Can we see it?

[michel123456]

Nope. What I'm saying is that the lines represent object throughout time. The moving dot makes sense if you want to show what the world looked like from one perspective, but there's a time axis on the graph for a reason.

 

Or, more pointedly, what's the point of a time axis on a graph if you insist on only showing the object at one time? The time axis is there to show what the object did in the past.

 

 

In my understanding, the line is the trajectory. Not the object itself.

[Cap'n Refsmmat]

Sure. And you could do a similar mass-time diagram showing the mass of the object over time.

 

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.

 

Agreed?

[michel123456]

Sure. And you could do a similar mass-time diagram showing the mass of the object over time.

 

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.

 

Agreed?

 

Yes Yes Yes.

 

________________________

 

That means that an object is not a line. An object is always "somewhere" upon the diagram. The same object cannot be at 2 sets of coordinates "at the same time".

And once it is placed at a certain set of coordinates upon the diagram, the laws of physics apply: he cannot observe what exactly precedes him, he cannot observe what exactly follows him. And he cannot go backwards.

 

For the existence living in that point, the diagram is almost empty: the only objects he is able to observe are those placed upon or near the surface of his light-cone. But Iggy will shout again I am messing lined-objects with events...

Edited April 16, 2010 by michel123456

[Iggy]

For the existence living in that point, the diagram is almost empty: the only objects he is able to observe are those placed upon or near the surface of his light-cone. But Iggy will shout again I am messing lined-objects with events...

You see only the events on the surface of your past light cone. I think you've agreed that objects, or mass, cannot hide inside your past light cone. An object that was in your past light cone will have intersected it at some point in the past.

[michel123456]

I say this

 

 

Sorry for the poor graphics.

[Iggy]

That's fine.

 

Let's say that the red and black observers are astronomers looking out of their telescopes separated by a few years. So, presumably they should see the same things--the same stars, the same galaxies--that type of thing. So, why do their light cones look so different? Shouldn't the same things, the same objects, be intersecting them both?

 

Maybe if you drew world-lines it would be a bit easier to understand.

[Spyman]

I say this

Another 'subverse' moving behind or before us in time?

[michel123456]

Another 'subverse' moving behind or before us in time?

 

Here is only one. You can put as many as you wish.

 

If you can explain the moving dot concept in any configurations, you must conceive that there must be "empty shelves" behind & before us.

 

The next step is simply to fill the "empty shelves" with something. It is extremely speculative.

 

The interesting thing is that this "something" is nothing strange or weird. It is natural matter, stars planets & galaxies. The thing is that they are not observable.

 

But:

 

It is not compatible with the BB Theory.

 

But but:

 

Since we are speaking about another universe, infinitely larger than the one we are observing, why not?

 

As you see, the key point is the moving dot concept. If you refute it, everything collapses back to our actual point of vue of the Universe. If you accept it, the door is wide open.

[Spyman]

What thickness would such shelves typically have then?

[michel123456]

What thickness would such shelves typically have then?

 

They would have the same distribution than the well-known universe. The observable universe (the surface of the light-cone) would be a diagonal slice of the full-feature, representing an idea of the normal distribution of matter.

 

In this case any observator from any point of vue should have a similar view of the universe i.e. not seeing the same things, but something that looks similar.

If you mutiply all those points of vue, and what they see, upon the diagram, you obtain a surface with points everywhere.

 

That should mean the next slice is at some astronomical "distance", not so close to us.

[Spyman]

I am sorry but I don't seem to be able to interpret your answer...

 

[EDIT] Sounds like a normal Universe that we observe today.

[michel123456]

I am sorry but I don't seem to be able to interpret your answer...

 

[EDIT] Sounds like a normal Universe that we observe today.

 

Yes. But much bigger.

 

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

 

I still have doubts about all that. Don't figure I am too sure of what I am saying.

 

I continue looking at my own diagram, and from time to time I believe I am completely wrong. But if I am wrong, then Iggy is right.... and I am convinced of the contrary. I change my mind continuously....

Edited April 19, 2010 by michel123456

[Spyman]

Michel even if you are 'completely wrong' it doesn't mean that Iggys view is correct, but you still need to figure out and correct your own troubles.

[michel123456]

Michel even if you are 'completely wrong' it doesn't mean that Iggys view is correct, but you still need to figure out and correct your own troubles.

 

Yeap. Working on it. But I don't have enough time.

[Iggy]

Michel,

 

would you label your time axis like this?

 

 

Maybe not with those specific dates, but that's the idea, yes? Red and black are moving through time?

[michel123456]

That's the trap.

There is a confusion in this moving diagram.

Lets see it again.

We are at the big black dot in the center.

