Comparing Event Occurrence Across PORs

[whosapopstar?]

Is it possible for an event to occur in one POR and never occur in another POR?

 

[Matterwave]

POR? You mean FOR frame of reference?

It sort of depends on what you mean by "event occurs in a FOR".

The constantly acclerated observer's "reference frame" (accelerating forever), for example is disconnected from some portions of space-time (creating an event-horizon like surface, called the Rindler Horizon). Some events cannot even send light signals to this observer. In that sense, you could make some case for the event "not occurring" in this accelerated observer's reference frame. Perhaps more appropriate, however, would be to say that the accelerated observer's coordinates do not cover the entire manifold (it's only a coordinate patch), and so it really has more to do with the coordinates being local coordinates rather than global coordinates.

Similar things occur in the Schwarzschild solution for events inside the event horizon and observers outside the event horizon.

 

[whosapopstar?]

I meant in FORs that move at constant speed (i took Point Of View and Frame Of Reference and 'meshed' them together, are they the same? LOL).

 

[ghwellsjr]

I meant in FORs that move at constant speed (i took Point Of View and Frame Of Reference and 'meshed' them together, are they the same? LOL).

There's no precise and standard definition for PoV like there is for an inertial FoR in Special Relativity so you can never tell when someone talks about a PoV if they really mean a FoR in which an observer is at rest or if they mean what the words imply--what someone can actually see. A FoR does not in any way improve on what an observer can actually see because he still has to wait some time for the image of remote events to propagate to him at the speed of light. Furthermore, if the observer ever accelerates, then he is no longer at rest in his initial inertial FoR and once again, there is no precise and standard definition for a non-inertial FoR.

So if I could control the vocabulary, I would reserve PoV to mean what an observer can actually see and not allow it to be equal to FoR, but since I don't, you will have to figure out from the context or ask what a person means when they use the term PoV.

But to answer your original question, in Special Relativity, there is no event that can occur in one FoR that does not occur in any other FoR you wish to choose. The Lorentz Transform has no limits on it for the events it can handle, just the limit on the value of v--it has to be less than c.

 

[Matterwave]

ghwells, it seems you are restricting frames to global inertial reference frames, isn't that too restrictive? Surely, what an accelerating observer can measure by putting rigid rulers and clocks in his accelerating rocket should still count as a reference frame...albeit a local one.

 

[ghwellsjr]

ghwells, it seems you are restricting frames to global inertial reference frames, isn't that too restrictive? Surely, what an accelerating observer can measure by putting rigid rulers and clocks in his accelerating rocket should still count as a reference frame...albeit a local one.

I am restricting it to what the Lorentz Transform can handle which is what I thought the OP was asking about.

 

[Passionflower]

Is it possible for an event to occur in one POR and never occur in another POR?

Sure, that's is because there are event horizons.

Similar when the Sun is beyond a horizon it can no longer be seen. :)

 

[whosapopstar?]

OK, at this point I will take the answer as "No, if you, 'the measurer', move at constant speed, and an event occurred, it is not possible that you will never be able to observe that event." My intent is to take the question further, to perhaps another direction. To be continued soon, or aborted if not able to ask more in what seems coherent terms.

 

[Passionflower]

OK, at this point I will take the answer as "No, if you, 'the measurer', move at constant speed, and an event occurred, it is not possible that you will never be able to observe that event."

I told you you are wrong it appears you simply ignore what you do not like. What is the point in asking if you ignore the answers.

 

[whosapopstar?]

Here we go with the emotional stuff. Yes, i read what you wrote and if you had not wasted the time berating me, but instead jut repeat again and again as much as needed, probably i would already get it. Yes, since i already read what you wrote please try to rephrase it or let other people explain what i don't understand.

 

[whosapopstar?]

OK, i will stop asking until I will be sure i understand the answer to the first question.

 

[Passionflower]

One example is events that take place inside a black hole outsiders cannot observe these.

 

[whosapopstar?]

