The Hubble constant , which measures the expansion rate , together with the total energy density of the Universe , sets the size of the observable Universe , its age , and its radius of curvature .
Excellent progress has been made recently toward the measurement of the Hubble constant : a number of different methods for measuring distances have been developed and refined , and a primary project of the Hubble Space Telescope has been the accurate calibration of this difficult-to-measure parameter .
The recent progress in these measurements is summarized , and areas where further work is needed are discussed .
Currently , for a wide range of possible cosmological models , the Universe appears to have a kinematic age less than about 14 \pm 2 billion years .
Combined with current estimates of stellar ages , the results favor a low–matter–density universe .
They are consistent with either an open universe , or a flat universe with a non-zero value of the cosmological constant .