Lawrence Schulman explains, "If the Sun were to explode, you would not know about it until 8 minutes after the event" because it takes 8 minutes for light to travel from the Sun to the Earth.
After the Big Bang, there were only charged particles in the universe until the charged positive and negative particles came together during recombination (cosmology). Thermal time hypothesis is a proposal that time isn't a fundamental reality!
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After the Big Bang, there were only charged particles in the universe until the charged positive and negative particles came together during recombination (cosmology). Thermal time hypothesis is a proposal that time isn't a fundamental reality!
Thanks for watching. Follow for more videos.
#cosmosspacescience
#throughthewormhole
#episode10
#season5
#cosmology
#astronomy
#spacetime
#spacescience
#space
#nasa
#spacedocumentary
#time
#morganfreeman
Category
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LearningTranscript
00:01We all float along the river of time.
00:04But does that river have a source?
00:08How is time unleashed?
00:12Some believe time flows smoothly and eternally.
00:16Others say it doesn't flow at all.
00:19It pops into existence every fraction of a second.
00:23The finest minds in physics can't agree.
00:27But new experiments may hold the answer to the greatest unsolved mystery
00:32in the history of the universe.
00:36The mystery of when time began.
00:44Space.
00:46Time.
00:48Life itself.
00:51The secrets of the cosmos lie through the wormhole.
00:57When were you born?
01:12Sounds like a simple question.
01:14You just say a certain year, month, and day.
01:17But around the world, we reckon time differently.
01:20In Saudi Arabia, it's the 15th century.
01:23In Israel, it's the 58th.
01:26And we live in 24 different time zones.
01:30We all measure time relative to some starting point,
01:33a point we have chosen.
01:35But if we really want to know what time it is,
01:38we need to know when the cosmic clock started to tick.
01:43Did time begin when the universe began?
01:46Or did it start some other way?
01:53Once I was in a bike race,
01:56I wanted to impress some friends with my terrific speed.
01:59So I gave it everything I had.
02:06It was a close race.
02:08So close, I thought it was a tie.
02:12One kid said my opponent was quickest,
02:15but another said I was faster.
02:18So whose perception of time was correct?
02:21In a way, we were all right.
02:29Time is a measure of change.
02:34But how do we know things change?
02:37We rely on what our senses tell us.
02:39And primarily, we rely on what we can see.
02:43We rely on light.
02:45In the vacuum of space,
02:48light travels at a fixed speed
02:50of 186,000 miles per second.
02:55This is accepted as an absolute truth of the universe.
03:00And that, says cosmologist Jan Levin,
03:03gives light a unique relationship to time.
03:07It's actually completely remarkable
03:10the speed of light is an absolute.
03:11It's never faster, it's never slower.
03:13To understand the relativity of time,
03:16we really need to understand light.
03:18And once we start thinking about the nature of light,
03:21all of our familiar intuitions are turned on their heads.
03:25If the speed of light is constant,
03:27then time and space must shift and distort
03:31depending on your particular point of view.
03:35Einstein had this very profound insight
03:39when he started to think about something as simple as light.
03:42And he realized that if light was going to be the same
03:47for everybody in the universe,
03:48regardless of how fast they were moving
03:50or where they were in the universe,
03:52then space and time had to be different
03:54for different observers.
03:56This means time is very personal.
03:59It depends on where you are
04:01and how fast you are moving.
04:03And the way you see your movement through time
04:06may not be the way others see your movement through time.
04:15Say, for instance,
04:17Jana has a doppelganger
04:18that rides the subways and taxes of New York.
04:21If Jana's doppelganger gets in a cab
04:26and that cab travels at incredible speeds,
04:29time will flow differently for each woman.
04:36If she flies past me in a taxi,
04:38it will appear to me that her time is running slower.
04:41From my doppelganger's point of view,
04:44the street with me on it,
04:46we're flying past her in the opposite direction.
04:48And as far as she's concerned,
04:49her time is normal.
04:50It's my time that's running slow.
04:54To understand why this happens,
04:58imagine Jana turns on a double-sided laser
05:01whose pulsing beams bounce off the sidewalk below her
05:05and the balcony above her head.
05:07The pulses form a light clock.
05:09Each bounce of the laser beam is one tick.
05:14Jana sees the light go straight up and down,
05:16but her cab riding double
05:18sees something quite different.
05:21From the perspective of the cab,
05:24the light appears to take a long diagonal.
05:27And so it seems as though my clock
05:29is taking too long to tick.
05:32So it seems like my time is running slow.
05:35If Jana's doppelganger turns on the laser in the taxi,
05:38she will see the beam hitting the ceiling and floor
05:41right above and below her.
05:44But the Jana on the street
05:46sees the beam move diagonally.
05:49Because the beam has longer to travel,
05:52its tick looks slower.
