Through the Wormhole s05e10 Episode Script
When Did Time Begin?
We all float along the river of time.
But does that river have a source? How was time unleashed? Some believe time flows smoothly and eternally.
Others say it doesn't flow at all -- it pops into existence every fraction of a second.
The finest minds in physics can't agree.
But new experiments may hold the answer to the greatest unsolved mystery in the history of the universe.
The mystery Of when time began.
Space Time Life itself.
The secrets of the cosmos lie through the wormhole.
captions paid for by discovery communications When were you born? Sounds like a simple question.
You just say a certain year, a month, and day.
But around the world, we reckon time differently.
In Saudi Arabia, it's the 15th century.
In Israel, it's the 58th.
And we live in We all measure time relative to some starting point -- a point we have chosen.
But if we really want to know what time it is, we need to know when the cosmic clock started to tick.
Did time begin when the universe began? Or did it start some other way? Once, I was in a bike race.
I wanted to impress some friends with my terrific speed.
So I gave it everything I had.
It was a close race -- so close, I thought it was a tie.
One kid said my opponent was quickest.
But another said I was faster.
So, whose perception of time was correct? In a way, we were all right.
Time is a measure of change.
But how do we know things change? We rely on what our senses tell us, and primarily, we rely on what we can see.
We rely on light.
In the vacuum of space, light travels at a fixed speed of 186,000 miles per second.
This is accepted as an absolute truth of the universe.
And that, says cosmologist Janna Levin, gives light a unique relationship to time.
It's actually completely remarkable that the speed of light is an absolute.
It's never faster.
It's never slower.
To understand the relativity of time, we really need to understand light, and once we start thinking about the nature of light, all of our familiar intuitions are turned on their heads.
If the speed of light is constant, then time and space must shift and distort depending on your particular point of view.
Einstein had this very profound insight when he started to think about something as simple as light, and he realized that if light was going to be the same for everybody in the universe regardless of how fast they were moving or where they were in the universe, then space and time had to be different for different observers.
This means time is very personal.
It depends on where you are and how fast you are moving.
And the way you see your movement through time may not be the way others see your movement through time.
Say, for instance, Janna has a doppelganger that rides the subways and taxis of New York.
If Janna's doppelganger gets in a cab and that cab travels at incredible speeds time will flow differently for each woman.
If she flies past me in a taxi, it will appear to me that her time is running slower.
From my doppelganger's point of view, the street with me on it, we're flying past her in the opposite direction, and as far as she's concerned, her time is normal.
It's my time that's running slow.
To understand why this happens, imagine Janna turns on a double-sided laser whose pulsing beams bounce off the sidewalk below her and the balcony above her head.
The pulses form a light clock.
Each bounce of the laser beam is one tick.
Janna sees the light go straight up and down, but her cab-riding double sees something quite different.
From the perspective of the cab, the light appears to take a long diagonal and so seems as though my clock is taking too long to tick.
So it seems like my time is running slow.
If Janna's doppelganger turns on the laser in the taxi, she will see the beam hitting the ceiling and floor right above and below her.
But the Janna on the street sees the beam move diagonally.
Because the beam has longer to travel, its tick looks slower.
From my perspective on the street, if I'm looking into the taxi, I see their light take a long diagonal, and so I think it's taking their clock too long to tick.
From my perspective, their clocks are running slow.
The effect increases the faster you go.
If the cab approaches the speed of light, the speed limit of the universe, time outside the cab appears to stand still.
If that taxi was to fly by at the speed of light, it would look like my clock was never going to tick, like my time had stood still, like time was frozen.
So, which observer is correct? The Janna who's standing still? Or the Janna in motion? My doppelganger and I just fundamentally disagree on the passage of time, and it's true.
We're both right -- time is relative.
Relativity means that there can be no single universal time.
However, there was one moment when all perspectives on time must have been the same -- a moment when everything existed in one single place The big bang.
One of the hardest things to grasp about the idea of the big bang and the creation of the universe is the idea that time itself may have begun in that big event, that space was created in the big bang and time began to tick.
Before our big bang, there might not have been space or time.
Janna believes the big bang was probably when all the various time streams in the universe began and that, since then, time has passed differently in different places depending on how those places have moved.
But could we create places in our universe where time can appear to stop and then begin again? If we could hide an event from light, could we also hide it from time? These are questions Professor Alex Gaeta asked himself.
A former competition-tennis player, Alex is a physicist at Cornell university specializing in ultra-fast optics.
This technology is usually used for high-speed data transmission.
But after reading a paper written by theorists at imperial college, he realized it could also create a gap in time.
You know, light is an electromagnetic disturbance.
The minute things start changing, that's an indication that time is passing.
So all these changes that are occurring are creating all these electromagnetic disturbances that we can detect and measure as passage of time.
What we've figured out is a way of essentially turning off the lights, turning them back on without, you know, you sensing that they've ever actually been turned off.
What would happen if you turned off the light shining on time long enough to hide an event? Say, for instance, Alex is in a close game with his son, Max.
He's coming up to match point, and he wants to win.
If Alex could create a hole in time, no one could see him do this To observers, including his son, Alex wins the set without pause.
Right now, this is impossible.
But all great things start small.
This is the key component of Alex's experiment -- the split-time lens.
It focuses light signals and time the way a glass lens focuses light in space.
In a vacuum, the speed of light is constant, but that speed changes when light passes through a material or when it runs into another light beam.
Alex's split-time lens uses both tricks.
Alex shoots a laser into a beam of light, slowing it ever so slightly.
The beam then passes through a glass fiber where it splits into two parts, each with a different wavelength.
The lower wavelength pulls ahead of the higher wavelength, leaving a gap of absolute darkness.
Anything within that gap is impossible to observe since there is no light there.
