[yor_on]

You first need to understand one thing. There is no standard for what is a 'universal time'. It doesn't exist. What you use is your wrist watch, that is what defines time dilation's when you compare it to other 'frames of reference'. It doesn't really matter where you are for this. Your clock will always be equivalent your life expectancy.

The rest of it is a question of how you look at the universe. From what I call a 'global view' it's 'oberver dependent' aka comparing your clock to others. From a local point of view, aka, your life expectancy relative your wrist watch, it never changes. This is loosely speaking though. From a scaling point of view there should be differences relative for example standing up relative laying down. aka the Nist experiments. But frames of reference is a abstract idea, as much as anything else you will meet in physics or for that sake 'real life'.

Just take 'money'

[Bill S]

Read the above quotes in the light of those 2 events.

That’s about where I started.  These two events, in My case, are separated by a lot of years, each of which constitutes a sequence of events. So I looked at events that were closer together, and wondered if a point could be reached where there could be said to be nothing between two events.  Would they then have to become one event?  That didn’t make sense.  I felt it must be possible to have two events that were contiguous, but were still distinct, but in that case, what separated them?

[Bill S]

There is probably a meditation method somewhere that suggests this

Perhaps Fred Alan Wolf could find us a yogi who could help.

  I am the only person in existence and everything is in my imagination!? I'm not sure why, but I find that quite interesting.

Have you read Edwin Abbot’s “Flatland”?  His description of the occupant of “Pointland” might make you wonder how interesting it would be.

[Colin2B]

So I looked at events that were closer together, and wondered if a point could be reached where there could be said to be nothing between two events.  Would they then have to become one event? 

Not if they are separated by distance.
Also you need to think what you mean by an event, what causes you to think of events as separate.

[Recher]

Identical twins are separated at birth. One stays on Earth while the other is whisked away in a rocket traveling 2/3 the speed of light. After 60 Earth years, the rocket returns. The 60 year old earth  bound twin is there to greet his thirty year old twin astronaut. Time dilation. The faster an object of mass is moving relative to the sped of light ageing is slowed and time dilated. From the earth the rocket twin and his clock are moving at half speed while the astronaut views earthlings and their clocks moving at double time relative to his clock.

[yor_on]

There is quite a problem in defining what you will measure your speed against as no stars, as far as relativity knows, are 'unmoving'. The best you can do there possibly is to place yourself as being 'at rest' with some star, then arbitrarily define that as a 'zero speed' and then accelerate. The other thing one might be able to do is to use what's called 'fixed stars', being so far away that they to us become 'unmoving'. Then again, all uniform motion is from a black box perspective equivalent. No way to measure a difference, So?

Relativity has only two modes, uniform motion and accelerations in where acceleration is a equivalence to gravity, and in where all uniform motions becomes a equivalence too. Defining it as standing still or moving doesn't matter from a black box perspective..
=

Presuming you to, at all times, accelerating you could use a lightbulb placed at some absolute center, inside your ship, and then check if it blue and red shift I think, but that will only tell you that you're accelerating, not your 'speed'. And as soon you're back in uniform motion that light bulb will be without red and blue shifts. Using stars outside the black box  (ship) though you should be able to tell a difference between the way they were before your acceleration relative after (blue and red shift)

[Bill S]

 

…. what causes you to think of events as separate.

Oxford Dictionary: Event:  Physics: A single occurrence of a process.

.  I felt it must be possible to have two events that were contiguous, but were still distinct, but in that case, what separated them?

I progressed from there to the idea that “reality” is made up of a “series of snapshots”.   Barbour and Deutsch use these concepts in different ways; in Barbour’s case, it is to argue against the “reality” of time. 

He says:  “….when we think we see motion at some instant, the underlying reality is that our brain at that instant contains data corresponding to several different positions of the object perceived to be in motion.  My brain contains, at any one instant, several ‘snapshots’ at once.  The brain, through the way in which it presents data to consciousness, somehow ‘plays the movie’ for me.”

