time hijack from the mind + 4D-spacetime = the experience of the unfolding of the events moment by moment in the actual moment by an observer

[swansont]

8 minutes ago, michel123456 said:

No. As far as i see it, even in my interpretation, there is no physical way to change our own past. It is not observable and not reachable.

But the question is still there: If we are "flying" along the time dimension, if the spacetime diagram describes what I call a path, what Eise calls "process", then does that mean that our past coordinates are empty?

I'm not sure what you mean by coordinates being "empty"

If you were at location x1, y1, z1 at time t1, that won't change, even though your current coordinates are different. As you say, you can't change the past.

 

 

[michel123456]

15 minutes ago, swansont said:

I'm not sure what you mean by coordinates being "empty"

I am not there anymore. There is no object at this spacetime coordinate. There is only an event: Michel was there.

Edited February 26, 2020 by michel123456

[dimreepr]

2 minutes ago, michel123456 said:

There is only an event: Michel was there.

We can only determine an event if it's discernable.

Imagine if the event was lost in the noise.

[michel123456]

And not to say that the signal of the event is spreading at c all around, leaving the coordinate completely empty. What all observers will agree with is the signal that they will receive from the event.

[swansont]

44 minutes ago, michel123456 said:

I am not there anymore. There is no object at this spacetime coordinate. There is only an event: Michel was there.

It makes no sense to say you aren't there anymore, referring to a 4-d coordinate — you are giving two pieces of information about the time. It only makes sense of you use a 3D coordinate.  

Events are probably what we have to refer to.

[michel123456]

30 minutes ago, swansont said:

It makes no sense to say you aren't there anymore, referring to a 4-d coordinate — you are giving two pieces of information about the time. It only makes sense of you use a 3D coordinate.  

Events are probably what we have to refer to.

 

My point is: since we all agree (do we?) that we "fly" in time, each one of us occupies only one single spacetime coordinate, objects are not 4D extending back & forward in time.

If you are in the present, you are not in the past (anymore) and you are not in the future (yet)

As a consequence, if we are using only one set of coordinates, then the other sets are free.

 

 

[MigL]

18 minutes ago, michel123456 said:

each one of us occupies only one single spacetime coordinate, objects are not 4D extending back & forward in time.

Why not ?

You can occupy only a single space co-ordinate at a specific time.
Or you can be at a specific  place different times.
But you're not understanding the concept of space-time.

If you were at a specific location at a specific time ( say at the mall by your house, yesterday at 1 pm ), you will always be there at that time.
The next day your location for the previous day at 1 pm will NOT have changed ( or else you'd remember it differently ).
The next year, or 50 years from now, you will still be at that location, yesterday at 1 pm.

[michel123456]

19 minutes ago, MigL said:

Why not ?

You can occupy only a single space co-ordinate at a specific time.
Or you can be at a specific  place different times.
But you're not understanding the concept of space-time.

If you were at a specific location at a specific time ( say at the mall by your house, yesterday at 1 pm ), you will always be there at that time.
The next day your location for the previous day at 1 pm will NOT have changed ( or else you'd remember it differently ).
The next year, or 50 years from now, you will still be at that location, yesterday at 1 pm.

See, that is the difference between you and me (and Eise).

You are supporting the concept that objects are 4D. That I am extending in time from my birth till my death. Eise said that no, spacetime is full of events, not objects. You are saying that spacetime is full of objects. You are disagreeing with the concept of 3D entities "flying" in time. You prefer the concept where entities are "extruded" in time.

 

 

Edited February 26, 2020 by michel123456

[geordief]

21 minutes ago, MigL said:

Why not ?

You can occupy only a single space co-ordinate at a specific time.
Or you can be at a specific  place different times.
But you're not understanding the concept of space-time.

If you were at a specific location at a specific time ( say at the mall by your house, yesterday at 1 pm ), you will always be there at that time.
The next day your location for the previous day at 1 pm will NOT have changed ( or else you'd remember it differently ).
The next year, or 50 years from now, you will still be at that location, yesterday at 1 pm.

I have always thought locations were only relative and you could never return to the "same" location.

[michel123456]

If "flying" in time is so much different from "moving" in space, how can we compute mathematical theories where the one rotates to become the other? Is it possible that "flying" in time corresponds to Copy? When we all know that a move in space is a ... move.

 

[MigL]

You experience space and you experience time.
That is four distinct dimensions ( as per the definition of dimension ) that you experience ( unless you live in 'flatland' ).

If you consider yourself 3Dimensional, you are experiencing 'groundhog day', always at the same moment in time.
( you do repeat the same thing, over and over )

 

1 hour ago, geordief said:

locations were only relative and you could never return to the "same" location

Who said anything about returning ?
The fact that it is now, today, does not change where you were yesterday !
Space and time are relative; space-time, as per the block universe, is not.

