The high red-shift supernovae are perhaps most notably the key to the accelerating universe, and they've been seen to a red-shift of 1.0 or so.

 

And here's a more up-to-date reference again from Ned Wright that supernovae have now been measured up to z=1.75. Also a good discussion on how all the data fits together with the cosmological models.

 

http://www.astro.ucla.edu/~wright/sne_cosmology.html

Edited July 21, 200817 yr by scalbers

These photons are certainly very experienced. Do you think one of them relates to one atomic emission in a galaxy?

I'm a little unsure of the various alternatives you contemplate here if you care to elaborate. A supernova probably emits energy in fairly exotic ways. If it's thermal emission from a hot gas of some type, then atomic emission seems reasonable. I think they can survive the long journey fairly intact.

I am not so concerned about emission details as to the possibility of detecting even one photon from such a distance. Quantum theory seems to say there is a broader wave function than the tiny angle over which the mirror gathers energy. One possible theoretic picture I wonder about: let's say there is a certain probability distribution (are coherent and decoherent different?), whatever, that projects in the far, and we are talking really far. Could this concept be combined with stochastic vacuum energy which is part of things, to where we can visualize this larger, spacelike front, as scintillating here or there, and detection probability occuring thus?

Well since there are so many photons being emitted this might compensate for the weakening of the associated traveling waves as they spread out.

 

Speaking of photon wave functions (a good Google search phrase), here is a nice little paper that does briefly mention vacuum polarization:

 

http://arxiv.org/abs/quant-ph/0508202

Edited July 21, 200817 yr by scalbers

I am reading Feynman lectures, I-37-5: "We make an electron gun... box with a hole in it... The trouble is that the apparatus would have to be made on an impossibly small scale to show the effect we are interested in." We know this was done some years later with magnetic 'whiskers' of iron. Just how broad is the extent of coherent photon interference?!?

I guess I would have to learn more about what comprises coherent photon interference and how that differs from incoherent photons or waves. I can say that I've personally seen electron diffraction in physics class using crystals as gratings.