I found much of Barbour’s book quite heavy going, and the idea of progressing from one “snapshot” to another, without the aid of time was an example of my inability to feel sure I grasped what he was saying.

[alancalverd]

I progressed from there to the idea that “reality” is made up of a “series of snapshots”. 

This is not possible. If a rock were to roll in a series of discrete jumps you would need to apply an infinite force for an infinitesimal time, first forward and then backward, to make it do so.

The assertion is the basis of Zeno's paradox and as with every other paradox, it is founded on philosophy rather than physics. Unfortunately the adoption of digital information processing has led to many similar misconceptions, including the redefinition of a circle as 360 straight lines and the notion that the human eye has a consistent scan or frame rate.

[Bill S]

As points, you can discuss such geometric relations as their separation and such.

Separation in space is a related, but rather different, issue. It was “separation” in time I was trying to understand.

Not sure what contiguous events are.  Points are not usually described as being contiguous.

I interpreted “contiguous” as having nothing by which they are separated.  We were talking earlier about the events of birth and death.  Obviously, these are not contiguous, in normal circumstances. Using the “snapshot” idea I was trying to imagine a situation in which it would be possible to have “snapshots” that didn’t exist in time, but could be “interpreted” sequentially by the brain; using “unreal” time.  It didn’t make sense to me, but Barbour is a professional and I an ill-informed amateur, so I was trying to follow his reasoning.

OK, so you're talking about quanta of time, sort of like frames of a movie.  Somehow I suspect our brains don't process reality at the frame rate of the universe, if there is any such thing.

Another of my stumbling blocks.  How could the Universe have a frame rate if time didn’t exist?

[Bill S]

This is not possible.

That was my initial reaction.  I’ve explained, above, why I didn’t leave it at that.

If a rock were to roll in a series of discrete jumps you would need to apply an infinite force for an infinitesimal time, first forward and then backward, to make it do so.

I tried a few simpler “thought experiments”, but they all raised the same question as yours.  How could they work in a timeless Universe? 

[Halc]

Separation in space is a related, but rather different, issue. It was “separation” in time I was trying to understand.

Two events separated by space but not time are termed 'simultaneous', not 'contiguous'.  It is a frame dependent relation.  Those events will be simultaneous in one frame but not another, and using the word 'contiguous' doesn't change that.

I interpreted “contiguous” as having nothing by which they are separated.

That would be the same point then.

Using the “snapshot” idea I was trying to imagine a situation in which it would be possible to have “snapshots” that didn’t exist in time

I don't see how there could be a 'snapshot' without there being a time to which the snapshot corresponds.  I have photos taken of me, but all of them were taken at some moment in time.

but could be “interpreted” sequentially by the brain; using “unreal” time.

Sounds like a dualistic set of philosophical assumptions, having little to do with physics, including brains.  The usual term is 'mind', which is is not the 'brain', which is incapable of processing during a snapshot.

OK, so you're talking about quanta of time, sort of like frames of a movie.  Somehow I suspect our brains don't process reality at the frame rate of the universe, if there is any such thing.

Another of my stumbling blocks.  How could the Universe have a frame rate if time didn’t exist?

If time doesn't exist, then there would be no meaning to my age, or the velocity of this here rock.  Of course time exists.
A frame rate is another thing.  I have no reason to support a claim that spacetime is discreet and that there is such a thing as successive moments or adjacent locations in space.  Sure, there is Planck length and Planck time, but that's just the limits of measurability, not a model of how anything works.  Such a model would seem to violate all conservation laws.

[Bill S]

Two events separated by space but not time are termed 'simultaneous', not 'contiguous'.

Precisely. Remember that I was trying to grasp Barbour’s idea of “Platonia” as illustrated by the “snapshot” concept. I was trying to get away from the semantics to see if that would help. It didn’t.

That would be the same point then.

