  We investigate the propagation of certain non-plane wave solutions to
Maxwell's equations in both flat and curved spacetimes. We find that such
solutions (or rather parts of them) exhibit accelerative behaviour, and in
particular do not propagate on straight lines. Having established these
results, we then turn to their conceptual significance -- which, in brief, we
take to be the following: (i) one should not assume that the part of
electromagnetic waves from outer space that is subject to detection is
localised onto null trajectories; therefore (ii) astrophysicists and
cosmologists should at least be wary about making such assumptions in their
inferences from obtained data, for to do so may lead to incorrect inferences
regarding the nature of our universe.
