[yor_on (OP)]

Let's set it up this way. Assume that I color my beam, green, red and blue in predefined variances, meaning different things. Then let the arc beam come to be at that far distance. Assume that the guy observing those colors are some lightyear/minutes away btw I have now sent information faster than light, although we still need to agree on what that information means beforehand, and that will need 'light speed' to get agreed on. you might want to think that there is some universal way of decoding information, as starting with primes etc and then building from that, but ignoring that? And it should be ignored as it only can be hypotheses. So what we call 'information' won't necessarily become some others as i think. Decoding a unknown piece takes time.

So what is information then? Well, if you believe what I say then information as a description is meaningless without a common ground to decode it from. And then we have the idea of a beam constantly 'hanging together' no matter how far it propagate (to then later) or what lateral speed it moves subsequently. That I addressed with those photo electric cells as an example asking about the 'energy' received? And that one gets weirder the further that beam travels as it seems to me?
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You can't define 'photons' as losing energy, though it should be possible to relate it to relativity and frames of reference, finding them red shifted at both sides, becoming more so as the angle widen from your position? So maybe that could work out from each point on the disc as each point represent one 'frame of reference'. But each point for itself must receive the full impact of energy from that 'photon' finding its path ending there. if you see how I mean?

You seem to be referring to 'photons' Guthers? How would you define them as they sweep the disc FTL, elongated sideways? they are 'point particles' to me, or 'energy quanta'.
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To clarify my thoughts. To make that work, assuming a equivalence between 'waves' and 'photons' (duality). you will have to give up the idea of x amount photons representing one type of wave/energy. Or do you know a way to fix it that I miss?

[JP]

Again, there's no way for the guy to observe at more than one point, so he can't get any information FTL.

There's no question that things can "happen" FTL, such as the beam sweeping out space in this case.  What's forbidden is to send information from one observer to another FTL.

[yor_on (OP)]

Then one can refute this example JP? Because, as I think, that arc of light on the 'sphere' will be instantaneous at some point, assuming a infinite universe, and placing the guy some light year(s) away should give him a good view of it. Then he just need to know what the color combination stands for, and I think this to work even if placing him further away. And that would be FTL as I think. But it also assume there to be some common ground for understanding what he sees predefined. Although, trusting in the idea of mathematics as a 'universal language', you might take one step more then and assume that you don't need to know combinations beforehand, and even after decoding it still get the info faster than it being sent piecemeal.

[JP]

This is a case where you have to be very precise in your thought experiments to see what's going on.  What's forbidden here is for me to send any part of a signal faster than light to another observer.  So you're dealing with sender-to-observer transfer here.  That's important.

You can swing your laser so the signal strikes many points on the sphere nearly instantaneously, but the sphere isn't an observer.  The observer lives at one point on the sphere and only knows about the light that has arrived at his eyes.  The instant the signal arrives, the observer doesn't know that it's splashed across the whole sphere.  He only has the one piece of it that hit him directly.  The next instant, he sees light that was reflected from nearby him that has moved (at the speed of light) into his eyes.  As time goes on, he sees parts of the beam that are reflected from points further and further away.  So even though the signal almost instantly hit a huge region of the sphere, the observer doesn't know this and doesn't know what information the signal carried until it reflects into his eyes, which takes time.

Once you understand that, it's easy to see why the signal doesn't reach the observer FTL.  The reflected light always takes a longer path from sender to receiver than if you sent it directly to him.  It has to hit the sphere and reflect to his eyes rather than going directly to his eyes, which will always take longer.

And that's the information limit.  There is no way to encode data onto that beam and have it reach the observer in less total time than if you sent it directly to him.

