Wouldn’t be happening if more wasn’t also going on:
“The consensus now is that it is a small effect that does not, in the end, cause too much trouble,” Nadathur said. But that 2% could yet prove consequential. Durrer is investigating whether backreaction might help resolve a growing cosmological crisis. The crisis, known as the Hubble tension, is that the nearby universe appears to expand about 9% faster than what the standard model predicts for the universe’s overall expansion rate. Many explanations have been floated, including radical new ingredients in the cosmos. But Buchert argued last year that the broad-brush cosmological principle might be to blame for the apparent discrepancy. In a lumpy universe, one would expect emptier patches to expand faster than the average. Durrer is simulating the effects of backreaction to calculate the odds that we could have landed in the middle of such an empty, expansive section of space. “Even if [backreaction] is not sufficient to explain the accelerated expansion, it might be marginally sufficient to solve the Hubble tension,” she said, although she doesn’t expect it to provide the whole answer.Charlie Wood, “Cosmologists Parry Attacks on the Vaunted Cosmological Principle” at Quanta (December 13, 2021)
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