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last mo.

New Cosmology Tests Hint the Universe May Not Be Uniform on the Largest Scales

The signals fall short of discovery standards, leaving confirmation to larger surveys.

A long exposure photo shows the series of white star streaks across the night sky above a circular observatory.
DESI’s 3-year map of the universe shows the distribution of matter across space-time. New studies based on DESI and other survey data hint that our standard model of cosmology may need an update.
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Overview

  • Three new arXiv papers test whether the universe is uniform on the largest scales using Pantheon+ supernovas, DESI galaxy maps, and BAO signals.
  • The studies report 2 to 4 sigma departures from FLRW, the model that assumes matter is spread evenly and looks the same in every direction.
  • The team ran generalized distance–expansion consistency checks and a model‑free tool that searches the data for simple equations.
  • They highlight two candidate effects: light favoring empty voids, known as the Dyer–Roeder bias, and structure growth that nudges average expansion, called backreaction.
  • Because the work is not yet peer‑reviewed, the authors call for larger surveys to confirm the hints, which could reshape ideas about dark energy and gravity if upheld.