ways but why does time only seem to move
4:59 in one way and is this movement a
5:02 fundamental property of the universe or
5:05 just an illusion of human
5:07 perception one of the key to these
5:10 questions lie in something that at first
5:12 glance appears unrelated something
5:15 hidden in the fabric of reality
5:19 itself it was the dawn of the Industrial
5:23 Revolution steam engines were driving
5:25 trains across continents powering
5:28 factories and transforming
5:30 Society but despite the Practical
5:32 Mastery of these engines there was still
5:34 a fundamental mystery at
5:37 play what exactly was happening inside
5:40 these machines and why did they seem to
5:42 waste so much energy why couldn't they
5:45 run
5:47 forever Rudolph clausius was a curious
5:50 man and these questions stuck with him
5:53 heat he knew wasn't a substance it
5:55 wasn't some invisible fluid that moved
5:58 between objects as s scientists once
6:00 believed it was energy in motion
6:03 transferred from one system to another
6:06 but something about this energy puzzled
6:08 him when steam engines burned fuel to
6:11 create motion a lot of heat seemed to
6:14 disappear into the environment wasted
6:16 and
6:17 unusable why clausius wondered did
6:20 energy seem to flow in only one
6:22 direction from hot to cold from useful
6:26 to
6:27 useless and more importantly
6:30 why couldn't you reverse the process to
6:32 recover the lost
6:35 energy what was this invisible barrier
6:38 that made some Transformations possible
6:40 and others
6:43 impossible Claus's moment of insight
6:46 came when he began to see heat not as a
6:49 magical flowing entity but as energy
6:52 that obeyed strict rules rules that
6:55 couldn't be broken no matter how
6:57 cleverly you built your engine
6:59 after years of experiments calculations
7:02 and thought he formulated a principle
7:05 that would forever change our
7:07 understanding of the universe the second
7:10 law of
7:12 Thermodynamics and it states in any
7:15 closed system the total entropy will
7:18 always increase over time energy will
7:21 always spread out and become more
7:23 disordered making some processes
7:27 irreversible imagine a steam steam
7:29 engine with two Chambers one filled with
7:32 hot steam the other cooler as the steam
7:35 flows from the hot side to the cold side
7:38 it pushes a piston converting some of
7:40 the heat energy into mechanical work
7:43 like moving a wheel but here's the catch
7:46 not all the energy from the steam is
7:49 converted into useful work some of it
7:52 leaks out as waste heat spreading into
7:54 the environment no matter how well you
7:57 design the engine you can't stop this
8:00 leakage heat always flows from the hot
8:03 side to the cold side never the other
8:06 way
8:07 around this flow is what Claus realized
8:11 was the heart of the second law in
8:14 nature energy spreads out hot things
8:17 cool down order becomes disorder this
8:21 tendency toward disorder this Relentless
8:24 March toward Randomness is what clausius
8:27 named entropy and once entropy increases
8:30 it's nearly impossible to reverse
8:33 it let's take a simple example picture a
8:37 box filled with a 100 marbles at first
8:41 you arrange all the red marbles on one
8:44 side and all the blue marbles on the
8:46 other this is a state of low entropy
8:49 highly ordered and organized now shake
8:52 the Box the marbles will scatter
8:54 randomly mixing together after a few
8:58 shakes you'll see a chaotic jumble of
9:01 colors this mixed state is high entropy
9:04 the marbles are no longer arranged
9:05 neatly and it would take considerable
9:07 time and effort to separate them again
9:11 now shake the Box
9:13 continuously what are the chances that
9:15 by sheer luck all the red marbles will
9:17 spontaneously regroup on one side
9:21 essentially zero that's the essence of
9:26 entropy once a system becomes disordered
9:29 the mods of it returning to a highly
9:30 ordered state are so small that it's
9:33 effectively impossible energy like those
9:36 marbles naturally spreads out in
9:40 thermodynamics it means heat spreads
9:42 from hot areas to cold ones and it never
9:45 flows backward on its
9:47 own you could build the most advanced
9:49 machine imaginable and still it would
9:53 never extract energy from cold steam to
9:56 heat it up again entropy would always
9:59 have the final
10:00 word Claus's law didn't just explain the
10:03 workings of engines it had profound
10:05 implications for time
10:07 itself the second law of Thermodynamics
10:11 suggests that the direction of time is
10:13 tied to the increase of entropy the
10:16 reason we experience time as moving
10:18 forward rather than backward is that
10:21 entropy is always
10:23 increasing you remember the past the
10:26 time when the marbles were neatly
10:28 separated because it was a state of
10:30 lower
10:31 entropy but you don't remember the
10:33 future because that's where the marbles
10:35 are mixed the steam has cooled and the
10:38 energy has spread
10:41 out consider your morning coffee when
10:44 you pour it the steam Rises and The
10:47 Coffee quickly cools the heat energy
10:50 from the coffee spreads into the
10:51 surrounding air increasing the entropy
10:54 of the system it's impossible to undo
10:57 this process you'll never see the steam
11:00 gather back into the coffee to make it
11:02 hot again in fact the only way to reheat
11:05 the coffee is to add new energy perhaps
11:09 by placing it in a
11:11 microwave this too increases the overall
11:14 entropy of the system because the
11:16 microwave uses electricity which itself
11:20 generates waste heat every time we do
11:23 work or transfer energy entropy
11:25 increases somewhere in the universe
11:29 or think of an egg before it's cracked
11:32 the egg is a highly ordered
11:34 system its yolk and whites are neatly
11:37 contained within a
11:38 shell but the moment you crack it open
11:41 the eggs entropy increases the whites
11:44 and yolk mixed together and as you cook
11:47 it heat spreads through the liquid
11:49 changing its
11:51 structure you'll never get the egg back
11:53 into its original low entropy State
11:56 you'd have to manipulate each molecule
11:58 with impossibly fine Precision putting
12:01 every drop of Yol back into the exact
12:04 place it was
12:06 before the increase in entropy makes the
12:09 transformation irreversible and it's
12:12 that irreversibility that gives time its
12:15 forward Arrow entropy ensures that time
12:18 always moves forward from unburned match
12:21 to ashes from whole egg to breakfast
12:25 it's what gives our experience of time a
12:28 kind of Arrow always pointing in the
12:30 same direction but for most of human
12:33 history people didn't think of time in
12:35 terms of entropy or physics they thought
12:38 of it in terms of Cycles sunrise and
12:41 sunset the changing seasons the phases
12:45 of the
12:46 moon in ancient times people's
12:49 relationship with time was Inseparable
12:52 from the natural
12:53 world before clocks ticked off the
12:56 minutes and smartphones buzzed with
12:58 reminders
12:59 the movements of the sky the phases of
13:02 the moon and the Turning of the seasons
13:05 were the only clocks people knew the
13:08 cycles of nature not only told people
13:10 when to plant Harvest or celebrate but
13:13 also gave rise to some of the earliest
13:15 calendars tools that shaped our weeks
13:19 months and years in ways that still
13:22 influence us today in ancient Egypt the
13:25 Rhythm of Life was set by the flooding
13:28 of the Nile
13:30 River each year the river swelled with
13:33 Waters from distant rains spilling over
13:35 its banks and transforming parched
13:38 Fields into fertile land to the
13:41 Egyptians this wasn't just an annual
13:43 inconvenience it was a Divine event both
13:46 destructive and lifegiving the flood
13:49 marked the beginning of a new
13:51 agricultural cycle a natural reset
