Can we see it?

[michel123456]

I'd like a gif of this,( but i have no time lately) with a single Earth, a single spaceship, and a single Moon, where both the Earth and the Moon observe continuously the spaceship in the past.

And after that, another gif with the spaceship replaced by a luminous signal, traveling at C.

[Spyman]

I'd like a gif of this,( but i have no time lately) with a single Earth, a single spaceship, and a single Moon, where both the Earth and the Moon observe continuously the spaceship in the past.

 

The spaceship flashes with a red light every 0.2 seconds to visualise how light travels outward from it.

 

 

And after that, another gif with the spaceship replaced by a luminous signal, traveling at C.

 

The laserbeam and objects have their past locations colored in grey to show their paths trough spacetime.

[michel123456]

Thank You.

The diagrams look O.K. to me.

 

As you can see, both gifs are terrebly empty.

Lets have a look at your second diagram.

What happens if you insert inside the grey zone a 2nd "Earth", traveling behind us. As I can see it, its image will miss the Moon.

[insane_alien]

michel, you can't have two times at once. the vertical axis is time.

 

you could have the earth emit two signals at different times if you wanted, but all the diagram will show is that the signals arrice i nthe order they were transmitted.

[Spyman]

What happens if you insert inside the grey zone a 2nd "Earth", traveling behind us. As I can see it, its image will miss the Moon.

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

 

 

michel, you can't have two times at once. the vertical axis is time.

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:

The space-time diagram doesn't say the object exists at all time (although that could be true depending on how you interpret time). It just describes where it was at each time.

 

 

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?

[Sisyphus]

 

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

 

I don't think so. I know you're having a huge involved discussion here and I'm just dipping in, but IA is right: that diagram doesn't make any sense. You have time represented both by the vertical axis and by real time. Having both is nonsensical.

 

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?

 

I believe that is a difference only of outlook. You're not debating differences in physical reality, you're just having trouble reconciling time as a dimension vs. human perception of time (as evidenced by that screwy gif).

 

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.

 

"Leaving old pictures empty" would mean that the Earth did not exist yesterday. Is that what you're arguing?

 

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?

 

See that question reveals the same problem. You're treating it as a dimension and as the normal human conception. "Change" means a difference between two points in time. "Change the past" is meaningless.

[michel123456]

Spyman's gifs are perfectly correct.IMHO.

There is no twice time. It is time unfolded.

Instead of having all time frames superposed, the one vanishing after the other, they are placed the one above the other so that we can figure exactly what happens.

 

It has been a long thread, I understand Sisyphus don't want to go & read everything from the beginning.

 

I can assure him that Spyman has fully understood the question. I guess Iggy too. (Iggy still disagrees, but not about the question, he disagrees about the answer: at the question, is the grey zone full or empty, Iggy says full, Spyman says empty, and I say, lets fill it) (edited)

 

What is wrong with Spyman's diagrams?

Edited April 23, 2010 by michel123456

[Sisyphus]

What is wrong with the diagram was illustrated by Iggy in posts 103 and 106. It is using 2 different time dimensions. That's not unfolding, it's obfuscating.

[michel123456]

 

You surely know Flatland. If you look at this representation through the thin edge of the screen, you will see an object moving in real-time. What's the problem? IMO there is nothing wrong in it.

If you freeze it, it is a regular spacetime diagram.

[Iggy]

What is wrong with Spyman's diagrams?

 

This diagram:

 

 

would be ok if we added world-lines and recognized that the dots (the moving things) are events--an object at a specific time:

 

 

Otherwise, why is there a time axis?

 

 

As you can see, both gifs are terrebly empty.

 

Empty of directly observable events, yes. Not empty of objects. Looking through a telescope, you will not see Neil Armstrong walking on the moon. That event is inside our past light cone. This does not mean that Neil Armstrong and the moon cannot be observed. They are objects, we can observe them today, and objects cannot hide inside a past light cone.

 

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.

 

You are thinking that objects move though spacetime in the same way that objects move through space. That interpretation is unusual and requires two different variables of time--one for the object's movement through space and another for the object's movement through spacetime. Movement is change in distance divided by change in time. It requires time.

