Of course, if you want to get scientific, there is always the Drake Equation....
N= [r* x fp x ne x fl x fi x fc] L
where:
N= number of possible civilizations to communicate with
R* = is the rate at which stars capable of sustaining like are formed
fp = the fraction of these stars which have planets
ne = the number of planets similar to Earth in the planetary system
fl = the fraction of the Earth-like planets that hold life
fi = the fraction of life that becomes an intelligent civilization
fc = the fraction intelligent civilizations that attempt to communicate
L= the number of years the civilization remains able to communicate.
N= [r* x fp x ne x fl x fi x fc] L
where:
N= number of possible civilizations to communicate with
R* = is the rate at which stars capable of sustaining like are formed
fp = the fraction of these stars which have planets
ne = the number of planets similar to Earth in the planetary system
fl = the fraction of the Earth-like planets that hold life
fi = the fraction of life that becomes an intelligent civilization
fc = the fraction intelligent civilizations that attempt to communicate
L= the number of years the civilization remains able to communicate.