Edited February 26, 2020 by MigL

[geordief]

3 hours ago, MigL said:

 

Who said anything about returning ?
The fact that it is now, today, does not change where you were yesterday !
Space and time are relative; space-time, as per the block universe, is not.

No you didn't talk about returning  to a "same location".

That was a bit of a bee in my bonnet.

 

I wonder if it helps at all to introduce a notion of subjective time to the discussion (perhaps off topic)

The relativity model does call out to be interpreted (although its predicted results do not) and perhaps we cannot help introducing this subjective understanding of time into our interpretation.

 

This is for me a very confusing topic but I found that French video quite illuminating .

 

I see that we are in philosophy so I am not sure whether confusion is an asset or a hindrance. 

[MigL]

I'm not sure I know what you mean, Geordief.

The block universe is a 4dimensional manifold, where each point (x,y,z,t) is an 'event'.
The spatial dimensions each have 2 degrees of freedom; you can travel in the positive, or negative, direction along each of the x-axis, y-axis or z-axis. So returning to a spatial location is obviously possible. As a matter of fact, standing still ensures you are at the same spatial co-ordinate while the time co-ordinate keeps incrementing.
That is the difference, along the temporal dimension we only have one degree of freedom; we can only move in the positive direction.
This 'movement' along the t-axis is constrained ( slowed ) by certain conditions.
One such is the 'spacing' of the co-ordinate grid, which is in effect, space-time curvature, or, gravity.
The other is ( relativistic ) motion through the co-ordinate grid.

Michel's life is then, a set of points, in this 4dimensional co-ordinate grid, where the x,y,z co-ordinates are centered on Greece ( at the moment ) as it revolves around the Earth, sun, galaxy, local cluster , etc., and the t co-ordinate started when he was born, and draws out a line through the 4dimensional manifold, that ends at his death.
Since a line is composed of multiple points ( or events ), no point is vacated when he 'moves' to the next moment in time.

That is my understanding/interpretation of the block universe. Any corrections to this viewpoint, will be appreciated and taken into consideration.

[geordief]

36 minutes ago, MigL said:

I'm not sure I know what you mean, Geordief.

The block universe is a 4dimensional manifold, where each point (x,y,z,t) is an 'event'.
The spatial dimensions each have 2 degrees of freedom; you can travel in the positive, or negative, direction along each of the x-axis, y-axis or z-axis. So returning to a spatial location is obviously possible. As a matter of fact, standing still ensures you are at the same spatial co-ordinate while the time co-ordinate keeps incrementing.
That is the difference, along the temporal dimension we only have one degree of freedom; we can only move in the positive direction.
This 'movement' along the t-axis is constrained ( slowed ) by certain conditions.
One such is the 'spacing' of the co-ordinate grid, which is in effect, space-time curvature, or, gravity.
The other is ( relativistic ) motion through the co-ordinate grid.

Michel's life is then, a set of points, in this 4dimensional co-ordinate grid, where the x,y,z co-ordinates are centered on Greece ( at the moment ) as it revolves around the Earth, sun, galaxy, local cluster , etc., and the t co-ordinate started when he was born, and draws out a line through the 4dimensional manifold, that ends at his death.
Since a line is composed of multiple points ( or events ), no point is vacated when he 'moves' to the next moment in time.

That is my understanding/interpretation of the block universe. Any corrections to this viewpoint, will be appreciated and taken into consideration.

I am not qualified to comment here on the BU (I am aware of the concept but have a lot to learn)

 

Just to try and explain what I was trying to say in my last post(perhaps a repetition),the model of spacetime seems to make extraordinarily precise predictions  that were quite unthinkable not so long ago.

The interpretation of all this  is another area ,possibly more important and possibly less so (unless  we can subject any interpretation to experimental verification or disproof then any number of alternative interpretations might be theoretically possible)

What I was musing out loud was whether the often brought up distinction between "time as measured by clocks" and the subjective idea of time that we have might have some kind of an input into  the way relativity might be interpreted as either a Block Universe or ,perhaps as some may be inclined to see it as a Universe that is continuously recreating itself at every step of the way.

There is probably nothing  in it .....

 

Edit : I hope  I am right to say that the Block Universe is an interpretation of Relativity and not actually fundamental to it 

[michel123456]

5 hours ago, MigL said:

Since a line is composed of multiple points ( or events ), no point is vacated when he 'moves' to the next moment in time.

My understanding is that the points that form this line are mutually exclusive. If I am at t=100, I am not anywhere else. If I am at t=2, I am not at t=3. The physical entity is only one point of the line. The whole line is a path.

[Eise]

15 hours ago, michel123456 said:

I firmly believe that the concept of time is more close to that of space than is commonly assumed. There is no reason it would be fundamentally different otherwise how would it be possible for time to change into distance & reversely.