05:54From my perspective on the street,
05:56if I'm looking into the taxi,
05:57I see their light take a long diagonal.
06:00And so I think it's taking their clock too long to tick.
06:03From my perspective, their clocks are running slow.
06:09The effect increases the faster you go.
06:12If the cam approaches the speed of light,
06:15the speed limit of the universe,
06:17time outside the cam appears to stand still.
06:20If that taxi was to fly by at the speed of light,
06:25it would look like my clock was never going to tick.
06:27Like, my time had stood still.
06:29Like, time was frozen.
06:31So which observer is correct?
06:34The Jana who's standing still
06:36or the Jana in motion?
06:39My doppelganger and I just fundamentally disagree
06:42on the passage of time.
06:43And it's true. We're both right.
06:45Time is relative.
06:46Relativity means that there can be
06:50no single universal time.
06:53However, there was one moment
06:55when all perspectives on time
06:57must have been the same.
06:59A moment when everything existed
07:01in one single place.
07:04The Big Bang.
07:06One of the hardest things to grasp
07:08about the idea of the Big Bang
07:10and the creation of the universe
07:11is the idea that time itself
07:14may have begun in that big event.
07:17That space was created in the Big Bang
07:20and time began to tick.
07:23Before our Big Bang,
07:25there might not have been space or time.
07:28Jana believes the Big Bang
07:30was probably when all the various time streams
07:32in the universe began.
07:35And that since then,
07:37time has passed differently in different places,
07:40depending on how those places have moved.
07:42But could we create places in our universe
07:46where time can appear to stop
07:48and then begin again?
07:52If we could hide an event from light,
07:55could we also hide it from time?
08:00These are questions
08:02Professor Alex Gaeta asked himself.
08:05A former competition tennis player,
08:08Alex is a physicist at Cornell University
08:10specializing in ultra-fast optics.
08:15This technology is usually used
08:17for high-speed data transmission.
08:20But after reading a paper
08:21written by theorists at Imperial College,
08:25he realized it could also create a gap in time.
08:28You know, light is an electromagnetic disturbance.
08:32The minute things start changing,
08:33that's an indication that time is passing.
08:35So all these changes that are occurring
08:37are creating all these electromagnetic disturbances
08:40that we can detect and measure as passage of time.
08:44What we've figured out is a way of essentially
08:48turning off the lights, turning them back on
08:50without, you know, you sensing
08:53that they've never actually been turned off.
08:59What would happen
09:00if you turned off the light shining on time
09:03long enough to hide an event?
09:06Say, for instance,
09:08Alex is in a close game with his son, Max.
09:11He's coming up to match point,
09:13and he wants to win.
09:15If Alex could create a hole in time,
09:19no one could see him do this.
09:25To observers, including his son,
09:29Alex wins the set without pause.
09:34Right now, this is impossible.
09:37But all great things start small.
09:45This is the key component of Alex's experiment,
09:48the split-time lens.
09:51It focuses light signals in time
09:53the way a glass lens focuses light in space.
09:57In a vacuum, the speed of light is constant,
10:01but that speed changes
10:02when light passes through a material
10:04or when it runs into another light beam.
10:08Alex's split-time lens uses both tricks.
10:12Alex shoots a laser into a beam of light,
10:17slowing it ever so slightly.
10:19The beam then passes through a glass fiber
10:22where it splits into two parts,
10:24each with a different wavelength.
10:26The lower wavelength pulls ahead
10:28of the higher wavelength,
10:30leaving a gap of absolute darkness.
10:33Anything within that gap is impossible to observe,
10:37since there is no light there.
10:39The light then passes through another time lens
10:42that reunifies the beam with no visible change.
10:50Using this device,
10:52Alex has created gaps
10:53that last almost a billionth of a second.
10:57That may not sound like much,
10:59but in the world of high-speed information transfer,
11:02it's significant.
11:04Let's say you have a data stream
11:06and you don't want to interrupt it at all.
11:08But you want to put some information
11:09into that data stream
11:11and then take it out.
11:13So by creating this gap,
11:14you can create the gap,
11:15not disturb the light stream,
11:17insert a little bit of data,
11:19transmit it,
11:20and then later on pull out that data
11:22and then put the data stream back together.
11:25And that information
11:26would be hidden from the passage of time.
11:29Today,
11:33creating a light gap
11:35that lasts for one second
11:37would require a machine
11:38186,000 miles long.
11:41So,
11:42Alex will have to win
11:44his tennis matches
11:44the hard way.
11:46But the technology
11:48is rapidly evolving.
11:50In principle,
11:51there have been demonstrations
11:52where you can slow down light
11:53by factors of 10 to the 7th,
11:5610 to the 8th.
11:57In the near future,
11:58it could be even more.
