Data collected by the DESI spectroscope over three years suggest that dark energy has weakened over the past 4.5 billion years. This challenges previous assumptions that dark energy is a cosmological constant responsible for the accelerating expansion of the universe. If these findings are confirmed, they could require a revision of the standard cosmological model.
Located in Arizona, DESI analyzes light from distant galaxies, allowing astronomers to measure baryon acoustic oscillations and reconstruct the universe’s expansion history. According to the traditional model, dark energy became the dominant force about 5 billion years ago, driving accelerated expansion. However, DESI data indicate that this expansion is now slowing, calling into question the idea of unchanging dark energy.
Last year, the DESI collaboration proposed a hypothesis of evolving dark energy, which better explains observations of supernovae. A recent analysis suggests that dark energy’s density has decreased by approximately 10% over the past 4.5 billion years, contradicting the cosmological constant model. However, the statistical precision of the data is not yet sufficient to draw definitive conclusions.
Additionally, researchers from New Zealand have questioned the very concept of accelerated expansion, finding that the way light from supernovae propagates suggests an uneven expansion of the universe. This could imply that dark energy is not needed to explain cosmic evolution, radically reshaping our understanding of the universe.
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