Great, and besides black holes? Any other example that exclude a black hole scenario? thanks.

 

[Passionflower]

Great, and besides black holes? Any other example that has nothing to do with a black holes? thanks.

Sure because our universe is expanding certain events cannot be observed as well namely those that are outside the observable universe.

 

[whosapopstar?]

OK so we have: outside the observable universe and black holes. This still enables me to ask further, i think. Any other possibilities?

 

[Passionflower]

OK so we have: outside the observable universe and black holes. This still enables me to ask further, i think. Any other possibilities?

Apart from possibly more exotic situations that pretty much covers it.

 

[whosapopstar?]

OK. Please look at the attached diagram. Will any spaceship from the group 'spaceship x', observe any change in light speed, before or after light enters detectors d1 and d2, located on spaceship3?

 

[Matterwave]

The three common "event horizons" to appear are those for black holes, the one for the observable universe, and the Rindler's horizon for accelerating observers.

None of these can really be fully dealt with using only special relativity. In the Rindler's case, one can do some of the analysis using only SR. One can, for example, deduce that constantly accelerated observers travel on hyperbolas.

 

[Matterwave]

All local measurements of the speed of light will result in c. This is true also in general relativity.

 

[ghwellsjr]

But since whosapopstar clarified his original question with more information from post #3 saying he meant a Frame of Reference moving at a constant speed (with respect to another FoR), I gave my answer in post #4 from the context of Special Relativity. In SR, the Lorentz Transform can handle any event. It's important for whosapopstar to understand the different ways his question can be interpreted. In the context of SR and LT the answer to his original question is no. In other contexts, such as General Relativity, the answer could be yes, but then, I don't know why he brought up the issue of constant speed.

 

[ghwellsjr]

OK. Please look at the attached diagram. Will any spaceship from the group 'spaceship x', observe any change in light speed, before or after light enters detectors d1 and d2, located on spaceship3?

I thought we resolved your questions with regard to your diagram in posts 10 through 15 of Why is light speed constant in all reference frames?

 

[whosapopstar?]

This question goes further. But Indeed, first i need to be as sure as possible, of the meaning, of what i am asking, for the answerers may render the rest of the question redundant.

 

[whosapopstar?]

I thought we resolved your questions with regard to your diagram in posts 10 through 15 of Why is light speed constant in all reference frames?

I was totally unable to say, even what I don't unserstand, when it got at that thread, to post #16.

 

[ghwellsjr]

I was totally unable to say, even what I don't unserstand, when it got at that thread to post #16.

Post #16 was not addressing your question so you don't have to understand it. You did say in post #15 that you understood my explanation in post #14. Are you now reconsidering?

 

[whosapopstar?]

Post #16 was not addressing your question so you don't have to understand it. You did say in post #15 that you understood my explanation in post #14. Are you now reconsidering?

When i read that answer i felt satisfied, but now i read it again and i am totally lost. i guess i will read it again and again now for a while, although i do think that i am asking things differently.

Thanks and will be back shortly, if not back to an understanding point.

 

[whosapopstar?]

Yes,
Did connect again with the explanation, and now, might know what kind of questions popped up in my mind afterwards, which boiled some months later to what i actually want to ask today:
1. What about, 'slow transport'? Which means as much as I understand, that each detector has already a clock, that was synchronized at one point, and then they where moved very slowly to their places at detector 1 and 2.
2. Is the reason that i can see a laser, when standing at point C, while the laser is actually pointed from point A to B, is that there is refraction with the air and smoke etc...or does it also occur in space? e.g. that i can observe the laser 'from the side'? (Space e.g. no gravity, no air etc...)

 

[ghwellsjr]

Yes,
Did connect again with the explanation, and now, might know what kind of questions popped up in my mind afterwards, which boiled some months later to what i actually want to ask today:
1. What about, 'slow transport'? Which means as much as I understand, that each detector has already a clock, that was synchronized at one point, and then they where moved very slowly to their places at detector 1 and 2.