11:59You could essentially
12:00almost stop light,
12:01store light,
12:01for relatively long periods of time,
12:03seconds,
12:04and then essentially release it
12:06to travel again
12:07back at the speed of light.
12:10Alex and Jana's work
12:12explores the deep connection
12:13between observers,
12:15light,
12:16and the passage of time.
12:18It begs the question,
12:20does time exist
12:21if there is no one
12:22around to see it?
12:24One scientist says no.
12:27Time began
12:28much later than we think.
12:36How often have you
12:37woken up in a darkened room
12:39and had no idea
12:41what time it was?
12:43Have you been out
12:44for minutes
12:45or hours?
12:47When you are sleeping,
12:50you have no sense
12:51that time is passing.
12:54Perhaps the cosmos
12:55experiences time
12:56in the same way.
12:58The Big Bang
12:59was the moment
12:59our universe was born,
13:01but what if it didn't
13:03wake up right away?
13:06Could there have been
13:07a time when the universe
13:09had no time?
13:10Professor Larry Shulman
13:17is a little out of place
13:19in Dresden, Germany.
13:20His home base
13:21is New York's
13:22Clarkson University,
13:24which often sits
13:25under a static sheet of ice.
13:28Not so different,
13:29Larry says,
13:29from the state
13:30of the early universe
13:31when he claims
13:32time did not exist.
13:35Larry explores
13:40the behavior
13:40of systems
13:41composed of large
13:42numbers of particles,
13:44such as the water
13:45in this fountain
13:45or the universe.
13:48Statistical mechanics
13:49can also tell us
13:50about the relationship
13:51of light to time.
13:54Light carries information
13:55about events.
13:57We use it
13:58to determine
13:58what is happening now.
14:00But because light
14:01has a speed limit,
14:02everything we see
14:04actually took place
14:05in the past.
14:08The time it would take,
14:09for example,
14:10from the sun
14:10is about eight minutes
14:12because it's 93 million miles
14:14and you configure
14:15with a velocity
14:15of 186,000 miles per second.
14:17That's how long
14:18the light would take.
14:19So if the sun
14:20were to explode,
14:21for example,
14:22you would not know
14:23about it until
14:24eight minutes
14:24after the event.
14:27The light
14:28of the most distant
14:29parts of the universe
14:30has been traveling
14:31toward us
14:31for 13.8 billion years.
14:34This is when
14:35the universe began
14:36in the Big Bang.
14:42The early universe
14:43was nothing but
14:44a field of charged particles,
14:46a dense hot cloud
14:48of plasma.
14:50Photons,
14:51particles of light,
14:52could not travel
14:53very far
14:54in this soup.
14:56Then,
14:56about 380,000 years
14:58into the life
14:59of the universe,
15:00there was a sudden change
15:02called recombination.
15:04This is when
15:05atoms began to form.
15:08Prior to recombination,
15:09if an electron
15:10and a proton
15:10would approach
15:11and bind temporarily,
15:13they would be whacked
15:14by a photon
15:15coming along
15:15and be knocked apart.
15:17Recombination
15:18is a process
15:19in which the electrons
15:21and the protons,
15:22which were previously
15:23loose and separated
15:24from each other
15:24and the plasma
15:25finally can get together.
15:32It's a bit like hockey.
15:34If you imagine
15:35a hockey puck
15:35is a photon.
15:38This is the River Elba,
15:40and sometimes
15:42it freezes over.
15:44Supposing I would
15:44wait for that
15:45and go out there
15:46with my hockey puck,
15:47I could knock it
15:48through the bank
15:49with no problem.
15:50But the universe
15:51just after the Big Bang
15:52was full of obstacles.
15:54Now suppose
15:55that surrounding me
15:56were a bunch of goalies,
15:58not protecting a goal,
16:00but just making sure
16:01that my hockey puck
16:02didn't pass them.
16:03So all these goalies
16:04are standing around,
16:05and every time
16:06I hit the puck,
16:07one of them stops it.
16:08This puck is not
16:09going to get through.
16:11This, Larry says,
16:12is the early universe.
16:14Photon pucks
16:15couldn't get past
16:16the electron and proton
16:17goalies,
16:18so light didn't flow.
16:21On the other hand,
16:22these goalies
16:23are a little bit unusual,
16:24and they alternate,
16:25boy, girl, boy, girl.
16:26But at first
16:27they didn't know that
16:28because of their big masks.
16:29After a while,
16:30one of them removes the mask,
16:32and the guy next to her
16:33says, oh.
16:35Then the puck
16:36can get right through.
16:37Once the photons
16:38could escape easily,
16:40the world changed dramatically.
16:45In the early universe,
16:47photons could never move freely,
16:49and there was no way
16:50to measure change.
