Evidence for the KOK Hypothesis
There appears to be more infrared light in the universe than can be accounted for by current theories:
There's also the possibility the light might come from civilizations in apparently-empty parts of the universe.
Prof Jamie Bock from Nasa's Jet Propulsion Laboratory, one of the report's authors, described the extragalactic background light (EBL) as "kind of a cosmic glow".
"It's very faint - but basically the spaces between the stars and galaxies aren't dark. And this is the total light made by stars and galaxies during cosmic history," Prof Bock told the BBC.
Earlier measurements from rockets and satellites had shown that there was more fluctuation in this background than the sum total of known galaxies could explain.
At least two proposals were made to account for the extra light: it might come from very early, distant galaxies that formed when the universe was much younger, or it might come from stray stars outside galactic boundaries.