But the word “most” is important. The ACT team’s findings are consistent with his CMB studies, made with instruments such as the European Space Agency’s Planck telescope, which cover the first eight billion years of the universe’s lifetime. But there are still big discrepancies between these discoveries about the young universe and the observations made by tracking what happened over the past billion years. recent past.)
The ACT findings suggest that: something It may have changed in the last 5 billion years or so, causing the expansion of the universe to appear to have accelerated slightly and the distribution of matter to appear more clumped. This reconstructs physicists’ view of the cosmic crisis, and means that CMB-based models still work most of the time, but not for the entire history of the universe.
“The exciting prospect is that there may be some new physics going on here,” says Madhavacheril.For example, in the standard model, approximately 32 percent Specifically, a particular flavor called “cold dark matter particles” that move relatively slowly. But he thinks it’s worth investigating the existence of other possible options, such as hypothetical particles called axions, that could form different structures than very light, cold dark matter. I’m here.
Another idea, he says, is that perhaps gravity has slightly different effects on vast spatial scales. In that case, the effects of gravity would gradually change the shape of the universe, and Einstein’s theory of gravity might need to be revised.
But to justify such a radical solution, scientists must really TRUE Check their measurements. Enter Wendy Friedman, an astronomer at the University of Chicago. She is an expert in using pulsating Cepheid stars as “standard candles”. These stars have known distances and brightnesses that can be used to calibrate measurements of the expansion of the universe. She and her colleagues are using the powerful James Webb Space Telescope, which has ten times the sensitivity of Hubble’s and four times the resolution of hers, to evaluate the new Hubble star. Her team compares the results to her ACT measurements of the Hubble constant, as well as Planck’s previous measurements. antarctic telescope.
Until then, she argues, caution should be exercised in determining whether a model is broken. “It’s important to get it right. Planck set the bar very high. We’re getting there, but we’re not there yet,” says Freedman.
That said, Friedman thinks the ACT measurements promise to agree, despite being a very different project than Planck’s. “It’s a different experiment, and they have different detectors. They’re on the ground, they have different frequencies, they have different groups analyzing the data. It’s a completely independent measurement and they They match very well,” she says.
Other astrophysicists, such as Yale University’s Priyamvada Natarajan, who specializes in cosmology, are also impressed with the ACT map. “This is a beautiful piece of work,” she says.