Can we see it?

[Sisyphus]

I think you misunderstand me. If you're really going to treat time as a dimension, then every statement you make about time you should be able to make about spatial dimensions, without invoking time at all. And please note that "traveling through space" IS invoking time.

 

So, explain the "leaving empty" concept again, only using the three spatial dimensions. You have a 3D pyramid. What is empty?

[michel123456]

Let's say the pyramid is a piece of wood, placed upon a chess board.

The pyramid is at place A (0,0).

Then, you begin to play, and put the pyramid at place B (0,1).

Speed has no importance, and sequence has no importance too.

 

 

If you say that both places A & B are occupied, there are 2 pyramids.

If you play with only one object, the pyramid cannot occupy 2 places at the same instant (here, time is unavoidable).

When the pyramid is at point B, point A is free.

 

That's the way we describe displacement in space.

That's the way I imagine displacement in time.

[Sisyphus]

I said don't invoke time. You can't have it at two different locations. All you have is length, width, and height.

 

How about this, to make it even more specific. You have a 3D coordinate system. In that system is a cube, 1 unit on a side, with 1 vertex at (0,0,0) and the opposite vertex at (1,1,1). What part of it is "empty?"

 

Now have it exist in time. You have a "hypercube" with 1 unit each of length, width, depth, and duration. One vertex is at (0,0,0,0), the other at (1,1,1,1). What part of it is "empty?"

Edited April 29, 2010 by Sisyphus

[michel123456]

I said don't invoke time. You can't have it at two different locations. All you have is length, width, and height.

 

How about this, to make it even more specific. You have a 3D coordinate system. In that system is a cube, 1 unit on a side, with 1 vertex at (0,0,0) and the opposite vertex at (1,1,1). What part of it is "empty?"

 

Now have it exist in time. You have a "hypercube" with 1 unit each of length, width, depth, and duration. One vertex is at (0,0,0,0), the other at (1,1,1,1). What part of it is "empty?"

 

O.K. Let's work on the cube.

take a single object. Where will you put it? At vertex (0,0,0) or at vertex(1,1,1)?

You have to choose. You can't put it at both points, otherwise you don't have a single object anymore, you'll have 2 objects.

Agree?

[Sisyphus]

It is a 3 dimensional object, not a dimensionless point. So no, I don't agree.

[michel123456]

Are you playing Sisyphus?

 

Do you want me to explain displacement?

 

I am a patient guy. Usually.

 

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

Sorry, that was unappropriate.

 

I cannot explain displacement without the use of an object.

Edited April 30, 2010 by michel123456

[Spyman]

I have been stubborn and not able to understand Sisyphus and Iggy, but I was wrong and they are correct.

 

If we treat time as a *pure* spatial dimension then there can't be any movement at all, either in space or time. All objects in such a universe must also consist of four spatial dimensions, they would have length, width, depth, and duration.

 

The Universe would then have a spacetime like frozen jelly, which would be deformed, both compressed and streached, objects inside would look like threads piercing through it.

 

However that 4D view of the Universe also has some problems, or at least I am not able to fully imagine it yet and might still be confused about it:

 

1) Such an universe seem to me to be absolute, if we were able to step outside of that 4D universe and look at it from outside then even if two observers inside is not able to agree on the order of events, from an outside view it would be possible to imagine a translated version of this universe with a released tension in the jelly and from the relaxed view one could decide which event took place first or last.

 

2) This universe would also be fully determined, even if observers inside it can't predict the future it would still be there already fixed, to every small detail. If nothing ever changes then the start or end of objects are locked. From an outside view everything would be known and all actions have already happened.

 

3) Objects inside this universe consists of different "time" slices which are not able to relay information to each other in any direction. From the outside it would be possible to look at a human or a computer and make the observation that it is processing information, as each slice in the row is slightly different. But on the inside where the slices are separated and where each slice is not able to on its own be conscious or perform a series of operations, this row would not be observable, the series of unconnected slices would not be able to notice that they are part of a changing serie.

