R* x FP x Ne x FL x FI x FC x L [Interlude] [Chorus] Are We Alone? Are humans unique and alone in the vast universe? [Verse 1] N : The number of civilizations in the Milky Way galaxy whose electromagnetic emissions are detectable. R* : The rate of formation of stars suitable for the development of intelligent life (number per year). fp : The fraction of those stars with planetary systems. ne : The number of planets, per solar system, with an environment suitable for life. [Chorus] Are We Alone? Are humans unique and alone in the vast universe? [Verse 2] fl : The fraction of suitable planets on which life actually appears. fi : The fraction of life bearing planets on which intelligent life emerges. fc : The fraction of civilizations that develop a technology that produces detectable signs of their existence. L : The average length of time such civilizations produce such signs (years). [Verse 2] fl : The fraction of suitable planets on which life actually appears. fi : The fraction of life bearing planets on which intelligent life emerges. fc : The fraction of civilizations that develop a technology that produces detectable signs of their existence. L : The average length of time such civilizations produce such signs (years). [Chorus] Are We Alone? Are humans unique and alone in the vast universe? [Guitar solo] [Instrumental interlude] [Chorus] Are We Alone? Are humans unique and alone in the vast universe? [End] [Guitar solo] [Instrumental] [Chorus] Are We Alone? Are humans unique and alone in the vast universe? [End]
