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Drake Equation: Difference between revisions
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* formulated in 1961 by Dr. Frank Drake | * formulated in 1961 by Dr. Frank Drake | ||
N = R* | <blockquote>'''''<big>N = R<sub>*</sub> • ƒ<sub>p</sub> • n<sub>e</sub> • ƒ<sub>1</sub> • ƒ<sub>i</sub> • ƒ<sub>c</sub> • L</big>''''' | ||
'''''<big>R<sub>*</sub></big>''''' = the average rate of star formation in our Galaxy | |||
'''''<big>ƒ<sub>p</sub></big>''''' = the fraction of those stars that have planets | |||
'''''<big>n<sub>e</sub></big>''''' = the average number of planets that can potentially support life per star that has planets | |||
'''''<big>ƒ<sub>1</sub></big>''''' = the fraction of planets that could support life that actually develop life at some point | |||
'''''<big>ƒ<sub>i</sub></big>''''' = the fraction of planets with life that actually go on to develop intelligent life (civilizations) | |||
'''''<big>ƒ<sub>c</sub></big>''''' = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space | |||
'''''<big>L</big>''''' = the length of time for which such civilizations release detectable signals into space | |||
from [[wikipedia:Drake_equation#Equation|Drake Equation (wikipedia)]]</blockquote> | |||
* Drake's estimate: | |||
<blockquote>'''''R''<sub>∗</sub>''' = 1 yr<sup>−1</sup> (1 star formed per year, on the average over the life of the galaxy; this was regarded as conservative) | |||
'''''f''<sub>p</sub>''' = 0.2 to 0.5 (one fifth to one half of all stars formed will have planets) | |||
'''''n''<sub>e</sub>''' = 1 to 5 (stars with planets will have between 1 and 5 planets capable of developing life) | |||
'''''f''<sub>l</sub>''' = 1 (100% of these planets will develop life) | |||
'''''f''<sub>i</sub>''' = 1 (100% of which will develop intelligent life) | |||
'''''f''<sub>c</sub>''' = 0.1 to 0.2 (10–20% of which will be able to communicate) | |||
'''''L''''' = 1000 to 100,000,000 communicative civilizations (which will last somewhere between 1000 and 100,000,000 years) | |||
= between 1000 and 100,000,000 planets with civilizations in the Milky Way Galaxy</blockquote> | |||
* [[wikipedia:Fermi_paradox|Fermi paradox]] | |||
** in 1950, physicist Enrico Fermi casually thought up the paradox that, if extraterrestrial life is so probable (likely), then we would have encountered it by now | |||
*** "But where is everybody?" Fermi asked | |||
* a 2018 paper called, "[https://arxiv.org/abs/1806.02404 Dissolving the Fermi Paradox]" concluded that the probability of intelligent life outside of earth is unlikely | |||
** the authors incorporated additional models of chemical and genetic transitions into life | |||
*** thus we should not be surprised by Fermi's conclusion, "But where is everybody?" | |||
</blockquote> | |||
[[Category:Cool stuff]] | [[Category:Cool stuff]] | ||