 

I'm not aware of any philosophy that has such an interpretation of spacetime.

 

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.

 

It should be clear that your concept has two different kinds of yesterday. 1) yesterday that has an earth and 2) yesterday that has no earth.

 

If there is an earth tomorrow then instantly traveling to tomorrow you would find an earth. This is possible using relativity. If you traveled near the speed of light for roughly one light-day (about 10^10 kilometers) then you would near-instantly arrive at earth's tomorrow. The earth would still be here otherwise conservation laws would have a big problem.

 

..not that the objects still exists in the past...

 

If there is only one kind of time then "still exists in the past" is not a logical statement. In the past the object exists in the past. In the present the object exists in the present. To say that the object simultaneously exists in the past and present is a contradiction in term.

[michel123456]

Time is such a weird thing that I prefer not follow the road of what we usualy believe is true about time and simply look at the diagrams.

 

I observed carefully Iggy's last diagram, and I have no problem with it. Nor do I have any problem with Spyman's. All diagram are showing a single Earth traveling in time, & a single Moon.. I still disagree with Iggy's comments "(...) that the dots (the moving things) are events". I open my eyes, look at the diagram, and see an object sliding. How is it possible that Iggy and I look at the same thing and see different things?

 

When the Earth leaves a point of coordinates in spacetime, it leaves the point: it is exactly the same as motion in space, and I really don't know why it is a problem to anyone. Time is not so different from space, we know that from the basic concepts of Relativity. And the diagram is 100% relativist.

 

Also, I do not see any monstruous error, no object flowing backwards in time, no object moving faster than C, nothing incorrect. Although it leaves an unusual & maybe unpleasant notion of "yesterday".

 

Please notice that signals always travel upon the horizontal line between Earth & Moon. Due to the translation in Time, they appear coming from the past.

That leaves plenty of space (sorry, plenty of time) for other Earths & Moons before & after us.

[Iggy]

I still disagree with Iggy's comments "(...) that the dots (the moving things) are events".

 

By definition, an event is a specific place at a specific time. By the definition of coordinate, a dot on a spacetime diagram is a specific place at a specific time. What I said is simply true by definition.

 

When the Earth leaves a point of coordinates in spacetime, it leaves the point: it is exactly the same as motion in space, and I really don't know why it is a problem to anyone. Time is not so different from space, we know that from the basic concepts of Relativity. And the diagram is 100% relativist.

 

People have issues with it because it is not correct. Motion is change in position over change in time. On a spacetime diagram motion is depicted by run over rise, or tilt. Like wikipedia shows:

 

 

I think you would benefit from reading that wikipedia article,

 

Trivial examples of spacetime curves

 

Three different world lines representing travel at different constant speeds. t is time and x distance.

 

A curve that consists of a horizontal line segment (a line at constant coordinate time), may represent a rod in spacetime and would not be a world line in the proper sense. The parameter traces the length of the rod.

 

A line at constant space coordinate (a vertical line in the convention adopted above) may represent a particle at rest (or a stationary observer). A tilted line represents a particle with a constant coordinate speed (constant change in space coordinate with increasing time coordinate). The more the line is tilted from the vertical, the larger the speed.

 

Two world lines that start out separately and then intersect, signify a collision or "encounter." Two world lines starting at the same event in spacetime, each following its own path afterwards, may represent the decay of a particle in to two others or the emission of one particle by another.

 

World lines of a particle and an observer may be interconnected with the world line of a photon (the path of light) and form a diagram which depicts the emission of a photon by a particle which is subsequently observed by the observer (or absorbed by another particle).

http://en.wikipedia.org/wiki/World_line

 

Spacetime does not make motion in time like motion in space--that's a mistaken understanding. Spacetime makes the dimension of time like the dimension of space. Motion then becomes geometric. A line tilted Δx/cΔt on the diagram represents an object moving through space with the speed Δx/cΔt.

Edited April 25, 2010 by Iggy

[michel123456]

Conversation goes in circle.

The "tilt" is an angle, representing speed (or velocity). Angle 45 degrees is C (by convention). Angle zero is infinite speed (trigonometrically speaking), and angle 90 degrees is zero speed (object at rest). We are not disagreeing about this.