Einstein was well aware of slow transport of clocks and he rejected it in favor of his prescribed convention for establishing Coordinate Time. A clock keeps Proper Time. What we want is Coordinate Time. Once we adopt Einstein's theory of Special Relativity, we can see that the slow transport of clocks does not result in the same time on them as what we need for Coordinate Time except in a particular rest frame. In other frames, the slow transport of clocks does not correspond with the Coordinate Time.

2. Is the reason that i can see a laser, when standing at point C, while the laser is actually pointed from point A to B, is that there is refraction with the air and smoke etc...or does it also occur in space? e.g. that i can observe the laser 'from the side'? (Space e.g. no gravity, no air etc...)

Yes, the laser beam illuminates particulate matter floating around in the air which scatters the light so that you can see it. In a vacuum, either in space or in a vacuum chamber on earth, you won't be able to see the beam. When the astronauts were walking on the moon, the sky was black. The could not see any sunbeams or effects from their silhouettes casting shadows.

 

[Mentz114]

Here we go with the emotional stuff. Yes, i read what you wrote and if you had not wasted the time berating me, but instead jut repeat again and again as much as needed, probably i would already get it. Yes, since i already read what you wrote please try to rephrase it or let other people explain what i don't understand.

If you define an event as a relationship between worldlines then it will be observable in all frames without exception.

For instance, the ringing of a bell is the confluence of the WL of the bell and the WL of the clapper. If this happens in one frame, it happens in all.

Similarly, if two WLs are approaching then they will be seen to be approaching all frames.

 

[whosapopstar?]

I might need to add some kind of 'intergalactic dust' to my diagram, in order to be able to ask what i want to ask, but still there is probably a distance to make, before i am sure the scenario i want to represent, is coherent.

In order for that to happen, what i want to ask now, is this:
Regarding slow transport:

I do not understand how to separate into categories or 'kinds of explanations' some terms which are: 'slow transport', 'coordinate system', 'proper time' and 'rest frame':

1.It is a mathematical error to assume there is a rest frame.
2.There is no mathematical problem assuming a rest frame, but experimentally this rest frame never appears.
3.Under the mathematical description used by SR, which interprets experimental results, the term 'rest frame' has no meaning.

The biggest problem i might have, when trying to understand this, is related with number 3 and with the notion (that is probably an error of understanding on my side), that there is a legitimate situation where one can say: this or that question has no meaning, under such and such terms, conditions or situations.

I am saying all that, because i want to ask: under what 'kind' of explanation (1,2,3 or another or a combination) would this question fall:

Is the speed of light the same or is it not the same when moving 'between' the frames or reference? Does the speed of light change or does it not change when it is moving from one FOR to another?

Somehow, i had the notion, that the answer to that question is number 3: 'This question has no meaning', since a rest frame does not appear in experiments, or for other reasons. If this is the case, i don't understand what 'has no meaning' means, and i have to put some intergalactic dust in my diagram, so i can ask the question in more coherent terms.

These more coherent terms, are supposedly relevant, since they are, supposedly (and probably by error) able to bring up a scenario that proves, that you can only say: 'Yes light speed changes when moving between FORs' or you can say: 'No, light speed does not change when moving between FORs', and most important, that there is no 'middle' possibility e.g. to say that there is 'no meaning' to this question.

 

[Mentz114]

These more coherent terms, are supposedly relevant, since they are, supposedly (and probably by error) able to bring up a scenario that proves, that you can only say: 'Yes light speed changes when moving between FORs' or you can say: 'No, light speed does not change when moving between FORs', and most important, that there is no 'middle' possibility e.g. to say that there is 'no meaning' to this question.

Different frames of reference use different coordinates. The speed of ligh measured with non-local coordinates can change. But in any frame, using local coordinates the speed of light is always the same.

The term 'rest frame' is not meaningless. If you are considering a scenario with many inertial observers you can nominate anyone of these to be your rest frame. It makes no difference which one you choose, the physics is the same. So it is not meaningless, it is irrelevant.