16:52Larry argues
16:53that means time
16:55did not exist.
16:57Only after recombination,
16:59when the universe cooled
17:00and atoms formed,
17:02did light begin
17:03to move around freely.
17:05That, says Larry,
17:07is when the universe's clock
17:09began to tick.
17:11The very earliest point
17:12was never even a time.
17:14But eventually,
17:15there was something
17:15called time,
17:16which was keeping track
17:18of the way things changed.
17:21This could explain
17:22the birth of time
17:23in our universe.
17:26But if our universe ends,
17:29will time die with it?
17:32This physicist thinks
17:34time is truly fundamental.
17:37Time is always here.
17:38It is space
17:39that comes and goes.
17:41Time moves forward,
17:47never backward.
17:49Physicists say
17:50that is because energy
17:51always dissipates.
17:55If you wind time
17:57back far enough,
17:58you would see
17:59the entire energy
18:00of the universe
18:01coming together.
18:03At the Big Bang,
18:05everything is focused
18:06on a single point.
18:07You can't wind time
18:09back any more
18:10than this.
18:12Or can you?
18:16Physicist Sean Carroll
18:18of the California
18:19Institute of Technology
18:20has spent much
18:21of his career
18:22contemplating time.
18:25Though the origin
18:26of time is a mystery,
18:28Sean is certain
18:29of one thing.
18:30In our universe,
18:31time has a direction.
18:33An arrow that runs
18:36through everything.
18:38Time is a measure
18:39of change in the universe.
18:43If nothing were changing
18:45in the world,
18:46there'd be no way
18:46of knowing that time
18:47was passing.
18:48Everything would be the same
18:49at every single moment.
18:50There'd be no clocks.
18:51Time itself would basically
18:52have no meaning.
18:57As long as something
18:58is changing,
18:59no matter how small,
19:01time is flowing.
19:02And our universe
19:04is in a constant
19:05state of change.
19:07At the dawn of the universe,
19:09an enormous amount
19:10of energy was compressed
19:12into a single point.
19:14Then came the Big Bang.
19:17Since then,
19:18with every passing second,
19:20that energy has become
19:22more and more spread out.
19:24The measure of that
19:25spreading of energy
19:26is called entropy.
19:29Sean believes
19:30the forward movement
19:31of time,
19:32time's arrow,
19:33is the steady movement
19:35from low entropy
19:36to high entropy.
19:38But what set
19:39time's arrow in motion?
19:42The puzzle that we have
19:44is that entropy
19:44tends to increase.
19:46But our Big Bang
19:47was a condition
19:48of very, very low entropy.
19:49So how did it get that way?
19:51Where could it have come from?
19:53Everything we know
19:54in physics
19:55is things
19:56increasing in entropy.
19:58So if you go back
19:58to the Big Bang,
19:59there was no
20:00lower entropy place
20:01it could have come from.
20:03Sean suspects
20:05the answer is
20:06that our universe
20:06is the child
20:07of another universe.
20:10But what was
20:11that universe like?
20:13Maybe like this.
20:15Imagine a universe
20:16that's in equilibrium.
20:17It's in a high entropy state.
20:19It's emptied out.
20:20It's just sitting there
20:21quietly,
20:22much like the water
20:22in this tank.
20:23You don't see any motion.
20:26Now,
20:27imagine in this universe
20:28where all the energy
20:29is dissipated,
20:30suddenly an area
20:32of dense energy
20:33pops into existence,
20:35much like this bag
20:36of effervescent tablets.
20:39The seltzer starts
20:40small and dense
20:41in low entropy,
20:42just like our universe
20:43did near the Big Bang.
20:45But then we expanded
20:46and cooled,
20:47galaxies formed,
20:48and the arrow of time
20:49progresses from past
20:51to future.
20:52Likewise,
20:53the seltzer fizzes
20:54and becomes higher entropy
20:55as it mixes
20:56with the water around it.
20:58And eventually,
20:59just like our universe
21:00will come back
21:01to equilibrium
21:02and the arrow of time
21:03will cease,
21:04the seltzer reaches equilibrium
21:05by mixing with the water
21:06around it
21:07and we're back to a state
21:08that doesn't change anymore,
21:10a state without
21:11any arrow of time.
21:13But how could
21:14a dead universe,
21:15one with no life,
21:17stars,
21:17or solid matter,
21:19give birth
21:19to another universe?
21:24According to quantum physics,
21:26even an empty void
21:28will experience
21:28tiny fluctuations
21:29of energy.
21:31This means that
21:32every once in a while,
21:35something can pop
21:36out of nothing.
21:38Think about
21:39the atomic nucleus
21:40of a radioactive element.
21:42It just sits there,
21:43you look at it,
21:44it's not changing
21:44as you look at it,
21:46but there is a possibility
21:47every second
21:48that it will decay,
21:49that it will spit out
21:50a new particle.
