A tale of four surveys:What have we learned about the variable sky?

Four tales concerning a set of photometric imaging surveys are spun. The reader is lead through a brief description of each survey and major results are presented. The four surveys are summarized in a few simple “rules”: 1) The fraction of point sources that are variable with respect to those that are found to be constant, increases as a power law as the photometric precision of the survey improves, and 2) This fact can be simply formulated as a power law function granting the user a predictive power. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)