 

Where you see a line, you see an object, and I see a trajectory, that is the difference.

I believe the word "event" comes from the static representation of the diagram as printed in a book, in order to differenciate the instant from the duration. I don't say diagrams in books are wrong, I simply say they are static representations of a dynamic phenomena. When you represent the same thing with a dynamic graph, duration is evident and the word "event" loses its meaning, because you see in front of your eyes the sliding object.

[Physicsfan]

if it was one 1 million light years away then light travelling from the star would take one million years to reach earth .if it exploded 2 million years ago.then the explosion would have been seen 1 million years ago......Right?

[Iggy]

I believe the word "event" comes from the static representation of the diagram as printed in a book, in order to differenciate the instant from the duration.

No, the word "event" has a precise definition which predates spacetime diagrams. The word doesn't come from the unusual circumstance of animation not yet being available. The word means "a specific place at a specific time".

 

An "instant" on a spacetime diagram is a single coordinate along the t axis. A "duration" is a range of coordinates along the t axis. This is true in a 'static' spacetime diagram in a book or an animated one.

 

I simply say they are static representations of a dynamic phenomena.

 

Incorrect. They show three dimensional dynamics in time. By introducing the idea of objects moving through spacetime you are imposing another dimension of time on spacetime. You fail to understand how these diagrams show the same thing:

 

 

Animating the second image would add another dimension of time.

 

When you represent the same thing with a dynamic graph, duration is evident and the word "event" loses its meaning

 

No, the word "event" has exactly the same meaning.

 

if it was one 1 million light years away then light travelling from the star would take one million years to reach earth .if it exploded 2 million years ago.then the explosion would have been seen 1 million years ago......Right?

 

Yes.

[Spyman]

I don't think so. I know you're having a huge involved discussion here and I'm just dipping in, but IA is right: that diagram doesn't make any sense.

The question is deeper than how to interpret a spacetime diagram and if you reread my post now that you have gotten your feet wet, you will see that I did not say IA was wrong, I was only trying to be helpful and bring him up to speed in the discussion.

 

You have time represented both by the vertical axis and by real time. Having both is nonsensical.

It might look wrong and probably is not the best way to visualize this model of spacetime, but that was what Michel was asking for and since he seems to understand it, it served its purpose.

 

I don't think the main thought of movement through time is "nonsensical" but I could be wrong, I will return to this further down.

 

I believe that is a difference only of outlook. You're not debating differences in physical reality, you're just having trouble reconciling time as a dimension vs. human perception of time (as evidenced by that screwy gif).

I don't think I understand what you are saying here, first you say it's only a opinion and not a physical difference, which I agree with, but then you say that I am the one having trouble. My perception of time could very well be wrong but then it's not a matter of opinion, then it can be proved by evidence.

 

We are not today able to go into the past or future as we want and by direct observation measure how the dimension of time behaves, if the past and future exists and what or how objects and events are contained. All we have is signals that arrive from here in the present that was emitted in the past. So we are forced to try to deduce from other experiments, like relativity, how the true four dimensional spacetime really are.

 

And btw, you neglected to tell us how you perceive time, am I correct in assuming that you share the view that Iggy has, that there are a infinite amount of Earths for every time the Earth has been to the end of Earth in the distant future?

 

"Leaving old pictures empty" would mean that the Earth did not exist yesterday. Is that what you're arguing?

No, nobody is arguing that the Earth didn't exist yesterday, are you arguing that the Earth still exists yesterday?

 

See that question reveals the same problem. You're treating it as a dimension and as the normal human conception. "Change" means a difference between two points in time. "Change the past" is meaningless.

I disagree, I don't think the thought "Change the past" is meaningless, from a philosophical standpoint it is very interesting and we need to ask this cind of questions to push our knowledge further.

 

"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.

 

Now if I say that the coordinates are (time,length,height,width) and that when a object is displaced in either of the space dimensions it will no longer remain in the old location, then no one will argue, but when I say that the displacement is in the time dimension then suddenly it is "obfuscating".

 

The basic of the question is if the temporal dimension can be treated like a spatial dimension or not and if it is possible to determine the properties of time itself.

 

IMHO, I think the question is valid even if the thought of moving through time will turn out to be wrong.