21:52What we're saying
21:52is that space-time itself
21:54can be radioactive
21:55just like that nucleus,
21:56except instead of
21:58spitting out
21:58a new particle,
21:59it can spit out
22:00an entirely new universe.
22:04New universes
22:06may constantly
22:07be popping
22:08into existence.
22:09A random
22:14quantum fluctuation
22:15in an ancient universe,
22:17a universe so old
22:19time fell apart,
22:21might even have
22:22given birth
22:22to our universe.
22:25This process
22:26of starting
22:26with no arrow of time,
22:28butting off
22:28a new universe,
22:29having an arrow,
22:30and the arrow
22:31only lasts
22:31for a little while
22:32as that universe
22:33expands and cools,
22:34but once it reaches
22:35equilibrium,
22:35the arrow stops.
22:37This could happen
22:37a many, many, many,
22:39many times,
22:40let's put it that way.
22:40Maybe an infinite
22:41number of times,
22:42but certainly
22:42a very, very large number,
22:44so it's possible
22:45that the universe
22:45we came from
22:46was nowhere near the first.
22:51Our Big Bang
22:52might not have been
22:54the beginning.
22:56Our cosmos's time
22:58could have ancestors
22:59that predated it
23:00and descendants
23:01after this universe
23:03is gone.
23:05But there may be
23:06an even deeper truth
23:07about time,
23:09a truth we will
23:10never learn
23:11until we accept
23:12that it doesn't
23:14really exist.
23:16What would we do
23:25without time?
23:27How could we keep track
23:28of the events
23:29in our lives
23:30without the steady pulse
23:32of minutes,
23:33days,
23:33and years?
23:35But it may be
23:36that none of that
23:38is real.
23:39It may be
23:41that time
23:42is nothing more
23:44than a mirage.
23:52This is the belief
23:54held by theoretical
23:55physicist Carlo Rovelli.
23:58As a student
23:58in his native Italy,
24:00Carlo was on the barricades
24:02fighting against
24:03the resurgent
24:04fascist movement.
24:06I was young
24:07in the 70s
24:08and there was
24:08the big dream
24:09of changing the world.
24:11We failed.
24:12We didn't change
24:13the world
24:13and so I think
24:15I moved to science
24:16because I thought
24:17it was another way
24:18of changing the world
24:19and perhaps I could
24:20be more successful there.
24:22Carlo leads
24:24the saunter
24:24of Physique Théorique
24:25de Lumine,
24:26a think tank
24:27in the south of France.
24:29But he's still
24:31breaking the rules.
24:32As the leading voice
24:34of the theory
24:34of thermal time,
24:36he is raising
24:37the banner
24:37for a paradigm shift
24:39in fundamental physics.
24:42In a nutshell,
24:42thermal time
24:44proposes
24:44that time
24:46does not exist,
24:47at least
24:48not at the fundamental
24:49level of reality.
24:51The idea
24:52that there is no time
24:53at the fundamental level
24:54is not so complicated
24:55after all.
24:55Let me give you an example.
24:57Imagine that you describe
24:58something happening
24:58in time,
24:59like this is
25:00oscillating in time.
25:01What do we mean?
25:02We mean that there is
25:03something that moves
25:04with respect to time.
25:05But what is time?
25:06Time is the
25:07position of the hand.
25:08So what we are really
25:10observing here,
25:11what we are really doing here,
25:12is comparing
25:13this movement
25:14with the movement
25:15of the hands
25:16of the clock.
25:17So we describe
25:18how the hands
25:18change in time,
25:19but what we really see
25:20is just how
25:21this angle
25:22changes with respect
25:24to this angle.
25:25So do without time
25:26means just to
25:27describe the world
25:28in terms of
25:29the way
25:30the various variables
25:31change with respect
25:31to one another
25:32without ever
25:33having to bring in
25:35this unobservable time
25:36into the picture.
25:41Isaac Newton
25:42introduced the idea
25:44of a variable T
25:45for time
25:46to describe
25:47how objects move.
25:49But quantum physics
25:50treats time
25:51differently
25:52than Newton's
25:53classical system.
25:54In fact,
25:55at the Planck scale,
25:57the smallest unit
25:58of the physical world,
25:59time variables
26:00simply don't work.
26:03Carlo thinks
26:04the only way
26:04to resolve
26:05this contradiction
26:06is to go back
26:07before Newton
26:08and get rid
26:09of the variable T.
26:11He has completely
26:12reformulated
26:13quantum theory
26:14without the use
26:15of time.
26:17But that's
26:18just the beginning.
26:20The interesting part
26:21is actually
26:22the second part
26:23because if we
26:24accept the idea
26:25that there is no time
26:26at the fundamental level,
26:27nevertheless,
26:28we do experience time.
