Leveraging the Dark Energy Spectroscopic Instrument (DESI), a cutting-edge apparatus situated upon NSF’s Nicholas U. Mayall 4-m telescope at the Kitt Peak National Observatory, astronomers have meticulously charted the distribution of nearly six million galaxies across an expanse of 11 billion years of cosmic evolution. These findings represent one of the most rigorous validations to date of Albert Einstein’s seminal general theory of relativity.
This artist’s impression shows the evolution of the Universe beginning with the Big Bang on the left followed by the appearance of the Cosmic Microwave Background. The formation of the first stars ends the cosmic dark ages, followed by the formation of galaxies. Image credit: M. Weiss / Harvard-Smithsonian Center for Astrophysics.
“While general relativity has been extensively scrutinized and confirmed within the confines of solar system dynamics, it was imperative to ascertain its validity across considerably vaster cosmic expanses,” articulated Dr. Pauline Zarrouk, a distinguished cosmologist affiliated with CNRS and the Laboratory of Nuclear and High-Energy Physics.
“By scrutinizing the tempo at which galaxies have emerged and coalesced, we are afforded a direct mechanism to assess our theoretical frameworks, and thus far, our observations align precisely with the predictions extrapolated from general relativity at cosmological scales.”
In their groundbreaking new investigation, Dr. Zarrouk and her collaborators have ascertained that gravitational forces operate precisely as stipulated by Einstein’s widely accepted general theory of relativity.
This definitive result substantiates our predominant cosmological model and simultaneously constrains the viability of alternative theories of modified gravity. Such alternative hypotheses have been posited as potential explanations for enigmatic cosmic phenomena, including the accelerating expansion of our Universe, a characteristic phenomenon typically attributed to the influence of dark energy.
The intricate analytical undertaking involved the examination of almost six million galaxies and quasars, thereby enabling researchers to peer back through the epochs of the cosmos for up to 11 billion years.
The findings presented today constitute an extensive re-evaluation of the initial year’s worth of data acquired by DESI. This comprehensive dataset, released in April, successfully generated the most extensive three-dimensional cartography of our Universe to date and hinted at the possibility that dark energy may not be a static entity but rather one that evolves over time.
The April revelations specifically focused on a particular cosmological signature known as baryon acoustic oscillations (BAO), which manifests in the clustering patterns of galaxies.
The current analysis expands upon this by undertaking a comprehensive measurement of the spatial distribution of galaxies and matter across a diverse range of scales.
Furthermore, this comprehensive study has yielded enhanced constraints on the elusive mass of neutrinos, the sole class of fundamental particles whose mass has not yet been precisely quantified.
Although neutrinos exert a subtle influence on the aggregated structures of galaxies, this effect is sufficiently discernible to be measured with the exceptional fidelity of DESI’s observational data.
Consequently, the constraints derived from DESI represent the most stringent obtained to date, serving as a valuable complement to the information gathered from terrestrial laboratory experiments.
The execution of this study necessitated several months of diligent supplementary investigation and rigorous verification processes. Mirroring the methodology of prior research, a sophisticated technique was employed to withhold the results from the scientific team until the culmination of the analysis, thereby preempting any inadvertent bias.
“This endeavor is central to one of DESI’s core scientific objectives: to elucidate fundamental aspects of our Universe on vast scales, encompassing the architecture of matter distribution and the dynamics of dark energy, alongside the fundamental properties of elementary particles,” stated Dr. Stephanie Juneau, an astronomer at NSF’s NOIRLab and a contributing member of the DESI Collaboration.
“Through a comparative analysis of how the distribution of matter has evolved throughout the Universe against established theoretical predictions, including Einstein’s general relativity and its competing hypotheses, we are effectively narrowing the range of plausible gravitational models.”
“Dark matter constitutes approximately one-quarter of the Universe’s total mass-energy content, with dark energy accounting for roughly another 70%, and our understanding of either remains profoundly limited,” remarked Mark Maus, a doctoral candidate at Berkeley Lab and the University of California, Berkeley.
“The prospect that we can generate detailed observations of the cosmos and, in doing so, address these profound, foundational questions is truly astonishing.”
The full findings from the DESI Collaboration were disseminated today through the publication of several research papers on the pre-print server arXiv.org.
