I just observe that a lot of cosmology seems to be riding on the theory that the red shift is caused by an expanding universe.
This seems wrong to be. There's at least two independent lines of evidence for the Big Bang theory besides redshifts -- isotope abundances (particularly for light elements) and the cosmic background radiation.
What if it light just loses energy as it travels, so that the frequency shifts lower?
We would have to abandon our belief in energy conservation. And we would then wonder why energy seems to be conserved exactly in every interaction we can see. Also we would wonder why we see spontaneous redshifts not spontaneous blue shifts. Every known micro-scale physical process in the universe is reversible [1], and by the CPT theorem, we expect this to be true always. A lot would have to be wrong with our notions of physics to have light "just lose energy."
That seems like a perfectly natural solution. How do we know it isn't true?
This solution requires light from distant galaxies to behave in ways totally different from every other physical process we know about -- including physical processes in distant galaxies. It seems unnatural to say "the redshift is explained by a totally new physical process, and this process violates a lot of natural laws that hold everywhere else."
[1] I should say, reversible assuming you also flip the charges and parities. That's irrelevant here, though, since photons are uncharged and don't have any special polarization.
I am submitting this on behalf of MazeHatter, who originally posted it here in the most recent open tread. Go there to upvote if you like this submission.
Begin MazeHatter:
I grew up thinking that the Big Bang was the beginning of it all. In 2013 and 2014 a good number of observations have thrown some of our basic assumptions about the theory into question. There were anomalies observed in the CMB, previously ignored, now confirmed by Planck:
http://www.esa.int/Our_Activities/Space_Science/Planck/Planck_reveals_an_almost_perfect_Universe
We are also getting a better look at galaxies at greater distances, thinking they would all be young galaxies, and finding they are not:
http://carnegiescience.edu/news/some_galaxies_early_universe_grew_quickly
http://mq.edu.au/newsroom/2014/03/11/granny-galaxies-discovered-in-the-early-universe/
B. D. Simmons et al. Galaxy Zoo: CANDELS Barred Disks and Bar Fractions. Monthly Notices of the Royal Astronomical Society, 2014 DOI: 10.1093/mnras/stu1817
http://www.sciencedaily.com/releases/2014/10/141030101241.htm
http://www.nasa.gov/jpl/spitzer/splash-project-dives-deep-for-galaxies/#.VBxS4o938jg
Although it seems we don't have to look so far away to find evidence that galaxy formation is inconsistent with the Big Bang timeline.
http://www.natureworldnews.com/articles/7528/20140611/galaxy-formation-theories-undermined-dwarf-galaxies.htm
http://arxiv.org/abs/1406.1799
Another observation is that lithium abundances are way too low for the theory in other places, not just here:
http://news.nationalgeographic.com/news/2014/09/140910-space-lithium-m54-star-cluster-science/
It also seems there is larger scale structure continually being discovered larger than the Big Bang is thought to account for:
http://www.sciencedaily.com/releases/2014/11/141119084506.htm
D. Hutsemékers, L. Braibant, V. Pelgrims, D. Sluse. Alignment of quasar polarizations with large-scale structures. Astronomy & Astrophysics, 2014
http://www.sciencedaily.com/releases/2013/01/130111092539.htm
These observations have been made just recently. It seems that in the 1980's, when I was first introduced to the Big Bang as a child, the experts in the field knew then there were problems with it, and devised inflation as a solution. And today, the validity of that solution is being called into question by those same experts:
http://www.physics.princeton.edu/~steinh/0411036.pdf
What are the odds 2015 will be more like 2014 where we (again) found larger and older galaxies at greater distances, or will it be more like 1983?