The Number Of Possible CETIs Within Our Galaxy And The Communication Probability Among These CETIs

As the only known intelligent civilization, human beings are always curious about the existence of other communicating extraterrestrial intelligent civilizations (CETIs).

Based on the latest astrophysical information, we carry out Monte Carlo simulations to estimate the number of possible CETIs within our Galaxy and the communication probability among them. Two poorly known parameters have a great impact on the results.

One is the probability of life appearing on terrestrial planets and eventually evolving a into CETI (fc), and the other determines at what stage of their host star’s evolution CETIs would be born (F). In order to ensure the completeness of the simulation, we consider a variety of combinations of fc and F. Our results indicate that for optimistic situations (e.g. F=25% and fc=0.1%), there could be 42777+267−369 CETIs and they need to survive for 3+17−2 yr (2000+2000−1400 yr) to achieve one-way communication (two-way communication). In this case, human beings need to survive 0.3+0.6−0.298 Myr to receive one alien signal.

For pessimistic situations (e.g. F=75% and fc=0.001%), only 111+28−17 CETIs could be born and they need to survive for 0.8+1.2−0.796 Myr (0.9+4.1−0.88 Myr) to achieve one-way communication (two-way communication). In this case, human beings need to survive 50+250−49.6 Myr to receive one signal from other CETIs. Our results may quantitatively explain why we have not detected any alien signals so far. The uncertainty of the results has been discussed in detail and would be alleviated with the further improvement of our astronomical observation ability in the future.

Wenjie Song, He Gao

Comments: Published in ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Popular Physics (physics.pop-ph)
Cite as: arXiv:2204.05479 [astro-ph.EP] (or arXiv:2204.05479v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2204.05479
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Related DOI:
https://doi.org/10.3847/1538-4357/ac561d
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Submission history
From: He Gao
[v1] Tue, 12 Apr 2022 02:11:20 UTC (352 KB)
https://arxiv.org/abs/2204.05479
Astrobiology, SETI