Ask Ethan: Could The Shape Of Our Universe Be Closed Instead Of Flat?
“I thought that the curvature parameter had been essentially settled upon by WMAP, Planck, and other astronomical measurements. I am curious what you think about the validity of this recent paper. Is the Universe actually closed with a detectable positive curvature as the authors of the Nature Astronomy paper suggest? If the Universe is spherical, then how big would the sphere be according their measurements?”
About 2 weeks ago, a team of scientists took a detailed look at the latest Planck results, the most sophisticated, highest-precision map of the Cosmic Microwave Background ever obtained. But rather than look simply at the temperature fluctuations, they looked at a different signal: the effect of gravitational lensing. And instead of finding the flat Universe that other types of analysis yield, they favored a closed, positively-curved Universe at about the 4.4% level, creating a greater-than-3-sigma tension with the rest of the Planck data.