26:29Time passes for us,
26:30right?
26:31We live in time.
26:32So where does
26:33this time
26:34we experience
26:34come from?
26:36The answer,
26:42Carlo thinks,
26:43is heat.
26:44When you add
26:45heat to matter,
26:47irreversible processes
26:48begin to take place.
26:50Events that can't
26:51be undone.
26:53Things begin
26:54to change
26:55in time.
26:56So every time
26:57there is some
26:58lack of reversibility
27:00in time,
27:01there's heat.
27:01so time
27:03is tied
27:04to heat
27:04and I think
27:05the key idea
27:06is not that
27:07heat comes from time
27:08but is that
27:08time comes from heat
27:09and heat is
27:10thermodynamics
27:11and we have understood
27:12that thermodynamics
27:14is statistics.
27:15So time
27:16is tied
27:17to statistics.
27:18We don't know
27:20the fine details
27:21of nature.
27:21We only understand
27:23the average.
27:25We have only
27:26a statistical
27:26knowledge.
27:31Say Carlo
27:32has an oven.
27:33To measure
27:34all the quantum
27:35interactions
27:36inside the oven,
27:37he would need
27:38to make billions
27:39of measurements.
27:40But no one
27:41can do that.
27:42So instead,
27:44he says,
27:44this oven
27:46is 450 degrees.
27:49Temperature
27:50is an average
27:51of the energies
27:52in the countless
27:53particles
27:53in a system.
27:55It's what we get
27:56when we give up
27:56describing what's
27:57happening
27:57in the quantum world
27:59and,
28:00Carlo says,
28:00so is time.
28:02If we could see
28:03all the details
28:04of the world,
28:04we would see
28:05a timeless world
28:06in some sense.
28:07We wouldn't see
28:08this thing
28:08that we feel
28:09as time.
28:12To Carlo,
28:16time is just
28:17a statement
28:17of limited information.
28:20The fundamental
28:21level of the universe
28:22is timeless.
28:23But at larger
28:24levels of reality,
28:26when the interactions
28:27of matter and heat
28:28begin to have
28:29visible effects,
28:31the thing we call
28:32time is born.
28:35Time began
28:36when some system,
28:37instead of interacting
28:38just with its neighbors,
28:40interacted with a big
28:41set of systems.
28:42So times began
28:43when some system
28:45started having
28:46partial information,
28:47not complete information
28:48about its surrounding.
28:49Time began
28:50with our ignorance
28:51and grows
28:52with our ignorance.
28:54It's a radical view
28:55of the universe,
28:56but Carlo has never
28:58been afraid
28:59to challenge
28:59the status quo.
29:01Is Carlo correct?
29:04Is time really
29:05just our failure
29:06to comprehend
29:07the dispersion
29:08of heat?
29:08This woman says
29:11there is another possibility.
29:13Time is real,
29:15but it is born
29:16and reborn
29:17a trillion,
29:18trillion times
29:20a second.
29:25When I move
29:26from place to place,
29:28my senses tell me
29:30it happens
29:30in one continuous sweep.
29:32but according
29:33to quantum mechanics,
29:36any movement
29:37is actually
29:38a series
29:39of microscopic
29:40jitters
29:40through space.
29:43No one has yet
29:44worked out
29:45how to apply
29:46the theory
29:46of quantum mechanics
29:47to time,
29:49but some scientists
29:50are getting
29:50very close.
29:52If they succeed,
29:54we will have to
29:55accept a strange
29:56new idea.
29:57Every minute fraction
30:00of a second,
30:02time bursts
30:03into existence
30:04over and over.
30:11Like all of us,
30:13Faye Dalka
30:14experiences
30:14a flow of time.
30:17She was a girl,
30:18then a university student,
30:20and now she's
30:21a physicist
30:22at London's
30:23Imperial College.
30:25Nothing is more
30:26fundamental
30:26to our experiences
30:27than that we have
30:28those experiences
30:29in time.
30:30We're aware
30:31of time passing.
30:33Time seems to flow.
30:35We can hardly
30:35make sense
30:36of our lives
30:37except in the context
30:38of some fixed
30:39past of events
30:39that have already
30:40happened
30:41and that can
30:41never be changed,
30:43and some open
30:43future of events
30:45that are free
30:46and haven't happened
30:47yet,
30:48and some mysterious
30:49and elusive
30:50moment of now
30:50that appears
30:51to separate the two.
30:56This idea
30:57seems obvious,
30:58but actually
30:59it goes against
31:00our best scientific
31:02theory of how
31:03the universe works.
31:05The theory of relativity
31:07tells us space
31:09and time
31:09are inextricably
31:10joined.