The light then passes through another time lens that re-unifies the beam with no visible change.
Using this device, Alex has created gaps that last almost a billionth of a second.
That may not sound like much, but in the world of high-speed information transfer, it's significant.
Let's say you have a data stream and you don't want to interrupt it at all but you want to put some information into that data stream and then take it out.
So, by creating this gap, you can create the gap, not disturb the light stream, insert a little bit of data, transmit it, and then later on, pull out that data and then put the data stream back together.
And that information would be hidden from the passage of time.
Today, creating a light gap that lasts for one second would require a machine 186,000 miles long.
So Alex will have to win his tennis matches the hard way.
But the technology is rapidly evolving.
In principle, there have been demonstrations where they can slow down light by factors of 10 to the 7th, 10 to the 8th.
In the near future, it could be even more.
You could essentially almost stop light, store light for relatively long periods of time, seconds, and then essentially release it to travel, again, back at the speed of light.
Alex and Janna's work explores the deep connection between observers, light, and the passage of time.
It begs the question, does time exist if there is no one around to see it? One scientist says no -- time began much later than we think.
How often have you woken up in a darkened room and had no idea what time it was? Have you been out for minutes or hours? When you are sleeping, you have no sense that time is passing.
Perhaps the cosmos experiences time in the same way.
The big bang was the moment our universe was born, but what if it didn't wake up right away? Could there have been a time when the universe had no time? Professor Larry Schulman is a little out of place in dresden, Germany.
His home base is New York's Clarkson university, which often sits under a static sheet of ice.
Not so different, Larry says, from the state of the early universe, when, he claims, time did not exist.
Larry explores the behavior of systems composed of large numbers of particles such as the water in this fountain or the universe.
Statistical mechanics can also tell us about the relationship of light to time.
Light carries information about events.
We use it to determine what is happening now.
But because light has a speed limit, everything we see actually took place in the past.
The time it would take, for example, from the Sun is about 8 minutes because it's 93 million miles, and you figure with a velocity of 186,000 miles per second, that's how long the light would take.
So, if the Sun were to explode, for example, you would not know about it until eight minutes after the event.
The light of the most distant parts of the universe has been traveling toward us for 13.
8 billion years.
This is when the universe began in the big bang.
The early universe was nothing but a field of charged particles, a dense, hot cloud of plasma.
Photons, particles of light, could not travel very far in this soup.
Then about 380,000 years into the life of the universe, there was a sudden change called recombination.
This is when atoms began to form.
Prior to recombination, if an electron and a proton would approach and bind temporarily, they would be whacked by a photon coming along and be knocked apart.
Recombination is a process in which the electrons and the protons, which were previously loose and separated from each other in the plasma, finally can get together.
It's a bit like hockey.
If you imagine the hockey puck is a photon.
This is the river elbe, and sometimes it freezes over.
Supposing I would wait for that and go out there with my hockey puck, I could knock it to the bank with no problem.
But the universe just after the big bang was full of obstacles.
Now suppose that surrounding me were a bunch of goalies not protecting a goal, but just making sure that my hockey puck didn't pass them.
So all these goalies are standing around, and every time I hit the puck, one of them stops it.
This puck is not gonna get through.
This, Larry says, is the early universe.
Photon pucks couldn't get past the electron and proton goalies, so light didn't flow.
On the other hand, these goalies are a little bit unusual, and they alternate boy, girl, boy, girl, but at first, they didn't know that because of their big masks.
After a while, one of them removes the mask, and the guy next to her says, "oh.
" Hmm.
Then the puck can get right through.
Once the photons could escape easily, the world changed dramatically.
In the early universe, photons could never move freely, and there was no way to measure change.
Larry argues, that means time did not exist.
Only after recombination, when the universe cooled and atoms formed, did light begin to move around freely.
That, says Larry, is when the universe's clock began to tick.
The very earliest point, there's never even a time.
But eventually, there was something called time, which was keeping track of the way things changed.
This could explain the birth of time in our universe.
But if our universe ends, will time die with it? This physicist thinks time is truly fundamental -- time is always here.
It is space that comes and goes.
Time moves forward, never backward.
Physicists say that is because energy always dissipates.
If you wind time back far enough, you would see the entire energy of the universe coming together.
At the big bang, everything is focused on a single point.
You can't wind time back any more than this.
Or can you? Physicist Sean Carroll of the California institute of technology has spent much of his career contemplating time.
Though the origin of time is a mystery, Sean is certain of one thing -- in our universe, time has a direction, an arrow that runs through everything.
Time is a measure of change in the universe.
If nothing were changing in the world, there'd be no way of knowing that time was passing.
Everything would be the same at every single moment.
There'd be no clocks.
Time itself would basically have no meaning.
As long as something is changing, no matter how small, time is flowing.
And our universe is in a constant state of change.
At the dawn of the universe, an enormous amount of energy was compressed into a single point.
Then came the big bang.
Since then, with every passing second, that energy has become more and more spread out.
The measure of that spreading of energy is called entropy.
Sean believes the forward movement of time, time's arrow, is the steady movement from low entropy to high entropy.
But what set time's arrow in motion? The puzzle that we have is that entropy tends to increase, but our big bang was a condition of very, very low entropy, so how did it get that way? Where could it have come from? Everything we know in physics is things increasing in entropy.
So if you go back to the big bang, there was no lower entropy place it could've come from.
Sean suspects the answer is that our universe is the child of another universe.
But what was that universe like? Maybe like this Imagine a universe that's in equilibrium.
It's in a high-entropy state.
It's emptied out.
It's just sitting there quietly, much like the water in this tank.
You don't see any motion.
Now imagine in this universe where all the energy is dissipated, suddenly an area of dense energy pops into existence, much like this bag of effervescent tablets.
