Is Time Real?

[music]

>> San Francisco, 1870.

A railroad passenger traveling to

Washington state would have to set his

watch over 200 times [music] if he

wanted to match the local time of every

passing town.

The world didn't have standard time yet.

Each country, each city, sometimes each

village kept its own time.

Not too consequential until the advent

of railroad travel and railroad [music]

schedules.

On November 18th, 1883,

the railroads imposed a uniform time at

the stations to end the confusion at the

depots.

The rest of the world soon followed.

In 1884, representatives from around the

world met in Washington, D.C. to

establish a common standard for time.

They [music] divided Earth's surface

into 24 regions called time zones.

World standard time divides our [music]

timekeeping into tidy, uniform packages.

But what exactly are we measuring?

>> [music]

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>> Think of how we speak of time.

Time sure flies. I'm out of time. Just

in the nick of time. I'm wasting my

time.

But what are we describing?

Is time part of our physical world? We

can't see it, touch it, hear it. Yet

don't we all somehow feel it passing?

What is time?

>> On the one side there is the time of the

world. I'd say it ignores me completely.

It is a time of millions of millions of

years and human time is chopped up like

a very thin branch out of this cosmic

one.

So what makes it time?

It is the fact that we observe and

measure it.

We count it.

>> Ancient civilizations' creation of the

calendar connected our mortal time with

the immensity of cosmic time.

>> How to make coincide the repetitive

structures of the cosmic time with the

rhythm of human actions?

Or a calendar is an instrument for

measuring time but for humans.

That is to say for the one who is

marking the intervals of human action.

For dynasties' reigns, time is for

festivities.

Time's for work.

Time's for rest.

And the calendar is constructed as an

instrument of exchange between the time

which we can call cosmic, cosmological,

and the time of the soul, psychological

time, the phenomenological time.

>> Our lives are brief in comparison with

the immensity of the world's history.

Yet as Ricoeur writes, there is the real

paradox. On a cosmic scale, our lifespan

is insignificant.

Yet this brief period of time when we

appear in the world is the moment during

which all meaningful questions arise.

>> The lifespan of the earth, several

billion billion years. The the lifespan

of the universe

and then human time is such a tiny speck

in there. But on the other hand,

everything that is important happens in

that tiny tiny little bit of time.

So that's sort of

tension built into our

looking at time like our looking at the

universe generally to

to have the significant things not lose

their significance by being

geared into that enormous context where

it seems that it that it really means

nothing.

>> We live in this cosmic time [music] with

our own timekeeping.

We know we live just not in the present,

but with memories of the past and

anticipation of the future.

Physicist Paul Davies writes that our

very notion of personal identity,

[music]

the self, the soul, is closely bound up

with memory and [music] enduring

experience.

It is not sufficient to proclaim, I

exist at this instant. [music]

To be an individual implies a continuity

of experience together with some linking

feature, such as memory.

>> And now when we as human beings relate

to the world around us, then time plays

a very important role.

Because when we structure the world, we

don't structure it as just something

that is there just now, but our

structuring extends backwards and

forwards through time.

We

encounter things in the world as having

been there even before we set our eye on

them and remaining there even when we

turn to other things later.

>> We treasure traces of the past. We frame

cherished photographs, [music]

dig for fossils of prehistoric ages,

erect monuments as reminders [music] of

historic moments.

But for many of us, there seems to be

[music] less time to reflect on

yesterday as we race forward with our

plans [music] for tomorrow.

>> I think that like most modern people, we

when we think about it, we will notice

that our

notion of ourselves, our temporal

existence is very much permeated by

time measurements,

by the clock. I know when I had to get

up from this chair and go somewhere

else, by the almanac, the agenda, and

that perhaps is very different from the

sort of experience of time that people

had before calendars, before the clock,

etc.

Uh

and if I should speak about my

experience of time,

most of the time it's completely taken

up by thoughts about what to do next.

>> Is this division of time into past,

present, [music] and future as neat and

tidy as our date books make it out to

be?

Aristotle formulated one of the basic

paradoxes [music]

of time.

>> Time, whether limitless or any given

length, is made up of the no longer and

not yet.

How can we conceive of that which is

composed of nonexistence?

>> Uh

Aristotle, when he

treats time in the physics starts with a

riddle that he never answers that goes

something like this.

