Editing Cosmic microwave background (section)

===Observations after COBE===
{{Main|List of cosmic microwave background experiments}}
[[File:PIA16874-CobeWmapPlanckComparison-20130321.jpg|thumb|240px|Comparison of [[CMB]] results from [[Cosmic Background Explorer|COBE]], [[WMAP]] and [[Planck (spacecraft)|Planck]]<br />(March 21, 2013)]]
Inspired by the initial COBE results of an extremely isotropic and homogeneous background, a series of ground- and balloon-based experiments quantified CMB anisotropies on smaller angular scales over the next decade. The primary goal of these experiments was to measure the angular scale of the first acoustic peak, for which COBE did not have sufficient resolution. These measurements were able to rule out [[cosmic string]]s as the leading theory of cosmic structure formation, and suggested [[cosmic inflation]] was the right theory.

During the 1990s, the first peak was measured with increasing sensitivity and by 2000 the [[BOOMERanG experiment]] reported that the highest power fluctuations occur at scales of approximately one angular degree. Together with other cosmological data, these results implied that the geometry of the universe is [[flat spacetime|flat]]. A number of ground-based [[interferometer]]s provided measurements of the fluctuations with higher accuracy over the next three years, including the [[Very Small Array]], [[Degree Angular Scale Interferometer]] (DASI), and the [[Cosmic Background Imager]] (CBI). DASI made the first detection of the polarization of the CMB and the CBI provided the first E-mode polarization spectrum with compelling evidence that it is out of phase with the T-mode spectrum.