 

I want to stress this part:

A thought has a nonzero time dimension.

A slice of a thought has a nonzero time dimension but without a connection with the other slices it is no longer a thought, it is only one single slice in a unobservable serie of different slices. I don't think we are able to have this thought or be aware of it without the changes between the slices being observable.

 

Thus without a serie of actions or a progress of events the slices are doomed to be lifeless in a frozen surronding and not on their own be able to consciousness and be aware of how time flows or be able to perform a calculation. In this universe it seems impossible for a human to think and remember.

[michel123456]

Spyman you have been hit.

 

Space wins and time looses.

 

What is a *pure* spatial dimension?

 

You think it is a dimension without time. I don't think so.

 

In your imagination, you have transformed time in space, and everything became frozen. That is wrong. You are still enslaved by the concepts of space being different from time.There is no struggle between space & time. They are the one and same thing.

 

I have been stubborn and not able to understand Sisyphus and Iggy, but I was wrong and they are correct.

 

This statement shows how a wonderful thinking person you are.

You were not wrong. You are just in doubt.

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

(editing)

I told you to slow down. Instead of reducing speed you have accelerated. Now you have to stop, and come back a few steps.

[PaulS1950]

Can space/time be compared (in principal) to mass/energy?

[michel123456]

I am definitely NOT proposing that one objects exists both in the past and at the present simultaneously.

 

Have you change your mind?

 

PS Sorry to PaulS to bypass his question.

 

Spyman wrote

"Change" could be a difference between two points in time or between two points in space. In a four dimensional coordinate system there is no obvious difference between a displacement from coordinate (1,1,1,1) to (1,2,1,1) as from a displacement from coordinate (1,1,1,1) to (2,1,1,1), besides from different end locations, but in both cases the displacement has been of one unit.

 

Is that so wrong?

[Spyman]

Have you change your mind?

No, I agree with Sisyphus and Iggy about this:

If we treat time as a *pure* spatial dimension then there can't be any movement at all, either in space or time. All objects in such a universe must also consist of four spatial dimensions, they would have length, width, depth, and duration.

But not to the idea that the Universe can be viewed as stricktly spatial 4D.

 

 

I am still waiting for Sisyphus or Iggy to continue to explain the following:

3) Objects inside this universe consists of different "time" slices which are not able to relay information to each other in any direction. From the outside it would be possible to look at a human or a computer and make the observation that it is processing information, as each slice in the row is slightly different. But on the inside where the slices are separated and where each slice is not able to on its own be conscious or perform a series of operations, this row would not be observable, the series of unconnected slices would not be able to notice that they are part of a changing serie.

 

I want to stress this part:

A thought has a nonzero time dimension.

A slice of a thought has a nonzero time dimension but without a connection with the other slices it is no longer a thought, it is only one single slice in a unobservable serie of different slices. I don't think we are able to have this thought or be aware of it without the changes between the slices being observable.

 

Thus without a serie of actions or a progress of events the slices are doomed to be lifeless in a frozen surronding and not on their own be able to consciousness and be aware of how time flows or be able to perform a calculation. In this universe it seems impossible for a human to think and remember.

One slice can not be aware on its own, and for a line of slices to be aware together they need to be connected which they can't be in a *pure* spatial 4D Universe.

[Charlatan]

You can put it everywhere in our past without us being able to see it from anywhere in the present.

 

IA the question goes a little deeper than how to read a spacetime diagram...

 

Do you belive that time is a dimension similar to space which we travel through or that our past is frozen stiff with our past selfs and everything included?

 

If we view time lika a filmstrip in a movie, then the objects either can remain frozen in all the pictures or they could travel from frame to frame, leaving old pictures empty.

 

IF objects travels through time you could not go back to Earths 'yesterday' and find 'yesterdays' Earth there, instead you would find an empty location since the Earth had moved on towards the future and is here in the present now.

