For nearly 25 years, we thought we knew how the Universe would end. Now, new measurements point to a profoundly different conclusion.

If you can measure the Universe’s expansion rate today and how its expansion rate has changed over its history, you should be able to determine what it’s made of and, therefore, what its ultimate fate will be.

Starting in the late 1990s, combinations of large-scale structure data, supernova data, and CMB data all pointed toward a single picture: a dark energy-dominated Universe that would end in a “big freeze.”

Now in 2024, however, the picture has gotten a lot murkier. The Hubble tension, along with new results from DESI, throw our consensus picture into doubt. Here’s why we now question the fate of the Universe.