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{{short description|Hypothetical travel between galaxies}} |
{{short description|Hypothetical travel between galaxies}} |
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{{Spaceflight sidebar}} |
{{Spaceflight sidebar}} |
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⚫ | '''Intergalactic travel''' is the hypothetical [[Human spaceflight|crewed]] or [[Uncrewed spacecraft|uncrewed]] travel between [[galaxy|galaxies]]. Due to the enormous distances between the [[Milky Way]] and even its [[List of nearest galaxies|closest neighbors]]—tens of thousands to millions of [[light-year]]s—any such venture would be far more technologically and financially demanding than even [[interstellar travel]]. Intergalactic distances are roughly a hundred-thousandfold (five orders of magnitude) greater than their interstellar counterparts.{{efn| Between small galaxies, which are the majority of galaxies, distances are typically a few hundred thousand light-years. Between large galaxies like the Milky Way and M31, they are typically a few million light-years.}} |
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[[File:LH 95.jpg|thumb|upright=1.5|The [[Large Magellanic Cloud]], a [[dwarf galaxy]]. At a distance of 163,000 light-years, it is the third closest galaxy to the Milky Way.]] |
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⚫ | '''Intergalactic travel''' is the hypothetical [[Human spaceflight|crewed]] or [[Uncrewed spacecraft|uncrewed]] travel between [[galaxy|galaxies]]. Due to the enormous distances between the [[Milky Way]] and even its [[List of nearest galaxies|closest neighbors]]—tens of thousands to millions of [[light-year]]s—any such venture would be far more technologically demanding than even [[interstellar travel]]. Intergalactic distances are roughly a hundred-thousandfold (five orders of magnitude) greater than their interstellar counterparts.{{efn| Between small galaxies, which are the majority of galaxies, distances are typically a few hundred thousand light-years. Between large galaxies like the Milky Way and M31, they are typically a few million light-years.}} |
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The technology required to travel between galaxies is far beyond humanity's present capabilities, and currently only the subject of speculation, hypothesis, and [[science fiction]]. |
The technology required to travel between galaxies is far beyond humanity's present capabilities, and currently only the subject of speculation, [[hypothesis]], and [[science fiction]]. |
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However, theoretically speaking, there is nothing to conclusively indicate that intergalactic travel is impossible. There are several hypothesized methods of carrying out such a journey, and to date several academics have studied intergalactic travel in a serious manner.<ref name="burruss">{{cite journal | |
However, theoretically speaking, there is nothing to conclusively indicate that intergalactic travel is impossible. There are several hypothesized methods of carrying out such a journey, and to date several academics have studied intergalactic travel in a serious manner.<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> |
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==Possible methods== |
==Possible methods== |
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| issue = 6158 |
| issue = 6158 |
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| pages = 687–689 | bibcode = 1988Natur.331..687H |
| pages = 687–689 | bibcode = 1988Natur.331..687H |
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| doi = 10.1038/331687a0 | url = https://zenodo.org/record/1233107 |
| doi = 10.1038/331687a0 | s2cid = 4250308 | url = https://zenodo.org/record/1233107 | url-access = | url-status = | archive-url = | archive-date = }}</ref> and observed in 2005,<ref name='HVS1'>{{cite journal |
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| first = Warren R. | last = Brown |author2=Geller, Margaret J. |author3=Kenyon, Scott J. |author4=Kurtz, Michael J. |
| first = Warren R. | last = Brown |author2=Geller, Margaret J. |author3=Kenyon, Scott J. |author4=Kurtz, Michael J. |
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| title = Discovery of an Unbound Hypervelocity Star in the Milky Way Halo | journal = Astrophysical Journal | year = 2005 |
| title = Discovery of an Unbound Hypervelocity Star in the Milky Way Halo | journal = Astrophysical Journal | year = 2005 |
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| volume = 622 |
| volume = 622 |