 

In such a view a spacetime diagram would only show how objects and signals moved through that episode of time and space, and not that the objects still exists in the past spacetime locations nor that the past events still continues to happen in the past.

 

I think Cap'n Refsmmat said it well in post #127:

 

What Michel seems to be asking is:

If anything changes in our past, when it already is in our past, would we be able to notice it now in the present?

and

If we leave our past empty how can we know if 'new' alien objects aren't causing 'new' events back there?

 

If you were to want to see an object from the past, you will. You will see images that gather on your eye lens and then you will see the history of a nano second ago.

 

The thing with stars and celestial bodies makes them very far away, so that nano sceond becomes quite a bit longer, as light travles at a speed, you do not see anything until it condenses on your lens. If you want to see the moon you cannot see it if it is between the earth and you. The earth rotates and that means that if you were on the other side of the earth you would see them still. Stars emit light themselves, constantly, until they burn out, so, you will see what happened a while ago.

 

Things happen all the time, we get it a little later, like a rerun... yeah!

[michel123456]

We are getting off the road.

 

If discussion goes into what we "think" may or may not be a 4d world made entirely of space, we are lost.

Here we are not able to represent clearly what our world is made of.

 

I am sure that our common representation of what we call Space, is incorrect. We represent Space as an unmovable framework, and Time as "another dimension" that allows motion. Although we know from Relativity that it is not true. We know that SpaceTime is a continuum. There are no frontiers between Space & Time. There is no unmovable framework, no frozen dimensions versus timed dimension.

 

This thread was not intented to solve the mystery of time. Only to specify some aspect of its nature.

Such as the fact that, yes Charlatan, we are observing objects in the past, but not all the objects of the past, only some of them. (here Iggy gets mad, replace the word "objects" by "events").

And then discussion went on the "object" versus "event" interpretation, so that nobody gets mad.

Next step (I expected to be at post #5, not post #235463789) should be to ask whether those "eventobjects" hidden in the past have any influence on other "eventobjects" placed upon the conic surface of our observable universe.

Because, if they have no influence, or if there is nothing "hidden in the past", that's it: discussion collapses in front of an hypothetical subject that resolves nothing.

But if they have influence, bingo.

[Charlatan]

We are getting off the road.

 

If discussion goes into what we "think" may or may not be a 4d world made entirely of space, we are lost.

Here we are not able to represent clearly what our world is made of.

 

I am sure that our common representation of what we call Space, is incorrect. We represent Space as an unmovable framework, and Time as "another dimension" that allows motion. Although we know from Relativity that it is not true. We know that SpaceTime is a continuum. There are no frontiers between Space & Time. There is no unmovable framework, no frozen dimensions versus timed dimension.

 

This thread was not intented to solve the mystery of time. Only to specify some aspect of its nature.

Such as the fact that, yes Charlatan, we are observing objects in the past, but not all the objects of the past, only some of them. (here Iggy gets mad, replace the word "objects" by "events").

And then discussion went on the "object" versus "event" interpretation, so that nobody gets mad.

Next step (I expected to be at post #5, not post #235463789) should be to ask whether those "eventobjects" hidden in the past have any influence on other "eventobjects" placed upon the conic surface of our observable universe.

Because, if they have no influence, or if there is nothing "hidden in the past", that's it: discussion collapses in front of an hypothetical subject that resolves nothing.

But if they have influence, bingo.

 

Actually I have visualised the fourth dimension, and, it is generated on wiki. They of course got the image from my vast knowledge on the subject, but I wil let this one slide... ulp!

[Iggy]

Objects inside this universe consists of different "time" slices which are not able to relay information to each other in any direction.

 

Why not? Why can't an event at T=1 cause an event at T=2? Try reading: http://en.wikipedia.org/wiki/Spacetime

 

But not to the idea that the Universe can be viewed as stricktly spatial 4D.