The other black dots are representing the coordinates of objects as observed by us at a specific time. That means at January 5th, we can see all the black dots (see below). That does not mean the black dots are actually there, its a fake.

So, the diagram represents the "fake" image as we see it, it does not represent what actually is. The diagonals are the observational "now" of the observator. On the 5th of January, the light coming from the black dots have reached us. That's now, every day.

 

The basic idea of moving dots & empty shelves must be right. The representation has a problem. Working on it.

[Iggy]

I understand what you're saying. Certainly I agree that the dots along the light cone represent what the observer at the apex sees. All I'm looking for is if the time axis is labeled right. Did I label it the way you meant for it to be understood, or is there another way that I can label it?

[Spyman]

The representation has a problem.

That seems to be the basis of Iggys arguments, spacetime diagrams are not meant to visualise objects with different presents moving through time at some interval between each other.

 

But whether spacetime diagrams are able to show this or not, can't be used to conclude if objects truly moves through time or not in the real world.

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Merged post follows:

Consecutive posts merged

I change my mind continuously....

Michel have you ever observed a fast and loud airplane cross the horizon at low altitude?

 

I still carry a faint memory of a small boy, standing beside his father and watching a military aircraft roar very fast across the skye, just above the treetops. The little boy made a remarkable discovery, when he looked towards the sound of the aircraft it wasn't there, it was instead moving ahead of its own sound. The location where the sound came from was empty and the location where the vision came from was silent. When the aircraft had vanished in the distance, the boys father tried to explain to his child that sound and vision travels with different speed through air and since vision is much much faster, the sound only seems to come from an empty place, but when the sound was emitted the aircraft was actually there making the sounds. The boy however was still to young to grasp the concept that sound and vision was also something moving through the air like the aircraft.

 

Now I understand that light travels with such high speed that it seem to be instant for us humans locally down here on Earth, and that when we observe stars moving in space the distance is great enough for the location where we percive the vision of the stars to come from, to be empty when the light reaches our eyes, because during the travel time for the vision the stars has also moved, like with the airplane and its sound.

 

Maybe I am rambling to much but what I am trying to say that a key part of the understanding is that the signals themselves are also progressing through time along their own worldlines, which happens to fit exactly with the lightcone if the signals are photons, but you could also have other signals moving with slower speed too.

 

Sometimes it can help to compare the views, how it could seem to look differnet if the signals would be moving slower or even faster than light, but in reality there would still only be one trajectory from where the object are sending out the signals we recieve simultaneous, but the transmitting takes place at different events from different timestamps and locations.

 

I don't know what else to say, you need to find and ask the question which will enlighten and reveal the information you need to complete your understanding.

Edited April 20, 2010 by Spyman
Consecutive posts merged.

[michel123456]

(...)"a key part of the understanding is that the signals themselves are also progressing through time along their own worldlines, which happens to fit exactly with the lightcone if the signals are photons, but you could also have other signals moving with slower speed too." (...)

 

Like what?

Neutrinos?

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Merged post follows:

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I understand what you're saying. Certainly I agree that the dots along the light cone represent what the observer at the apex sees. All I'm looking for is if the time axis is labeled right. Did I label it the way you meant for it to be understood, or is there another way that I can label it?

 

I cannot explain what i haven't fully understood.

Yes it is the basic idea. I made once such a labelling, but there are problems. I have to redo the whole construct in order to show how a signal propagates into the diagram.

[Iggy]

I cannot explain what i haven't fully understood.

Yes it is the basic idea. I made once such a labelling, but there are problems. I have to redo the whole construct in order to show how a signal propagates into the diagram.

 

Ok. No trouble, mate.

 

I'll also post this:

 

 

to represent, like you said: "On the 5th of January, the light coming from the black dots have reached us. That's now, every day."

 

So that the black dot is understood to be now. It is understood to be the present, like us moving through time.

 

If you are doing a new diagram my biggest recommendation would be that a single day not have two different-looking past light cones. For example, on January 3rd black sees something different from what red sees on January 3rd:

 

 

 

It would make more sense if the past light cone of black on Jan. 3rd were the same as the past light cone of red on Jan. 3rd. Otherwise, it is hard to explain how the universe looks two different ways from the same location on the same day. In other words: the way we observe the universe today should be the same as we remember it looking two days from now.

[Spyman]

Like what?

Neutrinos?

That's not important, it's the idea that counts, think of it more like a thought experiment and not about what cind of signals we have or not.

(But did you somehow miss the part about sound going slower than light?)

[michel123456]

That's not important, it's the idea that counts, think of it more like a thought experiment and not about what cind of signals we have or not.

(But did you somehow miss the part about sound going slower than light?)

 

I didn't miss anything, this time. Just didn't feel any need to comment what was so elegantly said.

