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| N | = | R* | ∙ | fp | ∙ | ne | ∙ | fl | ∙ | fi | ∙ | fc | ∙ | L | ||
N: The number of civilisations in our galaxy with which communication might be possible.
R*: The average rate of star formation in our galaxy.
fp: The fraction of stars which have planets.
ne: The average number of potentially life-supporting planets per star which has planets.
fl: The fraction of potentially life-supporting planets on which life does arise.
fi: The fraction of life-hosting planets on which intelligent life arises.
fc: The fraction of civilisations which exhibit a detectable technosignature.
L: The length of time for which these civilisations exhibit a detectable technosignature.