Not necessarily. Two areas of land are said to be contiguous if they share a common boundary.  Two of Barbour’s snapshots would be contiguous if their borders were together, but none of this sheds any light on the “mechanism” by which a timeless array of snapshots can become sequential without time in which to make that change.

  I don't see how there could be a 'snapshot' without there being a time to which the snapshot corresponds.

Exactly.  I felt there must also be a specific time in which each snapshot was observed. I couldn’t equate that with the timelessness of “Platonia”.

I have photos taken of me, but all of them were taken at some moment in time.

I suspect the analogy was not intended to be taken that far. 

The usual term is 'mind', which is is not the 'brain',

Barbour’s term, not mine.

If time doesn't exist, then there would be no meaning to my age, or the velocity of this here rock.  Of course time exists.

It’s some years since I read “The End of Time”, but that was roughly the point I was at when I reached the end; with the proviso: Of course time exists, in our Universe.

[Bill S]

Unfortunately the adoption of digital information processing has led to many similar misconceptions, including the redefinition of a circle as 360 straight lines

I think Edwin Abbot beat them to that "definition" of a circle.

[Halc]

That would be the same point then.

Not necessarily. Two areas of land are said to be contiguous if they share a common boundary.

Areas of land are not points.

Two of Barbour’s snapshots would be contiguous if their borders were together

That would be two simultaneous snapshots if there were no temporal distance separating them.
I know, this is somehow a discreet model where there is a concept of successive instants.  I find that contradictory, but that's me.

Exactly.  I felt there must also be a specific time in which each snapshot was observed.

How can a snapshot be observed at any other time than the time of the snapshot?  I can't observer yesterday.  At 5 PM I have no choice but to observe the 5PM snapshot.  Introducing a second sort of time (one of the snapshot, and another for when it is observed) is dualistic: The former being when the movie was shot with the camera, and the latter being when it is observed at the cinema.
Find and dandy to make a model like that, but it makes no predictions and thus isn't science.

It’s some years since I read “The End of Time”, but that was roughly the point I was at when I reached the end; with the proviso: Of course time exists, in our Universe.

That is well put.  I agree with that more than you know.

[Bill S]

Areas of land are not points.

And analogies are not perfect representations of the things with which they are compared. I would rather not get into a discussion of the nature of points here.  I’m still waiting for clarifications elsewhere. I’m not going to suggest that continued waiting is “pointless”.

I know, this is somehow a discreet model where there is a concept of successive instants.  I find that contradictory, but that's me.

It’s certainly not just you, but it’s another of those subjects that seem to be interminable.

How can a snapshot be observed at any other time than the time of the snapshot?

I think the main thrust of Barbour’s reasoning was that there is no “time of the snapshot”.  The illusion of time is added by the observer.  I had (have) trouble with this because if there is no time before the observation is made, how can it be made?

That is well put.  I agree with that more than you know.

Thanks. This is probably not the place for it, but I would love to hear more about your ideas on that. Possibly another thread.  What would be the best question to ask to evoke an appropriate response?

[guest4091]

One of my favorite forum subjects.
A few questionable lines.

#3

Each physicist can see his own clock and the other’s with no time delay for information transfer.

If light speed is finite, there must be a time delay, which alters perception. Without a delay you can’t measure distance.

#6

For the purposes of the OP's question we can say clocks measure rates of change

Clocks measure amount of activity in terms of a human defined standard event (clock cycle). Rate of change or time dilation, is calculated from observations.

#7

It becomes convenient to talk of changes in the rate of time’s flow, or of the rate of our passage through time, and to treat time as though it were an entity with existence that was independent of the things being measured and those doing the measuring; which may not be the case.

Not the case. Time flow is the mental sequential perception of the current event following the previous event in memory. Because perception is a real mental process, it is difficult to separate it from physical processes occurring outside the mind. It cannot be independent of those doing the measuring, since it's a human convention, and the reason for subjective time.

