Dark Energy Is Not Constant: A New Look at the Universe's Acceleration ⚡ экспресс
Cosmological implications of BAO measurements in the Lyman-alpha forest from DESI DR2 are analyzed in combination with galaxy BAO, type Ia supernovae (Pantheon+, DES-Dovekie, Union3), and the cosmic microwave background (CamSpec). Six parameterizations of dynamical dark energy, wCDM, and non-flat extensions are considered. Parameter constraints and Bayesian evidence are derived using MCMC. Non-flat models are consistent with flatness (Ω_k ≈ 0). The data favor dynamical dark energy with w₀ > -1, wₐ < 0, and w₀ + wₐ < -1 (Quintom-B). For the combination of Lyman-alpha forest + CMB + galaxy BAO, the preference over ΛCDM reaches ~3.1σ, but adding supernovae reduces it to ≲2σ (inconclusive). The Bayes factor strongly depends on the dataset: wCDM and owCDM have moderate evidence for Lyα+CMB+galaxies, while with Pantheon+ or DES-Dovekie, owCDM receives strong evidence.
The Universe is a grand highway where galaxies, like cars, are moving apart faster and faster. The gas pedal is controlled by mysterious dark energy. In 1998, Saul Perlmutter, Brian Schmidt, and Adam Riess discovered this acceleration using supernovae, but they thought the pedal was pressed evenly. The new DESI survey, covering 11 billion years of cosmic history, challenges the model of uniform expansion. Scientists measured the recession of galaxies and also studied the light of quasars passing through clouds of hydrogen. These clouds act like road signs: dark lines in the spectrum shift more the faster space stretches. Adding the afterglow of the Big Bang, the team compared models. It turned out that the version with dark energy that 'revs' unevenly—barely touching the pedal in the first few billion years and now flooring it—fits the data slightly better than the constant-speed model. As of now, the statistical significance is below the discovery threshold, but if the trend is confirmed, our understanding of the cosmic 'engine' will change.
🎯 Quasar light leaves a 'road track' of hundreds of dark bands on the spectrum. Each band marks a hydrogen cloud, and its shift reveals the expansion rate at the moment the light passed it. It works like a cosmic speedometer from billions of years ago.
🎬 Science fiction writers eagerly imagine universes with changing physics. In Greg Bear's novel *Eon*, the variability of fundamental forces leads to disasters.