The seltzer starts small and dense and low entropy just like our universe did near the big bang, but then we expanded and cooled, galaxies formed, and the arrow of time progresses from past to future.
Likewise, the seltzer fizzes and becomes higher entropy as it mixes with the water around it.
And eventually, just like our universe will come back to equilibrium and the arrow of time will cease, the seltzer reaches equilibrium by mixing with the water around it, and we're back to a state that doesn't change anymore, a state without any arrow of time.
But how could a dead universe, one with no life, stars, or solid matter, give birth to another universe? According to quantum physics, even an empty void will experience tiny fluctuations of energy.
This means that every once in a while, something can pop out of nothing.
Think about the atomic nucleus of a radioactive element.
It just sits there.
You look at it.
It's not changing as you look at it, but there is a possibility every second that it will decay, that it will spit out a new particle.
What we're saying is that space-time itself can be radioactive just like that nucleus, except instead of spitting out a new particle, it can spit out an entirely new universe.
New universes may constantly be popping into existence.
A random quantum fluctuation in an ancient universe -- a universe so old, time fell apart -- might even have given birth to our universe.
This process of starting with no arrow of time, budding off a new universe, having an arrow, and the arrow only lasts for a little while as that universe expands and cools, but once it reaches equilibrium, the arrow stops -- this could happen many, many, many, many times.
Let's put it that way -- maybe an infinite number of times, but certainly a very, very large number, so it's possible that the universe we came from was nowhere near the first.
Our big bang might not have been the beginning.
Our cosmos' time could have ancestors that predated it and descendents after this universe is gone.
But there may be an even deeper truth about time, a truth we will never learn until we accept that it doesn't really exist.
What would we do without time? How could we keep track of the events in our lives without the steady pulse of minutes, days, and years? But it may be that none of that is real.
It may be that time is nothing more than a mirage.
This is the belief held by theoretical physicist Carlo Rovelli.
As a student in his native Italy, Carlo was on the barricades, fighting against the resurgent fascist movement.
I was young in the '70s, and there was the big dream of changing the world.
We failed.
We didn't change the world.
And so I think I moved into science because I thought it was another way of changing the world, and perhaps I could be more successful there.
Carlo leaves the centre de physique theorique de luminy, a think tank in the South of France.
But he's still breaking the rules.
As the leading voice of the theory of thermal time, he is raising the banner for a paradigm shift in fundamental physics.
In a nutshell, thermal time proposes that time does not exist -- at least not at the fundamental level of reality.
The idea that there's no time on the fundamental level is not so complicated after all.
Let me give you an example.
Imagine that you describe something happening in time, like this is oscillating in time.
What do we mean? We mean that there is something that moves with respect to time.
But what is time? Time is the position of the hand.
So what we are really observing here, what we're really doing here is comparing this movement with the movement of the hands of the clock.
So we describe how the hand's changing time, but what we really see is just how this angle changes with respect to this angle.
So, do without time means just to describe the world in terms of the way the various variables change with respect to one another without ever having to bringing this unobservable time into the picture.
Isaac Newton introduced the idea of a variable, "t" for "time," to describe how objects move.
But quantum physics treats time differently than Newton's classical system.
In fact, at the planck scale, the smallest unit of the physical world, time variables simply don't work.
Carlo thinks the only way to resolve this contradiction is to go back before Newton and get rid of the variable "t.
" He has completely reformulated quantum theory without the use of time.
But that's just the beginning.
The interesting part is actually the second part because if we accept the idea that there's no time on the fundamental level, nevertheless we do experience time.
Time passes for us, right? We live in time.
So where does this time experience come from? The answer, Carlo thinks, is heat.
When you add heat to matter, irreversible processes begin to take place, events that can't be undone.
Things begin to change in time.
So, every time there is some lack of reversibility in time, there's heat.
So time is tied to heat, and I think that the key idea is not that heat comes from time, but is that time comes from heat.
And heat is thermodynamics, and we have understood that thermodynamic is statistics.
So time is tied to statistics.
We don't know the fine details of nature.
We only understand the average.
We have only a statistical knowledge.
Say Carlo has an oven.
To measure all the quantum interactions inside the oven, he would need to make billions of measurements.
But no one can do that.
So, instead, he says, aah! "This oven is 450 degrees.
" Temperature is an average of the energies in the countless particles in a system.
It's what we get when we give up describing what's happening in the quantum world, and, Carlo says, so is time.
If we could see all the details of the world, we would see a timeless world in some sense.
We wouldn't see this thing that we feel as time.
To Carlo, time is just a statement of limited information.
The fundamental level of the universe is timeless.
But at larger levels of reality, when the interactions of matter and heat begin to have visible effects, the thing we call "time" is born.
Time began when some system, instead of interacting just with its neighbor, interacted with a big set of systems.
So time began when some system started having partial information, not complete information about its surrounding.
Time begin with our ignorance and grows with our ignorance.
It's a radical view of the universe, but Carlo has never been afraid to challenge the status quo.
Is Carlo correct? Is time really just our failure to comprehend the dispersion of heat? This woman says there is another possibility.
Time is real.
But it is born and reborn a trillion, trillion times a second.
When I move from place to place, my senses tell me it happens in one continuous sweep.
But according to quantum mechanics, any movement Is actually a series of microscopic jitters through space.
Huh? No one has yet worked out how to apply the theory of quantum mechanics to time, but some scientists are getting very close.
If they succeed, we will have to accept a strange, new idea -- every minute fraction of a second, time bursts into existence over and over.
Like all of us, fay dowker experiences a flow of time.
She was a girl Then a university student And now she's a physicist at London's imperial college.
Nothing is more fundamental to our experiences than that we have those experiences in time.
We are aware of time passing.
Time seems to flow.
