In message bF%Pe.286864$_o.243143@attbi_s71, Sam Wormley
writes
Jonathan Silverlight wrote:

I'm in a nit-picking mood :-) so I'll note that should presumably
photons, not just light.
But there's also neutrinos, though we don't yet have the ability to
detect them at cosmological distances.

I'm not sure what you mean in this context by cosmological distances.
We captured neutrino's from another (nearby galaxy) in 1987. Some of
the SN 1987A Neutrino Burst and Visible Explosion Data:


I should have excluded SN 1987A, but that's the limit at the moment. A
supernova in M31 would require a much more sensitive detector, as it
would presumably produce less than one event.
Neutrinos are (also presumably) reaching us from behind the last
scattering surface and could tell us about conditions there.