Day after day, do you wonder and fret over why ET hasn't dropped by Earth yet?
Even within the confines of our own little Milky Way, you'd expect that we are not the only curd.
At least that's what I've long believed.
I may have been wrong. (Hey, it happens.)
Way back in 1961, radio astronomer Frank Drake doodled away for a bit and came up with a suppositional formula for estimating the number of technological civilizations that reside in our galaxy:
N = R fp ne fl fi fc LN is the number of communicative civilizations, R is the rate of formation of suitable stars, fp is the fraction of those stars with planets, ne is the number of Earth-like planets per solar system, fl is the fraction of planets with life, fi is the fraction of planets with intelligent life, fc is the fraction of planets with communicating technology, and L is the lifetime of communicating civilizations.
Cool bananas, we can work out the likelihood of other live forms loitering without intent somewhere in our neighborhood.
But things aren't so rosy when you work out "L" = lifetime of communicating civilizations.
Taking the only data we have - Earth - the lifetime of communicating civilizations is, on average, pitifully short, which is in itself a sad and sorry thing, but also bodes something less than perky in terms of getting one's act together for the time and trials needed for intergalactic travel.
Taking 60 Earth bound civilizations, including Sumeria, Mesopotamia, Babylonia, the eight dynasties of Egypt, the six civilizations of Greece, the Roman Republic and Empire, and others in the ancient world, plus various civilizations since the fall of Rome, such as the nine dynasties (and two republics) of China, four in Africa, three in India, two in Japan, six in Central and South America, and six modern states of Europe and America, apparently they endured for, in total, 25,234 years. Making for an "L" of a paltry 420.6 years - that is, "L" being years from inception to demise, or to the present.
Civilizations, in other words, aren't exactly robust entities.
But it gets worse.
More modern and technological societies have an even shorter L, with the 28 civilizations since the fall of Rome averaging only 304.5 years.
If we toss these figures into the Drake equation, this is what we get: where L = 420.6 years, N = 3.36 civilizations in our galaxy; where L = 304.5 years, N= 2.44 civilizations in our galaxy.
And that folks, might explain why we're still waiting for something to wipe its feet on the Earthly extraterrestrial visitor's welcome mat.