We can hardly make sense of our lives except in the context of some fixed past of events that have already happened and that can never be changed and some open future of events that are free and haven't happened yet and some mysterious and elusive moment of now that appears to separate the two.
This idea seems obvious.
But, actually, it goes against our best scientific theory of how the universe works.
The theory of relativity tells us space and time are inextricably joined.
All time that will exist already exists in a block we call "space-time.
" As we pass from birth to death, we glimpse our own individual trails through this frozen space-time landscape.
But fay believes the universe is not a frozen block.
It is a growing pile made of quantum grains of space and time.
Space-time seems smooth and continuous to us, but that's just because we're very large and we see things at large scales.
So, if we imagine that a solid cube of something, say a sugar cube, represents a piece of space-time, then from far away, that looks solid.
It looks like a chunk.
But we know that if you zoom in on it and look at its more fundamental structure, we see that it breaks up into grains.
The idea with a granular model of space-time is similar.
At fundamental, tiny scales, it's grainy and particulate.
At large scales, it appears smooth and continuous.
We don't notice that granularity.
Just how small is a grain of space-time? Inconceivably small.
Roughly a million, trillion, trillion, trillionth of a second.
This is what physicists believe is the smallest possible unit of measurement.
Fay thinks space-time is built from a prodigious stack of these impossibly tiny grains, which she calls "space-time atoms.
" This marries together two concepts -- that space-time is fundamentally atomic or bitty or granular at very tiny scales with the notion of causality, the fact that cause must precede effect.
So, for example, if I hear a loud noise then that will startle me, and I might drop my cup of coffee.
So the cause was the loud noise.
The effect was the dropping of my cup of coffee.
If, as relativity insists, all of space and time already exist, the coffee cup will always fall, is always falling, has always fallen.
But in fay's view, the universe is a set of events that is forever growing.
When we observe these connected sequences of events, what she calls a causal set, we perceive that time is passing.
A causal set can grow by the accumulation of new space-time atoms.
And this birth of new space-time atoms could be the passage of time as we know it.
What we experience as the present is the birth of these new space-time atoms.
The old atoms don't die.
They pile up into the thing we call "the past.
" The future has yet to be born.
Once a space-time atom is born and exists, it will then form part of the past.
So, in that sense, it also realizes our sense that the past is fixed, that the past has happened, and that it cannot be changed.
Time may not be a continuous river, but rather an endless rain of events.
So, which concept of time is correct? Are we getting closer to the origin of time? We may soon know.
In this laboratory, researchers are working on a new experiment that could forever change our understanding of time and the universe.
Time may have begun at the big bang.
It may have always been flowing.
Or it could be born trillions of times every second.
This debate could go on for decades.
Or it could end any day now.
Because we may finally have an experiment that reveals the true nature of time.
At the Berkeley campus of the university of California, Professor Hartmut haeffner is building a time ring -- an object that will rotate like this disk.
But while this metal ring is levitated using electromagnetic force, a time ring will be driven by a jitter in time.
If it works, this experiment will prove a controversial theory -- the quantum fluctuations that have been observed in space also exist in time.
We physicists like symmetries, and one symmetry is like space and time.
We would like to treat them on the same footing, so whatever we observe in space, we think we should also see in time, and this would actually simplify the description of the universe or make it more elegant.
Nanotechnologist Tongcang Li, also at Berkeley, devised the time-ring experiment.
He approached Hartmut, an expert in trapping and studying atomic particles.
But Hartmut had his doubts.
In the beginning, I mean, I was thinking, "I mean, they are crazy.
I mean, this is a ridiculous idea," and then we start to talking, and I realized, "oh, wait.
"This is really weird, but they are right.
This is the way it should be.
" On this electrode, inside a space the width of a human hair, Hartmut and his team will create a perfectly static landscape -- a landscape isolated from outside energy.
To further reduce energy in the system, he must trap and cool calcium ions down to a few billionths of a degree above absolute zero -- colder than anything has ever been cooled before.
This will take the ions down to their ground state -- the state of minimum possible energy.
Only then can the effects of space be separated from time.
Imagine these ball bearings are calcium ions and we're going to inject 100 of these calcium ions into our vacuum chamber.
So, at normal temperatures, these ions move around rapidly in random directions, but when we cool them, they form this ring and they slow down, and you would expect that at some point, this ring stops moving.
It wouldn't rotate, but if this theory is correct, that ring should move, rotate, spin.
An object at ground state shouldn't move, because it neither consumes nor produces energy.
But quantum mechanics tells us zero does not mean zero.
Even at ground state, there will still be quantum fluctuations.
In quantum mechanics, there's always this finite jitter motion in the ground state.
Things will still move, but they will move in an undirected way.
What we are after is something where there is still motion in a particular direction.
It would be different in the sense that it's directed.
Freezing the ions will allow them to make only tiny, random movements in space -- too small to make the ring move.
But if the ion ring begins to turn anyway, it will mean there has been a fluctuation in time.
From the theory perspective, it's not at all clear what is going to happen at these low temperatures.
There are people who say that this ring should move, and others say it shouldn't.
If the time ring works, then both space and time fluctuate.
That might support fay dowker's theory that space-time is constantly generating itself in quantum dips.
At the very least, it will demonstrate that space and time are inextricably linked in the quantum realm.
So, we have these quantum fluctuations in space, but time we treat as something which you can know very precisely.
Well, actually, what I would be feeling much more happy with is if quantum mechanics would also assume that time is fuzzy, so to speak, that you can't tell what time it is exactly, only approximately, that you have fluctuations of time.
And I've never worked with something where time fluctuates, so When I see it, maybe then it becomes natural to me, too.
If we find the origins of time, we will answer one of the deepest riddles of creation.
But we might also learn that time is meaningless to the universe -- time only matters to us because it anchors us between our memories of the past And the mystery of the future.
