Editing Space colonization (section)

===Beyond the Solar System===
{{Further|Interstellar travel}}
Beyond the Solar System colonization targets might be identified in the [[List of nearest stars|surrounding stars]]. The main difficulty is the vast distances to other stars.

To reach such targets travel times of millennia would be necessary, with current technology. At average speeds of even 0.1% of the speed of light (''c'') interstellar expansion across the entire [[Milky Way galaxy]] would take up to one-half of the Sun's galactic orbital period of ~240,000,000 years, which is comparable to the timescale of other galactic processes.<ref>{{cite web|url=https://hypertextbook.com/facts/2002/StacyLeong.shtml|work=The Physics Factbook|last=Leong|first=Stacy|year=2002|title=Period of the Sun's Orbit around the Galaxy (Cosmic Year)|access-date=19 April 2025}}</ref> Due to fundamental energy and reaction mass consideration such speeds would be with current technology limited to small spaceships. If humanity would gain access to a large amount of energy, on the order of the mass-energy of entire planets, it may become possible to construct spaceships with [[Alcubierre drive]]s.<ref>{{Cite news |last=Williams |first=Matt |date=1 March 2020 |title=Scientists Are Starting to Take Warp Drives Seriously, Especially This One Concept |work=ScienceAlert.com |url=https://www.sciencealert.com/scientists-are-starting-to-take-warp-drives-seriously-especially-this-one-concept |access-date=19 April 2025}}</ref>

The following are plausible approaches with current technology:
* A [[generation ship]] which would travel much slower than light, with consequent interstellar trip times of many decades or centuries. The crew would go through generations before the journey was complete, so none of the initial crew would be expected to survive to arrive at the destination, assuming current human lifespans.<ref name="hein-pak-putz-revisited">{{cite journal |last1=Hein |first1=Andreas M. |last2=Pak |first2=Mikhail |last3=Pütz |first3=Daniel |last4=Bühler |first4=Christian |last5=Reiss |first5=Philipp |title=World ships—architectures & feasibility revisited |journal=Journal of the British Interplanetary Society |date=2012 |volume=65 |issue=4 |page=119|url=https://www.researchgate.net/publication/236177990 }}</ref>
* A [[sleeper ship]], where most or all of the crew spend the journey in some form of [[hibernation]] or [[suspended animation]], allowing some or all to reach the destination.<ref>{{cite news|title=Sleeper spaceship could carry first humans to Mars in hibernation state
|first=Ben |last=Brumfield |date=7 October 2014 |url=https://www.cnn.com/2014/10/07/tech/innovation/mars-hibernation-flight/index.html |publisher=CNN|access-date=18 April 2025}}</ref>
* An [[embryo space colonization|embryo-carrying interstellar starship]] (EIS), much smaller than a generation ship or sleeper ship, transporting human [[embryo]]s or DNA in a frozen or dormant state to the destination. (Obvious biological and psychological problems in birthing, raising, and educating such voyagers, neglected here, may not be fundamental.)<ref name="Crowl, 2012">{{cite web|last=Crowl|first=Adam|title=Embryo Space Colonisation to Overcome the Interstellar Time Distance Bottleneck|url=http://www.jbis.org.uk/paper.php?p=2012.65.283|work=Journal of the British Interplnanetary Society, 65, 283-285, 2012|display-authors=etal}}</ref>
* A [[nuclear fusion]] or [[nuclear fission|fission]] powered ship (e.g. [[ion drive]]) of some kind, achieving velocities of up to perhaps 10% ''c''&nbsp; permitting one-way trips to nearby stars with durations comparable to a human lifetime.<ref>{{cite news|title=Nuclear Pulse Propulsion: Gateway to the Stars|date=27 March 2013 |first=Stan |last=Tackett |url=https://www.ans.org/news/article-1294/nuclear-pulse-propulsion-gateway-to-the-stars/ |publisher=American Nuclear Society|access-date=19 April 2025}}</ref>
* A [[Project Orion (nuclear propulsion)|Project Orion]]-ship, a nuclear-powered concept proposed by [[Freeman Dyson]] which would use [[nuclear bomb|nuclear explosions]] to propel a starship. A special case of the preceding nuclear rocket concepts, with similar potential velocity capability, but possibly easier technology.<ref>{{Cite web |title=The Case For Orion |url=https://www.spacedaily.com/news/nuclearspace-03h.html |access-date=2023-08-03 |website=www.spacedaily.com |archive-date=August 3, 2023 |archive-url=https://web.archive.org/web/20230803065646/https://www.spacedaily.com/news/nuclearspace-03h.html |url-status=live }}</ref>
* [[Solar sail|Laser propulsion]] concepts, using some form of beaming of power from the Solar System might allow a [[solar sail|light-sail]] or other ship to reach high speeds, comparable to those theoretically attainable by the fusion-powered electric rocket, above.<ref>{{cite journal|title=Roundtrip interstellar travel using laser-pushed lightsails |first=Robert L. |last=Forward |date=April 1984 |url=https://doi.org/10.2514/3.8632 |journal=Journal of Spacecraft|volume=21|number=2|access-date=19 April 2025}}</ref> These methods would need some means, such as supplementary nuclear propulsion, to stop at the destination, but a hybrid (light-sail for acceleration, fusion-electric for deceleration) system might be possible.
* [[Mind uploading|Uploaded human minds]] or [[artificial intelligence]] may be transmitted via radio or laser at light speed to interstellar destinations where [[self-replicating spacecraft]] have traveled subluminally and set up infrastructure and possibly also brought some minds. [[Extraterrestrial intelligence]] might be another viable destination.<ref>{{cite web|title= Uploaded e-crews for interstellar missions |date= 12 December 2012 |url= https://www.thekurzweillibrary.com/uploaded-e-crews-for-interstellar-missions |website= kurzweilai.net| access-date= 19 April 2025}}</ref>

====Intergalactic travel====
{{Main|Intergalactic travel}} 
[[File:Interstellar vessel of Island One size, ion-driven, Don Davis, 1977.gif|thumb|upright=1.2|Proposed interstellar vessel based on [[Gerard K. O'Neill]]'s Island One version of [[Bernal sphere]] space habitat]]
The distances between galaxies are on the order of a million times farther than those between the stars, and thus intergalactic colonization would involve voyages of millions of years via special self-sustaining methods.<ref name="burruss">{{cite journal | first1 = Robert Page | last1 = Burruss | first2= J. | last2= Colwell | title = Intergalactic Travel: The Long Voyage From Home | journal = The Futurist | date=September–October 1987 | volume= 21 | issue= 5 | pages = 29–33}}</ref><ref>{{cite journal | author= Fogg, Martyn | title= The Feasibility of Intergalactic Colonisation and its Relevance to SETI | journal= Journal of the British Interplanetary Society | volume= 41 | number= 11 | date= November 1988 | pages= 491–496 | url= https://www.academia.edu/4166742 | bibcode= 1988JBIS...41..491F }}</ref><ref>{{cite journal | author= Armstrong, Stuart | author2= Sandberg, Anders | url= http://www.fhi.ox.ac.uk/intergalactic-spreading.pdf | title=Eternity in six hours: intergalactic spreading of intelligent life and sharpening the Fermi paradox | journal= Acta Astronautica | year= 2013 | volume= 89 | pages= 1–13 | publisher= Future of Humanity Institute, Philosophy Department, Oxford University| doi= 10.1016/j.actaastro.2013.04.002 | bibcode= 2013AcAau..89....1A }}</ref>