13:53 button that dictated when to sew seeds
13:56 and reap harvests
13:59 Egyptian priests closely monitored the
14:01 sky for signs of the star Sirius whose
14:04 rising in the dawn sky coincided with
14:07 the floods over time this observation
14:10 became the backbone of the Egyptian
14:12 solar
14:13 calendar a 365-day year divided into
14:17 three seasons AET the flood pet the
14:22 planting season and Shemu the dry
14:25 harvest
14:26 season but tracking entire years was not
14:29 enough people needed to measure the
14:31 hours of the day
14:33 too the Egyptians pioneered Su dials
14:36 carving stone markers to follow the
14:38 movement of shadows as the sun arked
14:41 across the sky early Sund dials weren't
14:44 precise by modern standards they divided
14:47 the day into broad segments offering
14:49 more of a general sense of morning
14:52 midday and evening life at that time
14:55 didn't need the Precision of modern
14:57 schedules it was enough to know when it
14:59 was time to tend the fields or return
15:01 home before dark time was measured in
15:04 rhythms not in minutes and the aurban
15:07 flow of daily life mirrored the slower
15:10 pulse of the natural world the Egyptians
15:13 also developed water clocks or klep
15:16 cidra these were vessels with a tiny
15:18 hole near the bottom that allowed water
15:20 to drip out slowly marking the passage
15:23 of time as the water level dropped it
15:27 revealed different markings that
15:28 indicated ated how much time had passed
15:32 water clocks were used in temples to
15:34 track ritual activities at night when
15:36 the sun and therefore the Sundial was no
15:39 longer of use time to them was a sacred
15:43 thing tied to their ceremonies prayers
15:46 and the great rhythm of life and death
15:49 governed by the
15:51 gods over time measuring tools became
15:55 more refined but their purpose remained
15:57 the same to line human life with the
16:00 patterns of nature for most of History
16:04 time wasn't rigid it was flexible
16:07 responding to the cycles of light and
16:09 dark the seasons of growth and
16:12 rest Farmers rose with the sun and slept
16:16 when it
16:17 set in this world time was a guide not a
16:21 tyrant helping people navigate life's
16:23 uncertainties but never dictating every
16:27 second the sh shift from natural time to
16:30 Mechanical time began quietly like the
16:33 first few ticks of a clock barely
16:35 noticed by the world it would soon
16:38 reshape it all started in the late 13th
16:41 century when the first mechanical clocks
16:43 were installed in European Church
16:46 Towers these early Clocks Were cruded by
16:49 today's standards instead of hands
16:51 moving across a dial they used bells to
16:54 Mark the hours ringing out across
16:57 villages to call monks to pray
16:59 or signal towns people to gather for
17:02 markets time which had once been
17:04 personal and local was becoming
17:06 something public something heard not
17:09 just felt but even at this stage time
17:13 still served The rhythms of daily life
17:16 the bells didn't demand obedience they
17:19 simply announced the passing of
17:21 hours the real shift came in the 17th
17:24 century with Christian haggens a Dutch
17:27 scientist whose rest mind turned a
17:30 casual observation into one of the most
17:32 transformative inventions of all time
17:35 the pendulum clock hens was fascinated
17:39 by the precise movement of the heavens
17:41 the way planets swung around the Sun the
17:44 moon circled the earth and the Stars
17:46 returned to the same points in the sky
17:50 night after night nature haens believed
17:54 operated on a grand Mechanical Rhythm
17:57 one that could be understood stood and
17:59 measured but the timekeeping devices of
18:02 his era Sund dials and water clocks were
18:05 crude and prone to
18:08 drift time slipped through their
18:11 cracks what if Higgens thought it was
18:14 possible to create a clock that never
18:16 faltered a machine that ticked as
18:19 reliably as the cosmos moved haan's
18:23 breakthrough came from a curious
18:24 observation about pendulums a swinging
18:27 pendulum he noticed followed a steady
18:29 and predictable Rhythm it always took
18:32 the same amount of time to swing back
18:34 and forth regardless of the size of the
18:36 Ark this was a property now known as
18:39 isochronism and it intrigued
18:42 him if this natural regularity could be
18:45 harnessed hens realized it could serve
18:47 as the engine of a new kind of clock one
18:50 far more accurate than anything the
18:52 world had seen
18:54 before in 1656 haggens built the first
18:58 pendulum clock capable of measuring time
19:01 with an accuracy of within 10 seconds
19:03 per day a vast improvement over anything
19:06 available at the
19:08 time around the same time as haan's
19:11 pendulum clock revolutionized the
19:13 measurement of time another figure was
19:15 also working on ideas that would forever
19:17 reshape our understanding of the world
19:20 Isaac Newton both higens and Newton
19:24 lived in the 17th century an era of
19:27 scientific transformation
19:30 while Higgens was perfecting the
19:31 mechanics of pendulums and timekeeping
19:34 Newton was developing a framework that
19:36 would define how we think about time and
19:39 space for centuries classical
19:42 mechanics Newton's Laws of Motion laid
19:45 out in his seminal work often just
19:48 called the principia described a
19:50 universe that operated like a perfectly
19:52 engineered machine in this view time
19:56 flowed uniformly and independently
19:59 unaffected by anything happening in the
20:01 world Newton wrote absolute true and
20:05 mathematical time of itself and from its
20:08 own nature flows equably without
20:11 relation to anything external in other
20:14 words time in Newton's Universe was like
20:18 the steady tick of a pendulum constant
20:21 unwavering and
20:23 eternal it marched forward regardless of
20:25 the events unfolding within it
20:28 to understand Newton's concept of time
20:31 think of it like a cosmic stage where
20:34 events
20:35 unfold the stage is unchanging and the
20:38 actors the planets stars and every
20:41 object on earth move according to well-
20:43 defined
20:44 rules these rules are Newton's Laws of
20:47 Motion which describe how forces cause
20:51 objects to
20:52 move the beauty of these laws is their
20:55 Simplicity and precision just as haan's
20:58 pendulum clock made time measurable in
21:00 seconds and minutes Newton's equations
21:03 made it possible to predict the motion
21:05 of objects with almost frightening
21:08 accuracy a cannonball fired into the air
21:12 a planet orbiting the Sun or even an
21:15 apple falling from a tree all could be
21:18 described using the same basic
21:21 principles in this Newtonian Universe
21:24 time was absolute and space was an empty
21:27 three-dimensional Grid in which objects
21:30 existed and
21:33 moved an easy way to visualize this is
21:36 to draw a graph with three axes length
21:39 width and height this grid represents
21:43 space and every object in the universe
21:46 occupies a specific point on it now time
21:49 is a separate invisible line that
21:52 stretches forward into the future the
21:56 objects in space move along this time
21:59 but time itself doesn't Bend or change
22:02 it simply advances second by second like
22:05 the steady tick of haan's
22:07 pendulum Newton's Laws made it possible
22:10 to predict how objects would move
22:12 through this grid of space and time for
22:14 example if you were to throw a ball into
22:16 the air Newton's second law where Force
22:19 equals mass time acceleration would
22:22 allow you to calculate exactly how high
22:24 the ball would go and when it would
22:27 return to the ground time played a
22:29 crucial role in these calculations
22:32 acting as the invisible framework that
22:34 held the entire system together but
22:37 crucially time itself wasn't affected by
