The Drake Equation:
N = R * f_p n_e f_l f_i f_c L B_s
N: Number of communicating civilizations in our galaxy
n_e: Number of life-supporting planets per solar system
f_i: Probability that life on a planet becomes intelligent
B_s: Amount of bullshit you're willing to buy from Francis Drake
{{ title text: But seriously, there's loads of intelligent life. It's just not screaming constantly in all directions on the handful of frequencies we search. }}