Suppose that I am looking in my telescope to a distant star

[swansont]

How many "you" do you see in this diagram?

 

Shot124.jpg

 

I see at least two. in fact an infinity of "yous" in the interval.

 

The diagram gives the impression that there is a "you' at all time stamps, that all coordinates x,t are inexorably occupied by "you".

It is a completely different concept from motion.

I believe it is wrong.

IMHO the diagram describes a path.

 

It's the same "you" at all of the time stamps, just like if you move from point A to B, there is just one "you" at each point along the path. Unless you are insisting that motion requires duplication.

[michel123456]

It's the same "you" at all of the time stamps, just like if you move from point A to B, there is just one "you" at each point along the path. Unless you are insisting that motion requires duplication.

if i understand correctly, we share the same POV.

Yes it's the same "you". There is only one single "you" traveling through time, describing a path exactly as the path when you move from A to B.

 

Suppose you were once at coordinate x100,y100,z100,t=1, now you are at coordinate x100,y100,z100,t100.

IOW coordinate x100,y100,z100,t=1 is free. You have gone from it.

I still don't understand why you think your head and feet are at different times. Mine aren't.

If the distance was huuge, like the distance between 2 galaxies, would you say that they share the same time?

Edited November 29, 2014 by michel123456

[Strange]

If the distance was huuge, like the distance between 2 galaxies, would you say that they share the same time?

 

If the 2 galaxies are sufficiently far apart, that metric expansion is relevant, then no. But if my head and feet were that far apart then they would not be affected by expansion because they are held together by inter-atomic forces, so yes.

 

Asking physically impossible questions rarely leads to sensible answers.

Edited November 29, 2014 by Strange

[michel123456]

I do see where you get the idea of an 'extension in time' though.

Since light takes a finite time to get from your head to your feet, by necessity, the local 'now' at your head must be different from the local 'now' at your feet. This is a minute amount and trivial. GR being a classical theory means it treats all particles as dimensionless points, so although the aggregate 'you' may have a fuzzy ( how long does light take to get from your head to your feet ) , local 'now', the individual particles that make 'you' up all have an explicit local 'now'.

[MigL]

Here is a simple experiment, Michel123456...

 

Set up a camera to take a picture of the same location at two different times.

It is very easy for you to be in both photos, is it not ? You stand in front of the camera yesterday, and there you are, yesterday, in the photo. Similarily, you stand in front of the camera today, and there you are again, today, in the photo. And I have no doubt that if you repeat your efforts tomorrow, you'll be there again, tomorrow, in the photo. And even if you look at these photos in a month or a million years, you'll still be there in the photos. The fact that time has progressed doesn't mean that you disappear from that space-time co-ordinate.

 

Now set up two cameras, side by side, to take a picture of two different locations at the same time. Can you be in both photos ? Without Photoshop of course. Why do you think that is ? And if you can't, does that mean you need to re-examine the similarities and differences between spatial and temporal dimensions ?

 

Maybe they don't 'work' the same way and are not as similar as you think.

Maybe you should stop applying your preconceived notions about movement through the spatial dimensions, to movement in the temporal dimension

Edited November 29, 2014 by MigL

[michel123456]

Here is a simple experiment, Michel123456...

 

Set up a camera to take a picture of the same location at two different times.

It is very easy for you to be in both photos, is it not ? You stand in front of the camera yesterday, and there you are, yesterday, in the photo. Similarily, you stand in front of the camera today, and there you are again, today, in the photo. And I have no doubt that if you repeat your efforts tomorrow, you'll be there again, tomorrow, in the photo. And even if you look at these photos in a month or a million years, you'll still be there in the photos. The fact that time has progressed doesn't mean that you disappear from that space-time co-ordinate.

 

Now set up two cameras, side by side, to take a picture of two different locations at the same time. Can you be in both photos ? Without Photoshop of course. Why do you think that is ? And if you can't, does that mean you need to re-examine the similarities and differences between spatial and temporal dimensions ?

 

Maybe they don't 'work' the same way and are not as similar as you think.

I am not "in the photo". If I was, I would have duplicate and nobody here like the idea.

My image has imprint the photographic paper, yes.

it is a print, like the print of your feet in the sand while walking on the beach. It does not prevent anyone else to make a new footprint onto yours.

 

Maybe you should stop applying your preconceived notions about movement through the spatial dimensions, to movement in the temporal dimension

Maybe.

Maybe not.

[Endy0816]

It's like this:

 

____You(4D)___

| |

You₁-You₂-You₃

 

You have to think of it as 3D slices being connected across time resulting in the 4D object. It has slices at all those different points, it doesn't need to duplicate or move.

 

Really best advice I can give is to look at shapes in different numbers of dimensions.