I cannot comment on that, because I do not know what 'is commonly assumed'. The idea of the block universe comes from physicists (Einstein also adhered to the idea), so if physicists are 'not common' then you might be right. As I said before, space and time are intimately linked in spacetime, but they do not play exactly the same role. As a simple example: one can always return to some space coordinate, but nothing can go back to a previous time coordinate. And then, as I already said in another thread, the way time appears in the flat spacetime metric is not the same as the space coordinates:

d² = x² + y² + z² - (ct)².

15 hours ago, michel123456 said:

So, if we are "flying" through time, doesn't that mean that our past coordinates are free? And our future are free also?

No idea what you mean, especially that 'our past coordinates are free'. 

14 hours ago, michel123456 said:

From what I understand from Eise's post, the past & the future are full of events. Objects belong solely to the present.

No, that is not what I mean. Objects are 3-dimensional things that persist in time. 

14 hours ago, michel123456 said:

... does that mean that our past coordinates are empty? And that all our future coordinates are empty also?

No, of course not. As I said, the evening before yesterday I was in the shop. Nothing empty. Because I am not in the shop now, does not mean I was not there that evening.

14 hours ago, michel123456 said:

I am not there anymore. There is no object at this spacetime coordinate. There is only an event: Michel was there.

If you say 'spacetime coordinate', then of course Michel is there. There is not Michel now, i.e. there is no Michel at that space coordinates there and now. 

I think you only get more and more confused by equating space and time too much.

12 hours ago, michel123456 said:

See, that is the difference between you and me (and Eise).

I do not see a difference. I fully agree with MigL, except that I would not use the expression that we are 4-D objects. But the gist of his argument seems clear to me: if it is true today that I was in the shop the evening before yesterday, so at 25.02.2020, then this will still be true at 21.06.2030. These coordinates are definitely 'occupied' (so 'not free'). Nobody else can take these exact spacetime coordinates, otherwise I would describe a collision I had with somebody in the shop; but I did not collide with anybody.

12 hours ago, michel123456 said:

If "flying" in time is so much different from "moving" in space, how can we compute mathematical theories where the one rotates to become the other?

Under the right coordinate transformations, the Lorentz transformations mathematically behave just as a rotation in 3D space. But without these transformations, they completely differ. Again, do not confuse the land with the map. Even if the map is perfect, you can do thing with the map you cannot do with the land (e.g. one can fold a map, but it does not follow that you can fold the land). Spacetime diagrams are maps to help orienting in Relativity Land.

12 hours ago, michel123456 said:

Is it possible that "flying" in time corresponds to Copy?

No. What is 'flying' in time is one and same object, persisting in time.

There is a story about Thales of Milete: as an astronomer and philosopher he was walking and wondered himself about the stars in the sky. So he did not see the ditch for his feet, and he fell in. A woman standing by laughed, remarking that he was seeing the stars, but did not see the ditch at his own feet. 

 

[michel123456]

2 hours ago, Eise said:

What is 'flying' in time is one and same object, persisting in time.

Oh, what a disappointment. I thought we were on the same stance when you posted:

22 hours ago, Eise said:

Objects can overlap in time, because at the moment t + 1 the object is not at t anymore, so there is nothing there to overlap with. 2 Objects cannot be at the same place at the same time, but they can perfectly at different times. A spacetime diagram is a diagram of events, not of objects. And as a diagram it is just a simplified model of what is going on. You confuse the model with reality.

Now you seem to support the idea that objects are 4D entities when you say that they persist in time.

You said:

4 minutes ago, michel123456 said:

A spacetime diagram is a diagram of events, not of objects

 

[swansont]

16 hours ago, michel123456 said:

 

My point is: since we all agree (do we?) that we "fly" in time, each one of us occupies only one single spacetime coordinate, objects are not 4D extending back & forward in time.

If you are in the present, you are not in the past (anymore) and you are not in the future (yet)

As a consequence, if we are using only one set of coordinates, then the other sets are free.

If you can't access the coordinates, I don't see how they are "free"

If an event happened at x1, y1, z1, t1 in some frame of reference, those will always be the coordinates for that event. That set of coordinates is not "free".

[michel123456]

25 minutes ago, swansont said:

If you can't access the coordinates, I don't see how they are "free"

If an event happened at x1, y1, z1, t1 in some frame of reference, those will always be the coordinates for that event. That set of coordinates is not "free".

If you can't access the coordinates then you cannot change what happened then. We agree. But that doesn't mean that there is something there, or that there isn't. We simply don't know. We are assuming (guessing).

4 hours ago, michel123456 said:

My understanding is that the points that form this line are mutually exclusive. If I am at t=100, I am not anywhere else. If I am at t=2, I am not at t=3. The physical entity is only one point of the line. The whole line is a path.

Quoting myself: am I wrong saying that?

