An anonymous reader shared this report from the BBC: There is growing controversy over recent evidence suggesting that a mysterious force known as dark energy might be changing in a way that challenges our current understanding of time and space. An analysis by a South Korean team has hinted that, rather than the Universe continuing to expand, galaxies could be pulled back together by gravity, ending in what astronomers call a "Big Crunch". The scientists involved believe that they may be on the verge of one of the biggest discoveries in astronomy for a generation. Other astronomers have questioned these findings, but these critics have not been able to completely dismiss the South Korean team's assertions... The controversy began in March with unexpected results from an instrument on a telescope in the Arizona desert called the Dark Energy Spectroscopic Instrument (Desi)... The data hinted that acceleration of the galaxies had changed over time, something not in line with the standard picture, according to Prof Ofer Lehav of University College London, who is involved with the Desi project. "Now with this changing dark energy going up and then down, again, we need a new mechanism. And this could be a shake up for the whole of physics," he says. Then in November the Royal Astronomical Society (RAS) published research from a South Korean team that seems to back the view that the weirdness of dark energy is weirder still. Prof Young Wook Lee of Yonsei University in Seoul and his team went back to the kind of supernova data that first revealed dark energy 27 years ago. Instead of treating these stellar explosions as having one standard brightness, they adjusted for the ages of the galaxies they came from and worked out how bright the supernovas really were. This adjustment showed that not only had dark energy changed over time, but, shockingly, that the acceleration was slowing down... If, as Prof Lee's results suggest, the force that is pushing galaxies away from each other — dark energy — is weakening, then one possibility is that it becomes so weak that gravity begins to pull the galaxies back together. Read more of this story at Slashdot.