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Therefore the math is simple: There are about 10,000,000,000,000,000,000,000 = $10^{22}$ planets out there.   This number is extremely large, apparently larger than the\href{http://www.npr.org/blogs/krulwich/2012/09/17/161096233/which-is-greater-the-number-of-sand-grains-on-earth-or-stars-in-the-sky}{ number of grains of sand} found in every beach and every desert on Earth.  If you got this far I bet you are mind is racing trying to deal with the implications of this notion. And of course you are not alone. How But how  many of these planets host life? And in particular,\textbf{ how many planets host intelligent life we might be able to communicate with}? In order to estimate the number of technological civilizations that might exist among the stars, in 1961 Frank Drake proposed the following simple equation   $N = R \times f_p \times n_e \times f_l \times f_i \times f_c \times L$  It is a product of factors giving the number $N$ of civilizations in the Milky Way Galaxy with whom we could make contact. The terms in the equation are: