[ExI] Faster than light??
anders at aleph.se
Tue Sep 27 11:36:26 UTC 2011
Tomaz Kristan wrote:
> I don't think that enough Relativity remains, that the "light cone"
> for example, is a meaningful concept anymore.
The light cone can still be defined as the events that are hit by a
spherically expanding wavefront of light. Even if you throw out the
theoretical apparatus of SR that gives it a somewhat privileged position
it remains as a set of points.
And we have fairly good empirical evidence that for timelike
trajectories inside observed lightcones the symmetries of space behave
like SR says, so any generalisation that turns into SR for "low"
velocities must also have nearly the same symmetries inside the
lightcone. I am no expert, but it looks like one needs a rather
nonlinear symmetry group to patch that together with a very non-SR
behavior (whatever is needed to save causality) outside the light cone.
One of the key conceptual selling points of SR is that it is the
simplest theory you can get by insisting on identical physics in
inertial frames and constancy of observed lightspeed; you get the
Poincare group from that. Of course, a trans-SR theory might drop
symmetries like boost invariance, but then it better either provide
amazingly good empirical evidence or some profoundly satisfying
conceptual explanation. Ever since Emma Noether we have a pretty solid
reason to regard symmetries as important.
Future of Humanity Institute
James Martin 21st Century School
More information about the extropy-chat