Intergalactic travel

Intergalactic travel is the hypothetical travel between galaxies. Because the Milky Way and its closest neighbors are separated by millions of light-years, any such venture would also require millions of years based on current physics. Thus, intergalactic travel is impossible within the human lifetime. 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.

Possible methods

Hypervelocity stars

Theorized in 1988,^[1] and observed in 2005,^[2] hypervelocity stars move faster than the escape velocity of the Milky Way, and are traveling out into intergalactic space.^[3] 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 some 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.^[4] Intergalactic travel using these stars would involve entering into an orbit around them and waiting for them to reach another galaxy.^[5]^[6]

Time dilation

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.^[7] 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.^[8]

Superluminal Methods

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.^[9]

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.^[10]

References

^ Hills, J. G. (1988). "Hyper-velocity and tidal stars from binaries disrupted by a massive Galactic black hole". Nature. 331 (6158): 687–689. Bibcode:1988Natur.331..687H. doi:10.1038/331687a0. S2CID 4250308.
^ Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J.; Kurtz, Michael J. (2005). "Discovery of an Unbound Hypervelocity Star in the Milky Way Halo". Astrophysical Journal. 622 (1): L33–L36. arXiv:astro-ph/0501177. Bibcode:2005ApJ...622L..33B. doi:10.1086/429378. S2CID 14322324.
^ "The Hyper Velocity Star Project: The stars". The Hyper-Velocity Star Project. 6 September 2009. Retrieved 20 September 2014.
^ Watzke, Megan (28 November 2007). "Chandra discovers cosmic cannonball". Newswise.
^ Villard, Ray (24 May 2010). "The Great Escape: Intergalactic Travel is Possible". Discovery News. Archived from the original on 14 November 2012. Retrieved October 18, 2010.
^ Gilster, Paul (26 June 2014). "Intergalactic Travel via Hypervelocity Stars". centauri-dreams.org. Retrieved 16 September 2014.
^ Gilster, Paul (25 June 2014). "Sagan's Andromeda Crossing". centauri-dreams.org. Retrieved 16 September 2014.
^ "The Relativistic Rocket". math.ucr.edu. Retrieved 4 April 2018.
^ Alcubierre, Miguel (1994). "The warp drive: hyper-fast travel within general relativity". Classical and Quantum Gravity. 11 (5): L73–L77. arXiv:gr-qc/0009013. Bibcode:1994CQGra..11L..73A. doi:10.1088/0264-9381/11/5/001. S2CID 4797900.
^ Matthews, Robert (20 December 2019). "Wormholes: Could we travel through a black hole into another galaxy?". Sciencefocus.com. Retrieved 13 June 2021.

Notes

[1] Hills, J. G. (1988). "Hyper-velocity and tidal stars from binaries disrupted by a massive Galactic black hole". Nature. 331 (6158): 687–689. Bibcode:1988Natur.331..687H. doi:10.1038/331687a0. S2CID 4250308.

[HVS1-2] Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J.; Kurtz, Michael J. (2005). "Discovery of an Unbound Hypervelocity Star in the Milky Way Halo". Astrophysical Journal. 622 (1): L33–L36. arXiv:astro-ph/0501177. Bibcode:2005ApJ...622L..33B. doi:10.1086/429378. S2CID 14322324.

[3] "The Hyper Velocity Star Project: The stars". The Hyper-Velocity Star Project. 6 September 2009. Retrieved 20 September 2014.

[4] Watzke, Megan (28 November 2007). "Chandra discovers cosmic cannonball". Newswise.

[5] Villard, Ray (24 May 2010). "The Great Escape: Intergalactic Travel is Possible". Discovery News. Archived from the original on 14 November 2012. Retrieved October 18, 2010.

[6] Gilster, Paul (26 June 2014). "Intergalactic Travel via Hypervelocity Stars". centauri-dreams.org. Retrieved 16 September 2014.

[7] Gilster, Paul (25 June 2014). "Sagan's Andromeda Crossing". centauri-dreams.org. Retrieved 16 September 2014.

[8] "The Relativistic Rocket". math.ucr.edu. Retrieved 4 April 2018.

[Christopher_Pike-9] Alcubierre, Miguel (1994). "The warp drive: hyper-fast travel within general relativity". Classical and Quantum Gravity. 11 (5): L73–L77. arXiv:gr-qc/0009013. Bibcode:1994CQGra..11L..73A. doi:10.1088/0264-9381/11/5/001. S2CID 4797900.

[10] Matthews, Robert (20 December 2019). "Wormholes: Could we travel through a black hole into another galaxy?". Sciencefocus.com. Retrieved 13 June 2021.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

v t e Space colonization
Core concepts	Interplanetary spaceflight Interstellar travel Intergalactic travel Planetary habitability Space and survival Space settlement Terraforming
Space habitats	Bishop Ring McKendree cylinder O'Neill cylinder Stanford torus
Colonization targets	Lagrange points Solar System Mercury Venus Mars Asteroids mining Moon Titan Trans-Neptunian objects Free space
Terraforming targets	Mars Venus Europa
Organizations	Mars Society NASA National Space Society SpaceX The Planetary Society