22:39 the ball's motion it ticked forward
22:42 evenly just as it would if the ball had
22:45 never been thrown at all Newton's view
22:48 of time as an unchanging Universal
22:50 backdrop was so compelling that it
22:53 shaped the scientific world for
22:56 centuries his laws governed everything
22:58 from the swing of hen's pendulum to the
23:01 trajectory of planets creating a vision
23:03 of A Clockwork Universe where time
23:05 flowed like a river steady and
23:09 predictable haan's pendulum ticking in
23:12 perfect harmony with Newton's equations
23:14 seemed to capture the very essence of
23:16 time's
23:18 regularity in this world every second
23:21 was identical to the last and every
23:23 event could be traced back to precise
23:25 causes and Claus's work on entropy
23:28 introduced a new dimension to the flow
23:31 of time Claus's second law of
23:34 Thermodynamics revealed that while
23:36 Newton's equations might predict the
23:38 motion of objects and time they said
23:41 nothing about the direction of time
23:43 Claus's entropy law pointed to an
23:45 irreversible Arrow of time where systems
23:48 naturally moved from order to disorder
23:51 never the other way around time wasn't
23:54 just a passive River anymore it had a
23:56 direction a purpose an inevitable March
23:59 towards the
24:00 future and so the universe began to seem
24:04 less like Eternal clock and more like a
24:06 one-way street with entropy as its
24:10 guiding force the steady rhythm of
24:13 haan's pendulum was still there but now
24:16 something else was at play a cosmic
24:18 Trend towards chaos that Newton's tidy
24:22 equations could not explain but what if
24:25 this Arrow of time isn't as
24:27 straightforward as it seemed
24:29 what if everything we think we know
24:30 about time about its flow its direction
24:34 could be
24:35 [Music]
24:45 overturned Albert Einstein was a dreamer
24:47 long before he was a
24:49 scientist growing up in the small German
24:51 Town of ol the Young Einstein was known
24:54 more for his daydreaming than for his
24:56 academic prowess
24:59 he found the rigid schooling systems of
25:00 his youth stifling far more interested
25:03 in the mysteries of the universe than in
25:05 rote memorization or mechanical
25:09 obedience but there was one thing that
25:11 captured his imagination like nothing
25:13 else
25:15 time it seemed to Young Einstein that
25:19 time was something more mysterious than
25:20 a clock ticking in the corner of the
25:23 room what he wondered if time wasn't as
25:26 constant as it appeared what if time
25:29 could
25:30 Bend Einstein's early curiosity about
25:34 time was ignited by a thought experiment
25:36 that would forever change the course of
25:38 physics he began to realize that time
25:41 might not be the fixed entity everyone
25:43 assumed it to be what if time like space
25:47 could be affected by motion what if time
25:50 itself could
25:51 Bend in 1905 as a young clerk in a Swiss
25:55 patent office his thought experiments
25:57 fin crystallized into what we now know
26:01 as the special theory of
26:03 relativity in this Theory Einstein
26:06 proposed something revolutionary time
26:08 and space were not separate entities but
26:10 part of a single fabric woven together
26:13 into what he called
26:15 SpaceTime the motion of objects through
26:18 space he argued could actually affect
26:20 the passage of
26:22 time the faster you moved through space
26:25 the slower time passed for you it was a
26:28 a startling conclusion one that flew in
26:30 the face of centuries of classical
26:32 physics where Newton said that space and
26:35 time act separately in a future not too
26:39 distant from us there were two identical
26:41 twins Alice and Bob they were born on
26:44 the same day at the same time and lived
26:47 their entire childhood together always
26:50 the same age but one day Alice ever the
26:54 adventurer decided to set off on a
26:56 journey to the Stars Alice boards a
26:59 spaceship capable of incredible speeds
27:02 close to the speed of light Bob on the
27:05 other hand stays back on earth watching
27:08 his sister take off into the vast
27:11 unknown now here's where things get
27:14 interesting according to Einstein's
27:16 theory of special relativity time
27:19 behaves differently for Alice the one
27:21 speeding through space than it does for
27:23 Bob who remains stationary on Earth the
27:27 faster Alice travels the slower time
27:29 ticks for her compared to Bob Alice's
27:33 Journey takes her to a distant star
27:35 system many light years away let's say
27:38 it's a round trip she speeds out into
27:41 the cosmos reaches a far off star and
27:44 then turns around to head back to Earth
27:47 from Alice's point of view the trip
27:48 seems relatively short after all her
27:51 clock isn't ticking as fast as Bob's but
27:54 Bob watching from Earth experiences a
27:57 very different reality finally Alice
28:01 returns to earth the Moment of Truth
28:04 arrives Bob runs out to greet his sister
28:08 but there's a shocking difference Bob is
28:10 now much older than Alice while only a
28:13 few years may have passed for Alice on
28:15 her high-speed Journey Bob has aged far
28:18 more during her
28:19 absence how could this be this is the
28:23 heart of the twin paradox two twins born
28:27 at the same time time but due to one
28:29 traveling near the speed of light they
28:31 no longer age at the same rate the
28:34 faster Alice traveled the slower time
28:36 passed for her relative to Bob and when
28:39 they reunite the difference is
28:41 undeniable time has bent and
28:45 stretched the twin paradox isn't just a
28:48 hypothetical thought experiment it's
28:50 been tested and the results consistently
28:53 support Einstein's
28:55 predictions in 1971 the world witnessed
28:58 an experiment that seemed straight out
29:00 of Science Fiction the harle keting
29:03 experiment as it would come to be known
29:05 was a direct test of one of the
29:07 strangest consequences of Einstein's
29:09 theory of relativity gravitational time
29:13 dilation Joseph huffle a physicist and
29:16 Richard keting an astronomer were
29:19 determined to test whether gravitational
29:21 time dilation and the relativistic
29:23 effects of motion what's called
29:25 kinematic time dilation could be
29:28 observed using modern technology by the
29:31 late 1960s and early 1970s atomic clocks
29:35 had become precise enough to measure
29:37 tiny differences in time down to Nan
29:41 seconds this development paired with the
29:43 relatively high speeds of commercial
29:45 jetliners and the ability to fly at high
29:48 altitudes open the door for a truly
29:52 novel
29:53 experiment the duo theorized that by
29:56 flying atomic clocks around the world
29:58 they could observe the twin paradox in
30:01 action even if on a much smaller scale
30:04 the idea was simple planes fly at high
30:08 altitudes where Earth's gravitational
30:10 pool is weaker and they move at high
30:13 speeds relative to the ground both of
30:15 these conditions should cause time on
30:17 the planes to tick differently from time
30:20 on the ground in effect they wanted to
30:23 replicate the twin paradox with highly
30:26 sensitive clocks as their stand-ins for
30:28 the traveling twin and the twin on Earth
30:32 the real challenge lay in the details
30:35 coordinating flights ensuring Precision
30:38 in their measurements and accounting for
30:40 countless
30:42 variables in October 1971 hael and keing
30:46 boarded two commercial airliners with
30:48 four cesium beam atomic
30:52 clocks these tiny differences were
30:54 enough to demonstrate that time really
30:57 does behave differently depending on
30:59 speed and gravity the implications of
31:02 heril and King's experiment was beyond
31:05 what we imagined it was the foundation
31:07 for technologies that would soon become
31:10 Central to Modern Life Today systems
31:14 like GPS rely on an understanding of
