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## what will be the events relative to the ground observer , a time-like or space like?

 Quote by John232 Then it would only be a matter of turning a clockwise spin of particle into a 1 and a counterclockwise spin into a 0 to gain 1 bit of information that is FTL, more bits would require more particles spins being measured and the tricky part would be haveing them have the same common ancestor.
lol, yea, not quite "only a matter of".

To your point of the "common ancestor", I think you're missing the significance of this with regard to FTL information "transmission". If I give you a box, And you travel away from me to the other side of the world, and you open the box and find half a banana and deduce I have the other half that is not FTL transfer of information...

 Quote by ghwellsjr Please don't ignore my response to you on the previous page. And don't expect any of us to figure out what the solution to your problem is until you tell us what your problem is. We can't read your mind.
Really I dont. I am making up my mind but a bit slowly

 Quote by ghwellsjr My question was: why, since "all calculations are done in the train rest frame" do you need "v" in those calculations? Isn't it the case that the source of light emits a single flash at an instant of time? If this is true, why do you care where the source moves to after the flash has occurred? Couldn't the flash be emitted by a flash bomb that ceases to exist once it is set off? And if this is true, why do you care about its state of motion prior to it being set off?.
Firstly, I do not need it from the point of view of the train observer. But mathematically, I need a correlative tool with the ground frame so as to compare what will be the expected difference in time between A&B with an expected difference if light would have been emitted from A to B as a function of v! Exactly like the derivation of LT. so if every observer observes sequences related to light transmission from his frame point of view no LT would had ever come!

Secondly, this math could be considered as follow: The ground observer calculate what the train observer would see. So he must includes v

 Quote by ghwellsjr I think if you actually do what I'm suggesting, that is, break your scenario into two parts, one for the train with the flash occurring at a specific point and one where the speed of the ground observer determines where that point is, you will discover that at your special speed of 0.618, the flash actually occurs at location A and for higher speeds, it occurs to the right of A. But I don't know, because I still cannot figure out the second part of your scenario.
If the flash occurs at A, the light takes the same time to reach B that the source takes to reach the mid-point. In this case the v/c=0.5

 Quote by ghwellsjr You still have not told us where the train observer is located on the train or where the ground observer is located with respect to the light source.
There are 2 train observers at A and B
But there is just one ground observer to observe all events from the point where midpoint of the train coincides with the source

 Quote by ghwellsjr You only addressed my first question and you didn't even answer it: My question was: why, since "all calculations are done in the train rest frame" do you need "v" in those calculations? Isn't it the case that the source of light emits a single flash at an instant of time? If this is true, why do you care where the source moves to after the flash has occurred? Couldn't the flash be emitted by a flash bomb that ceases to exist once it is set off? And if this is true, why do you care about its state of motion prior to it being set.
Yes I guess that if all calculations would be done by the ground observer expecting what the train observer would see, this can also solve the problem raised up by Michel in my calculation that the events of receiving lights by A and the source reaching the midpoint of train are not simultaneous relative to the train observer but they are relative to the ground one!

 Quote by Adel Makram You are right I made my calculation based on Events 2 & 3 and Events 2 & 4 are simultaneously. So how the wrong math leads to the correct LT?
It doesn't! Your results for ta and tb are incorrect.

There's a simple relation between ta and tb which you can use to check your result. I'll label with "C" the place on the train from where the light flash starts. It's clear that the distances add up like this:

$CA+ CB = AB$

$CA$ is $t_{a}c$ and $CB$ is $t_{b}c$, so:

$t_{a}c + t_{b}c = AB$

and therefore:

$t_{a} + t_{b} = \frac{AB}{c}$

Since $t_{a}$ and $t_{b}$ are both positive (light isn't going backwards in time!), it's clear that their difference can never exceed $\frac{AB`}{c}$.

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