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'Hubble Tension' and the Nobel Prize Winner Who Wants to Replace Cosmology's Standard Model

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3 months 2 weeks ago
Adam Riess won a Nobel Prize in Physics for helping discover that the universe's acceleration is expanding, remembers The Atlantic. But then theorists "proposed the existence of dark energy: a faint, repulsive force that pervades all of empty space... the final piece to what has since come to be called the 'standard model of cosmology.'" Riess thinks instead we should just replace the standard model: When I visited Riess, back in January, he mentioned he was looking forward to a data release from the Dark Energy Spectroscopic Instrument, a new observatory on Kitt Peak, in Arizona's portion of the Sonoran Desert. DESI has 5,000 robotically controlled optic fibers. Every 20 minutes, each of them locks onto a different galaxy in the deep sky. This process is scheduled to continue for a total of five years, until millions of galaxies have been observed, enough to map cosmic expansion across time... DESI's first release, last year, gave some preliminary hints that dark energy was stronger in the early universe, and that its power then began to fade ever so slightly. On March 19, the team followed up with the larger set of data that Riess was awaiting. It was based on three years of observations, and the signal that it gave was stronger: Dark energy appeared to lose its kick several billion years ago. This finding is not settled science, not even close. But if it holds up, a "wholesale revision" of the standard model would be required [says Colin Hill, a cosmologist at Columbia University. "The textbooks that I use in my class would need to be rewritten." And not only the textbooks — the idea that our universe will end in heat death has escaped the dull, technical world of academic textbooks. It has become one of our dominant secular eschatologies, and perhaps the best-known end-times story for the cosmos. And yet it could be badly wrong. If dark energy weakens all the way to zero, the universe may, at some point, stop expanding. It could come to rest in some static configuration of galaxies. Life, especially intelligent life, could go on for a much longer time than previously expected. If dark energy continues to fade, as the DESI results suggest is happening, it may indeed go all the way to zero, and then turn negative. Instead of repelling galaxies, a negative dark energy would bring them together into a hot, dense singularity, much like the one that existed during the Big Bang. This could perhaps be part of some larger eternal cycle of creation and re-creation. Or maybe not. The point is that the deep future of the universe is wide open... "Many new observations will come, not just from DESI, but also from the new Vera Rubin Observatory in the Atacama Desert, and other new telescopes in space. On data-release days for years to come, the standard model's champions and detractors will be feverishly refreshing their inboxes..." And Riess tells The Atlantic he's disappointed when complacent theorists just tell him "Yeah, that's a really hard problem." He adds, "Sometimes, I feel like I am providing clues and killing time while we wait for the next Einstein to come along."

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