 

ie. Square(2d) -> Cube(3d) -> Tesseract(4d)

[MigL]

A photograph is a graphical representation, just like a space-time diagram is.

The fact that you're in the picture proves you were there. It is the same you in the picture from yesterday as the one from today. This does not imply the duplication that you seem to be obsessed with. It is the same you, yesterday, today and tomorrow.

But at different points in time !

 

It is also as much 'proof' of the past as you're going to get, just like memories are.

[michel123456]

A photograph is a graphical representation, just like a space-time diagram is.

Agree.

The fact that you're in the picture proves you were there.

Agree.

It is the same you in the picture from yesterday as the one from today.

Agree.

This does not imply the duplication that you seem to be obsessed with.

I am glad to hear that from you. Agree.

It is the same you, yesterday, today and tomorrow.

But at different points in time !

Agree.

 

It is also as much 'proof' of the past as you're going to get, just like memories are.

Agree.

 

If we agree on everything, then things must be very simple.

 

I say that, since it is the same you, since you have not duplicated, it means that you have moved through time. EXACTLY as you move in space. It means to me that you have changed coordinates.

I say nothing more.

For the moment.

[michel123456]

Now the moment has come:

 

If you have changed coordinates, it means your ancient coordinate is free: there is nothing there.

(opening parenthesis)

For example, if you could escape from time and go back to your ancient coordinate, you would find nothing: there would not be a second "you" at a younger age. You would not find your father, you would find nothing, you would not even find the Earth.

In order to find something there, you should not escape from time but rewind the entire machine of the universe.

(closing parenthesis)

 

And if someone takes into account that the ancient coordinate is not directly observable, also that future coordinates are not observable, that the only observable elements are those that collate upon the surface of the past-cone, then it opens the door to a very different and richer universe.

[swansont]

Scenarios based on violating the laws of physics ("escape from time") are not particularly illuminating.

[MigL]

So you lied when you agreed to all those points earlier ( 3 posts ago )?

Or are you indecisive and change your mind a lot?

[michel123456]

So you lied when you agreed to all those points earlier ( 3 posts ago )?

Or are you indecisive and change your mind a lot?

???

I don't change my mind. Maybe I do not explain my concepts very well.

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

Here is an analogy;

 

Say you are on the locomotive of a train.

Suppose that for an obscure reason the only thing you can observe is the locomotive itself, you cannot observe the wagons behind you.

On a parallel path, at one unit of distance, there is another train.

Suppose that , for the same obscure reason, from this train you can only observe the first wagon (the one just behind the locomotive)

Next to it, a second train at 2 units of distance from which you can observe only the second wagon.

And so on, a third train at 3 units of distance from which you observe only the third wagon.

And so on, and so on.

 

If you were able to travel back in your train, you would arrive and discover one of your own wagons, not the locomotive.

Or you should by the act of magic rewind back all trains in order to find back the ancient situation and then yes, find back the locomotive were it was.

 

That was an analogy, don't take it too seriously.

Edited December 7, 2014 by michel123456

[MigL]

If time were a train, we would call it a train.

 

There is no duplication of you in old co-ordinates, nor is there vacating of old co-ordinates when time progresses.

You were, are, and will be, at every co-ordinate you remember, are, or will be in the future ( disregarding QM effects ).

Why can you not grasp that time does not behave like position ( or atrain for that matter ).

 

That is what the best theory we have, that describes the properties of time, tells us.

Until something better than GR comes along, this is what we have. Suck it up.

[Strange]

There is no duplication of you in old co-ordinates, nor is there vacating of old co-ordinates when time progresses.

You were, are, and will be, at every co-ordinate you remember, are, or will be in the future ( disregarding QM effects ).

Why can you not grasp that time does not behave like position ( or atrain for that matter ).

 

It may have sounded, earlier, as if you and I were describing time differently (after all, I said that time and spatial dimensions were similar). But I think you have been very clear here.

 

If you compare [a moment in] time and position, then they behave very differently. As you say, you can't move from one time to another, but you can move from one place to another.

 

However, if you compare extent in time (.e.g lifetime) with extent in space (e.g height) then they seem more similar: you occupy all points in time corresponding to your period of existence, and you occupy all points in space corresponding to your height (and breadth and depth).

 

 

Until something better than GR comes along, this is what we have. Suck it up.

 

Quite. "I find that absolutely grotesque" is no substitute for a working, tested, scientific model.

Edited December 8, 2014 by Strange

[michel123456]

 

It may have sounded, earlier, as if you and I were describing time differently (after all, I said that time and spatial dimensions were similar). But I think you have been very clear here.

 

If you compare [a moment in] time and position, then they behave very differently. As you say, you can't move from one time to another, but you can move from one place to another.