>> [snorts]

>> Think about time

as divided into the past, the present,

and the future.

And then think for a while about what

the present is.

How thick is the present?

The present is just a limit between the

past and the future.

Then you get the paradox.

Uh because the past is something that

does not exist.

It has existed, but it does not exist

any longer. The future is something that

does not exist. It will exist, [music]

but it doesn't exist. And the present is

nothing.

So, time seem to be a nothing dividing

something non-existent from something

non-existent.

>> J.M.E. McTaggart considered the ideas of

past, present, and future and wrote a

pivotal essay called [music] The

Unreality of Time.

McTaggart points out that however

unnatural it may feel [music] to assert

that time is unreal, many thinkers have

treated it as such. And he thought they

were right.

>> Past, [music] present, and future are

incompatible determinations.

Every event must be one or the other,

but no event can be more than one.

>> [clears throat]

>> And it is because the distinctions of

the past, present, and future seem to me

to be essential for time

that I regard time as [clears throat]

unreal.

>> McTaggart's argument is that these

notions are in some sense

self-contradictory.

And perhaps the easiest thing easiest

way to

uh

think about that is to think about the

present. There's only one present.

This moment is the only present moment.

On the other hand, every moment is

present.

Uh this

How do we reconcile these things? What

is unique about the present moment being

present and not past?

>> Does the present enjoy some sort of

privileged status in terms of its

reality

or is temporal becoming just a

subjective illusion of human

consciousness?

For persons in 2000 BC, that time is

real and present. For persons in 2050,

that time is real and present for them.

For us, our time now is real and

present. Is this just a subjective

illusion or is there in fact some sort

of privileged status, privileged reality

that the present possesses which the

past and future do not?

>> There are two basic views about what a

time is. Time the present time could

consist of of all the events that are

occurring at present.

So that you and I all our events and our

movements are part of time or time could

be

um

kind of a substance or a particular or a

thing in its own right.

And so when we just occupy that thing.

So there are two different views of time

there. One's called the relational view

where all the events that are going on

now make up time and the other is

is that time is this entity in its own

right and then we were just occupying

it.

>> But are we too caught up with

correlating words like past, present,

and future to something real?

Immanuel Kant thought that such a

paradoxical thing as time could not

really exist.

Time, he asserted, is our own creation,

the way our minds organize our

experiences. [music]

>> The I think Kant was the first person,

the first philosopher to emphasize

is that time

seems to be basic to the way in which we

structure reality.

It is very hard to pinpoint anything in

our experience

that would account for our whole

conception of time.

Kant's solution was to say that there is

something in us, in the way in which our

mind works, that makes everything that

we experience through our senses be

located in time,

so that the physical world is simply

bound to be temporal because of the way

our mind works.

>> Time is the dimension

along which our own individual

experiences are

laid out.

He described that by calling it the form

of inner sense.

And for reasons that aren't all to do

with his views of time, he came to the

conclusion that time,

like space, isn't really, so to speak,

out there in the world at all.

It's a way in which we experience

everything in the world.

But, if you ask, "What's out there in

the world independent of our

thinking of it and experiencing it?"

then there's no time there. There's no

space.

Uh

space and time are

ways in which we think about the world,

not ways in which the world really is.

>> But, does that mean that there really

isn't any time? It's just the way we

think about the world.

Augustine sums up our confusion

precisely.

>> What then is time?

If no one asks [music] me, I know.

If I want to explain it to someone who

does ask me,

I do not know.

>> Time is such an important thing for us.

It pervades everything we are,

everything we think is important is

connected. Time, life, death, youth, old

age.

Expectation, sorrow, everything is

connected to time. And it's such a

familiar thing. We wake up every day.

Go to work.

Go home for dinner. Evening passes. We

go to bed again. Time passes. Nothing to

think about. But then on the other hand,

when you start thinking about time, it

gives rise to riddles, philosophical

riddles. And you start thinking about it

scientifically. Scientific theories of

time seem to be very give us a very

different picture from the from the

usual our usual way of looking at time.

>> What does science tell us about time?

Until the 20th century,

>> [music]

>> the dominant view of time was embedded

in the mechanics of Isaac Newton.

Newton was seeking to lay down the laws

that would govern the motions of all

bodies.

>> Newton's theory of absolute time is the

idea that you think of time

as something that could exist even if

there wasn't anything in it.