#12

If time separates sequential events, does this mean that something exists between events that is not, in itself an event, and that that something is time?  (Smolin)
Alternatively, does it mean that our perception of time allows us to distinguish as sequential events something that is essentially continuous? (Barbour)

Time is not a causal factor. The time of an event is recorded after the event occurs, after awareness of the event. It's an historical account for a multitude of purposes.

[Bill S]

A few questionable lines.

Possibly some lines become more "questionable" when taken out of context.

[yor_on]

Halc

"  Any snapshot of the universe contains the state of every clock, each of which nicely indicates the time of the snapshot.  So I find that pretty contradictory reasoning. "

That would then be the perspective from someone 'outside' this universe of clocks. If it's a 'inside perspective' then it's not a privileged one, as no observer inside has a way of defining his clock to be the 'golden standard' from where this snapshot should be taken. And if that observer would happen to ask others what they though the observers clock rate to be, the answers would vary widely. That's from what I call a 'global view', which I think you're evoking here?

If we stop using that, and stay local then it doesn't matter where you are or how fast you go. your life expectancy will be the same relative your wrist watch, and that goes for all observers inside this universe. The 'global view' is filled with traps.
=

Thinking of it even the 'outside' observer should have the same problem, presuming he's using a clock. And actually, from a 'global view' the observers clockrate then will depend on what he compares it too, if he now would want to define it as a 'golden standard'. What physics offer in this case is Lorentz transformations, and they don't talk about a 'golden standard', they just prove that it's possible to translate that clock rate into another. And if that wasn't possible we would have to give up on logic and instead prepare ourselves for a 'magic universe'

[MikeFontenot]

Each observer "sees" [concludes that] clocks moving relative to himself to be [are] running slower.  That is true for all observers, [...]

Not true for ALL observers.  It is true for all inertial observers.  It is NOT generally true for accelerating observers.  Accelerating observers sometimes conclude that some distant clocks are rapidly running forward, and sometimes conclude that they are rapidly running backward.

[guest4091]

A few more questionable lines.


#27

Presuming you to, at all times, accelerating you could use a lightbulb placed at some absolute center, inside your ship, and then check if it blue and red shift I think, but that will only tell you that you're accelerating, not your 'speed'.

Doppler shift requires a relative velocity between source and detector.


#31

Using the “snapshot” idea I was trying to imagine a situation in which it would be possible to have “snapshots” that didn’t exist in time, but could be “interpreted” sequentially by the brain; using “unreal” time.

How could the Universe have a frame rate if time didn’t exist?

The mind requires a few milliseconds to register sensory input, which can be the duration of your snapshot.

Does the universe need a clock to exist?


#33

If time doesn't exist, then there would be no meaning to my age, or the velocity of this here rock. 

The measurements of time and space have a purpose and thus meaning for the observer.


#36

How can a snapshot be observed at any other time than the time of the snapshot?  I can't observer yesterday.  At 5 PM I have no choice but to observe the 5PM snapshot.  Introducing a second sort of time (one of the snapshot, and another for when it is observed) is dualistic:

There are 'a' events, the physical occurrence of the event E, and 'b' events, the awareness of the event E. In the SR theory, Einstein defines the 'time' of the event E relative to the local clock of the observer, i.e. the 'b' event. Since light is the messenger, for local events there is very little difference between 'a' and 'b'. For  'remote' events on an astronomical scale, the difference is many magnitudes of 'large'.

The 'a' time requires additional knowledge of the distance to E. All observations are therefore historical. Just as the time is recorded after the event occurs, the image of E can only be seen after E occurs. Astronomers observe the past every night.

----------------------------------------

My personal thought about the never ending debate of 'time', philosophical, scientific, or otherwise, is the desire for a permanence of life. Humanity wants an assurance that 'time' will not end, thus maintaining their  presence. There should be an (invisible) entity working behind the scenes, planning events. A psychological desire similar to wanting a solid foundation for security. When portions of the earth shift, people get anxious!
This security blanket makes it difficult to separate fact from fiction.