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| issue = 1 | pages = L33–L36 | bibcode = 2005ApJ...622L..33B |
| issue = 1 | pages = L33–L36 | bibcode = 2005ApJ...622L..33B |
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| doi = 10.1086/429378 |arxiv = astro-ph/0501177 }}</ref> [[hypervelocity stars]] move faster than the [[escape velocity]] of the Milky Way, and are traveling out into intergalactic space.<ref>{{cite news| url=http://hvsproject.blogspot.com/2009/09/hyper-velocity-star-project.html |
| doi = 10.1086/429378 |arxiv = astro-ph/0501177 | s2cid = 14322324 }}</ref> [[hypervelocity stars]] move faster than the [[escape velocity]] of the Milky Way, and are traveling out into intergalactic space.<ref>{{cite news| url=http://hvsproject.blogspot.com/2009/09/hyper-velocity-star-project.html |
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| title=The Hyper Velocity Star Project: The stars| publisher=The Hyper-Velocity Star Project| date=6 September 2009| access-date=20 September 2014}}</ref> There are several [[Stellar kinematics#Origin of hypervelocity stars|theories for their existence]]. One of the mechanisms would be that the [[supermassive black hole]] at the center of the [[Milky Way]] ejects stars from the galaxy at a rate of about one every hundred thousand years. Another theorized mechanism might be a supernova explosion in a binary system.<ref>{{cite news |
| title=The Hyper Velocity Star Project: The stars| publisher=The Hyper-Velocity Star Project| date=6 September 2009| access-date=20 September 2014}}</ref> There are several [[Stellar kinematics#Origin of hypervelocity stars|theories for their existence]]. One of the mechanisms would be that the [[supermassive black hole]] at the center of the [[Milky Way]] ejects stars from the galaxy at a rate of about one every hundred thousand years. Another theorized mechanism might be a supernova explosion in a binary system.<ref>{{cite news |
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| url=http://newswise.com/articles/view/535733/ |
| url=http://newswise.com/articles/view/535733/ |
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| title=Chandra discovers cosmic cannonball |
| title=Chandra discovers cosmic cannonball |
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| first=Megan | last=Watzke | date= 28 November 2007 |
| first=Megan | last=Watzke | date= 28 November 2007 |
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| publisher=Newswise }}</ref> Intergalactic travel using these stars would involve entering into an orbit around them and waiting for them to reach another galaxy.<ref>{{cite news| url=http://news.discovery.com/space/the-great-escape-intergalactic-travel-is-possible.html| title=The Great Escape: Intergalactic Travel is Possible| author=Villard, Ray| date=24 May 2010| publisher=Discovery News| access-date=October 18, 2010}}</ref><ref>{{cite news | author= Gilster, Paul | date= 26 June 2014 | url= http://www.centauri-dreams.org/?p=30936 | title= Intergalactic Travel via Hypervelocity Stars | website= centauri-dreams.org | access-date= 16 September 2014}}</ref> |
| publisher=Newswise }}</ref> Intergalactic travel using these stars would involve entering into an orbit around them and waiting for them to reach another galaxy.<ref>{{cite news| url=http://news.discovery.com/space/the-great-escape-intergalactic-travel-is-possible.html| title=The Great Escape: Intergalactic Travel is Possible| author=Villard, Ray| date=24 May 2010| publisher=Discovery News| access-date=October 18, 2010| archive-date=14 November 2012| archive-url=https://web.archive.org/web/20121114090512/http://news.discovery.com/space/the-great-escape-intergalactic-travel-is-possible.html| url-status=dead}}</ref><ref>{{cite news | author= Gilster, Paul | date= 26 June 2014 | url= http://www.centauri-dreams.org/?p=30936 | title= Intergalactic Travel via Hypervelocity Stars | website= centauri-dreams.org | access-date= 16 September 2014}}</ref> |
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===Artificially propelling a star=== |
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{{See also|Stellar engine}} |
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Another proposal is to [[Stellar engine#Class A .28Shkadov thruster.29|artificially propel a star]] in the direction of another galaxy.<ref>{{cite news| author=Gilster, Paul| date=27 June 2014| url=http://www.centauri-dreams.org/?p=30941| title=Stars as Stellar Engines| website= centauri-dreams.org | access-date=16 September 2014}}</ref><ref>{{cite news| author=Gilster, Paul| date=30 June 2014| url=http://www.centauri-dreams.org/?p=30948| title=Building the Bowl of Heaven| website= centauri-dreams.org | access-date=16 September 2014}}</ref> |
