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Evolution of the number of communicative civilizations in the Galaxy: implications on Fermi paradox

Published online by Cambridge University Press:  23 April 2020

Giorgio Spada Open the ORCID record for Giorgio Spada [Opens in a new window]  and
Daniele Melini
Giorgio Spada*
Affiliation:
Dipartimento di Scienze Pure e Applicate (DiSPeA), Università di Urbino ‘Carlo Bo’, Urbino, Italy
Daniele Melini
Affiliation:
Istituto Nazionale di Geofisica e Vulcanologia (INGV), Roma, Italy
*
Author for correspondence: Giorgio Spada, E-mail: giorgio.spada@gmail.com
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Abstract

It has been recently proposed DeVito [(2019) On the meaning of Fermi's paradox. Futures, 389–414] that a minimal number of contacts with alien radio-communicative civilizations could be justified by their logarithmically slow rate of growth in the Galaxy. Here we further develop this approach to the Fermi paradox, with the purpose of expanding the ensemble of the possible styles of growth that are consistent with the hypothesis of a minimal number of contacts. Generalizing the approach in DeVito (2019), we show that a logarithmic style of growth is still found. We also find that a style of growth following a power law would be admissible, however characterized by an exponent less than one, hence describing a sublinear increase in the number of communicative civilizations, still qualitatively in agreement with DeVito (2019). No solutions are found indicating a superlinear increase in the number of communicative civilizations, following for example an exponentially diverging law, which would cause, in the long run, an unsustainable proliferation. Although largely speculative, our findings corroborate the idea that a sublinear rate of increase in the number of communicative civilizations in the Galaxy could constitute a further resolution of Fermi paradox, implying a constant and minimal – but not zero – number of contacts.

Keywords

alien civilizationsFermi paradoxpopulation dynamics
Type
Research Article
Information
International Journal of Astrobiology , Volume 19 , Issue 4 , August 2020 , pp. 314 - 319
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Copyright
Copyright © The Author(s) 2020. Published by Cambridge University Press

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