31:16 both General and special relativity to
31:19 function satellites orbiting Earth must
31:22 account for the fact that their clocks
31:24 far from the gravitational pull of the
31:26 planet and moving at High high speeds
31:28 tick faster than those on the ground
31:32 without these Corrections GPS systems
31:34 would quickly become inaccurate leading
31:37 to navigation errors of miles in just a
31:40 day GPS satellites orbit the Earth at an
31:43 altitude of about 20,200 km and move at
31:47 speeds of roughly 14,000 km
31:51 hour each satellite carries an extremely
31:53 accurate atomic clock just like the ones
31:56 used in the harle keting experiment
31:58 these clocks are synchronized with
32:00 clocks on the ground but as Einstein
32:02 predicted they don't stay synchronized
32:05 for long first because the satellites
32:08 are moving quickly relative to the
32:10 Earth's surface special relativity comes
32:13 into play slowing down time for them
32:16 compared to an observer on the ground
32:19 this is kinematic time
32:21 dilation but the satellites are also far
32:24 from the gravitational pull of Earth so
32:26 according to general relativity time
32:28 ticks faster for them than it does for
32:30 clocks on
32:32 Earth the combined effect of these two
32:34 forms of time dilation is critical for
32:38 the accuracy of
32:40 GPS special relativity predicts that the
32:42 satellite clocks should tick about 7
32:45 micros seconds 7 millionths of a second
32:48 slower each day compared to Earthbound
32:51 clocks meanwhile general relativity
32:54 predicts that because the satellites are
32:56 farther from the Earth's gravity their
32:58 clocks should run about 45 micros faster
33:01 per
33:02 day the net effect is the time on the
33:05 GPS satellites ticks about 38 micros
33:09 faster per day than clocks on the ground
33:13 while 38 microsc may seem like a tiny
33:15 difference GPS depends on the
33:17 synchronization of time to calculate
33:21 position the system works by
33:23 triangulating signals from multiple
33:26 satellites calculating how long it takes
33:28 for a signal to reach a receiver from
33:30 different
33:31 satellites if the satellite clocks were
33:34 even slightly off this timing error
33:36 would Cascade into navigational errors
33:40 in fact without accounting for these
33:42 relativistic effects GPS systems would
33:44 accumulate errors of around 10 km about
33:48 6 m per day thus to ensure the accuracy
33:52 of GPS the system Engineers apply
33:55 precise corrections to compensate a time
33:58 dilation every GPS satellite has a
34:01 system that adjusts its clocks to
34:04 account for both the speed of the
34:05 satellite and the weaker gravitational
34:07 field at high altitude but as Engineers
34:11 have learned to adjust for time dilation
34:13 for GPS A new challenge has emerged in
34:16 keeping
34:18 time you see the Earth's rotation is not
34:20 perfectly steady it slows down over time
34:23 due to Tidal forces and other factors
34:26 our standard measure measurement of time
34:28 however based on atomic clocks is
34:31 extremely steady over months and years
34:34 the slight variations in Earth's
34:36 rotation accumulate causing atomic time
34:39 and Earth's rotational time to drift out
34:41 of sink to bridge this growing Gap
34:45 scientists introduce a leap second this
34:48 extra second is added to coordinated
34:51 universal time UTC to keep it in line
34:55 with the solar time usually at the end
34:57 of June or December and here's where the
35:00 problems begin most computers and
35:03 servers worldwide run on a system of
35:05 continuous ever forward counting time
35:09 they don't expect a second to repeat or
35:11 disappear when a leap second is added
35:14 clocks on computers must account for a
35:16 rare and irregular second unfortunately
35:19 this tiny hiccup can trigger major
35:21 malfunctions in software systems leading
35:24 to crashes freezes or even more
35:27 dangerous
35:28 consequences one of the most infamous
35:30 cases occurred in 2012 when a leap
35:33 second was added on June
35:36 30th major websites and online services
35:40 including Reddit Mozilla and Linkedin
35:43 experienced significant
35:45 outages the root cause these systems
35:49 weren't programmed to handle the leap
35:51 second correctly most servers rely on
35:54 the network time protocol ntp to to keep
35:57 their clocks in sync when ntp informed
36:01 them that an extra second had been
36:02 inserted many systems tried to process
36:05 this additional second but the software
36:07 wasn't prepared to handle the
36:09 irregularity leading to crashes and
36:11 timeouts time is critical in these
36:14 industries where every second or even
36:16 millisecond can make a difference in
36:18 trades and
36:19 transactions when the leap second
36:21 disrupted the normal flow of Time
36:24 Financial systems had to scramble to
36:26 compensate
36:27 Engineers have developed Creative
36:29 Solutions to minimize the impact of leap
36:33 seconds one such solution is called leap
36:37 smearing which was introduced by
36:39 companies like Google instead of adding
36:41 a leap second all at once Google's
36:44 servers gradually spread the leap second
36:46 over a 24-hour period by slightly
36:49 lengthening each second leading up to
36:52 the event this process Smooths the
36:55 transition and prevents the disruptions
36:58 caused by the sudden addition of an
37:00 extra second but what if instead of
37:03 merely adjusting seconds we could stop
37:06 them Al together what if for a brief
37:09 moment time itself could be Frozen not
37:13 just in theory but in
37:17 practice there are Whispers in the
37:19 scientific Community hidden within the
37:22 equations of quantum mechanics of
37:24 phenomena that could stretch the
37:26 boundaries of time beyond recognition
37:29 and perhaps just perhaps we're closer to
37:32 uncovering the first real glimpse of
37:35 this elusive chilling concept than
37:38 anyone is prepared to
37:41 [Music]
37:48 admit in the spring of 1963 a young Kip
37:52 Thorne fresh from a PhD program at
37:55 Princeton stood in awe as he visited
37:58 John archal Wheeler's office wheeler one
38:02 of the great theoretical physicists of
38:04 the 20th century was famous for pushing
38:06 the boundaries of human understanding
38:09 from quantum mechanics to general
38:12 relativity Thorn's first encounter with
38:14 the concept of black holes began in that
38:17 office a conversation that would change
38:19 the course of his life wheeler spoke
38:22 about the then controversial idea that
38:25 massive stars could collapse into INF
38:27 itely dense points regions where gravity
38:30 would overpower all other forces and
38:33 distort the very fabric of SpaceTime
38:36 wheeler called them black
38:39 holes at that moment Thorn became
38:43 hooked from that day the young physicist
38:46 dedicated himself to uncovering the
38:49 relationship between black holes gravity
38:52 and time over the next few decades Kip
38:55 Thorn became one of the leading voice
38:57 voices in the study of general
38:59 relativity focusing particularly on how
39:02 extreme gravitational phenomena influen
39:06 time his career was built on the idea
39:09 that black holes were not only real but
39:11 that they held the key to unlocking
39:14 profound truths about the nature of time
39:18 itself Thorne realized early on that
39:21 Einstein's theory of general relativity
39:24 predicted something
39:25 extraordinary the Clos you get to a
39:28 massive gravitational field like the
39:30 edge of a black hole the more time
39:32 stretches and distorts for thorn
39:36 understanding this time dilation was not
39:37 just about equations it was about
39:40 answering a haunting question could time
39:43 ever stop and if so what would that
39:47 mean in technical terms the relationship
39:50 between time and gravity can be traced
39:53 to Einstein's field equations which
