Editing Interstellar travel (section)

===== Wormholes =====
[[Wormhole]]s are conjectural distortions in spacetime that theorists postulate could connect two arbitrary points in the universe, across an [[Einstein–Rosen Bridge]]. It is not known whether wormholes are possible in practice. Although there are solutions to the Einstein equation of general relativity that allow for wormholes, all of the currently known solutions involve some assumption, for example the existence of [[negative mass]], which may be unphysical.<ref>{{cite web |url=http://www.nasa.gov/centers/glenn/technology/warp/ideachev.html#worm |title=Ideas Based On What We'd Like To Achieve: Worm Hole transportation |date=11 March 2015 |publisher=NASA Glenn Research Center |access-date=4 September 2012 |archive-date=24 September 2013 |archive-url=https://web.archive.org/web/20130924060726/http://www.nasa.gov/centers/glenn/technology/warp/ideachev.html#worm |url-status=live }}</ref> However, Cramer ''et al.'' argue that such wormholes might have been created in the early universe, stabilized by [[cosmic string]]s.<ref>{{cite journal | author= John G. Cramer| author2= Robert L. Forward| author3= Michael S. Morris| author4= Matt Visser| author5= Gregory Benford| author6= Geoffrey A. Landis | title= Natural Wormholes as Gravitational Lenses | journal= Physical Review D | volume= 51 | issue= 3117 | date= 15 March 1995 | pages= 3117–3120 | doi= 10.1103/PhysRevD.51.3117 | pmid= 10018782| arxiv= ph/9409051|bibcode = 1995PhRvD..51.3117C | s2cid= 42837620}}</ref> The general theory of wormholes is discussed by Visser in the book ''Lorentzian Wormholes''.<ref>{{cite book | author= Visser, M. | date= 1995 | title= Lorentzian Wormholes: from Einstein to Hawking | publisher= AIP Press, Woodbury NY | isbn= 978-1-56396-394-0}}</ref>