Wilkinson Microwave Anisotropy Probe
The Wilkinson Microwave Anisotropy Probe allowed that comparison to be made. The initial observations, released in 2003, suggested that reionization took place from 11 &lt;"z" &lt; 30. This redshift range was in clear disagreement with the results from studying quasar spectra. However, the three year WMAP data returned a different result, with reionization beginning at "z" = 11 and the universe ionized by "z" = 7. This is in much better agreement with the quasar data.