"In April 2024 the Dark Energy Spectroscopic Instrument (DESI) collaboration made headlines with a stunning announcement. Data from the first year of a galaxy survey that captured precise measurements of more than 13 million galaxies revealed slight but significant evidence that dark energy may be weakening with time. That is, the mysterious force or substance that is causing the expansion of the universe to accelerate might be fading away."
"For years cosmologists have struggled with the so-called Hubble tension, a discrepancy between measurements of the present-day expansion rate based on the nearby universe compared with extrapolations taken from the ancient, distant cosmos. But to see out into the wider universe and make these grand measurements, we must first look through the nearby cosmos, and that may bias our observations."
Modern cosmology probes the earliest light, maps millions of galaxies, and measures subtle accelerations of cosmic expansion. In April 2024 the Dark Energy Spectroscopic Instrument (DESI) released first-year data showing slight but significant evidence that dark energy may be weakening with time. The leading LCDM model faces growing tensions, including the persistent Hubble tension between local expansion measurements and extrapolations from the distant universe. Accurate understanding of the nearby cosmos is essential because local structures and motions can bias observations of cosmic expansion. The local neighborhood remains poorly mapped and poorly understood, limiting confidence in interpretations of large-scale surveys.
Read at www.scientificamerican.com
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