- Joshua SokolScience 10 Mar 2017:
Vol. 355, Issue 6329, pp. 1010-1014
There is a vigorous new debate over the Hubble constant, the expansion rate of the universe. New techniques suggest that the Hubble constant
is 8% lower than a leading number that astronomers had mostly settled on. For nearly a century, they have calculated it by meticulously measuring
distances in the nearby universe and moving ever farther out. But lately, astrophysicists have measured the constant from the outside in, based on
maps of the cosmic microwave background, the dappled afterglow of the big bang that is a backdrop to the rest of the visible universe. By making
assumptions about how the push and pull of energy and matter in the universe have changed the rate of cosmic expansion since the microwave
background was formed, the astrophysicists can take their map and adjust the Hubble constant to the present-day, local universe. The numbers
should match. But they don't. It could be that one approach has it wrong. But if the disagreement holds, it will be a crack in the
firmament of modern cosmology that points to new physics.
Why would it be controversial that the expansion of the universe is not smooth in all directions. The Hubble constant is not a constant it has varied ever since the beginnings of time. The CBR is not even and this would seem to reflect that it is not even. The uniform inflationary stage of the universe by Guth was superceded by Lindes inflationary model which takes into account that inflation was not uniform.