Hubble constant tension continues
A NEW STUDY of a special class of red giant stars fuels a dispute about the rate at which today’s universe is expanding.
The universe’s expansion rate has changed expansion rate that doesn’t match measurements of galaxy recession speeds. Observations of the cosmic microwave background (CMB) pin today’s expansion rate, also called the ( ), between 66.9 and 67.9 km s Mpc . However, measurements of galaxies’ recession speeds — based on so-called such as Cepheid variable stars — find to be significantly higher, between 73 and 76 km s Mpc .
