Cosmic microwave background radiation was verified in the 1960s by Penzias and Wilson, and this discovery favoured the big bang at the expense of the steady state scenario. Later work was by Smoot et al. (1989), among other contributors, using data from the Cosmic Background explorer (CoBE) and the Wilkinson Microwave Anisotropy Probe (WMAP) satellites that refined these observations. The 1980s (the same decade of the COBE measurements) also saw the proposal of inflation theory by Alan Guth.