[yor_on (OP)]

Nope JP, that's not my example. I'm placing him away from the sphere, at a comfortable distance receiving the reflected 'arc beam' I refer too, assuming the light to fill in all 'points' as it sweeps FTL. Then I assume some way of manipulating that original flashlight sending the beam to code information. I used colors but? I suspect you can get in more information other ways. What I'm using is the idea of the light moving transversely faster, the further away it gets, assuming it to become a instant phenomena for that far observer at some point, as we define it FTL and then we have no limits. And the other case is about the energy perceived at that far disc if we replace the disc with light sensitive detectors at each point. Will they all receive the same 'energy', will it have changed under its propagation, and what happens when we move the detectors one trillion ly further away and that beam gets even wider. It becomes illogic to me.
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My spell correcter seems bugged today

[JP]

Oh, then you've basically compressed the beam in time.  But the total time from sending to receiving each bit of information is still longer than if you sent it directly to him.  Draw the line of each ray that hits the sphere and bounces to his eyes--it's longer than if you sent it directly to him, and that's basically the proof.  You can roughly treat each ray as carrying a piece of information--to get any piece of information to transmit FTL, it would have to take a shorter path than a straight line to him, which is impossible. 

In other words, he gets the information very quickly, but it takes him much longer to get the first bit of it than if you sent it directly to him, so overall the total time to get the signal is slower than if you sent it directly to him.  So no piece of information went from the sender to receiver FTL.

[Guthers]

I've thought a bit more about what an observer standing on the shell would actually see.

Let's say you have a flashlight which can emit a beam of light while rotating at a constant rate. The emitted beam falls on a distant spherical shell upon which the observer is situated.

From the flashlight's initial orientation (A) the beam hits a point on the shell (P) (arbitrarily) 10 light minutes away from the observer, and after 10 seconds the flashlight has rotated to its final orientation (B) so it is pointing directly at the observer (O). After hitting the shell some of the light is scattered so that the observer can see it. It can be seen that the point of illumination on the shell might be considered to be travelling at considerably more than the speed of light, 10 light minutes in 10 seconds (although changing position would be more accurate).

When the flashlight reaches B, the light emitted from A is already 10 seconds away on its journey, and this difference is maintained until the light reaches the shell a time t seconds later, so it is obvious that while the light from B reaches O after t seconds, light from A, travelling the path APO by scattering, takes t + 600 seconds. In fact it can be seen that all light which reaches O after being scattered off the shell will not arrive there until after light seen directly from B.

What O will see then, is a flash directly from the flashlight, then a bright spot on the surface of the shell receding from O, until it appears to disappear at P, 590 seconds later, representing the time at which the flashlight was switched on.

Incidentally, if O has a powerful enough telescope she could observe the flashlight start to rotate 10 seconds before seeing the flash of light from B.

[yor_on (OP)]

JP, what I'm using is the idea of light being instantaneous for that observer, giving him a arc of light to observe, if we assume the lateral motion to be 'continuous' at that distance. Then all colors will reflect from that sphere simultaneously from that observers point of view, as a assumption. The other way to see it is to assume that as each 'lightpath' must be transmitted at 'c', and each one belonging to the motion of that wrist, furthermore sent in 'steps' as in a casualty chain. Then that beam, although more 'stretched out' laterally the more you remove the 'sink' from the 'source, still need to obey 'c'. But, assuming this I find it real hard to accept the idea of a continuous arc of light from the far observers view, and then the question of what 'continuous' energy those detectors would measure at each point of the sphere? It's just though experiments from my side but bringing with it very strange conclusions, if they are possible to follow that is

PS: just been undergoing surgery so if my thoughts seem jumbled up, I will blame it on that  

[yor_on (OP)]

Guther, I will need to reread that

What you might be referring to is that geometrically one could assume each light path, now thinking 'photons', should become more removed from its closest neighbors in time as it propagate in SpaceTime, which may be one way to see it? But then we have the wave/particle duality and a wave should indeed be continuous, without breaks in its light paths (in time and seen as a causality chain)?

[JP]

PS: just been undergoing surgery so if my thoughts seem jumbled up, I will blame it on that  

Hope you have a speedy recovery!  I didn't quite follow your post, but we can continue when you're feeling better.