39:55 describe how mass and energy warps
39:59 SpaceTime at the heart of this Theory
40:01 lies the concept of SpaceTime
40:04 curvature the idea that massive objects
40:07 bend the geometry of the universe the
40:10 stronger the gravitational field the
40:12 more pronounce this curvature and the
40:15 slower time flows in that region this
40:18 effect known as gravitational time
40:20 dilation has been confirmed through
40:22 experiments on Earth such as with
40:25 precise atomic clocks flowing on
40:27 airplanes but it reaches its extreme
40:30 near black
40:32 holes Alice wasn't content with just one
40:35 journey into the mysteries of time after
40:38 her light speed Adventure where she had
40:40 witnessed the effects of Relativity
40:42 firsthand there was something deeper she
40:44 needed to explore the nature of time
40:47 near a black hole where gravity Twisted
40:50 it to its Breaking Point her new mission
40:54 was set in the Sagittarius A system the
40:57 super massive black hole lurking at the
41:00 center of the Milky Way galaxy the black
41:03 hole a monstrous entity with a mass
41:05 millions of times that of the sun was
41:07 the perfect place to push the limits of
41:09 everything she and Bob had
41:11 learned the journey from Andromeda to
41:14 Sagittarius A took weeks but to Alice in
41:18 her Lightspeed spacecraft it passed in a
41:22 blur the vast distances between Stars
41:25 felt inconsequential and as she hurtled
41:28 through space propelled by the ship's
41:30 Advanced Fusion drive her ship flew past
41:33 distant star clusters and through
41:36 regions of space rarely visited by
41:38 humans heading for the galactic
41:42 [Music]
41:44 core as the ship gets closer to the
41:46 black hole the dense region surrounding
41:49 Sagittarius A known as the accretion
41:51 disc glowed with radiation from matter
41:55 swirling around the black hole ho at
41:57 incredible
41:59 speeds but beyond that disc there was
42:02 only Darkness a void where light itself
42:05 couldn't
42:06 escape as Alice's spacecraft drifted
42:08 ever closer to the event horizon of
42:10 Sagittarius A the effects of
42:13 gravitational time dilation became more
42:16 and more pronounced the massive black
42:19 hole with its immense gravitational pull
42:22 was bending SpaceTime so severely that
42:25 it was no longer just a theoretic
42:27 concept on paper the deeper she ventured
42:30 into the black hool's gravity well the
42:33 more extreme the effects
42:35 became gravitational time dilation was
42:38 reaching its extreme but what exactly
42:41 happens to time at the Event Horizon to
42:44 answer this question we need to dive
42:47 deeper into the mathematics of general
42:50 relativity near the Event Horizon the
42:53 SpaceTime curvature becomes so intense
42:55 that the differential rate of time how
42:58 fast time flows reaches Zero from the
43:01 perspective of a distant
43:03 Observer this doesn't mean that time has
43:05 literally stopped for someone falling
43:07 into the black hole from their
43:09 perspective time would continue to pass
43:12 normally however for an external
43:15 Observer it would appear as though the
43:17 person falling in had been frozen in
43:19 place forever suspended in the last
43:22 moment before crossing the Event Horizon
43:25 this paradoxical nature of time time
43:27 flowing normally for one Observer while
43:30 appearing Frozen for another arises from
43:33 the relativity of
43:35 simultaneity Einstein showed that the
43:37 concept of now is not absolute but
43:40 depends on the observer's frame of
43:42 reference in the extreme environment
43:45 such as near a black hole this
43:47 relativity becomes starkly
43:49 apparent as an object continues to fall
43:52 into a black hole the story of time
43:54 takes on even more bizarre twists
43:58 from the perspective of a distant
43:59 Observer the infalling object appears to
44:02 slow down asymptotically approaching the
44:05 Event Horizon without ever actually
44:07 Crossing
44:08 it this phenomenon is tied directly to
44:11 the immense gravitational field which
44:14 distorts SpaceTime in such a way that
44:17 light emitted from the object is
44:19 stretched into longer wavelengths a
44:22 process known as gravitational red shift
44:26 event the object becomes invisible as
44:29 the light is red shifted Beyond
44:31 detection but what happens from the
44:33 Viewpoint of the object itself for
44:37 someone falling in the event horizon
44:39 marks no special boundary they would
44:42 cross it without noticing anything
44:44 unusual at that precise moment and time
44:47 would seem to flow
44:50 normally however as they approach The
44:52 Singularity the core of the black hole
44:55 where SpaceTime curvature becomes
44:57 Infinite Space and Time themselves
44:59 become so warped that the very concepts
45:02 of Direction and time cease to have
45:04 conventional
45:06 meanings the equations of general
45:08 relativity break down here and quantum
45:11 mechanics must be invoked to describe
45:13 the fundamental structure of SpaceTime
45:16 but if the object seems to disappear
45:18 from the universe what happens to all
45:20 the information it contained its mass
45:23 energy and every detail about its
45:26 existence
45:27 does this information simply vanish
45:30 defying the laws of physics or could it
45:32 be preserved in a way we can't easily
45:37 perceive this brings us to the
45:38 holographic principle a concept that has
45:41 emerged from the study of black holes
45:44 and quantum
45:45 gravity the principle traces its roots
45:48 to the groundbreaking work of Dutch
45:50 theoretical physicist Gerard Hof and its
45:54 later development by Leonard saskin
45:58 both were grappling with a central
45:59 problem in black hole physics the black
46:02 hole information
46:04 Paradox Gerard Hof already a prominent
46:07 physicist in the 1980s had spent much of
46:10 his career thinking about the
46:12 relationship between quantum mechanics
46:14 and
46:15 gravity as a scientist deeply influenced
46:18 by the work of Steven Hawking Hof was
46:21 fascinated by the realization that black
46:23 holes radiate energy a process now known
46:27 as Hawking
46:28 radiation according to Hawking's
46:30 calculations this radiation causes a
46:33 black hole to lose mass and eventually
46:36 evaporate but there was a catch if black
46:39 holes eventually disappear where does
46:42 the information contained within them go
46:45 this presented a crisis in
46:48 physics according to Quantum Theory
46:51 information about a physical system is
46:53 never truly lost but Hawking's work
46:56 seems to suggest that when a black hole
46:58 evaporated all the information about the
47:01 matter it had swallowed would be
47:03 irretrievably
47:04 erased this violation of the principles
47:07 of quantum mechanics led to the
47:09 so-called information
47:11 Paradox Hof's thought process was shaped
47:15 by this Paradox he knew that either
47:17 quantum mechanics or general relativity
47:20 or both had to be
47:23 incomplete one day while contemplating
47:26 the event arising of a black hole he had
47:28 a key Insight what if the information
47:31 about everything that falls into a black
47:33 hole doesn't get lost but is somehow
47:35 stored at the Horizon itself this would
47:38 mean that the event horizon acts like a
47:40 two-dimensional surface capable of
47:43 encoding the three-dimensional
47:44 information of everything that enters
47:47 the black
47:48 hole this line of thinking though
47:51 speculative resonated with the strange
47:54 mathematics of black holes H began to
47:57 suspect that the entire universe might
47:59 operate similarly where the information
48:02 of all physical processes could be
48:04 encoded on a distant boundary just like
48:07 the Event Horizon of a black hole it was
48:11 Leonard saskin an American physicist
48:14 known for his work in string theory who
48:16 would later expand on Hof's
