[ExI] Pesky Neutrinos

[Adrian Tymes]

On Tue, Nov 1, 2011 at 3:36 PM, Anders Sandberg <anders at aleph.se> wrote:
> I did a simple worked example here on a roleplaying forum of how a twice
> lightspeed signal to a relativistic observer in SR can produce a loop where
> you can get a return message before you sent your message:
> http://www.eclipsephase.com/faster-speed-light-how-would-it-change-ep-if-all#comment-22275
>
> Another version (final section relates to in-game assumptions, not the real
> world):
> http://www.eclipsephase.com/faster-speed-light-how-would-it-change-ep-if-all#comment-22422

Thanks, but this appears to be simply incorrect.  For example:

> Now, an observer moving with a speed of 94% light-speed (which makes
> gamma 3) happens to be there to receive it. In his coordinate system,
> which we assume is synchronized with mine so that we both agree on
> the origin, the coordinate is 1.58 and the time is -1.32 - he will get the
> message before I sent it, at least according to his clock

No he won't.  Not unless he's set his clock to your clock plus light speed
lag, in which case, you sent it "before" you sent it too (and, in theory, he
could calculate when - by his clock, at least - you sent it if he knew where
you were relative to him at the time), though the light of you sending it
won't reach him until later.