The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.\n\nAnswer this question: the drake equation is used to predict the number of?
Think hard. Detailed solution:
active , communicative extraterrestrial civilizations in the Milky Way galaxy
The relevant information is: The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.

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The answer: active , communicative extraterrestrial civilizations in the Milky Way galaxy