[bizerl]

Another summary for this armchair scientist.

I'm not entirely sure why people think that this is a way for information to be sent FTL. If I have a beam and I sweep it between two observers between two points on this enormous sphere, the signal will pass between them FTL but any information and any changes I make, still take the 1/2 a year to get to the edge of the sphere, and there is no way for one observer to control the information being swept across without relaying information back to me at light speed, then me changing the signal and sending it back, which would take double the time.

If I have two beams pointed at two different observers on the sphere, I can transfer the information simultaneously to both observers, but no information has been exchanged between the two observers.

I'm sure the light from distant stars are reaching other observers at the same time they are reaching us, despite being light years away, but there is still no "FTL travel" in all of this, either with information or particles.

Again, have I missed something?

Oh, and yes, get well soon yor_on!

[yor_on (OP)]

Thnx. The surgery went fine, now it's just convalescence and painkillers

Anyway, if you think of it as particles, 'photons' assuming paths to them it must follow that as the distance grows each unique path must find itself for ever more separated to the next 'photon path' as the flashlight moves its arc. If you instead consider it waves then? Well, can we spit a wave into 'quantum bits' at a smallest scale? If they are a continuous phenomena then we have this unbroken beam laterally too, although we then have to redefine photons as 'particles' as I see it. You could assume a photon a excitation in a field, but what would that make a wave?

[JP]

Good to hear you're doing well. 

Bizerl's point is pretty much the point I'm making, too.  Information might hit other observers at the same time as you, but until they pass their information to you, you can't make use of what they got.  That transfer from them to you limits the whole process to the speed of light.    As I mentioned before, since light moves at a constant speed, the signalling time is proportional to the length it has to travel.  The shortest possible path from source to observer is a straight line, indicating direct communication.  Any path involving hitting a sphere and reflecting off it is automatically longer than that straight line, so it's slower than that limit.  The only way you'd have FTL communication is if you somehow had a line that was shorter than a straight line. 

As for breaking up a signal into pieces, the way you do it isn't really important.  The easiest way is to think of the laser as being flicked off or on to indicate a stream of bits.  There are more sophisticated ways to encode information on a classical wave, but you can rigorously show that the limit is the same.  The problem is that even if this on/off beam is spread across the entire sphere at the same time, the observer has to somehow obtain the whole signal to get all the information contained in it.

You can generalize all this to photons, but its not really worth going down that path until you understand the classical case fully, since it builds upon the classical case, since photons aren't "little bullets" and are difficult to deal with in a rigorous way.

[yor_on (OP)]

Yeah

B u t )

To make the statement work, that you have a continuous beam moving laterally at our 'sphere', you need to some pretty drastic brain gymnastics as it seems to me? Because the further away you place that sphere the more pronounced your motion of the wrist must become as that beam finally hits. And that's why I put it in terms of the energy receives at each 'spot'' of the sphere, all of this assuming our standard interpretations of radiation being timeless etc. And that one is not 'observer dependent' as you can assume that no matter what your frame of reference is, radiation will move at 'c' relative it.

Or alternatively build a case in where the only thing differing that sphere from the lights origin is the 'distance' that light has propagated. Gravity, etc, being the same. To me it becomes geometry, and assuming 'photons' existing, which they do, their 'paths' (relative each other that is:) if seen classically will widen. As for a wave you then have the question of the energy received at the 'sphere'? by that waves motion laterally over each spot, as defined by the spots light detectors changing output? If you would find the energy to change with distance it would become a problem, ignoring expansion here. But if it doesn't change with the distance? Where would the extra energy needed come from? Always assuming a smooth motion of that beam laterally?
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What is the time for correcting spelling, words, etc for TNS those days?
To short for me anyway
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It's geometry, and then a question of the duality relative a smooth lateral beam motion moving over the sphere. And thinking of it able to do it FTL just make it become more interesting to me

[JP]

First, let me nitpick a bit, since this is one of my pet peeves about SR:

. . .assuming our standard interpretations of radiation being timeless etc. . .

