y Way galaxy. The solution was an equation, now known as the Green Bank equation, though also widely referred to as the 'Drake equation' after Frank Drake the astronomer who proposed the core of the expression. The equation seeks to quantify the number, N which is the number of technical civilizations in our galaxy.4 The equation is as followsN = R fp np fl fi fc Lwhere:R = mean rate of star formation in the Milky Wayfp = the fraction of those stars which form planetary systemsnp = the number of planets in those systems which are ecologically suitable for life forms to evolvefl = the number of those planets on which life forms do actually developfi = the number of those life forms which evolve to an intelligent formfc = the number of advanced intelligent life forms which develop the capability of interstellar radio communicationL = the lifetime of those advanced technically advanced civilizationsValues for most of these factors are far from being certain, but some have been estimated. In fact, only the value of L has been altered to any significant degree since the SETI conference in 1961. The estimations include:R = 10/yearfp = 0.5np = 2fl = 1fi fc = 0.01L = 34 So even if these estimates vary, the number N of technical civilizations only present in our galaxy equals 3.4. If technically advanced civilizations were to exist and have lifetimes of a few thousand years then a galactic community appears a distinct possibility. Other researchers and working groups, for example Sagan5 , have examined the question and concluded there could be 106 technologically advanced extraterrestrial civilizations in the galaxy. That’s 106 civilizations in our relatively small galaxy alone! Hubble’s Deep Field (taken near Ursa Major in the Big Dipper constellation) has found more than 1500 individual galaxies. For just this tiny region of space (about 2.6 (arc-min)2), N would equal 159,000 civilizations. In addition to these encour...
