special relativity mk2
e = mc2 relies on the concept of c = #t0. environmental speed of light, not subject to change.
it should be shown that c = #t4 and not #t0, where c = the stable speed of light in a region for your local time. if you're traveling, you still see light moving at 300mkm/s, and not c - your speed.
for this reason c#t4 = your speed in relation to stopping + c[#t0].
also note the impoverished surf physicist. he might know this explanation.