The universe might not actually be speeding up—gravity might just be messing with our perspective and making it look that way.
arXiv · March 13, 2026 · 2603.11377
Why it matters
While astronomers usually explain the universe's rapid expansion using a mysterious 'dark energy,' this paper suggests that dark energy might not exist at all. Instead, it argues that local gravitational potentials create a backreaction effect that makes the universe appear to accelerate from our perspective, even if it is actually slowing down.
From the abstract
In this manuscript, we develop a class of inhomogeneous relativistic cosmological models with the following properties: (i) They contain cosmological observers to whom the spatial geometry and the expansion are homogeneous and isotropic; (ii) Matter behaves closely to dust, as it is formed by an ensemble of massive particles whose number density $4$-vector is conserved and reacts viscously to the local tidal forces; (iii) They generalize the dust FLRW model; (iv) They give rise to effective mode