 

What is wrong with the diagram was illustrated by Iggy in posts 103 and 106. It is using 2 different time dimensions. That's not unfolding, it's obfuscating.

OK, this seems to be a main argument and since I promised to return to it, let's try to determine where/how our views differentiate about the rate of time.

 

I think that it is evident by the concept of the arrow of time and our unique position that always is placed in the present, that there clearly is something progressing.

 

If something is changing it doesn't have to involve extra dimensions, if I move 1 meter then I have moved 1 meter and nothing more, likewise if I move 1 second then I have moved 1 second. In a spacetime diagram you can see the revelance between time and space locations, so you can say that during 1 second you moved 1 meter which will give the speed of 1 m/s during the movement, but you can also say that during the transfer of 1 meter in space you moved 1 second in time. You don't need any extra dimensions to understand that concept, the progress through time have a rate just like a movement through space.

 

I once read that Einstein had said that: "we are all moving through spacetime with the speed of light", or something similar, I can't find and verify the quote, but with the theory of relativity time and space where united in a dynamical 4 dimensional geometry with a rate of time or scale of space that can change depending on frame of reference.

 

If there are two observers at rest with each other, one is in mostly empty space, inside a great void and the other is deep in a strong gravity field, like very close to a supermassive black hole, then they will not be able to agree on how fast time is ticking, they will be able to measure a large difference in their observed rate of time, this time dilation doesn't utilize or need different time dimensions.

 

How is this rate of time different than moving through time at a rate?

 

 

 

You are thinking that objects move though spacetime in the same way that objects move through space. That interpretation is unusual and requires two different variables of time--one for the object's movement through space and another for the object's movement through spacetime.

No, I don't think the rate of time needs another dimension, se above arguments.

 

Movement is change in distance divided by change in time. It requires time.

Not at all, movement is a displacement, a transfer between two different locations.

(Speed on the other hand is distance divided by time.)

 

I'm not aware of any philosophy that has such an interpretation of spacetime.

Well, you are now...

 

It should be clear that your concept has two different kinds of yesterday. 1) yesterday that has an earth and 2) yesterday that has no earth.

The concept allows for unobservable changes in the past, but all events that did happen when it were our present, when we passed through that spacetime location, did happen and their consequences are observable today.

 

If there is an earth tomorrow then instantly traveling to tomorrow you would find an earth. This is possible using relativity. If you traveled near the speed of light for roughly one light-day (about 10^10 kilometers) then you would near-instantly arrive at earth's tomorrow. The earth would still be here otherwise conservation laws would have a big problem.

Lets analyze this comment further:

1) Do you claim that the future is not only determined but that there is a future Earth already there?

2) Here you accept that time has a progression rate but also that it can differ between observers too?

3) For the observer moving close to SOL there will still only be one Earth in this 'tomorrow', he is not able to communicate with any Earths in his yesterday.

4) For the observer on Earth he would seem to arrive at the spaceships 'tomorrow' but he can also only communicate with one spaceship in his present.

5) In both your view and my view there will only be one Earth placed where it should be in each frame, so there is no violation of conservation laws.

 

If there is only one kind of time then "still exists in the past" is not a logical statement. In the past the object exists in the past. In the present the object exists in the present. To say that the object simultaneously exists in the past and present is a contradiction in term.

Well thats a big IF in there and thats why I marked it very clearly in my post which you omitted to quote.

 

IF objects travels through time then it would clearly be a different kind of time than what you think, but in THAT view it is a consistent logicall statement and not a contradiction at all.

 

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

[michel123456]

Pure orgasm. I was right...in waiting patiently your answer.

[Sisyphus]

 

It might look wrong and probably is not the best way to visualize this model of spacetime, but that was what Michel was asking for and since he seems to understand it, it served its purpose.

 

I didn't mean it as an attack on you. Whoever asked for it and for whatever purpose doesn't matter. I'm just saying that at best, it is needlessly convoluted, and at worst contrary to reality, depending on how it's interpreted.

 

I don't think the main thought of movement through time is "nonsensical" but I could be wrong, I will return to this further down.