So that

you think of it in a way as a sort of

container.

A series of locations

in which there may or may not be

something.

>> Newton's physical theories, which

concern the movement of bodies and their

effects on one another,

presupposed an absolute space.

An infinite empty void in which objects

from pebbles to planets would take their

places, moving and interacting among

each other.

Time was like an endless line,

stretching [music] from the infinite

past to the infinite future.

Events happened according to whatever

[music] standard of temporal measurement

we wish to apply.

He wrote,

>> "Absolute [music] space, in its own

nature, without relation to to external,

remains always similar and immovable.

>> Newton used certain a priori ideas about

time, namely that time is a

one-dimensional, as it were, line,

and that when an object moves in space,

its positions at any given moment are

correlated with the flow of time, which

is flowing along in one dimension.

And so,

Newton's mathematical theory of motion

has two components,

space geometry and time as the

independent variable with respect to

which

things change their position in space

and thereby move. So, both space and

time are a priori forms within which all

our experience happen.

>> But in the 20th century, a radically

different concept of time emerged.

>> Time is a very mysterious thing.

Uh,

we have learned a good deal about time

in the last 100 years. Most of what

we've learned has come from physics, and

most of that came from Albert Einstein.

Uh,

the special theory of relativity and the

general theory of relativity taught us

something that no one would have

suspected uh, before Einstein. It taught

us that space and time aren't

fundamentally different things.

>> Uh, in Einstein's special theory of

relativity that was developed in 1905,

this was his first theory of relativity,

Einstein came up with the idea that both

space and time were relative to the

observer or the state of motion of the

observer.

So, that if you and I are moving

relative to each other, especially if

I'm moving very fast relative to you,

almost the speed of light,

we will actually have different times

and different spaces associated with us.

>> I think um,

uh,

one of the most surprising and startling

things

that Einstein's uh, theory

brings into our understanding of time

is that it negates our whole

notion that what is happening now

right now in this room

is the same now as what is happening

across the earth in China

and other planets across the whole

universe.

As if there's this whole single one

time, the absolute now, that is

connecting the whole universe together.

And that this now divides off

the absolute past to the future from the

absolute future.

And the

this absolute now is a Newtonian view of

something that is is constantly moving

forwards into the future, like kind of

an absolute tide of becoming, if you

look at it that way.

Einstein said, "No, that's simply not

true at all."

>> What Einstein's theory seemed to tell us

was that time is not absolute and

universal. It can be changed by motion.

Each observer carries around his own

personal scale of time and it does not

absolutely agree with anybody else's.

>> And and the way they resolved the

paradoxes is to uh

realize that

the way you count time in Einstein's

theory is

very different from way it was counted

in Newton's theory. And the the key to

the idea of time in in Einstein's theory

is is just two simple things. One,

there's no absolute space.

Second one is that the speed of light

is

always perceived to be going at the same

velocity by anybody regardless of your

source or motion away from that speed of

light.

>> But not all agree that relativity

dismisses absolute time, just the way we

measure time.

>> And therefore, it seems to me that

Newton was absolutely right. We must

make a differentiation between time

itself and our measures of time. And

what is studied in modern physics uh and

in general philosophy of time

are the measures of time rather than

time itself. If Newton were presented by

Einsteinian relativistic evidence, he

would have felt no threat at all to his

doctrine of time.

Newton would have correctly said, "What

you're describing has nothing to do with

absolute time itself. It only has to do

with our physical measures of time."

What Newton did not realize and could

not have realized is that our physical

measures of time are relativistic.

Moving clocks run slow. He had no way of

knowing that. But presented with the

Einsteinian relativistic evidence

Newton would have been very happy to

have incorporated that into his doctrine

of physical time or relative time, but

it wouldn't have had any impact

whatsoever upon his doctrine of absolute

time.

>> But it does seem that the way we measure

time has been profoundly altered by 20th

century physics.

Time distortions are a mainstay of

science fiction [music] writing, but

there is nothing fictional about it.

Time warps could occur.

Consider the so-called twins effect.

One brother blasts off to a nearby star

approaching the speed of light.

The other twin remains on Earth.

10 years later, the rocket returns to

Earth.

The Earth-bound twin finds his brother

has aged only 1 year to his 10.

The high speed of his rocket means he

has experienced only 1 year of time

during which 10 years have passed on

Earth.

