Editing Primordial fluctuations (section)

{{More footnotes|date=October 2009}}
'''Primordial fluctuations''' are [[density]] variations in the early universe which are considered the seeds of all [[large-scale structure of the cosmos|structure]] in the universe. Currently, the most widely accepted explanation for their origin is in the context of [[cosmic inflation]]. According to the inflationary paradigm, the exponential growth of the [[Scale factor (cosmology)|scale factor]] during inflation caused [[quantum fluctuation]]s of the inflaton field to be stretched to macroscopic scales, and, upon leaving the [[Observable universe#Horizons|horizon]], to "freeze in".
At the later stages of radiation- and matter-domination, these fluctuations re-entered the horizon, and thus set the [[initial conditions]] for [[structure formation]].

The statistical properties of the primordial fluctuations can be inferred from observations of [[Anisotropy|anisotropies]] in the [[Cosmic microwave background radiation|cosmic microwave background]] and from measurements of the distribution of matter, e.g., galaxy [[redshift survey]]s. Since the fluctuations are believed to arise from inflation, such measurements can also set constraints on parameters within inflationary theory.