What is the value of the Hubble constant?
This is the question that professional astronomers ask the most frequently. For many decades the Sandage [Ho = 50] and de Vaucouleurs [Ho = 100] camps battled in a long lasting distance scale controversy. Many outsiders thought that the geometric mean of these values, Ho = 71 km/sec/Mpc, was a good compromise. The Sunyaev-Zeldovich effect has been used to determine Ho = 77 +/- 10 km/sec/Mpc. The Hubble Space Telescope Key Project team came up with the answer Ho = 72 +/- 8 km/sec/Mpc, the Cepheids in the nuclear maser ring galaxy NGC 4258 gave 74 +/- 6 km/sec/Mpc, and the double-lined eclipsing binary in M33 gave 61 +/- 4 km/sec/Mpc. These average to 71 +/- 5 km/sec/Mpc. In 2009 Riess et al. reported a new value of 74.2 +/- 3.6 km/sec/Mpc based Cepheids and Type Ia supernovae. Finally WMAP came up with: Ho = 71 +/- 3.5 km/sec/Mpc based on a flat Lambda-CDM model fit to the CMB angular power spectrum but I would rather see because it would be consistent with a simple Universe with dark m
