What one should conclude is the opposite of what some authors
have asserted in the past. For example, they claimed that ``
the coordinates that we use [for computation] are arbitrary and have
no physical meaning''
or ``It is the very gist of relativity that anybody
may use any frame [in his computations].''
Without delving into the logical
fallacies
underlying these claims, one should be aware
of their unfortunate consequences. They tend to discourage attempts to
understand natural processes whose very existence and identity one
learns through measurements and computations based on nonarbitrary
coordinate frames. The identification of radiation from bodies with
extreme acceleration is a case in point. For these, two complementary
frames are necessary: an accelerated frame to accommodate the source
(boost-invariant sector
and/or
) and the corresponding
expanding inertial frame (boost-invariant sector
) to observe the
information carried by the radiation coming from this source. These
frames are physically and geometrically distinct from static inertial
frames. They also provide the logical connecting link between the
concepts and the perceptual manifestations (via measurements) of these
radiation processes. Without these frames the concepts would not be
concepts but mere floating abstractions.