Editing Pp-wave spacetime (section)

{{more footnotes needed|date=July 2018}}
{{lowercase title|pp-wave spacetime}}
{{General relativity sidebar |solutions}}

In [[general relativity]], the '''pp-wave spacetimes''', or '''pp-waves''' for short, are an important family of [[exact solutions]] of [[Einstein's field equation]]. The term ''pp'' stands for ''plane-fronted waves with parallel propagation'', and was introduced in 1962 by [[Jürgen Ehlers]] and [[Wolfgang Kundt]].