48:19 idea saskin had been troubled by the
48:22 same Paradox and saw Hof's concept as
48:25 the key to resolving it building on
48:27 these ideas he developed the holographic
48:30 principle which posits that all the
48:32 information within a volume of space can
48:34 be represented on the surface enclosing
48:37 that volume this was a radical
48:40 rethinking of how space and time might
48:43 work at the deepest levels of reality
48:46 his analogy was simple think of a
48:49 hologram a hologram is a two-dimensional
48:52 surface yet it creates a
48:54 three-dimensional image
48:57 what if in a similar way the
48:58 three-dimensional Universe we experience
49:01 is actually a projection from a
49:03 two-dimensional surface in terms of time
49:07 this suggests that what we perceive as
49:10 the flow of time might be an intricate
49:12 projection of deeper lower dimensional
49:16 processes much like how the
49:17 three-dimensional world we experience
49:19 could be a holographic image emerging
49:22 from a more fundamental two-dimensional
49:25 reality
49:27 this possibility opens the door to
49:29 rethinking time not as something that
49:32 moves from past to future but as an
49:35 everpresent structure where all moments
49:37 coexist
49:40 simultaneously some suggest that past
49:43 present and future could all exist
49:45 together in a kind of unchanging Eternal
49:51 framework picture the loaf sitting on
49:53 your kitchen counter each slice
49:56 represents a particular Moment In Time a
49:58 specific event or experience in your
50:01 life the slice where you are now sitting
50:04 and viewing these video is what you
50:06 refer to as the present but crucially
50:11 the other slices are all there too the
50:13 day you were born your first day of
50:16 school that time you aced a test your
50:19 first love and perhaps even the moment
50:21 of your final breath none of these
50:24 slices disappear or get erased once
50:27 they've been experienced nor do they
50:29 need to be created As you move forward
50:31 through time they already exist side by
50:35 side within the
50:37 loaf now let's take this a step further
50:40 imagine that instead of a single loaf
50:42 there's a bakery full of loaves with
50:45 each loaf representing the life of a
50:47 different individual or the history of a
50:49 different object from the motion of
50:51 distant galaxies to the decay of
50:54 subatomic
50:55 particles these loaves don't exist in
50:58 isolation but are connected influencing
51:01 one another some slices in your loaf
51:04 might overlap with slices in other
51:05 loaves the moment you meet someone for
51:08 the first time for example or when a
51:11 historical event occurs that affects
51:13 Millions these intersections are moments
51:16 where different threads of the universe
51:18 weave together this idea is widely known
51:22 as a block Universe in this model of
51:25 reality the past present and future all
51:28 coexist fixed within A four-dimensional
51:31 Spacetime
51:33 block time is not something that flows
51:35 from moment to moment as we typically
51:37 experience it instead all moments exist
51:42 simultaneously like pages in a book
51:44 where the narrative is already written
51:46 from beginning to end this notion
51:50 fundamentally challenges our everyday
51:52 perception of time as a sequence of
51:54 events unfolding
51:57 but how did we arrive at such a strange
52:00 and often unsettling idea over the
52:03 following Century many physicists
52:06 expanded on this concept Carlo relli a
52:09 theoretical physicist known for his work
52:11 in quantum gravity is one such scientist
52:15 relli proposes a relational view of time
52:18 suggesting that what we call time is
52:21 simply a measure of change between
52:23 different configurations of matter in
52:25 the universe
52:27 from this perspective the idea of an
52:30 objective present moment doesn't make
52:32 sense instead all moments are equally
52:36 real existing in a relational web within
52:39 the block Universe framework this
52:42 deterministic view where the future is
52:44 already laid out just as the past is has
52:47 deep implications for how we understand
52:50 Free Will and the nature of reality
52:53 itself if time is a dimension in
52:55 SpaceTime then what we perceive as
52:57 Choice May simply be our journey through
53:00 an already determined path in the
53:03 Block in more recent work physicists
53:06 like sha Caroll have extended
53:08 discussions of the block Universe into
53:11 the realm of quantum mechanics and
53:13 cosmology from the perspective of
53:15 someone within the block time appears to
53:17 flow events seem to unfold and choices
53:21 seem to matter but at a deeper level all
53:24 these moments births and death s choices
53:27 and chances are simply coordinates in
53:30 SpaceTime all existing
53:32 simultaneously but this isn't the end of
53:34 the story let's take this idea even
53:37 further what if the loaf itself is an
53:40 illusion what if there is no before or
53:42 after not because all moments exist at
53:45 once but because the very concept of
53:47 moments of any sequence any progression
53:50 doesn't exist at all what if everything
53:52 we think of as reality every event every
53:56 me memory every tick of the clock isn't
53:59 just coexisting but is at its core
54:06 [Music]
54:11 nothing a self-described Outsider to the
54:14 academic establishment Julian Barber
54:17 never pursued the traditional path of
54:19 tenure or
54:20 professorship instead he worked as a
54:23 translator to fund his inquiries moving
54:25 from one project to another piecing
54:28 together his theory bit by bit he was an
54:31 anomaly a physicist without a university
54:34 affiliation working from his home in the
54:37 Oxfordshire
54:38 Countryside barbera's academic
54:40 background however was
54:42 solid his Early Education placed him at
54:45 the intersection of the two Fields
54:48 mathematics and physics that would
54:50 underpin his later work on time but even
54:53 with these credentials Barber chose to
54:55 follow an unconventional path in his
54:58 early career barar had deep doubts about
55:01 the nature of time as presented by
55:04 contemporary
55:05 physics his first doubts about the
55:07 nature of time emerged from his studies
55:10 of general relativity and quantum
55:12 mechanics in the 1960s while working on
55:16 his PhD dissertation at the University
55:18 of cologne Barbour became captivated by
55:21 Einstein's theory of general relativity
55:24 which treats time as part of a unified
55:27 fabric called
55:28 SpaceTime in this framework time does
55:31 not flow in the way we experience it
55:34 rather it is a coordinate no more
55:37 special than the three spatial
55:40 Dimensions events exist within the
55:42 SpaceTime fabric like dots on a map
55:45 simultaneously present without any one
55:48 event inherently becoming another but if
55:51 time did not flow in general relativity
55:54 barara wondered what was its real
55:57 nature around the same time he became
55:59 intrigued by quantum mechanics a field
56:02 where time plays A peculiar role in
56:05 shring as equation time is simply a
56:08 parameter and Quantum States evolve
56:11 deterministically yet when we observe a
56:13 Quantum system we experience seemingly
56:16 random discrete outcomes suggesting a
56:19 disconnect between the deterministic
56:21 equations and the probabilistic reality
56:24 we encounter
56:26 these inconsistencies between quantum
56:29 theory and relativity planted the first
56:31 seeds of doubt in Barber's mind what if
56:35 the problem wasn't with the theories
56:37 themselves but with how they used time
56:41 Barber's Quest For answers led him to
56:44 explore an obscure idea proposed by the
56:47 physicist John Wheeler that the Universe
56:50 might be described in terms of
56:52 configurations rather than evolving
56:55 States
56:56 wheeler had suggested that instead of