31:11All time
31:12that will exist
31:13already exists
31:14in a block
31:15we call
31:16space-time.
31:18As we pass
31:19from birth
31:20to death,
31:21we glimpse
31:21our own individual
31:23trails through
31:24this frozen
31:24space-time
31:25landscape.
31:27But Faye believes
31:28the universe
31:28is not a frozen
31:30block.
31:31It is a growing
31:32pile made
31:33of quantum grains
31:34of space
31:35and time.
31:37Space-time
31:38seems smooth
31:40and continuous
31:40to us,
31:42but that's just
31:42because we're
31:43very large
31:43and we see
31:44things at large
31:45scales.
31:46So if we
31:47imagine that
31:48a solid cube
31:49of something,
31:50say a sugar cube,
31:52it represents
31:53a piece
31:54of space-time,
31:55then from far
31:56away that looks
31:56solid,
31:57it looks like
31:58a chunk,
31:59but we know
32:00that if you
32:00zoom in on it
32:01and look at its
32:02more fundamental
32:02structure,
32:03we see that it
32:04breaks up
32:04into grains.
32:05The idea
32:06with a granular
32:07model of space-time
32:08is similar.
32:09At fundamental
32:10tiny scales
32:11it's grainy
32:12and particulate.
32:14At large scales
32:15it appears
32:15smooth and continuous,
32:16we don't notice
32:17that granularity.
32:20Just how small
32:22is a grain
32:22of space-time?
32:25Inconceivably
32:26small.
32:27Roughly
32:28a million trillion
32:29trillion trillion
32:30of a second.
32:32This is what
32:33physicists believe
32:34is the smallest
32:35possible unit
32:37of measurement.
32:39Faye thinks
32:39space-time
32:40is built
32:41from a prodigious
32:42stack of these
32:44impossibly tiny grains,
32:46which she calls
32:47space-time atoms.
32:49This marries together
32:52two concepts.
32:54That space-time
32:55is fundamentally
32:55atomic or bitty
32:57or granular
32:58at very tiny scales
32:59with the notion
33:02of causality,
33:03the fact that
33:04cause must
33:05precede effect.
33:07So, for example,
33:08if I hear a loud noise,
33:10then that will startle me
33:13and I might drop
33:14my cup of coffee.
33:15So, the cause
33:17was the loud noise,
33:18the effect
33:19was the dropping
33:20of my cup of coffee.
33:25If, as relativity insists,
33:28all of space
33:30and time
33:31already exist,
33:33the coffee cup
33:34will always fall,
33:35is always falling,
33:37has always fallen.
33:38But in Faye's view,
33:41the universe
33:42is a set of events
33:43that is forever growing.
33:45When we observe
33:47these connected sequences
33:48of events,
33:49what she calls
33:50a causal set,
33:51we perceive
33:52that time is passing.
33:55A causal set
33:56can grow
33:57by the accumulation
33:59of new
34:00space-time atoms.
34:02And this
34:02birth of new
34:04space-time atoms
34:05could be
34:06the passage of time
34:07as we know it.
34:10What we experience
34:11as the present
34:12is the birth
34:14of these new
34:15space-time atoms.
34:16The old atoms
34:17don't die,
34:19they pile up
34:20into the thing
34:20we call the past.
34:23The future
34:23has yet to be born.
34:26Once a space-time atom
34:27is born
34:28and exists,
34:30it will then
34:31form part of the past.
34:33So, in that sense,
34:34it also realizes
34:35our sense
34:35that the past
34:36is fixed,
34:37that the past
34:37has happened
34:38and that it
34:39cannot be changed.
34:44Time may not
34:45be a continuous river,
34:47but rather
34:48an endless
34:48reign of events.
34:50So,
34:51which concept
34:52of time
34:52is correct?
34:54Are we getting
34:55closer to the origin
34:56of time?
34:57We may soon know.
34:59In this laboratory,
35:02researchers are working
35:03on a new experiment
35:05that could forever
35:06change our understanding
35:08of time
35:08and the universe.
35:14Time may have begun
35:17at the Big Bang.
35:19It may have always
35:21been flowing,
35:22or it could be born
35:24trillions of times
35:26every second.
35:27This debate
35:29could go on
35:30for decades,
35:31or it could end
35:33any day now,
35:34because we may
35:36finally have
35:37an experiment
35:37that reveals
35:39the true nature
35:40of time.
35:45At the Berkeley campus
35:46of the University
35:47of California,
35:49Professor Hartmut Hefner
35:50is building
35:51a time ring,
35:53an object that
35:54will rotate
35:55like this disk.
35:58But while
35:59this metal ring
36:00is levitated
36:01using electromagnetic
36:02force,
36:04a time ring
36:04will be driven
36:05by a genuine time.
36:09If it works,
36:11this experiment
36:11will prove
36:12a controversial theory.
