A [[worldline.
Source: Acrocephalus_schoenobaenus_1_(Marek_Szczepanek).jpg. http://en.wiktionary.org/wiki/File:Acrocephalus_schoenobaenus_1_(Marek_Szczepanek)-2.jpg
Author: Acrocephalus_schoenobaenus_1_(Marek_Szczepanek).jpg: Marek Szczepanek derivative work: Bogbumper (ta