In a message dated 4/15/01 2:04:09 AM Eastern Daylight Time, jsd@MONMOUTH.COM
writes:
<< To say the same thing in slightly different words:
x) There is no absolute reference for position coordinates.
x') There is no absolute reference for velocity. It's all relative.
x'') The EM field *does* provide an absolute reference for
acceleration. We know what the ground state of the EM field looks like
(zero-temperature equilibrium). But if you accelerate past such a state,
in the accelerated frame it does not look like the ground state. It will
have nonzero temperature, including thermal photons.
>>
To me the possible very naive question is then is - Where does the inertia
come from? While of course it's true the no velocity of any object is
absolute only having meaning in terms it's relationship with another object
this isn't true for inertia. Also the acceleration of charged particles
produces effects which are perhaps not relative in this same sense either,
though as you have pointed out a simple minded identification between inertia
and radiation resistance is erroneous.
It's my opinion that there may be a deeper understanding of inertia
possible and if or when we ever come to that deeper understanding we will
have learned a whole lot more about this Universe.