  This paper examines an observable consequence for the diffuse extragalactic
background radiation (EGBR) of the hypothesis that if closed, our universe
possesses time symmetric boundary conditions. For simplicity, attention is
focused on optical wavelengths. The universe is modeled as closed Friedmann-
Roberston-Walker. It is shown that, over a wide range of frequencies,
electromagnetic radiation can propagate largely unabsorbed from the present
epoch into the recollapsing phase, confirming and demonstrating the generality
of results of Davies and Twamley. As a consequence, time symmetric boundary
conditions imply that the optical EGBR is at least twice that due to the
galaxies on our past light cone, and possibly considerably more. It is
therefore possible to test experimentally the notion that if our universe is
closed, it may be in a certain sense time symmetric. The lower bound on the
"excess" EGBR in a time symmetric universe is consistent with present
observations. Nevertheless, better observations and modelling may soon rule it
out entirely. In addition, many physical complications arise in attempting to
reconcile a transparent future light cone with time symmetric boundary
conditions, thereby providing further arguments against the possibility that
our universe is time symmetric.
