In the Drake equation (Number of Civilizations = NHP × flife × fciv × fnow), what do we mean by fnow?
A)the fraction of civilizations in the universe that currently are sending messages to us
B)the fraction of planets with civilizations at the present time (as opposed to only in the past or future)
C)the fraction of planets in the galaxy on which a civilization could theoretically develop right now
D)the fraction of all species ever to exist that we currently are aware of

Question

Quizplus · Accepted Answer

fnow refers to the fraction of planets with civilizations at the present time, as opposed to only in the past or future. It takes into account the lifespan of civilizations and the likelihood that they exist in the current era.

In the Drake Equation (Number of Civilizations = NHP ×