But does that river have a source? How was time unleashed? Some believe time flows smoothly and eternally.
Others say it doesn't flow at all -- it pops into existence every fraction of a second.
The finest minds in physics can't agree.
But new experiments may hold the answer to the greatest unsolved mystery in the history of the universe.
The mystery Of when time began.
Space Time Life itself.
The secrets of the cosmos lie through the wormhole.
captions paid for by discovery communications When were you born? Sounds like a simple question.
You just say a certain year, a month, and day.
But around the world, we reckon time differently.
In Saudi Arabia, it's the 15th century.
In Israel, it's the 58th.
And we live in We all measure time relative to some starting point -- a point we have chosen.
But if we really want to know what time it is, we need to know when the cosmic clock started to tick.
Did time begin when the universe began? Or did it start some other way? Once, I was in a bike race.
I wanted to impress some friends with my terrific speed.
So I gave it everything I had.
It was a close race -- so close, I thought it was a tie.
One kid said my opponent was quickest.
But another said I was faster.
So, whose perception of time was correct? In a way, we were all right.
Time is a measure of change.
But how do we know things change? We rely on what our senses tell us, and primarily, we rely on what we can see.
We rely on light.
In the vacuum of space, light travels at a fixed speed of 186,000 miles per second.
This is accepted as an absolute truth of the universe.
And that, says cosmologist Janna Levin, gives light a unique relationship to time.
It's actually completely remarkable that the speed of light is an absolute.
It's never faster.
It's never slower.
To understand the relativity of time, we really need to understand light, and once we start thinking about the nature of light, all of our familiar intuitions are turned on their heads.
If the speed of light is constant, then time and space must shift and distort depending on your particular point of view.
Einstein had this very profound insight when he started to think about something as simple as light, and he realized that if light was going to be the same for everybody in the universe regardless of how fast they were moving or where they were in the universe, then space and time had to be different for different observers.
This means time is very personal.
It depends on where you are and how fast you are moving.
And the way you see your movement through time may not be the way others see your movement through time.
Say, for instance, Janna has a doppelganger that rides the subways and taxis of New York.
If Janna's doppelganger gets in a cab and that cab travels at incredible speeds time will flow differently for each woman.
If she flies past me in a taxi, it will appear to me that her time is running slower.
From my doppelganger's point of view, the street with me on it, we're flying past her in the opposite direction, and as far as she's concerned, her time is normal.
It's my time that's running slow.
To understand why this happens, imagine Janna turns on a double-sided laser whose pulsing beams bounce off the sidewalk below her and the balcony above her head.
The pulses form a light clock.
Each bounce of the laser beam is one tick.
Janna sees the light go straight up and down, but her cab-riding double sees something quite different.
From the perspective of the cab, the light appears to take a long diagonal and so seems as though my clock is taking too long to tick.
So it seems like my time is running slow.
If Janna's doppelganger turns on the laser in the taxi, she will see the beam hitting the ceiling and floor right above and below her.
But the Janna on the street sees the beam move diagonally.
Because the beam has longer to travel, its tick looks slower.
From my perspective on the street, if I'm looking into the taxi, I see their light take a long diagonal, and so I think it's taking their clock too long to tick.
From my perspective, their clocks are running slow.
The effect increases the faster you go.
If the cab approaches the speed of light, the speed limit of the universe, time outside the cab appears to stand still.
If that taxi was to fly by at the speed of light, it would look like my clock was never going to tick, like my time had stood still, like time was frozen.
So, which observer is correct? The Janna who's standing still? Or the Janna in motion? My doppelganger and I just fundamentally disagree on the passage of time, and it's true.
We're both right -- time is relative.
Relativity means that there can be no single universal time.
However, there was one moment when all perspectives on time must have been the same -- a moment when everything existed in one single place The big bang.
One of the hardest things to grasp about the idea of the big bang and the creation of the universe is the idea that time itself may have begun in that big event, that space was created in the big bang and time began to tick.
Before our big bang, there might not have been space or time.
Janna believes the big bang was probably when all the various time streams in the universe began and that, since then, time has passed differently in different places depending on how those places have moved.
But could we create places in our universe where time can appear to stop and then begin again? If we could hide an event from light, could we also hide it from time? These are questions Professor Alex Gaeta asked himself.
A former competition-tennis player, Alex is a physicist at Cornell university specializing in ultra-fast optics.
This technology is usually used for high-speed data transmission.
But after reading a paper written by theorists at imperial college, he realized it could also create a gap in time.
You know, light is an electromagnetic disturbance.
The minute things start changing, that's an indication that time is passing.
So all these changes that are occurring are creating all these electromagnetic disturbances that we can detect and measure as passage of time.
What we've figured out is a way of essentially turning off the lights, turning them back on without, you know, you sensing that they've ever actually been turned off.
What would happen if you turned off the light shining on time long enough to hide an event? Say, for instance, Alex is in a close game with his son, Max.
He's coming up to match point, and he wants to win.
If Alex could create a hole in time, no one could see him do this To observers, including his son, Alex wins the set without pause.
Right now, this is impossible.
But all great things start small.
This is the key component of Alex's experiment -- the split-time lens.
It focuses light signals and time the way a glass lens focuses light in space.
In a vacuum, the speed of light is constant, but that speed changes when light passes through a material or when it runs into another light beam.
Alex's split-time lens uses both tricks.
Alex shoots a laser into a beam of light, slowing it ever so slightly.
The beam then passes through a glass fiber where it splits into two parts, each with a different wavelength.
The lower wavelength pulls ahead of the higher wavelength, leaving a gap of absolute darkness.
Anything within that gap is impossible to observe since there is no light there.
The light then passes through another time lens that re-unifies the beam with no visible change.
