B Relativistic simultaneity and symmetry problem

[PAllen]

Thanks, PAllen. This helped. I believe 1) is the case I tried to describe in my question (except both twins are non-inertial). I think there's some confusion between c as the speed of light for the "world line [frame of ref?] of the non-inertial twin" and c as 299,792,458 m/s? Like where "the coordinate speed of the inertial twin may exceed c" it's clear you mean 299,792,458 m/s and not the coordinate speed of light (which would always be > the twin's). Maybe c is a constant with caveats...

That is a very good point! Even when coordinate speed of light may vary from event to event (in those coordinates), and may greatly exceed a standard value, you never have the trajectory of a material body overtaking nearby light.

 

[nitsuj]

Thanks, PAllen. This helped. I believe 1) is the case I tried to describe in my question (except both twins are non-inertial). I think there's some confusion between c as the speed of light for the "world line [frame of ref?] of the non-inertial twin" and c as 299,792,458 m/s? Like where "the coordinate speed of the inertial twin may exceed c" it's clear you mean 299,792,458 m/s and not the coordinate speed of light (which would always be > the twin's). Maybe c is a constant with caveats...

That is a very good point! Even when coordinate speed of light may vary from event to event (in those coordinates), and may greatly exceed a standard value, you never have the trajectory of a material body overtaking nearby light.

agreed it's a great way to illustrate the difference between measurements and calculations & physically fundamental constants. So often people use speed in quotes in the comment the "speed" of light. c less like some traditional or attainable speed / velocity.

 

[Dale]

Thanks, PAllen. This helped. I believe 1) is the case I tried to describe in my question (except both twins are non-inertial). I think there's some confusion between c as the speed of light for the "world line [frame of ref?] of the non-inertial twin" and c as 299,792,458 m/s? Like where "the coordinate speed of the inertial twin may exceed c" it's clear you mean 299,792,458 m/s and not the coordinate speed of light (which would always be > the twin's). Maybe c is a constant with caveats...

Personally, I try to consistently use "c" to mean the defined constant 299792458 m/s. I try to use "speed of light" to refer to the speed at which a pulse of light travels. In inertial frames they are the same. If I wish to refer to the frame invariant geometric concept then I try to say "invariant speed".

I wouldn't say there are caveats, just different concepts that are closely related with inconsistent terminology.