 

However, if you compare extent in time (.e.g lifetime) with extent in space (e.g height) then they seem more similar: you occupy all points in time corresponding to your period of existence, and you occupy all points in space corresponding to your height (and breadth and depth).

 

 

Quite. "I find that absolutely grotesque" is no substitute for a working, tested, scientific model.

 

Correct me:

 

Your understanding is that, while living in a 4D world, we are 4D objects.

My understanding is that we are 3D objects traveling in a 4D world.

[Strange]

If we are travelling through a 4D world, then it must take time to go from A to B. But time is one of those dimensions. So you need to introduce a 5th (time) dimension. And then you will say you are travelling through a 5D world which means that will take time. So you need to introduce a 6th (time) dimension. And then you will say ...

 

If you look at the 4D sapce-time manifold, it already constains time so you can't have chnage or movement. It is like a lump of hyperdimensional jelly with lines indicating the existence of things in time and space.

[Endy0816]

 

Correct me:

 

Your understanding is that, while living in a 4D world, we are 4D objects.

My understanding is that we are 3D objects traveling in a 4D world.

 

How are you alive and thinking if you maintain the same atoms?

[michel123456]

If we are travelling through a 4D world, then it must take time to go from A to B. But time is one of those dimensions. So you need to introduce a 5th (time) dimension. And then you will say you are travelling through a 5D world which means that will take time. So you need to introduce a 6th (time) dimension. And then you will say ...

 

If you look at the 4D sapce-time manifold, it already constains time so you can't have chnage or movement. It is like a lump of hyperdimensional jelly with lines indicating the existence of things in time and space.

Yes you need time, time is there, point.

Similarly, you don't need extra space to have space.

[Delta1212]

Yes you need time, time is there, point.

Similarly, you don't need extra space to have space.

No, but you need extra space to travel through space.

[Strange]

Yes you need time, time is there, point.

Similarly, you don't need extra space to have space.

 

Imagine a transparent cube which represents 2 spatial dimensions and 1 time dimension. You are outside it and looking at what happens.

 

In your model, you would see an object as a point which moves around in both time and space. But in order for you to observe it moving in time would have to pass for you - this is your time outside of the time dimension in the cube. Therefore you require some sort of meta-time or hyper-time to make your model work.

 

In the model used by GR, the cube is static and unchanging. A point that moves through space and time is represented as a (static) line. An object that moves through space and time is represented as a complex 3D (in this simplified model). No extra "external" time dimension is required because nothing changes.

[davidivad]

this really is the best way to look at it.

use einstein, it is easier to understand.

this is a great way to view time as a dimension but does not make wagers on such things.

one has to assume the model says anything at all about whether the future and past are real.

any reference to a real light cone is bologna, so we can use it because it works without having to say it is a real thing.

 

 

just thinking ahead.

[Strange]

 

so we can use it because it works without having to say it is a real thing.

 

Exactly.

[michel123456]

 

Imagine a transparent cube which represents 2 spatial dimensions and 1 time dimension. You are outside it and looking at what happens.

 

In your model, you would see an object as a point which moves around in both time and space. But in order for you to observe it moving in time would have to pass for you - this is your time outside of the time dimension in the cube. Therefore you require some sort of meta-time or hyper-time to make your model work.

 

In the model used by GR, the cube is static and unchanging. A point that moves through space and time is represented as a (static) line. An object that moves through space and time is represented as a complex 3D (in this simplified model). No extra "external" time dimension is required because nothing changes.

Let's take your model.

Nothing changes.

Thus I understand that Time acts like a scanner upon a sheet of paper. In the sheet of paper nothing changes. The past, the present, the future are static.

Is that it?

Then the scanner scans.

It moves, it translates. No?

Edited December 16, 2014 by michel123456

[imatfaal]

If you want a sheet of paper analogy then it is best to think on these lines - individual sheets in a block of paper; each spatial coordinate (only x,y) is a point on your sheet of A4 squared paper - you mark off your object at 12 cm left and 9 cm up from bottom left-hand corner on the first sheet, each sheet of paper in a ream of paper is a new time coordinate say one tenth of a second - these are marked from t=0 to t=499. On each sheet you mark the position in 2d-space of your object at the time corresponding to that sheet.

 

So your ream of paper contains the information of a block of 2d-space/1d-time - 21 cm in x-axis 29cm in the y-axis and 50 seconds in the t-axis; it is blocky ie. you might want more squares on the squared paper or more sheets of paper per second - but it is a representation.

 

That representation does not move - it contains the path of your test object for 50 seconds. You can observe the particle's position at a time by finding the sheet of that time coordinate and looking at the x,y coords. You can observe the particle's movement by looking at a progression of sheets . But nothing "moves" in the representation.