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===Time dilation=== |
===Time dilation=== |
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While it takes light approximately 2.54 million years to traverse the gulf of space between Earth and, for instance, the [[Andromeda Galaxy]], it would take a much shorter amount of time from the point of view of a traveler at close to the speed of light due to the effects of [[time dilation]]; the time experienced by the traveler depending both on velocity (anything less than the speed of light) and distance traveled ([[length contraction]]). Intergalactic travel for humans is therefore possible, in theory, from the point of view of the traveler.<ref>{{cite news| author=Gilster, Paul| date=25 June 2014| url=http://www.centauri-dreams.org/?p=30929| title=Sagan's Andromeda Crossing| website= centauri-dreams.org | access-date=16 September 2014}}</ref> For example, a rocket that accelerated at [[Standard gravity|standard acceleration due to gravity]] toward the Andromeda Galaxy and started to decelerate halfway through the trip would arrive in about 28 years, from the frame of reference of the observer.<ref>{{cite web|url=http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html|title=The Relativistic Rocket|website=math.ucr.edu|access-date=4 April 2018}}</ref> |
While it takes light approximately 2.54 million years to traverse the gulf of space between Earth and, for instance, the [[Andromeda Galaxy]], it would take a much shorter amount of time from the point of view of a traveler at close to the speed of light due to the effects of [[time dilation]]; the time experienced by the traveler depending both on velocity (anything less than the speed of light) and distance traveled ([[length contraction]]). Intergalactic travel for humans is therefore possible, in theory, from the point of view of the traveler.<ref>{{cite news| author=Gilster, Paul| date=25 June 2014| url=http://www.centauri-dreams.org/?p=30929| title=Sagan's Andromeda Crossing| website= centauri-dreams.org | access-date=16 September 2014}}</ref> For example, a rocket that accelerated at [[Standard gravity|standard acceleration due to gravity]] toward the Andromeda Galaxy and started to decelerate halfway through the trip would arrive in about 28 years, from the frame of reference of the observer.<ref>{{cite web|url=http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html|title=The Relativistic Rocket|website=math.ucr.edu|access-date=4 April 2018}}</ref> |
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===Superluminal Methods=== |
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===Possible faster-than-light methods=== |
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The [[Alcubierre drive]] is a hypothetical concept that is able to |
The [[Alcubierre drive]] is a hypothetical concept that is able to propel a spacecraft to speeds [[faster-than-light|faster than light]] (the spaceship itself would not move faster than light, but the space around it would). This could in theory allow practical intergalactic travel. There is no known way to create the space-distorting wave this concept needs to work, but the metrics of the equations comply with relativity and the limit of light speed.<ref name="Christopher Pike">{{cite journal|author=Alcubierre, Miguel|title=The warp drive: hyper-fast travel within general relativity|journal=[[Classical and Quantum Gravity]] |year=1994|volume=11|pages=L73–L77|doi=10.1088/0264-9381/11/5/001|arxiv = gr-qc/0009013 |bibcode = 1994CQGra..11L..73A|issue=5|s2cid=4797900}}</ref> |
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A [[wormhole]] is a hypothetical tunnel through space-time that would allow instantaneous intergalactic travel to the most distant galaxies even billions of light years away. Wormholes are allowed by [[general relativity]].<ref>{{cite web |url=https://www.sciencefocus.com/space/wormholes-could-we-travel-through-a-black-hole-into-another-galaxy/ |title=Wormholes: Could we travel through a black hole into another galaxy? |first1=Robert |last1=Matthews |date=20 December 2019 |publisher=Sciencefocus.com |access-date=13 June 2021 }}</ref> |
A [[wormhole]] is a hypothetical tunnel through space-time that would allow instantaneous intergalactic travel to the most distant galaxies even billions of light years away. Wormholes are allowed by [[general relativity]].<ref>{{cite web |url=https://www.sciencefocus.com/space/wormholes-could-we-travel-through-a-black-hole-into-another-galaxy/ |title=Wormholes: Could we travel through a black hole into another galaxy? |first1=Robert |last1=Matthews |date=20 December 2019 |publisher=Sciencefocus.com |access-date=13 June 2021 }}</ref> |