56:58 tracking the changes a system undergoes
57:00 over time physics could focus on the
57:03 possible Arrangements of matter in space
57:06 what Bara would later call the NS of
57:09 platonia this was one of the key moments
57:11 in barba's process was recognizing how
57:14 memory plays a role in our perception of
57:17 time he realized that the sense of flow
57:21 the feeling that the present arises from
57:23 the past and flows into the future might
57:26 be an illusion generated by how
57:28 information is stored in certain Nows
57:32 records of past configurations are
57:35 encoded giving us the impression that
57:37 events have unfolded in
57:39 sequence however Bara argued these
57:42 memories are just features of individual
57:45 configurations not evidence of an actual
57:48 passage of time the arrow of time our
57:51 perception that the past lies behind us
57:54 and the future ahead emerges from the
57:57 way information is structured within
57:59 specific configurations not from any
58:02 fundamental property of the universe in
58:05 1999 Barber published his Monumental
58:08 work the end of time a book that
58:11 crystallized his ideas and brought them
58:14 to a broader
58:15 audience in it he laid out his discovery
58:18 that time is not a fundamental aspect of
58:20 reality but an emergent illusion
58:24 platonia is the conceptual ual landscape
58:27 at the heart of Julian Barber's findings
58:30 named after the ancient Greek
58:32 philosopher Plato as a homage to his
58:34 theory of forms the idea representing
58:37 the collection of all possible
58:39 configurations of the universe each a
58:41 distinct Timeless
58:44 now in platonia these configurations
58:47 exist independently of one another
58:50 without any intrinsic order or sequence
58:53 instead of a continuous flowing timeline
58:56 Line Reality is composed of a vast
58:59 multi-dimensional space where every
59:02 moment exists
59:03 simultaneously complete in
59:07 itself there is no past or future only a
59:10 static array of possible States each
59:13 representing the entire universe at a
59:15 given
59:16 instant mathematically platonia is
59:19 analogous to a configuration space a
59:22 structure used in physics to describe
59:24 all possible states of a system a
59:27 helpful way to imagine platonia is to
59:29 think of a shuffled deck of cards spread
59:32 out on a table each card shows a unique
59:35 arrangement of symbols like Spades or
59:38 diamonds just as each point in platonia
59:41 represents a distinct configuration of
59:43 the universe the cards do not follow a
59:46 specific order unless we impose one
59:49 similarly in platonia there is no
59:51 inherent progression from one
59:53 configuration to another
59:56 time as we experience it arises only
59:59 when we mentally arrange some subset of
60:01 these states into a meaningful
60:04 sequence one of plutonia key strengths
60:08 lies in its ability to address the arrow
60:11 of Time problem the mystery of why time
60:14 seems to move only in One Direction in
60:19 traditional physics the equations
60:21 governing fundamental processes like the
60:23 motion of particles are time symmetric
60:26 they work equally well whether time
60:28 moves forward or
60:30 backward yet in the macroscopic world we
60:33 observe irreversible processes such as a
60:37 glass shattering but never
60:39 reassembling Bar's platonia offers a
60:42 different solution the arrow of time is
60:45 not fundamental but rather an emergent
60:48 property it exists only in regions of
60:51 platonia where configurations increase
60:54 in complexity such as the evolution of
60:56 our universe we perceive time's
60:59 Direction because the configurations we
61:01 experience happen to contain increasing
61:04 patterns of structure and Order barbar's
61:07 platonia shifts the Focus From Evolution
61:10 through time to the geometry of
61:13 configurations He suggests that the laws
61:15 of physics may be understood better as
61:18 constraints on the shape of this space
61:20 of possibilities rather than as rules
61:22 governing temporal
61:24 change for example general relativity
61:27 could be reinterpreted not as describing
61:30 how SpaceTime evolves but rather as
61:33 defining the relationships between
61:35 different states in
61:37 platonia in this way the geometry of
61:39 platonia becomes the fundamental fabric
61:42 of reality with time emerging only as an
61:45 illusion a byproduct of the paths we
61:49 imagine through this
61:51 space Julian barbar's work on time as an
61:54 illusion echoes the ancient tension
61:57 between Kronos and tempus two distinct
62:00 concepts of time Kronos originates from
62:03 Greek mythology where it refers to time
62:06 as a Relentless unfeeling force that
62:09 governs the physical
62:10 world it is the kind of time that can be
62:13 measured seconds ticking away on a clock
62:16 days marked by the rising and setting of
62:19 the
62:20 Sun in physics this idea of time
62:23 underpins our understanding of motion
62:26 causality and
62:28 change equations from Newton's laws to
62:31 Einstein's relativity rely on the notion
62:34 of time as a parameter that flows
62:36 forward enabling events to unfold in
62:40 sequence Kronos is objective and
62:42 consistent providing a shared framework
62:45 for organizing the world and tracking
62:48 progress however Kronos is also
62:51 indifferent it does not care about how
62:53 time is experienced by individuals
62:56 whether you are bored or exhilarated
62:59 time measured by a clock passes
63:02 uniformly in this way kronus embodies
63:05 the mechanical Clockwork nature of the
63:07 universe where everything proceeds along
63:10 a timeline in different to human emotion
63:13 or perception in contrast tempus is
63:16 subjective time the time of human
63:20 experience it is fluid and malleable
63:23 stretching or Contracting depending on
63:25 move
63:26 focus and context think of how time
63:29 seems to fly by when you are deeply
63:31 engrossed in a conversation or how it
63:34 drags during moments of
63:37 anxiety Tempest is not concerned with
63:39 Precision or measurement but with
63:41 meaning it reflects the way we interpret
63:44 our experiences and weave them into
63:46 narratives that give structure and
63:48 significance to our lives Tempest is
63:52 also closely tied to memory and
63:54 anticipation
63:56 our understanding of the present moment
63:58 is influenced by memories of the past
64:00 and expectations of the future creating
64:03 a sense of
64:05 continuity in this way tempus allows us
64:08 to feel connected to both where we've
64:10 been and where we hope to go forming the
64:13 emotional underpinnings of stories plans
64:16 and
64:17 identities unlike Kronos tempus is
64:20 personal and unique to each individual
64:23 our experience of time is deeply
64:25 subjective shaped by the brain's complex
64:28 processes and influenced by attention
64:31 memory emotion and
64:34 Physiology although we take it for
64:36 granted that the present moment is
64:38 unfolding seamlessly in real time
64:41 psychological research shows that our
64:43 perception of time is neither precise
64:46 nor objective in fact every experience
64:50 we have is already slightly in the past
64:53 by the time we consciously register it
64:56 the brain's construction of temporal
64:58 experience introduces subtle delays and
65:01 distortions meaning that what we
65:03 perceive as now is a best guess
65:05 reconstruction of events that have
65:07 already happened the brain processes
65:10 sensory input touch sight sound at
65:15 different
65:16 speeds vision for example is relatively
65:20 fast while tactile Sensations such as
65:23 touch can take longer to be processed
65:26 and auditory signals are processed
65:28 differently still to create the illusion
65:31 of a continuous present moment the brain
65:34 synchronizes inputs arriving at
65:36 different times stitching them into a
65:38 coherent narrative however this process
