In article ,
(Steve Willner) writes:
Observations of CN line ratios in distant galaxies indicate that the
microwave background was hotter in the past than it is now.

By coincidence, I just saw an ESO press release reporting a
measurement of the CMB temperature at redshift 2.4. At this
redshift, the lines measured are from CO, not CN, but the idea is the
same.

The press release is at
http://www.eso.org/public/outreach/p.../pr-13-08.html

and a preprint of the article is at
http://xxx.lanl.gov/abs/0804.0116

The refereed article is in A&A.

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Steve Willner Phone 617-495-7123
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