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Cosmology has undergone significant changes from 2000 to 2025, marked by an increased understanding of dark matter and dark energy's dominance in the Universe. Evidence gathered in the late 1990s pointed towards these mysterious components making up the majority of the cosmic energy budget, with normal matter contributing a mere 5%. Subsequent data from projects like the Hubble key project, WMAP, and Planck's Cosmic Microwave Background (CMB) observations, alongside extensive supernova and large-scale structure surveys, appeared to solidify this picture. However, tensions have emerged as these different data sets reveal inconsistencies, hinting at a potential need for a breakthrough in cosmological understanding.
The core issue revolves around the Hubble constant, a measure of the Universe's expansion rate. Measurements derived from supernova data, CMB observations, and large-scale structure surveys are not mutually compatible, leading to a significant debate within the scientific community. While some propose a crisis in cosmology, questioning the foundations of the Big Bang and the ΛCDM model, others argue that the situation is less dire. Alterations or modifications to the current cosmological model might be necessary to reconcile the discrepancies and restore order. The DESI survey, designed to measure the evolution of large-scale structure, is crucial in understanding how dark energy affects this evolution.
Furthermore, recent research indicates that dark energy may not be constant, challenging our established cosmological history. Astronomers are also finding the sky brighter than previously thought, necessitating a reanalysis of existing data. Studies involving Type Ia supernovae at high redshifts, as highlighted by the Union2 compilation of 557 supernovae, provide crucial data for refining the understanding of dark energy's equation-of-state parameter. These observations, made possible by telescopes such as the Hubble Space Telescope, Gemini, and the Very Large Telescope, are instrumental in probing the expansion history of the Universe and revealing potential variations in dark energy's behavior over cosmic time.
References :
- bigthink.com: How has cosmology changed from 2000 to 2025?
- theconversation.com: Article on dark energy and its potential non-constant nature.
- bigthink.com: How has cosmology changed from 2000 to 2025?
- hubblesite.org: How has cosmology changed from 2000 to 2025?
- Terence Tao: A new post, on intriguing hints from the DESI survey data that suggests that the cosmological constant (aka "dark energy) might not, in fact, be constant after all.
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