Light (I'm assuming that's what you mean by radiation) is not timeless.  Special relativity says it doesn't make sense to consider the reference frame of light, which is very different than light being timeless.

you can assume that no matter what your frame of reference is, radiation will move at 'c' relative it.

That is 100% correct, and doesn't require light to be "timeless." 

Or alternatively build a case in where the only thing differing that sphere from the lights origin is the 'distance' that light has propagated. Gravity, etc, being the same. To me it becomes geometry, and assuming 'photons' existing, which they do, their 'paths' (relative each other that is:) if seen classically will widen.

This is another problem.  Photons are not little bullets following paths between the source and detector.  They're smeared out over all space somehow.  You can detect them at a point, but their quantum wave is very non-bullet-like.  The "little bullet" paths you can draw out are actually rays, which are distinctly not photons and describe light's travel in the classical wave theory.

As for a wave you then have the question of the energy received at the 'sphere'? by that waves motion laterally over each spot, as defined by the spots light detectors changing output? If you would find the energy to change with distance it would become a problem, ignoring expansion here. But if it doesn't change with the distance? Where would the extra energy needed come from? Always assuming a smooth motion of that beam laterally?

Ok, what happens is that the classical model breaks down when the energy per unit area gets small enough.  The continuous classical wave model works because you have so much energy and so many photons at each point that you can average over them and treat everything as continuous.  If you make the sphere really big, the classical energy at each point will be small enough that you need to use a quantum/photon model.  This means you'll actually pick up discrete photons at the detector rather than a continuous wave.  There's no problem with energy conservation, since the total sum of photon energy received has to add up to what you sent out initially.

There is still no FTL signal, though proving so gets much harder if you rigorously deal with photons and not "little bullets." 

[yor_on (OP)]

Sweet stuff JP. Although, heh, astronomically the definition of light or any radiation is that it has to be timeless, as I understands it? If you assume otherwise you get so called 'tired light'. But I'm guessing that you might say that as it 'propagate' (speed), according to what we observe and define, it also takes a 'time' according to us?

[JP]

Sweet stuff JP. Although, heh, astronomically the definition of light or any radiation is that it has to be timeless, as I understands it? If you assume otherwise you get so called 'tired light'. But I'm guessing that you might say that as it 'propagate' (speed), according to what we observe and define, it also takes a 'time' according to us?

Again, it's important to be precise.  Timeless would mean that a photon has a reference frame in which it's clock measures no time passing.  That is in no way supported by relativity or any other physical theory that I know of.

Some tired light models propose that photons lose energy over time without interacting with matter.  As far as we can tell, photons are very stable (not losing energy or decaying unless they interact with other matter).  But that doesn't mean timelessness.

[yor_on (OP)]

A photon seems very much a invariant relation to any thought up 'frame of reference' to me in its modern interpretation. Tired light assumes it not being of a constant 'energy' as I understands it. And it does take time to 'propagate' from any frame of reference observing it. I think I'm rather precise myself well, at times at least.

In the absence of proofs for a 'internal clock' I will consider it 'timeless' over those astronomic distances we've measured, ahem

[JP]

In the absence of proofs for a 'internal clock' I will consider it 'timeless' over those astronomic distances we've measured, ahem

You are precise when you talk about it's invariant speed in any inertial reference frame and the lack of decay/energy loss in free propagation, but that is not equivalent to timelessness in terms of physics terminology.  But physics does not equate the word "timeless" with these properties, so it's a bit imprecise to use that term if you're trying to discuss physics.

[yor_on (OP)]

I stand corrected JP

And maybe I might agree, it opens for interesting possibilities, assuming a propagation and that a geodesic becomes a very strange thing in a vacuum, whose metric is defined as 'gravity'? Weird stuff.