Editing Fermi paradox (section)

=== Grabby Aliens ===
{{Main|Quiet and loud aliens}}
In 2021, the concepts of quiet, loud, and grabby aliens were introduced by Hanson ''et al.'' The possible "loud" aliens [[Space colonization|expand rapidly]] in a highly detectable way throughout the universe and endure, while "quiet" aliens are hard or impossible to detect and eventually disappear. "Grabby" aliens prevent the emergence of other civilizations in their [[sphere of influence]], which expands at a rate near the speed of light. The authors argue that if loud civilizations are rare, as they appear to be, then quiet civilizations are also rare. The paper suggests that humanity's existing stage of technological development is relatively early in the potential timeline of intelligent life in the universe, as loud aliens would otherwise be observable by astronomers.<ref>{{Cite journal |last1=Hanson |first1=Robin |last2=Martin |first2=Daniel |last3=McCarter |first3=Calvin |last4=Paulson |first4=Jonathan |date=November 30, 2021 |title=If Loud Aliens Explain Human Earliness, Quiet Aliens Are Also Rare |journal=The Astrophysical Journal |language=en |volume=922 |issue=2 |pages=182 |doi=10.3847/1538-4357/ac2369 |doi-access=free |arxiv=2102.01522 |bibcode=2021ApJ...922..182H |issn=0004-637X}}</ref><ref>{{Cite web |title=Grabby Aliens – a simple model by Robin Hanson |url=https://grabbyaliens.com/ |access-date=2024-06-29 |website=grabbyaliens.com}}</ref>

Earlier in 2013, Anders Sandberg and Stuart Armstrong examined the potential for intelligent life to spread [[Intergalactic travel|intergalactically]] throughout the universe and the implications for the Fermi Paradox. Their study suggests that with sufficient energy, intelligent civilizations could potentially colonize the entire Milky Way galaxy within a few million years, and spread to nearby galaxies in a timespan that is cosmologically brief. They conclude that intergalactic colonization appears possible with the resources of a [[Planetary system|single solar system]] and that intergalactic colonization is of comparable difficulty to interstellar colonization, and therefore the Fermi paradox is much sharper than commonly thought.<ref>{{Cite journal |last1=Armstrong |first1=Stuart |last2=Sandberg |first2=Anders |date=2013-08-01 |title=Eternity in six hours: Intergalactic spreading of intelligent life and sharpening the Fermi paradox |url=https://www.sciencedirect.com/science/article/pii/S0094576513001148 |journal=Acta Astronautica |volume=89 |pages=1–13 |doi=10.1016/j.actaastro.2013.04.002 |bibcode=2013AcAau..89....1A |issn=0094-5765}}</ref>