36:14The quantum fluctuations
36:16that have been observed
36:17in space
36:18also exist
36:19in time.
36:22We physicists
36:22like symmetries,
36:24and one symmetry
36:25is like space
36:27and time.
36:27We would like
36:28to treat them
36:29on the same footing,
36:30so whatever we observe
36:31in space,
36:32we think we should
36:33also see in time,
36:35and this would actually
36:36simplify the description
36:37of the universe
36:39or make it more elegant.
36:42Nanotechnologist
36:42Tong Kong Lee,
36:43also at Berkeley,
36:45devised
36:46the time ring experiment.
36:48He approached Hartmut,
36:50an expert in trapping
36:51and studying atomic particles.
36:53But Hartmut had his doubts.
36:56In the beginning,
36:57I mean,
36:57I was thinking,
36:58I mean,
36:58they are crazy.
36:59I mean,
36:59this is a ridiculous idea.
37:01And then we started talking,
37:03and I realized,
37:04oh, wait,
37:05this is really weird,
37:07but they are right.
37:07This is the way
37:08it should be.
37:11On this electrode,
37:12inside a space
37:14the width of a human hair,
37:16Hartmut and his team
37:17will create
37:18a perfectly static landscape,
37:21a landscape isolated
37:22from outside energy.
37:24To further reduce energy
37:26in the system,
37:27he must trap
37:28and cool calcium ions
37:30down to a few billionths
37:32of a degree
37:33above absolute zero,
37:35colder than anything
37:36has ever been cooled before.
37:40This will take the ions
37:42down to their ground state,
37:44the state of minimum
37:45possible energy.
37:47Only then
37:48can the effects of space
37:50be separated from time.
37:53Imagine these ball bearings
37:54are calcium ions,
37:56and we are going to inject
37:57a hundred of these calcium ions
37:59into our vacuum chamber.
38:01So at normal temperatures,
38:03these ions move around rapidly
38:05in random directions,
38:07but when we cool them,
38:08they form this ring
38:09and they slow down,
38:10and you would expect
38:11that at some point
38:13this ring stops moving.
38:14It wouldn't rotate,
38:16but if this theory is correct,
38:19that ring should move,
38:20rotate, spin.
38:24An object at ground state
38:27shouldn't move
38:28because it neither consumes
38:30nor produces energy.
38:33But quantum mechanics
38:34tells us zero
38:36does not mean zero.
38:39Even at ground state,
38:41there will still
38:41be quantum fluctuations.
38:44In quantum mechanics,
38:45there's always
38:45this finite jitter motion.
38:47In the ground state,
38:49things will still move,
38:50but they will move
38:51in an undirected way.
38:52What we are after
38:53is something where
38:54there is still motion
38:56in a particular direction.
38:58It would be different
38:59in a sense
39:00that it's directed.
39:05Freezing the ions
39:06will allow them
39:07to make only tiny,
39:09random movements
39:09in space,
39:11too small
39:11to make the ring move.
39:13But if the ion ring
39:15begins to turn anyway,
39:18it will mean
39:19there has been
39:20a fluctuation in time.
39:23From the theory perspective,
39:24it's not at all clear
39:26what is going to happen
39:27at these low temperatures.
39:29There are people
39:30who say that
39:30this ring should move,
39:32and others say
39:33it shouldn't.
39:35If the time ring works,
39:37then both space
39:38and time fluctuate.
39:40That might support
39:42Feynalk's theory
39:43that space-time
39:44is constantly generating
39:45itself in quantum bits.
39:49At the very least,
39:50it will demonstrate
39:52that space and time
39:53are inextricably linked
39:54in the quantum realm.
39:56So we have
39:57these quantum fluctuations
39:59in space.
40:01But time be treated
40:02as something
40:02that you can know
40:03very precisely.
40:05Actually,
40:06what I would be
40:07feeling much more happy with
40:08is if quantum mechanics
40:10would also assume
40:11that time is fuzzy,
40:12so to speak.
40:14That you can't tell
40:15what time it is
40:16exactly,
40:17only approximately.
40:19That you have
40:19fluctuations of time.
40:21And I've never worked
40:22with something
40:22where time fluctuates,
40:24so when I see it,
40:27maybe then it becomes
40:27natural to me, too.
40:29If we find
40:35the origins of time,
40:37we will answer
40:38one of the deepest
40:39riddles of creation.
40:42But we might also learn
40:44that time is meaningless
40:46to the universe.
40:48Time only matters to us
40:50because it anchors us
40:53between our memories
40:54of the past
40:55and the mystery
40:57of the future.
40:58The end of the future
41:01is where the future
41:04is.
41:05The end of the future
41:05is for the future.
41:06It's for the most
41:07we cannot wait
41:07for the future.
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