"Pmb" wrote in message . ..

"Dirk Van de moortel" wrote
in message ...

"Abonito" wrote in message
k...
Relativity Geometry
Relativity - Affine Geometry ?
Einstein's special theory of relativity is about measurements between
frames of reference in a state of non acceleration.

Not really. Special relativity can work with accelerated
objects and frames, but never mind.

The term "special relativity" was defined by Einstein to refer to the laws
of physics as they pertain to inertial systems,

Sure, but nothing, except perhaps some calculus related
complications, stops us from working with "instantaneously
comoving inertial frames".

i.e. Principle of
Relativity: The laws of physics are the same in all inertial frames of
reference." This is the same way that Schutz defines the term. However you
can choose to use it as you see fit but its best to explain it as Einstein
did and why you disagree with Einstein.

I don't think that applying the original principles to ICIF's
implies any kind of disagreement.

I understand that many people have
various reasons such as "We can always jump from one inertial frame to
another and use sr in each inertial frame" but that doesn't give you the
form the laws take in the frame you've chosen. A continuous jumping of
frames doesn't seem to me to be a frame itself.

If you like, this is where you can (together with Einstein
in his original article!) stop thinking in terms of "frames"
and work with coodinates and "coordinate systems".

In particular, if one did
see this as a frame of reference then the frame is not homogeneous nor is it
isotropic as each inertial frame is. For this reasin this "jumping" of
frames does not appear to have the same properties as a uniformly
acceleration of frames. Einstein did use this notion in one derivation of
the formula for gravitational redshift. But I assume Einstein had his
reasons for defining SR as he did.

See also Tom's reply.


Pete

Merry christmas!

Dirk Vdm