michel123456

I'll try this way: On the second diagram at this time frame: you agreed (was it you?) that point C is the point where the observer sees the light coming from. So, at this time frame, a scientist-observer living on the red dot will take a pencil and mark a black dot at point C, because it is what he is observing. If the scientist, at this same time-frame, do the same job for all the objects in the universe he observes the light coming from, he will make a regular space-time diagram with a bunch of C-points upon the diagonal. That is a space-time diagram: a diagram that represent the coordinates of objects as the scientist-observer observes here & now. And this diagram will ressemble a lot to the first blue-dot diagram, in which the diagonal is the mark of constancy of SOL but in which the path of a ray of light is not shown. The path of a ray of light is shown on the second yellow-dot diagram.

That's all very well. But you must know that in the real world a lot of taxes is used to pay interests on loans (debt), not schools or medicine.

You will stay unhappy, there is no light in this diagram. The last thing may help you is that the black dot in this diagram corresponds to point C of the other diagram.

I'd like to know what you have understood so far: 1.What does represent the first diagram? 2.what does represent the second diagram? 3.Why is the dot displaced in the 2 diagrams? 4.Do the dots represent the same thing?

Is this answer more clear? . . this diagram does not show light.

this diagram does not show light. As for the other diagram: Yes. Yes. That was my answer in post#206. And the (...) is important.

Sounds good, as long as you don't wrap too tightly. As you said, the air will do the job. Instead of cotton you could use cheaper toilet paper. The main problem will be the external structure. A thermos bottle is in fact a bottle inside a bottle, the 2 bottles join near the closing cap. You could use a small plastic bottle inside a large one that you have cut in the middle then taped together. Something like that. But you will need something to secure the inside bottle in position, because when you will fill it with liquid, it will become heavy and may very easily get out of place. (edit) IIRC in a regular thermos, the inside bottle is made of thin glass silvered, acting as a mirror from the inside to reflect radiation. Also I suppose your teacher will test the bottles. Think how he will do the tests, will he put boiling water in order to discard all the plastic bottles of the class? will he turn the bottle upside down? will he measure temperature? how will he do that? will he throw the bottle down to test its resistance? Or is this only a conceptual exercise?

You are both playing with me. Iggy is switching my answers. See my post #206 (Yes) and his post #209 (No, no, no) -edit: I'll report that. Spyman doesn't read what I am writing. It is not funny. I quit this thread

To which I have been arguing against since this thread started. But you agreed with your statement that: Which means: for the observer, all physics say that there is (was) an object at point C from which the observer gets light and feels gravity. All measurements, everything physically converges to the fact that there is (was) something at point C. This is what I called "our companions". All those "companions" are upon the surface of our PLC, like point C. We know (or we should know) that in the meanwhile, the object leaved coordinates C and went somewhere close to coordinates B, as you seemed to agree lately. But Iggy (and I still wonder about you) don't accept this as true, you are believing that coordinates C remain occupied by the object "persisting" in time. IMHO this last concept is wrong. There is no reason why translation in space (motion) should be so radically different from translation in time (duration). when you move in space, you change coordinates, you don't 'persist" from one point in space to another. The same must be true for time: as duration occurs, you change coordinates, you don't "persist".

Yes. IOW the green dot is not observable by the red dot. What the red dot observes at the coordinates of the green dot is something else (another black dot not mentionned on the diagram, above the green dot and left to the red dot = point B of the following diagrams). No, no, no. why do you insist mixing the diagrams, it is getting awesome. please re-read my explanations about the difference between the 2 diagrams. I get the feeling you don't want to understand. Why are you saying this at the moment you have perfectly understood my points? see below: Perfectly correct.

Looks like the army.

Again, again again you want to mix the 2 diagrams. If I draw a light ray from the black dot in this diagram, it will never reach the red dot. In this diagram, the black dot is the image of some object that was once there: it is a projection of what we see today, not what it is. As do all the space-time diagrams in the litterature.

What do the 2 stars mean near the Expert under the avatar. Are they all lieutenants?

Yes, but there is a gap between the instant the information was send and the instant the information was received. We 'see" things at the instant we receive the information, so what we "see" is not was actually "is". The blue-dot diagram that shows what we "see" is not what actually "is". The yellow-dot-diagram is closer to what happens. We "see" Paul at coordinates C although Paul is at coordinates B. The blue-dot diagram shows Paul at C, as we "see" it. It is clear like fresh water.

The 1st statement was about the blue-dot-diagram, which shows what we see. The 2nd statement was about the yellow-dot-diagram, which shows the path of a ray of light. I can't help you more. If you don't grasp the difference between the 2 diagrams, it is useless to continue.

Honestly I think you understand nothing.

Welcome. YES the red dot cannot see the green dot: welcome to my universe. The red dot sees the information carried by the yellow dot above collated to him. The red dot "observes" the black dot at C although the black dot is not at C anymore (as described by our friend HuMoDz) I say that what you see is not what it is. You see the black dot at point C when the black dot is at B. The information reaching my eye is different from what is (and it is also the difference between the 2 kind of diagrams). Here you are. YES, point C of course. Yes, the green dot is not observable from the red dot, is that what you are saying? The model works.

As I stated before: You have mixed the 2 diagrams: you made chili sauce with chocolate. It is wrong. Draw a ray of light from the green dot and you will see what happens. (edit) the diagram with the blue dot describes what we see, the diagram with the yellow dot describes the path of a ray of light: these are 2 different concepts, you cannot mix the one with the other. For the 3rd time, can anyone here answer my question: At this time frame, where do observer A sees the light coming from? From point B or point C ?

Yes.

See this PAL-V one

It is not physically possible to make the mass of the sun disappear just like that. The sun may blow out or shrink, its mass will not disappear.

try attention , it's probably some minor bug he can fix. Works fine to me. Indent inside indent gives result "to raise" above.

I know that. I play one against 2 for a while now. The black dot is the actual position of Paul in spacetime. It is never observed by anyone in his actual position, except by himself. Maybe the following diagram make things clearer: I added another ray of light (orange dot) to show that the red dot (Marion) constantly observes the black dot (Paul) in her past. BTW you didn't answer my question: At this time frame, where do observer A sees the light coming from? From point B or point C ?

yes. Imagine more blue dots. You have the same problem with Spyman. The only one blue dot is for simplification, in fact there are a lot of blue dots that make up the whole diagonal. O.K. O.K. Yes. That describes the effect of a mirror at the black dot. Your objection is like saying that light cannot be reflected by a mirror because it must have stopped in the meanwhile. The changing of slope is a result of direction in space. Direction in time is unchanged.

I don't see any "obvious" contadiction. I am not changing my mind, I maintain what I said and wrote down because I don't understand your arguments. Why isn't it the PLC in the 1st diagram? Why do you say that it is not "traveling with us in time"? and what do you call "dx/dt section of the black line" ? the black line is dx=0, the red dot is at rest. dx/dt is a ratio (represented by the angle of on the grey line), by convention 45 degrees.