Do you believe in possibility of life in other galaxies?

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There are three main categories of statistically independent signals (isotropic, narrow beams, and rotating beacons) needed to calculate the average number NG of emission processes present in the Galaxy and the average number of them crossing Earth, k¯⁠, which is a number amenable to statistical estimation from direct observations. We show that k¯ coincides with ND (Drake's number*) only for isotropic emissions, while k¯ can be orders of magnitude smaller than ND in the case of highly directional signals. We further show that while ND gives the number of emissions being released at the present time, NG (Galactic number) also considers the signals from no longer active emitters but whose emissions still occupy the Galaxy because they still remain in transit at light speed. We find that as long as the average longevity of the emissions is shorter than about 105 yr, NG is fully determined by the rate of emissions alone, in contrast to ND and k¯ which also depend on the emission longevity. Finally, using analytic formulas of NG, ND, and k¯ isn be determined for each type of emission process considered, and a comprehensive overview of the values of these quantities can possibly achieve the functions of the emission birthrates, longevities, and directionality of the civilizations sending these signals..

The contribution of each type of emission to the total number of processes crossing Earth's orbit strongly depends on the relative abundance of signal types and their longevities. As shown in the chart below, the contribution to k of isotropic processes and lighthouses in 2D would likely dominate over other types of emissions of similar birthrates.

Screen Shot 2021-07-16 at 2.15.30 PM.png

Under the assumption that the emission birthrates did not change during the recent history of the Galaxy, we have shown that k = ND only for isotropic processes and for emissions originating from rotating beacons sweeping the galactic disk. In all the other cases considered (beamed signals directed randomly and lighthouses with tilted rotation axis) k can be orders of magnitudes smaller than the Drake number, showing that the historic ND may largely overestimate the possible occurrence of signals that can be detected.

See: https://academic.oup.com/mnras/article-abstract/500/2/2278/5960163?redirectedFrom=fulltext

See: https://arxiv.org/pdf/2011.14147.pdf

* Drake's number:
{\displaystyle N=R_{*}\cdot f_{\mathrm {p} }\cdot n_{\mathrm {e} }\cdot f_{\mathrm {l} }\cdot f_{\mathrm {i} }\cdot f_{\mathrm {c} }\cdot L}

where:
N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);
and
R∗ = the average rate of star formation in our galaxyfp = the fraction of those stars that have planetsne = the average number of planets that can potentially support life per star that has planetsfl = the fraction of planets that could support life that actually develop life at some pointfi = the fraction of planets with life that actually go on to develop intelligent life (civilizations) fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space L = the length of time for which such civilizations release detectable signals into space.

While Drake's equation was a superb starting point when it was first presented in 1961 by Frank Drake to estimate the number of galactic civilizations, it has been fine tunes since then, most notably and recently by Claudio Grimaldi in his paper of 28 November 2020 "Demography of galactic technosignatures". He fully fleshes out his additions, such as failed or destroyed civilizations whose radio output is still traveling across the galaxy at the speed of light whose messages may cross the Earth's orbit at some future time. I find these ideas fascinating. As far as reaching the seat of these broadcasts, is it even possible - physically or financially to do so? Once sent, would we ever expect to hear from these pioneers again?
Hartmann352
 
Jun 16, 2021
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There is one theory about Proxima B :). I have heard some interesting ideas about Proxima B and some scientists are convinced that this exoplanet might be the second Earth. What do you think about that?
 
Jun 16, 2021
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Proxima B is one thing and one thing only and that thing is that Proxima B is the closest planet to Earth outside of our system. There is no reason to think that this makes it life supporting
Thank you for that information. But many people assume that Proxima B might have the same Environment as Earth. I guess we will have more detailed information when the James Webb Space Telescope will be launched
 

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