Using this device, Alex has created gaps that last almost a billionth of a second.
That may not sound like much, but in the world of high-speed information transfer, it's significant.
Let's say you have a data stream and you don't want to interrupt it at all but you want to put some information into that data stream and then take it out.
So, by creating this gap, you can create the gap, not disturb the light stream, insert a little bit of data, transmit it, and then later on, pull out that data and then put the data stream back together.
And that information would be hidden from the passage of time.
Today, creating a light gap that lasts for one second would require a machine 186,000 miles long.
So Alex will have to win his tennis matches the hard way.
But the technology is rapidly evolving.
In principle, there have been demonstrations where they can slow down light by factors of 10 to the 7th, 10 to the 8th.
In the near future, it could be even more.
You could essentially almost stop light, store light for relatively long periods of time, seconds, and then essentially release it to travel, again, back at the speed of light.
Alex and Janna's work explores the deep connection between observers, light, and the passage of time.
It begs the question, does time exist if there is no one around to see it? One scientist says no -- time began much later than we think.
How often have you woken up in a darkened room and had no idea what time it was? Have you been out for minutes or hours? When you are sleeping, you have no sense that time is passing.
Perhaps the cosmos experiences time in the same way.
The big bang was the moment our universe was born, but what if it didn't wake up right away? Could there have been a time when the universe had no time? Professor Larry Schulman is a little out of place in dresden, Germany.
His home base is New York's Clarkson university, which often sits under a static sheet of ice.
Not so different, Larry says, from the state of the early universe, when, he claims, time did not exist.
Larry explores the behavior of systems composed of large numbers of particles such as the water in this fountain or the universe.
Statistical mechanics can also tell us about the relationship of light to time.
Light carries information about events.
We use it to determine what is happening now.
But because light has a speed limit, everything we see actually took place in the past.
The time it would take, for example, from the Sun is about 8 minutes because it's 93 million miles, and you figure with a velocity of 186,000 miles per second, that's how long the light would take.
So, if the Sun were to explode, for example, you would not know about it until eight minutes after the event.
The light of the most distant parts of the universe has been traveling toward us for 13.
8 billion years.
This is when the universe began in the big bang.
The early universe was nothing but a field of charged particles, a dense, hot cloud of plasma.
Photons, particles of light, could not travel very far in this soup.
Then about 380,000 years into the life of the universe, there was a sudden change called recombination.
This is when atoms began to form.
Prior to recombination, if an electron and a proton would approach and bind temporarily, they would be whacked by a photon coming along and be knocked apart.
Recombination is a process in which the electrons and the protons, which were previously loose and separated from each other in the plasma, finally can get together.
It's a bit like hockey.
If you imagine the hockey puck is a photon.
This is the river elbe, and sometimes it freezes over.
Supposing I would wait for that and go out there with my hockey puck, I could knock it to the bank with no problem.
But the universe just after the big bang was full of obstacles.
Now suppose that surrounding me were a bunch of goalies not protecting a goal, but just making sure that my hockey puck didn't pass them.
So all these goalies are standing around, and every time I hit the puck, one of them stops it.
This puck is not gonna get through.
This, Larry says, is the early universe.
Photon pucks couldn't get past the electron and proton goalies, so light didn't flow.
On the other hand, these goalies are a little bit unusual, and they alternate boy, girl, boy, girl, but at first, they didn't know that because of their big masks.
After a while, one of them removes the mask, and the guy next to her says, "oh.
" Hmm.
Then the puck can get right through.
Once the photons could escape easily, the world changed dramatically.
In the early universe, photons could never move freely, and there was no way to measure change.
Larry argues, that means time did not exist.
Only after recombination, when the universe cooled and atoms formed, did light begin to move around freely.
That, says Larry, is when the universe's clock began to tick.
The very earliest point, there's never even a time.
But eventually, there was something called time, which was keeping track of the way things changed.
This could explain the birth of time in our universe.
But if our universe ends, will time die with it? This physicist thinks time is truly fundamental -- time is always here.
It is space that comes and goes.
Time moves forward, never backward.
Physicists say that is because energy always dissipates.
If you wind time back far enough, you would see the entire energy of the universe coming together.
At the big bang, everything is focused on a single point.
You can't wind time back any more than this.
Or can you? Physicist Sean Carroll of the California institute of technology has spent much of his career contemplating time.
Though the origin of time is a mystery, Sean is certain of one thing -- in our universe, time has a direction, an arrow that runs through everything.
Time is a measure of change in the universe.
If nothing were changing in the world, there'd be no way of knowing that time was passing.
Everything would be the same at every single moment.
There'd be no clocks.
Time itself would basically have no meaning.
As long as something is changing, no matter how small, time is flowing.
And our universe is in a constant state of change.
At the dawn of the universe, an enormous amount of energy was compressed into a single point.
Then came the big bang.
Since then, with every passing second, that energy has become more and more spread out.
The measure of that spreading of energy is called entropy.
Sean believes the forward movement of time, time's arrow, is the steady movement from low entropy to high entropy.
But what set time's arrow in motion? The puzzle that we have is that entropy tends to increase, but our big bang was a condition of very, very low entropy, so how did it get that way? Where could it have come from? Everything we know in physics is things increasing in entropy.
So if you go back to the big bang, there was no lower entropy place it could've come from.
Sean suspects the answer is that our universe is the child of another universe.
But what was that universe like? Maybe like this Imagine a universe that's in equilibrium.
It's in a high-entropy state.
It's emptied out.
It's just sitting there quietly, much like the water in this tank.
You don't see any motion.
Now imagine in this universe where all the energy is dissipated, suddenly an area of dense energy pops into existence, much like this bag of effervescent tablets.
