Dark energy could be getting weaker

New discoveries suggest that the Universe isn't expanding as we thought. So is it time for us to go back to the drawing board?

- DR KATIE MACK

The day after the Dark Energy Spectroscopic Instrument's (DESI) second data release papers came out, which presented evidence for a weakening of the dark energy accelerating the Universe's expansion, members of the cosmology group at my research institute received an email announcing a discussion group.

It was headed "The week that broke Cosmology!" and said that we would meet in an hour to hear a summary from a member of the DESI team and then "pick up the pieces and decide what comes next for cosmology."

It's not unusual to see breathless proclamations about cosmic crises in the media, but within the research community, most of us tend to be more cautious. Yes, it could be really interesting and important, but we shouldn't throw out the textbooks just yet. Yes, let's talk about possible implications, but let's also think about what could have gone wrong in the analysis and how new data could change the story.

Still, if the DESI announcement holds up, it'll require the first major rewriting of our cosmological paradigm in the last couple of decades: a rejection of the cosmological constant.