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==See also== |
==See also== |
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{{Portal|Spaceflight}} |
{{Portal|Spaceflight}} |
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* [[Galaxies in fiction]] |
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* [[Galaxy]] |
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* [[Intergalactic dust]] |
* [[Intergalactic dust]] |
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* [[Outer space#Intergalactic space|Intergalactic space]] |
* [[Outer space#Intergalactic space|Intergalactic space]] |
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* [[Interstellar travel]] |
* [[Interstellar travel]] |
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* [[Wormhole#Interuniversal_travel|Interuniversal travel]] |
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* [[Spaceflight]] |
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* [[ |
* [[Space travel in science fiction]] |
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* [[Uploaded astronaut]] |
* [[Uploaded astronaut]] |
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This article possibly contains original research. Please improve itbyverifying the claims made and adding inline citations. Statements consisting only of original research should be removed. (October 2017) (Learn how and when to remove this message)
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Intergalactic travel is the hypothetical crewedoruncrewed travel between galaxies. Due to the enormous distances between the Milky Way and even its closest neighbors—tens of thousands to millions of light-years—any such venture would be far more technologically and financially demanding than even interstellar travel. Intergalactic distances are roughly a hundred-thousandfold (five orders of magnitude) greater than their interstellar counterparts.[a]
The technology required to travel between galaxies is far beyond humanity's present capabilities, and currently only the subject of speculation, hypothesis, and science fiction.
However, theoretically speaking, there is nothing to conclusively indicate that intergalactic travel is impossible. There are several hypothesized methods of carrying out such a journey, and to date several academics have studied intergalactic travel in a serious manner.[1][2][3]
Theorized in 1988,[4] and observed in 2005,[5] hypervelocity stars move faster than the escape velocity of the Milky Way, and are traveling out into intergalactic space.[6] There are several theories for their existence. One of the mechanisms would be that the supermassive black hole at the center of the Milky Way ejects stars from the galaxy at a rate of about one every hundred thousand years. Another theorized mechanism might be a supernova explosion in a binary system.[7] Intergalactic travel using these stars would involve entering into an orbit around them and waiting for them to reach another galaxy.[8][9]
While it takes light approximately 2.54 million years to traverse the gulf of space between Earth and, for instance, the Andromeda Galaxy, it would take a much shorter amount of time from the point of view of a traveler at close to the speed of light due to the effects of time dilation; the time experienced by the traveler depending both on velocity (anything less than the speed of light) and distance traveled (length contraction). Intergalactic travel for humans is therefore possible, in theory, from the point of view of the traveler.[10] For example, a rocket that accelerated at standard acceleration due to gravity toward the Andromeda Galaxy and started to decelerate halfway through the trip would arrive in about 28 years, from the frame of reference of the observer.[11]
The Alcubierre drive is a hypothetical concept that is able to propel a spacecraft to speeds faster than light (the spaceship itself would not move faster than light, but the space around it would). This could in theory allow practical intergalactic travel. There is no known way to create the space-distorting wave this concept needs to work, but the metrics of the equations comply with relativity and the limit of light speed.[12]
Awormhole is a hypothetical tunnel through space-time that would allow instantaneous intergalactic travel to the most distant galaxies even billions of light years away. Wormholes are allowed by general relativity.[13]
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