Note: in the quote you can replace the word "if" with the word"when" and it becomes:

My understanding is that the points that form this line are mutually exclusive. When I am at t=100, I am not anywhere else. When I am at t=2, I am not at t=3. The physical entity is only one point of the line. The whole line is a path.

Edited February 27, 2020 by michel123456

[Eise]

1 hour ago, michel123456 said:

Oh, what a disappointment. I thought we were on the same stance

Sorry. Still friends? 😟

1 hour ago, michel123456 said:

Now you seem to support the idea that objects are 4D entities when you say that they persist in time.

You said:

1 hour ago, michel123456 said:

A spacetime diagram is a diagram of events, not of objects

 

Well, I think that is a kind of definition of an object: something that persists in time and space. Compare with an explosion. This is a very short event, and part of its essence is that it is a (huge) change. It is essentially a process, concentrated around some narrow spacetime coordinates. But e.g. a ball persists in existing in spacetime. It can change space coordinates when travelling in time, but is still identifiable as the same ball: on one side because of its own properties (it is red, plastic, and 20 cm in diameter, with some scratches made by Tony yesterday), and on the other side by its continuity in spacetime: it follows an uninterrupted path through spacetime (except at the moments of it being made, resp. destroyed).

Edited February 27, 2020 by Eise

[swansont]

49 minutes ago, michel123456 said:

If you can't access the coordinates then you cannot change what happened then. We agree. But that doesn't mean that there is something there, or that there isn't. We simply don't know. We are assuming (guessing).

No, we can have data that tells us this. No guesswork necessary.

 

 

[Eise]

44 minutes ago, michel123456 said:

My understanding is that the points that form this line are mutually exclusive. When I am at t=100, I am not anywhere else. When I am at t=2, I am not at t=3. The physical entity is only one point of the line. The whole line is a path.

No! When you were at the mall at t = 1, and today at t = 100 you are at home, it is still true that you were at the mall at t = 1. In a spacetime diagram time is depicted as a space coordinate. If I have the (magic) bird's view on 4D-spacetime, the question "where is Michel now" makes no sense: the Superbird does not know what 'now' means: for him you are the complete line. But you can ask the bird where Michel was at t = 1, or t = 100. Those questions make sense from the 4D perspective. 

[michel123456]

50 minutes ago, Eise said:

Sorry. Still friends? 😟

🙂 Sure. Educated disagreement is fine.

50 minutes ago, Eise said:

Well, I think that is a kind of definition of an object: something that persists in time and space. Compare with an explosion. This is a very short event, and part of its essence is that it is a (huge) change. It is essentially a process, concentrated around some narrow spacetime coordinates. But e.g. a ball persists in existing in spacetime. It can change space coordinates when travelling in time, but is still identifiable as the same ball: on one side because of its own properties (it is red, plastic, and 20 cm in diameter, with some scratches made by Tony yesterday), and on the other side by its continuity in spacetime: it follows an uninterrupted path through spacetime (except at the moments of it being made, resp. destroyed).

Yes, it follows an uninterrupted path through spacetime.

The word "persist" is disturbing me.

It looks like you are accepting that objects "move" into time along a path & also accept that the object persits in time.

I am afraid you have to choose the one or the other, these are incompatible statements.

37 minutes ago, Eise said:

No! When you were at the mall at t = 1, and today at t = 100 you are at home, it is still true that you were at the mall at t = 1. In a spacetime diagram time is depicted as a space coordinate. If I have the (magic) bird's view on 4D-spacetime, the question "where is Michel now" makes no sense: the Superbird does not know what 'now' means: for him you are the complete line. But you can ask the bird where Michel was at t = 1, or t = 100. Those questions make sense from the 4D perspective. 

Yes, the path is history carved into stone. You cannot change it. I do not disagree on that. But it remains a path. Julius Caesar & Napoleon are dead, they are not "persisting" in time, in another dimension. They are gone.

Oh sorry, maybe are you using the word "persist" to say that the object does not vanish in present time?

I had the wrong understanding that you believe that objects are persisting in the past.

I am confused.

Edited February 27, 2020 by michel123456
correcting

[geordief]

25 minutes ago, michel123456 said:

 

Yes, the path is history carved into stone. You cannot change it. I do not disagree on that. But it remains a path. Julius Caesar & Napoleon are dead, they are not "persisting" in time, in another dimension. They are gone.

 

How is J Caesar different from any other event in the past?

His atoms are dispersed and ,it is said we all have a few.

His experience of being alive is another matter  but that is not what this thread is about ,is it?

[swansont]

37 minutes ago, michel123456 said:

🙂 Sure. Educated disagreement is fine.

Yes, it follows an uninterrupted path through spacetime.

The word "persist" is disturbing me.

If the ball exists, it has a set of spacetime coordinates, has had spacetime coordinates, and will have spacetime coordinates.