 

While time is space-like in spacetime there are still some distinctions between the two. The most obvious is that space is measured with a measuring tape and time is measured with a clock. There are some others.

[Spyman]

Why not? Why can't an event at T=1 cause an event at T=2?

Ok, but it is you and Sisyphus who are the ones arguing that we can not have any movements, changes or progress in a 4D spatial universe without introducing a fifth dimension for the action to take place within.

 

Look here what you have said:

 

By introducing the idea of objects moving through spacetime you are imposing another dimension of time on spacetime.

 

The "trouble" is in trying to have it both ways, treating time like a spatial dimension and picturing "moving through it" as one would move through a spatial dimension, i.e. "over time." In other words, having time twice: as an extension and a duration.

I want to really, really stress the idea of the 4D object. To change it, you need a fifth dimension in which it can change.

 

 

 

Read my post again and then explain in which dimension or how this information from event T1 is moving to T2 if all four dimensions are already "locked" by representing locations.

 

If you are arguing that information can move from T1 to T2 in a 4D spatial universe then you seem to be "imposing another dimension of time".

---

Merged post follows:

Consecutive posts merged

We are getting off the road...This thread was not intented to solve the mystery of time. Only to specify some aspect of its nature.

Sorry Michel but I think the aspects that are being discussed are basic and therefor needed to be solved before we can continue.

 

I am sure that our common representation of what we call Space, is incorrect. We represent Space as an unmovable framework, and Time as "another dimension" that allows motion. Although we know from Relativity that it is not true. We know that SpaceTime is a continuum. There are no frontiers between Space & Time. There is no unmovable framework, no frozen dimensions versus timed dimension.

I would like you to extend this thought and explain more about it.

[Iggy]

Ok, but it is you and Sisyphus who are the ones arguing that we can not have any movements, changes or progress in a 4D spatial universe without introducing a fifth dimension for the action to take place within.

 

Movement is already represented in this static spacetime diagram,

 

 

The black object moves relative to the red one. It moves in space over time. The two objects interact at T=1. If they were thrown at T=0 toward each other then we would say that the T=0 events caused the T=1 event.

 

Two points in spacetime are connected (hence information about the one is available to the other) if they are connected by the world-line of a material particle. The existence of the world-line means that there is a causal relationship between the points. See: time-like interval.

 

Read my post again and then explain in which dimension or how this information from event T1 is moving to T2 if all four dimensions are already "locked" by representing locations.

 

The x,y,and z dimensions show location in space. The t dimension shows location in time. Since "movement" is a change in spatial location over a change in time it is already encoded on a static spacetime diagram. To have things moving through spacetime is to show two different kinds of motion. To have the coordinate (x,y,z,t) take on two different values would require another coordinate: (x,y,z,t,t2) so that x,y,z and t can change in t2.

 

This, for example,

 

 

That needs three coordinates (one of space and two of time). An object is at (x=1.5, tA=1, tB=2) but not at (x=1.5, tA=1, tB=3).

 

Take a look at this website: http://dev.physicslab.org/Document.aspx?doctype=5&filename=Kinematics_ConstantVelocityPositionTimeGraphs1.xml

 

It gives this diagram,

 

 

asking these questions:

1. which is at rest
   
2. which is traveling slowly in a positive direction
   
3. which is traveling quickly in a negative direction
   
4. which is traveling fast in a positive direction
   

The static diagram already represents the concept that we understand as movement or motion or change.

 

If you are arguing that information can move from T1 to T2 in a 4D spatial universe then you seem to be "imposing another dimension of time".

 

Four spatial dimensions is not exactly the same as spacetime.

 

An event at T1 can cause an event at T2 if an object (or a massless particle) intersects them both. In order for things to move through space you must add time. It is a parameter that allows motion through space. In order for things to move through spacetime you must add another dimension of time. It would be a parameter that allows motion through spacetime.