 

"Movement through time," depending on how literally the phrase is used, can simply be an intuitive perspective. What I said was "nonsensical" was the implication of the diagram, of trying to have both perspectives (that is, change over real time, and a spacetime diagram) at once.

 

I don't think I understand what you are saying here, first you say it's only a opinion and not a physical difference, which I agree with, but then you say that I am the one having trouble. My perception of time could very well be wrong but then it's not a matter of opinion, then it can be proved by evidence.

 

Allow me to explain. The matter of perspective is whether to think of time in the intuitive sense ("moving through") or in the dimensional sense, which is what a spacetime diagram represents and what is generally more useful in physics.

 

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.

 

As far as I can see, this entire thread is a repetitive attempt to smash those concepts together, resulting in nonphysical and nonsensical illustrations.

 

And btw, you neglected to tell us how you perceive time, am I correct in assuming that you share the view that Iggy has, that there are a infinite amount of Earths for every time the Earth has been to the end of Earth in the distant future?

 

How I perceive time depends on the context. In the everyday sense I think of myself as moving through it. When thinking about physics, especially relativity, it is more useful to think of time as a dimension, wherein objects have duration in the same way that they have length, width, and depth. I have no problem with either.

 

I think saying that the latter way implies "an infinite amount of Earths" is a poor phrasing. It is one Earth, of finite duration. One moment in time would be more like a 3D cross-sectional "slice" of the 4D whole.

 

To use an analogy, if you had a 2 by 2 by 2 block of wood, you wouldn't say "there are infinite amount of blocks of wood for every height, from the bottom to the top," though I suppose you could say you have a potentially infinite number of 2D slices.

 

No, nobody is arguing that the Earth didn't exist yesterday, are you arguing that the Earth still exists yesterday?

 

I am arguing that "still exists yesterday" is not a meaningful phrase. "Still" means present, "yesterday" means past. I would not ask if this end of the street exists at the other end.

 

Again, it seems to me this is born out of the confusion of having time both as intuitive "progress" and as a dimension. The question doesn't even make sense unless you're already trying to have it both ways.

 

"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.

 

Now if I say that the coordinates are (time,length,height,width) and that when a object is displaced in either of the space dimensions it will no longer remain in the old location, then no one will argue, but when I say that the displacement is in the time dimension then suddenly it is "obfuscating".

 

Ok. "Displacement in the time dimension" is again trying to have it both ways. Displacement means a change in spatial coordinates with respect to the time coordinate. If you are going to treat time as a dimension, then treat it as a dimension. So the objects are 4 dimensional. If you then have that 4-dimensional object change, then you have added a fifth dimension. Length, width, depth, duration, and whatever way in which this 4D object is changing.

 

When I say I move one meter, I mean that my spatial coordinates are not constant with respect to the time coordinate. What would it mean, dimensionally speaking, to say I move one second? That my time coordinate is not constant with respect to...... what?

 

The basic of the question is if the temporal dimension can be treated like a spatial dimension or not

 

Yes, it can. In fact I heartily encourage it.

 

re: the "arrow of time." What this tells us is that the time direction is special. "Entropy increases with time" or "there is more entropy in the future direction and less in the past direction." This is like saying that in the northern hemisphere on Earth, it is colder in the north direction and warmer in the south direction.

 

re: "rate of time" in gravity wells, etc. Yes, time can be compressed, as can the spatial directions. This is what relativity is all about. It is sometimes useful to think of it as the "rate of time," but it is still really the same as saying the "rate of length." Under length compression, my length is more compact compared to your length. Under time compression, my time is more compact compared to your time. The same. Really, though, IMO relativistic effects don't add anything to this discussion, which is more fundamental. It is probably best to sort perspective on a Euclidian universe before we start messing with it.

 

(BTW, your response over all seems kind of defensive. If that's the case then it's probably my fault, as I know I sometimes come across like I'm snapping at people. I mean no insult.)

Edited April 26, 2010 by Sisyphus

[michel123456]

(...)

How I perceive time depends on the context. In the everyday sense I think of myself as moving through it. When thinking about physics, especially relativity, it is more useful to think of time as a dimension, wherein objects have duration in the same way that they have length, width, and depth. I have no problem with either. (...)