But, what does that mean to us?

We aren't blasting off to different

solar systems.

What it means is that our conception of

time has changed.

Before, time was best described as

absolute, fixed, and universal,

independent of material bodies or

observers.

That means there is no universal present

moment. We typically think of the

present as existing with the past gone,

but remembered, and the future as yet to

be.

But, the theory of relativity is telling

us something different.

Science doesn't deny that for each of

us, there is an ordered sequence of

events with a definite before-after

relationship.

But, it does deny the existence of the

past, the present, and the future.

One person's past is another person's

present and another's future, depending

on the point of [music] reference.

Einstein said,

>> "You have to accept the idea

that subjective time,

with its emphasis on the now,

has no objective meaning.

The distinction between past, present,

and future is only an illusion,

however persistent."

>> McTaggart dismissed the idea of passage

of time on philosophical grounds, and

modern science seems to agree with him,

despite the conflict with common sense.

But, don't we all feel the flow of time?

We get older, the world around us

changes.

But, consider the phrase, "the flow of

time."

How can time move?

How fast does it move?

An hour per hour?

>> The nature of time as it appears in

human consciousness

is a puzzle because as many people will

tell you

the external world doesn't seem to

require the passage of time or the flow

of time. It's as if the world were

frozen, strung out in its temporal

dimension. And yet and yet from the

point of view of an individual

consciousness, we seem to be

climbing up a ladder

and there's this specious present. I'm

inclined to think that the impression of

a moving now

the impression of a now to begin with

and the impression that it's moving

is an impression that arises from the

peculiar way in which the human brain is

wired up.

It's a tool that evolution has given us

in order to deal with the world and it

allows us to deal quite successfully

with the world, but it may suggest

something to us about the structure of

the world that isn't true.

>> If the past and the future

are as real as the present then we are

the victims of a universal and gigantic

delusion

namely the illusion of temporal

becoming.

Every one of us experiences what we call

the passage of time that moments of time

elapse. The future doesn't exist. It's

pure potentiality. We we'll create the

future. The past no longer exists. It is

ceased to be.

And on this view that says that the past

and the future are equally real, we have

to say that all of this experience is

illusory. And to me that is so

counterintuitive. That's like the person

who says that the external world is

unreal, that in fact you're actually a

brain in a vat

of chemicals being stimulated by a mad

scientist to hallucinate the external

world. Why should you believe such a

thing? In a similar way, I would ask why

in the world should we believe that the

temporal becoming, the passage that we

experience is in fact nothing but an

enormous illusion.

>> No matter what we believe science tells

us, we feel the passage of time, of the

present becoming memories, and the

expectation of the future.

Sometimes it passes slowly. Sometimes it

flashes by much too quickly.

>> The beginning of Catch-22,

the the novel by Joseph Heller, there's

a there's a character there, Dunbar,

who works on increasing his lifespan

through having

as boring a life as he

as he can. So, he lies in his bed, he

doesn't do anything interesting because

as soon as he gets caught up in

something, then time flow flies by. So,

you have to

to have a long life, a good lifespan,

you have to be bored.

That's, of course, exploiting this

distinction between time as it feels to

us and time as it is because his life

won't get any longer in the objective

sense, but it will he will have the

feeling of a much longer life, at least

while it while it while it goes on.

Uh so, these are the sorts of thing that

you tend to say when you want when you

want to make that distinction between

uh

the lived phenomenological subjective

time and the objective time. Then again,

you might say there's no real

distinction here. There's just one time,

the objective time, and then you can

feel it differently. You can

uh

apprehend it differently so that the

distinction is really between uh

what's really there and how we think

about it.

>> What is really there?

In physics, all of the past and the

future are simply there, and time

extends in either direction from any

given moment, the way that space away

from any particular place.

Some people will say that the time of

physics is not real time.

We feel it pass, a sensation we can't

shake.

Others will say that whatever we

experience mentally, time does not pass,

and the past, present, and future don't

exist.

>> May I have your attention?

>> St. Augustine was surely correct in

saying that as soon as we try to

describe time, we become tongue-tied.

But time is essential to [music] our

view of the world.

And it is more than just a need for

chronology that we feel this passage of

time.

It is part of our identity, our

memories, and our [music] expectations

of what is to come.

>> [music]

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