[Spyman]

The static diagram already represents the concept that we understand as movement or motion or change.

I am NOT arguing this.

 

Four spatial dimensions is not exactly the same as spacetime.

Yes, I fully agree.

 

An event at T1 can cause an event at T2 if an object (or a massless particle) intersects them both. In order for things to move through space you must add time. It is a parameter that allows motion through space. In order for things to move through spacetime you must add another dimension of time. It would be a parameter that allows motion through spacetime.

Sure, you can have two 4D objects intersecting somewhere inside a 4D block of spacetime, but there is no flow of information from the past to the present in this view.

 

You don't seem to understand my argument at all, here let me repeat what you said again:

 

"In order for things to move through spacetime you must add another dimension of time."

 

Now I ask once more, how can information move from one slice of spacetime to another slice of spacetime without another dimension of time?

[michel123456]

I am feeling we are out of tracks. Anyway.

Originally Posted by michel123456

"I am sure that our common representation of what we call Space, is incorrect. We represent Space as an unmovable framework, and Time as "another dimension" that allows motion. Although we know from Relativity that it is not true. We know that SpaceTime is a continuum. There are no frontiers between Space & Time. There is no unmovable framework, no frozen dimensions versus timed dimension."

 

 

I would like you to extend this thought and explain more about it.

 

I once made a thread called " two faces of time?" http://www.scienceforums.net/forum/showthread.php?t=48803

Its a long thread, you can read my conceptions till post 21.

The main idea is that you cannot have distance without time, and is resumed in the following:

Quite right.

But you cannot travel a distance by zero time.

"how long it takes something to travel with a fixed speed" is another definition of distance, as you said. And I must agree on this.

To get time of travel=zero, you should need infinite speed. The "fixed speed" you mentioned cannot be infinite (that is told by physical reality, not by pure geometry).

It means that to describe physical distance is such a manner, you always need time. Time is inscribed into distance, you cannot get rid of it.

For example:

for D=zero, T=zero.

For D=infinite, T=infinite.

For D=anything (unit Meter), Time = anything (unit seconds)

Or, in other words, you can always describe distance in unit of time.

IMO it means that distance = time. from post 21.

[Sisyphus]

 

Now I ask once more, how can information move from one slice of spacetime to another slice of spacetime without another dimension of time?

 

Information "moving" would be just the same as objects "moving." In other words, information would also consist of 4D world lines, though more abstract ones. So information would "flow from the past to the present" in the sense that the world lines connect the two points.

 

Causality could be described as the shape a system of world lines in the future direction being dependent on its shape in the past direction.

[Iggy]

"In order for things to move through spacetime you must add another dimension of time."

 

Now I ask once more, how can information move from one slice of spacetime to another slice of spacetime without another dimension of time?

 

Information, like an object, does not 'move' through time. With conservation of energy we can prove that the energy making up the universe today will be here tomorrow. By conservation of phase space (or the conservation of information entropy) we can prove that the information here today will be here tomorrow. In spacetime it doesn't 'move' from one time slice to the next. It simply exists in both.

 

To have information move from one instant of time to another would indeed require another dimension of time as 'movement' is, by definition, change in location over change in time.

 

see: http://books.google.com/books?id=cxJCBRUNmVYC&pg=PA69&lpg=PA69&dq=%22information+conservation%22+%22in+both+classical+and+quantum+mechanics%22&source=bl&ots=liI3-3H-3w&sig=3jijcmInBVvZ7oSMQOh05BJPN2U&hl=en&ei=YhLgS6L6CI_iNYHWwM8J&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAYQ6AEwAA

 

To get time of travel=zero, you should need infinite speed.

 

I haven't read the other thread, but I might point out that relativity disagrees with your conclusion. The speed at which no time is needed to traverse a space is the speed of light. If you traveled very, very near the speed of light it would take you very, very close to zero seconds to get to the Andromeda galaxy.