 

_From your entire post, I think you have a problem with the "moving through it" interpretation because it requires to move at some "speed in time", which is a peculiar instance. But since everything is peculiar with the notion of time, that should not be an obstacle. After all, even if that suppose the existence of a 5th dimension, which IMHO is completely wrong, you could jump out of joy shouting "I just found a 5th dimension". That shouldn't stop you.*

 

_on the other hand , if you gently bypass this crucial question, I don't see anything "contrary to reality" in this diagram.

 

 

Except the grey zone, which is a reminiscence of personal feelings and previous static representations.

 

*besides, I can figure an explanation, and you surely can figure an explanation too, if you simply try to answer the question instead of refusing it right from the start.

Edited April 27, 2010 by michel123456

[Spyman]

(BTW, your response over all seems kind of defensive. If that's the case then it's probably my fault, as I know I sometimes come across like I'm snapping at people. I mean no insult.)

Well, I am trying to defend a concept so of course I appear defensive, but you don't have to worry I don't take it as a personal attack at all.

 

 

What I said was "nonsensical" was the implication of the diagram, of trying to have both perspectives (that is, change over real time, and a spacetime diagram) at once.

But I disagree, I think both perspectives should be able to fit with each other, they might be viewed from different angels but they should still be in agreement.

(Leaving out the representation of such a reality in spacetime diagrams.)

 

 

Again, it seems to me this is born out of the confusion of having time both as intuitive "progress" and as a dimension.

"Movement through time," depending on how literally the phrase is used, can simply be an intuitive perspective.

How I perceive time depends on the context. In the everyday sense I think of myself as moving through it. When thinking about physics, especially relativity, it is more useful to think of time as a dimension, wherein objects have duration in the same way that they have length, width, and depth. I have no problem with either.

Yes the concept tries to unite the two views of time, since in the true world time only has one set of properties, so one of our perceptions must be wrong, we can't have it both ways.

 

You seem to imply that the "intuitive perspective" of movement through time is only a illusion and does not fit with the true physical world.

 

In your physical view, how do you manage to explain that a "slice" of your 4D self is able to be conscious and be aware of how time flows?

 

 

When I say I move one meter, I mean that my spatial coordinates are not constant with respect to the time coordinate. What would it mean, dimensionally speaking, to say I move one second? That my time coordinate is not constant with respect to...... what?

SPACE - If you move one meter with respect to time, then similar you would also move one second with respect to space.

(I thought I was very clear on that in my previous post.)

It is sometimes useful to think of it as the "rate of time," but it is still really the same as saying the "rate of length." Under length compression, my length is more compact compared to your length. Under time compression, my time is more compact compared to your time. The same.

Yes, I agree, but look at your own words: "The same" and then look at the question you asked above.

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.

Displacement or movement might be the wrong words for it by definition but those are the only words I have, so I am forced to use them.

 

I tried to explain that since space and time are related, the relation goes both ways. If time dimension can be treated like a spatial dimension, then a 'movement' through time is similar to a movement through space but with changed positions by their relation. There is no need for extra dimensions.

 

Either we move through spacetime or we persist for a duration of spacetime, in the latter objects don't truly move through space either, they are then shaped in such a way that their slices are spread out in different space locations, but the individual slices don't move from one location to the other, they are fixed as firmly in space just like they are in time.

 

Can it be proved scientifically which is true and which is false?

 

 

If you are going to treat time as a dimension, then treat it as a dimension. So the objects are 4 dimensional.

wherein objects have duration in the same way that they have length, width, and depth.

But we don't know if objects are truly four dimensional, or if their size in the time dimension is the same as how long we can measure that they last.

 

For instance what happens to your vision of a 4D object when a "slice" of it reaches beyond the event horizon of a black hole?

(Where time becomes space and space becomes time.)

 

Can we by experiment measure and verify objects true size in time?

(The question is not necessary how long the object lasts.)

 

Also somewhat realted, if objects are 4D with the full duration like you assume, then how do your view fit with the uncertainty principle?

When is it determined when the object ends and how is it determined?

(Without something progressing through time it seems deterministic.)

 

 

Yes, it can. In fact I heartily encourage it.

But you cut the question in half and only answered the first part...

 

Is it possible to determine the properties of time itself?