We are on the same bandwith.

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It would make more sense if the past light cone of black on Jan. 3rd were the same as the past light cone of red on Jan. 3rd. Otherwise, it is hard to explain how the universe looks two different ways from the same location on the same day. In other words: the way we observe the universe today should be the same as we remember it looking two days from now.

 

Thats the totally counter intuitive part. Either it is simply wrong, right from the beginning, either it is a wrong conclusion from a wrong representation. Either it is right, but in this case it is terribly difficult to swallow.

 

There are other problems: the black dots upon the light-cone are observing some of the red dots: an object we can observe in the past (the Moon) looking towards the Earth, does not see the Earth but a red dot (not the Earth), which is totally crazy.

I think the whole diagram must be transformed.

 

It is a mess. The central black dot (the Earth) is the only really existing at the right place at the right time. The black dots are fake: they are the points where the little boy was looking at when hearing the airplane. There is nothing there. The real black dots are elsewhere. And the red dots too. Thats the problem.

Edited April 20, 2010 by michel123456
Consecutive posts merged.

[Iggy]

There are other problems: the black dots upon the light-cone are observing some of the red dots: an object we can observe in the past (the Moon) looking towards the Earth, does not see the Earth but a red dot (not the Earth), which is totally crazy.

I think the whole diagram must be transformed.

 

I think you see the problem clearly.

 

The way spacetime diagrams are understood and used in science, the red dot marks one point in the history of the earth. To be exact, it is how the earth was two days before the present. The physics community calls them events because the dot not only represents the earth, but the earth at a specific time. The red dot that the moon is seeing is the earth as it was in the past.

 

It is a mess. The central black dot (the Earth) is the only really existing at the right place at the right time.

 

If the black dots were supposed to be the location of the objects in the present then they would be out of place. But, they are supposed to be the location of events in the history of that object. In particular, they mark the event where light is emitted from that objects which earth sees now. And, the events are right where they should be.

 

The black dots are fake: they are the points where the little boy was looking at when hearing the airplane.

 

Yes, exactly. They mark where the airplane was previously in time. That's why there is a time axis on a spacetime diagram--to show where things were--to show what they were doing at all different times--the whole history of the object.

 

What we see is an event in the history of the object.

 

There is nothing there.

 

Correct. There was something there. It is understood that it is not there in the present. By the time we see/hear it, it has moved on to somewhere else. The event is in the past--lower than the observer on the spacetime diagram.

 

The real black dots are elsewhere. And the red dots too. Thats the problem.

 

It's not a problem if you understand that the black dots mark where the objects were (not are).

[michel123456]

To me it is a problem.

I went on representing a spaceship traveling from the Earth to the Moon (to a black dot) and I got the following:

The spaceship travels at speed less than SOL.

_From the Earth, I can observe continuisly the spaceship as long as it travels.

So that, from Earth, I must put the traveling spaceship continuously in Earth's past.

_From Moon's point of vue, the traveling spaceship is also observable all along, so the spaceship must be continuously in Moon's past.

 

Well, on this diagram, I obtain the spaceship, as seen from the Moon, coming from the Moon's future. Which is wrong. Conclusion: I have to redo it from scratch.

 

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

editing (adding)

 

The only way I can imagine to keep the scheme as it is, is to considerate the diagonal as a "line of reciprocity". In which case the black dots are "really" there, and we are obliged to flip the diagram in function of where is the observer i.e. the Earth's past is down, and Moon's past is up. To keep Moon's past down, we have to flip the diagram upside-down. There is no absolute future and no absolute past: the past is an angle less than 45 degrees. It may work but that looks a little bit complicated. Are you following?

 

 

The arrows indicate the flow of time as we see it.

Sounds weird...

Edited April 21, 2010 by michel123456

[Spyman]

To me it is a problem.

I went on representing a spaceship traveling from the Earth to the Moon (to a black dot) and I got the following:

The spaceship travels at speed less than SOL.

_From the Earth, I can observe continuisly the spaceship as long as it travels.

So that, from Earth, I must put the traveling spaceship continuously in Earth's past.

_From Moon's point of vue, the traveling spaceship is also observable all along, so the spaceship must be continuously in Moon's past.

All three observers, located at Earth, in the Spaceship or on the Moon sees the other two continuously. But the images they view are old and came from events in the past, the objects are no longer there, they have continued to the present.

 

 

Earth observer sees an 0.40 seconds old image of the Ship and an 1.30 seconds old image of the Moon.

Ship observer sees an 0.42 seconds old image of the Earth and an 0.88 seconds old image of the Moon.

Moon observer sees an 0.90 seconds old image of the Ship and an 1.30 seconds old image of the Earth.