The seltzer starts small and dense and low entropy just like our universe did near the big bang, but then we expanded and cooled, galaxies formed, and the arrow of time progresses from past to future.
Likewise, the seltzer fizzes and becomes higher entropy as it mixes with the water around it.
And eventually, just like our universe will come back to equilibrium and the arrow of time will cease, the seltzer reaches equilibrium by mixing with the water around it, and we're back to a state that doesn't change anymore, a state without any arrow of time.
But how could a dead universe, one with no life, stars, or solid matter, give birth to another universe? According to quantum physics, even an empty void will experience tiny fluctuations of energy.
This means that every once in a while, something can pop out of nothing.
Think about the atomic nucleus of a radioactive element.
It just sits there.
You look at it.
It's not changing as you look at it, but there is a possibility every second that it will decay, that it will spit out a new particle.
What we're saying is that space-time itself can be radioactive just like that nucleus, except instead of spitting out a new particle, it can spit out an entirely new universe.
New universes may constantly be popping into existence.
A random quantum fluctuation in an ancient universe -- a universe so old, time fell apart -- might even have given birth to our universe.
This process of starting with no arrow of time, budding off a new universe, having an arrow, and the arrow only lasts for a little while as that universe expands and cools, but once it reaches equilibrium, the arrow stops -- this could happen many, many, many, many times.
Let's put it that way -- maybe an infinite number of times, but certainly a very, very large number, so it's possible that the universe we came from was nowhere near the first.
Our big bang might not have been the beginning.
Our cosmos' time could have ancestors that predated it and descendents after this universe is gone.
But there may be an even deeper truth about time, a truth we will never learn until we accept that it doesn't really exist.
What would we do without time? How could we keep track of the events in our lives without the steady pulse of minutes, days, and years? But it may be that none of that is real.
It may be that time is nothing more than a mirage.
This is the belief held by theoretical physicist Carlo Rovelli.
As a student in his native Italy, Carlo was on the barricades, fighting against the resurgent fascist movement.
I was young in the '70s, and there was the big dream of changing the world.
We failed.
We didn't change the world.
And so I think I moved into science because I thought it was another way of changing the world, and perhaps I could be more successful there.
Carlo leaves the centre de physique theorique de luminy, a think tank in the South of France.
But he's still breaking the rules.
As the leading voice of the theory of thermal time, he is raising the banner for a paradigm shift in fundamental physics.
In a nutshell, thermal time proposes that time does not exist -- at least not at the fundamental level of reality.
The idea that there's no time on the fundamental level is not so complicated after all.
Let me give you an example.
Imagine that you describe something happening in time, like this is oscillating in time.
What do we mean? We mean that there is something that moves with respect to time.
But what is time? Time is the position of the hand.
So what we are really observing here, what we're really doing here is comparing this movement with the movement of the hands of the clock.
So we describe how the hand's changing time, but what we really see is just how this angle changes with respect to this angle.
So, do without time means just to describe the world in terms of the way the various variables change with respect to one another without ever having to bringing this unobservable time into the picture.
Isaac Newton introduced the idea of a variable, "t" for "time," to describe how objects move.
But quantum physics treats time differently than Newton's classical system.
In fact, at the planck scale, the smallest unit of the physical world, time variables simply don't work.
Carlo thinks the only way to resolve this contradiction is to go back before Newton and get rid of the variable "t.
" He has completely reformulated quantum theory without the use of time.
But that's just the beginning.
The interesting part is actually the second part because if we accept the idea that there's no time on the fundamental level, nevertheless we do experience time.
Time passes for us, right? We live in time.
So where does this time experience come from? The answer, Carlo thinks, is heat.
When you add heat to matter, irreversible processes begin to take place, events that can't be undone.
Things begin to change in time.
So, every time there is some lack of reversibility in time, there's heat.
So time is tied to heat, and I think that the key idea is not that heat comes from time, but is that time comes from heat.
And heat is thermodynamics, and we have understood that thermodynamic is statistics.
So time is tied to statistics.
We don't know the fine details of nature.
We only understand the average.
We have only a statistical knowledge.
Say Carlo has an oven.
To measure all the quantum interactions inside the oven, he would need to make billions of measurements.
But no one can do that.
So, instead, he says, aah! "This oven is 450 degrees.
" Temperature is an average of the energies in the countless particles in a system.
It's what we get when we give up describing what's happening in the quantum world, and, Carlo says, so is time.
If we could see all the details of the world, we would see a timeless world in some sense.
We wouldn't see this thing that we feel as time.
To Carlo, time is just a statement of limited information.
The fundamental level of the universe is timeless.
But at larger levels of reality, when the interactions of matter and heat begin to have visible effects, the thing we call "time" is born.
Time began when some system, instead of interacting just with its neighbor, interacted with a big set of systems.
So time began when some system started having partial information, not complete information about its surrounding.
Time begin with our ignorance and grows with our ignorance.
It's a radical view of the universe, but Carlo has never been afraid to challenge the status quo.
Is Carlo correct? Is time really just our failure to comprehend the dispersion of heat? This woman says there is another possibility.
Time is real.
But it is born and reborn a trillion, trillion times a second.
When I move from place to place, my senses tell me it happens in one continuous sweep.
But according to quantum mechanics, any movement Is actually a series of microscopic jitters through space.
Huh? No one has yet worked out how to apply the theory of quantum mechanics to time, but some scientists are getting very close.
If they succeed, we will have to accept a strange, new idea -- every minute fraction of a second, time bursts into existence over and over.
Like all of us, fay dowker experiences a flow of time.
She was a girl Then a university student And now she's a physicist at London's imperial college.
Nothing is more fundamental to our experiences than that we have those experiences in time.
We are aware of time passing.
Time seems to flow.