[Sisyphus]

Sorry I missed this earlier.

 

I

 

However that 4D view of the Universe also has some problems, or at least I am not able to fully imagine it yet and might still be confused about it:

 

1) Such an universe seem to me to be absolute, if we were able to step outside of that 4D universe and look at it from outside then even if two observers inside is not able to agree on the order of events, from an outside view it would be possible to imagine a translated version of this universe with a released tension in the jelly and from the relaxed view one could decide which event took place first or last.

 

If you're talking about the relativity of simultaneity, then I don't think that changes anything. A different frame of reference changes the angles of world lines, but it doesn't change their topology. The lines still intersect in all the same ways, it's just a distorted picture, and that doesn't bother me. The universe would still be 4D, just not Euclidian, and there wouldn't be a single preferred 4D Euclidian representation of it.

 

I would also stress that order of events does not have unlimited flexibility. The rule of thumb is that if light has time to travel between two events, then their order is fixed (though the amount of time between them depends on reference frame). This preserves world lines - line AB between events A and B exists in every reference frame, though its length and angle is not constant between them.

 

2) This universe would also be fully determined, even if observers inside it can't predict the future it would still be there already fixed, to every small detail. If nothing ever changes then the start or end of objects are locked. From an outside view everything would be known and all actions have already happened.

 

I suppose, sure. Though there isn't any "outside view," and the 4D universe is not necessarily a deterministic one. "Non-deterministic" would simply be defined as 3D slices in the future direction having traits that cannot be extrapolated from all the information in a past slice.

 

3) Objects inside this universe consists of different "time" slices which are not able to relay information to each other in any direction. From the outside it would be possible to look at a human or a computer and make the observation that it is processing information, as each slice in the row is slightly different. But on the inside where the slices are separated and where each slice is not able to on its own be conscious or perform a series of operations, this row would not be observable, the series of unconnected slices would not be able to notice that they are part of a changing serie.

 

I think I answered this above, unless I misunderstand you. Time slices are not "disconnected" any more or less than they are in spatial dimensions. Information flows in worldlines, also. Slices do not so much "relay" information between them as they are already connected.

[michel123456]

With conservation of energy we can prove that the energy making up the universe today will be here tomorrow. By conservation of phase space (or the conservation of information entropy) we can prove that the information here today will be here tomorrow. In spacetime it doesn't 'move' from one time slice to the next. It simply exists in both.

 

What exist in both? information or energy?

[Iggy]

What exist in both? information or energy?

 

Both. I was meaning to compare the two.

In both classical and quantum mechanics there is a very precise sense in which information is never lost from a closed isolated system.

http://books.google.com/books?id=cxJCBRUNmVYC&pg=PA69&lpg=PA69&dq=%22information+conservation%22+%22in+both+classical+and+quantum+mechanics%22&source=bl&ots=liI3-3H-3w&sig=3jijcmInBVvZ7oSMQOh05BJPN2U&hl=en&ei=YhLgS6L6CI_iNYHWwM8J&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAYQ6AEwAA#v=onepage&q=%22information%20conservation%22%20%22in%20both%20classical%20and%20quantum%20mechanics%22&f=false

[michel123456]

With conservation of energy we can prove that the energy making up the universe today will be here tomorrow.

 

Yes. I agree.

 

By conservation of phase space (or the conservation of information entropy) we can prove that the information here today will be here tomorrow.

 

I don't know, I don't understand. I guess it's right.

 

In spacetime it doesn't 'move' from one time slice to the next.

 

That is your interpretation, and it is the first part of the question. Maybe you're right, maybe you're wrong. I think you're wrong.

 

It simply exists in both.

 

If you are talking about energy, No. I disagree totally.

As far as I can understand, energy* is distributed the same way as matter** is, i.e. upon the surface of the light-cone.

 

* "observable" energy

**"observable" matter