65:42 introduces a delay often referred to as
65:45 the perceptual
65:47 lag by the time you become aware that
65:49 you've touched a surface your hand has
65:51 already been in contact with it for a
65:53 few
65:54 milliseconds experiments in Neuroscience
65:56 have demonstrated this time lag one
65:59 famous study conducted by Benjamin leet
66:02 in the 1980s investigated the
66:05 relationship between brain activity and
66:07 conscious
66:08 [Music]
66:10 awareness in this experiment
66:12 participants were asked to press a
66:14 button whenever they felt like it while
66:16 also noting the exact moment they made
66:19 the conscious decision to act
66:22 surprisingly Liber found that brain AC
66:25 ity associated with pressing the button
66:28 the Readiness potential began around 300
66:31 milliseconds before participants
66:33 reported being aware of their intention
66:36 to
66:37 act this suggests that decisions or at
66:40 least the processes leading to decisions
66:42 are initiated unconsciously with our
66:45 conscious mind becoming aware only after
66:48 the
66:49 fact other experiments have also
66:52 explored the subjective nature of time
66:54 perception
66:57 in a well-known phenomenon called
66:58 temporal binding the brain tends to
67:01 compress the time between two related
67:03 events such as pressing a button and
67:05 hearing a sound shortly
67:08 afterward this compression leads people
67:11 to experience the cause and effect as
67:13 occurring closer together in time than
67:16 they actually
67:17 did temporal binding reflects how the
67:20 brain works to smooth out discrepancies
67:23 making events appear more synchronized
67:25 than they really are which supports the
67:27 sense of a continuous flow of
67:30 time moreover the brain's clock isn't
67:33 perfectly uniform it can speed up or
67:35 slow down depending on various factors
67:38 such as attention emotion and
67:41 physiological
67:43 States for example when you are deeply
67:46 focused on a task or in a state of flow
67:49 time seems to pass quickly conversely
67:52 during moments of boredom or fear time
67:55 appears to drag in stressful situations
67:58 like an accident or emergency people
68:00 often report that time seemed to slow
68:03 down giving them more room to react
68:06 research suggests this experience occurs
68:09 because the brain's amydala which is
68:11 involved in emotional processing becomes
68:14 hyperactive enhancing memory encoding
68:17 and
68:18 perception as a result these moments are
68:21 remembered with greater detail which
68:23 tricks us into thinking they lasted
68:27 longer in addition to perceptual lag the
68:30 brain is limited by temporal resolution
68:33 which determines how finely it can slice
68:35 up
68:37 time neurophysiological studies indicate
68:40 that the brain processes sensory input
68:42 in chunks each about 30 50 milliseconds
68:46 long this discrete processing imposes
68:49 limits on how smoothly we experience
68:52 time for example even though visual
68:54 stimuli change continuously the brain
68:57 interprets them in these small intervals
69:00 somewhat like the frames of a
69:02 movie as a result rapid changes such as
69:06 a bird flying by are stitched into a
69:09 seemingly continuous motion though your
69:12 brain is processing them in discrete
69:15 steps this imperfect synchronization can
69:19 create interesting Illusions consider
69:21 the flashl effect a visual illusion
69:24 where a move moving object appears to be
69:26 a head of a flash that occurs at the
69:29 same time this illusion occurs because
69:32 the brain compensates for delays in
69:34 processing by predicting the motion of
69:37 the moving
69:39 object by the time the flash is
69:41 consciously registered the brain has
69:43 already updated its guess about where
69:45 the object should be causing the moving
69:48 object to appear further along its path
69:52 one of the more everyday ways you can
69:53 observe this delay in action is when you
69:56 stub your toe the tactile sensation of
69:59 the impact may seem to coincide with the
70:02 moment you feel pain but the two signals
70:05 touch and pain actually travel along
70:08 different neural Pathways at different
70:11 speeds by the time your brain assembles
70:13 the sensations into a coherent
70:15 experience some time has already passed
70:18 since the actual moment of
70:21 impact you are in effect always
70:24 experiencing the world's slightly behind
70:26 real time though your brain masks this
70:29 lag by aligning Sensations as closely as
70:32 possible the combination of these
70:34 effects perceptual lag temporal binding
70:38 emotional modulation and discrete neural
70:41 processing means that our experience of
70:43 time is far from the objective flow we
70:46 often assume time as we perceive it is a
70:50 psychological construction shaped by how
70:52 the brain integrates sensory inputs
70:55 manages memory and predicts future
70:59 events this suggests that the present
71:01 moment is an
71:03 illusion a kind of guesswork the brain
71:05 performs to keep our experiences feeling
71:08 coherent despite the underlying delays
71:11 and
71:12 inconsistencies if time as we feel it
71:15 stretching compressing slipping away
71:18 unnoticed or dragging endlessly is an
71:21 illusion shaped by our brain's imperfect
71:24 processing
71:25 and if even time as described by physics
71:28 measured in seconds flowing from past to
71:31 future is merely a mathematical tool
71:34 rather than a fundamental reality then
71:36 what is time
71:39 really if clocks calendars and timelines
71:42 are just constructs we impose on the
71:44 universe does time exist independently
71:47 at all or is it simply a convenient
71:50 fiction can we trust the feeling of now
71:53 if our conscious awareness is is always
71:55 slightly behind reality if the flow of
71:58 time is not intrinsic to the universe
72:00 but a product of human perception and
72:02 narrative what does that say about
72:05 causality memory and the Very idea of
72:09 change and if time is merely a sequence
72:11 of static moments as Julian Barber
72:14 suggests each existing independently in
72:17 a Timeless state so what is time
72:22 [Music]
72:26 time doesn't move the way we think every
72:29 moment in time is already out there we
72:31 feel like time is moving because we are
72:33 only able to experience one moment at a
72:36 time but in reality all a moments are
72:40 fixed and
72:41 unchanging it's like we are stuck in a
72:43 single frame unable to see the bigger
72:46 picture in this Theory the universe
72:49 isn't a place where things happen over
72:51 time it's a place where time itself is a
72:54 part of the structure everything is
72:57 locked into a four-dimensional block
73:00 past present future all fixed in place
73:04 your entire life from birth to death
73:06 already exist in the structure but they
73:09 are all out there
73:12 unchanging but what if everything is
73:14 already
73:15 written looking to the Future it's
73:18 conceivable that scientists will uncover
73:21 new insights that shed light on the true
73:24 nature of time with advancements in
73:27 technology and theoretical physics we
73:29 may eventually develop a framework that
73:32 clarifies its Essence whether it exists
73:35 independently is a dimensional aspect of
73:37 the universe or something entirely
73:40 different until then the ambiguity
73:43 surrounding time is a reminder of the
73:46 limits of our current
73:49 understanding rather than being caught
73:51 up in the debate about time's Essence we
73:53 might find more meaning in cherishing
73:56 the time we have whether time is real or
73:59 an illusion it's Central to The Human
74:02 Experience shaping our
74:05 relationships actions and identities by
74:09 focusing on the present on what we can
74:12 control we can live fulfilling lives
74:15 regardless of whether time exists as we
74:18 think it does