We can hardly make sense of our lives except in the context of some fixed past of events that have already happened and that can never be changed and some open future of events that are free and haven't happened yet and some mysterious and elusive moment of now that appears to separate the two.
This idea seems obvious.
But, actually, it goes against our best scientific theory of how the universe works.
The theory of relativity tells us space and time are inextricably joined.
All time that will exist already exists in a block we call "space-time.
" As we pass from birth to death, we glimpse our own individual trails through this frozen space-time landscape.
But fay believes the universe is not a frozen block.
It is a growing pile made of quantum grains of space and time.
Space-time seems smooth and continuous to us, but that's just because we're very large and we see things at large scales.
So, if we imagine that a solid cube of something, say a sugar cube, represents a piece of space-time, then from far away, that looks solid.
It looks like a chunk.
But we know that if you zoom in on it and look at its more fundamental structure, we see that it breaks up into grains.
The idea with a granular model of space-time is similar.
At fundamental, tiny scales, it's grainy and particulate.
At large scales, it appears smooth and continuous.
We don't notice that granularity.
Just how small is a grain of space-time? Inconceivably small.
Roughly a million, trillion, trillion, trillionth of a second.
This is what physicists believe is the smallest possible unit of measurement.
Fay thinks space-time is built from a prodigious stack of these impossibly tiny grains, which she calls "space-time atoms.
" This marries together two concepts -- that space-time is fundamentally atomic or bitty or granular at very tiny scales with the notion of causality, the fact that cause must precede effect.
So, for example, if I hear a loud noise then that will startle me, and I might drop my cup of coffee.
So the cause was the loud noise.
The effect was the dropping of my cup of coffee.
If, as relativity insists, all of space and time already exist, the coffee cup will always fall, is always falling, has always fallen.
But in fay's view, the universe is a set of events that is forever growing.
When we observe these connected sequences of events, what she calls a causal set, we perceive that time is passing.
A causal set can grow by the accumulation of new space-time atoms.
And this birth of new space-time atoms could be the passage of time as we know it.
What we experience as the present is the birth of these new space-time atoms.
The old atoms don't die.
They pile up into the thing we call "the past.
" The future has yet to be born.
Once a space-time atom is born and exists, it will then form part of the past.
So, in that sense, it also realizes our sense that the past is fixed, that the past has happened, and that it cannot be changed.
Time may not be a continuous river, but rather an endless rain of events.
So, which concept of time is correct? Are we getting closer to the origin of time? We may soon know.
In this laboratory, researchers are working on a new experiment that could forever change our understanding of time and the universe.
Time may have begun at the big bang.
It may have always been flowing.
Or it could be born trillions of times every second.
This debate could go on for decades.
Or it could end any day now.
Because we may finally have an experiment that reveals the true nature of time.
At the Berkeley campus of the university of California, Professor Hartmut haeffner is building a time ring -- an object that will rotate like this disk.
But while this metal ring is levitated using electromagnetic force, a time ring will be driven by a jitter in time.
If it works, this experiment will prove a controversial theory -- the quantum fluctuations that have been observed in space also exist in time.
We physicists like symmetries, and one symmetry is like space and time.
We would like to treat them on the same footing, so whatever we observe in space, we think we should also see in time, and this would actually simplify the description of the universe or make it more elegant.
Nanotechnologist Tongcang Li, also at Berkeley, devised the time-ring experiment.
He approached Hartmut, an expert in trapping and studying atomic particles.
But Hartmut had his doubts.
In the beginning, I mean, I was thinking, "I mean, they are crazy.
I mean, this is a ridiculous idea," and then we start to talking, and I realized, "oh, wait.
"This is really weird, but they are right.
This is the way it should be.
" On this electrode, inside a space the width of a human hair, Hartmut and his team will create a perfectly static landscape -- a landscape isolated from outside energy.
To further reduce energy in the system, he must trap and cool calcium ions down to a few billionths of a degree above absolute zero -- colder than anything has ever been cooled before.
This will take the ions down to their ground state -- the state of minimum possible energy.
Only then can the effects of space be separated from time.
Imagine these ball bearings are calcium ions and we're going to inject 100 of these calcium ions into our vacuum chamber.
So, at normal temperatures, these ions move around rapidly in random directions, but when we cool them, they form this ring and they slow down, and you would expect that at some point, this ring stops moving.
It wouldn't rotate, but if this theory is correct, that ring should move, rotate, spin.
An object at ground state shouldn't move, because it neither consumes nor produces energy.
But quantum mechanics tells us zero does not mean zero.
Even at ground state, there will still be quantum fluctuations.
In quantum mechanics, there's always this finite jitter motion in the ground state.
Things will still move, but they will move in an undirected way.
What we are after is something where there is still motion in a particular direction.
It would be different in the sense that it's directed.
Freezing the ions will allow them to make only tiny, random movements in space -- too small to make the ring move.
But if the ion ring begins to turn anyway, it will mean there has been a fluctuation in time.
From the theory perspective, it's not at all clear what is going to happen at these low temperatures.
There are people who say that this ring should move, and others say it shouldn't.
If the time ring works, then both space and time fluctuate.
That might support fay dowker's theory that space-time is constantly generating itself in quantum dips.
At the very least, it will demonstrate that space and time are inextricably linked in the quantum realm.
So, we have these quantum fluctuations in space, but time we treat as something which you can know very precisely.
Well, actually, what I would be feeling much more happy with is if quantum mechanics would also assume that time is fuzzy, so to speak, that you can't tell what time it is exactly, only approximately, that you have fluctuations of time.
And I've never worked with something where time fluctuates, so When I see it, maybe then it becomes natural to me, too.
If we find the origins of time, we will answer one of the deepest riddles of creation.
But we might also learn that time is meaningless to the universe -- time only matters to us because it anchors us between our memories of the past And the mystery of the future.