Edited April 27, 2010 by Spyman
Removing a cut&paste error

[michel123456]

Is it possible to determine the properties of time itself?

 

You are progressing too many steps.

[Sisyphus]

 

But I disagree, I think both perspectives should be able to fit with each other, they might be viewed from different angels but they should still be in agreement.

(Leaving out the representation of such a reality in spacetime diagrams.)

 

They do fit with one another, in that you can easily translate between them, and there is no contradiction. That is, unless you try to have two "time" concepts at the same time, no pun intended.

 

Yes the concept tries to unite the two views of time, since in the true world time only has one set of properties, so one of our perceptions must be wrong, we can't have it both ways.

 

The concepts of time as dimension and intuitive time are not contradictory. It is the "double time" that is self-contradictory.

 

You seem to imply that the "intuitive perspective" of movement through time is only a illusion and does not fit with the true physical world.

 

No, I don't.

 

In your physical view, how do you manage to explain that a "slice" of your 4D self is able to be conscious and be aware of how time flows?

 

I don't attempt to explain consciousness. However, I will point out that consciousness is a process that takes place over time, so a 3D instantaneous slice is in fact not aware of anything. A thought has a nonzero time dimension. If it's the human element that makes it tricky, think of a computer instead. Everything takes time.

 

SPACE - If you move one meter with respect to time, then similar you would also move one second with respect to space.

(I thought I was very clear on that in my previous post.)

 

No, not space. Space is already accounted for. You have a 4D object. 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. (And if you did, you could then describe the whole as a 5D object.) Much like to change a 3D object, you need a 4th dimension (time) in which it can change. Or to change a 2D object, you need a 3rd, etc.

 

Yes, I agree, but look at your own words: "The same" and then look at the question you asked above.

 

What?

 

I tried to explain that since space and time are related, the relation goes both ways. If time dimension can be treated like a spatial dimension, then a 'movement' through time is similar to a movement through space but with changed positions by their relation. There is no need for extra dimensions.

 

Yes, indeed. The relationship goes both ways. When treating time as a dimension, then everything is simply a 4D object. You don't have additional "motion" in time OR space. You see? What we think of as motion through space is simply a non-constant relation between time and space coordinates, much like you could describe a static 3D shape as having a varying relationship between length and width.

 

You have a 4D shape. Described by this shape is the relationship between space and time, i.e. everything we think of as "motion."

 

Imagine a 3D shape: a pyramid. The horizontal area is not constant with respect to height. You could say that it is a square that shrinks with height. That would be correct, but probably needlessly confusing, since it invokes temporal language. In fact, most of our language is based on intuitive perceptions of time. Do not be tripped up by this.

Either we move through spacetime or we persist for a duration of spacetime, in the latter objects don't truly move through space either, they are then shaped in such a way that their slices are spread out in different space locations, but the individual slices don't move from one location to the other, they are fixed as firmly in space just like they are in time.

 

Can it be proved scientifically which is true and which is false?

 

You are simply asking whether it is a 4D object or a 5D object.

 

For instance what happens to your vision of a 4D object when a "slice" of it reaches beyond the event horizon of a black hole?

(Where time becomes space and space becomes time.)

 

Unless you understand the math of a black hole, I'd say you're getting ahead of yourself. If Euclidian space doesn't make sense, relativistic space certainly won't either.

 

Can we by experiment measure and verify objects true size in time?

(The question is not necessary how long the object lasts.)

 

An object's "size in time" would indeed be how long the object lasts.

 

Also somewhat realted, if objects are 4D with the full duration like you assume, then how do your view fit with the uncertainty principle?

 

A future slice cannot be fully calculated based on a past slice.

 

When is it determined when the object ends and how is it determined?

(Without something progressing through time it seems deterministic.)

 

I don't understand this question.

 

Is it possible to determine the properties of time itself?

 

Nor this one.

[michel123456]

Imagine a 3D shape: a pyramid. The horizontal area is not constant with respect to height. You could say that it is a square that shrinks with height. That would be correct, but probably needlessly confusing, since it invokes temporal language.

 

Sisyphus, you're a genius!

You just explained how to transform space in time, and reversely.

 

As for the rest, I should be extremely cautious about the word "dimension", because it is not a very easy concept by itself, not easier that the concept of space or time. It is useless to try to explain something with concepts that rely upon the same bases. It is a bit circular reasoning.

 

Spyman is right, we are "moving" through time.

IMHO of course.

[Sisyphus]

Sisyphus, you're a genius!

You just explained how to transform space in time, and reversely.

 

Eh?

 

As for the rest, I should be extremely cautious about the word "dimension", because it is not a very easy concept by itself, not easier that the concept of space or time. It is useless to try to explain something with concepts that rely upon the same bases. It is a bit circular reasoning.

 

I don't think it's really circular reasoning. It's just taking the notion of a spatial dimension, and then treating time in exactly the same way.

 

Spyman is right, we are "moving" through time.

IMHO of course.

 

To the same extent that there is no pyramid, but rather a shrinking square moving upwards.

[michel123456]

Yes. To the same extent that a square is a moving line, and that a line is a moving dot.

There is no other way to represent a 4D object but through motion. take a cube (3D), put it in motion, and you get the 4th dimension. That we call Time.

And as you said, you can take a square (2D) and put it in motion, and you get the third dimension.

That is what you intended to mean, I suppose, when you wrote that "It's just taking the notion of a spatial dimension, and then treating time in exactly the same way."

 

And that was what i meant when I said that you explained how to transform space in time and reversely, because all 3 dimensions of space can be described in terms of time. I think it is nothing new, maybe my wording is incorrect, anyway we are not disagreeing on this point.

Spyman wrote;

I tried to explain that since space and time are related, the relation goes both ways.

 

It is another wording for the same thing. I think we all agree.

 

 

I'd like to go back on track and insist on this point:

either time is considered as a dimension, either as a kind of "motion", it should not matter. Both descriptions should describe correctly what we are observing.

 

Spyman wrote:

I think both perspectives should be able to fit with each other, they might be viewed from different angels but they should still be in agreement.

Sisyphus wrote;

They do fit with one another, in that you can easily translate between them, and there is no contradiction.

 

We all 3 agree on this. I don't know what Iggy has to say.

 

This kind of "motion" is usually represented through a Minskowski diagram, in which events are dots, and objects are lines.

I suppose here we can all agree. in order to put a stop on discussions about interpretations of Minkowski diagrams.

 

Now, Spyman wrote:

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.

 

Now if I say that the coordinates are (time,length,height,width) and that when a object is displaced in either of the space dimensions it will no longer remain in the old location, then no one will argue, but when I say that the displacement is in the time dimension then suddenly it is "obfuscating".

 

In my understanding, there is nothing "obsfuscating".

 

What we observe in reality, is that for regular matter the 4th coordinates (Time) is always changing. That is considered both as "normal" and as "a mystery".

 

And for me, this constant change of coordinates must be interpretated as a kind of "motion", meaning that when a piece of matter change from coordinates (0,0,0,T) to (0,0,0,t1), the new coordinate is occupied by this piece of matter, and original coordinate (0,0,0,T) is free.

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175 posts to get to such a simple statement. Things are harder than i presumed.

 

IF the first coordinate (0,0,0,T) is free, it does not mean it is empty.

The fact is: we are not able to reach this coordinate again in order to check out. We are not even able to have a look at it, because, as Iggy said, this first coordinate is inside our light cone.

 

So there are 3 possibilities:

A. the supposition is wrong, the coordinate is not free.

B. the supposition is right, the coordinate is free and empty.

C. the supposition is right, the coordinate has been left free and is occupied by "something else".

 

Possibilities A & B are the usual dilemna.

Proposition C looks totaly awkward, lets see if we can send it to the recycle bin.

 

C means: there is an object behind us, traveling in time. Can we see it? From our point of vue, the answer is no. Not more than we can see an event in our own past. Is there another way to check out?

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For example, we can travel to another planet, to the Moon, and look back to the Earth. We will see the Earth as it looked in the past, a few seconds ago. If we go further, we will see the Earth as it was a few hours ago, even a few years ago. But always, always, as it was after our departure. We will never get to observe the Earth as it was before our departure. Because to achieve that, we should travel faster than light, and that is impossible.