What if all the humans, barely a few thousands, died all 70 thousand years ago? Will the Earth be devoid of intelligence? So when on this futurism article they suggested that we may not be alone on Earth after all, I decided to play along. First of course I tried to locate the scientific source. Unfortunately this time I didn’t find it. Probably it was lead by Avi Loeb, the Harvard astrophysicist who said that Ommaumma, the first interestelar object detected, was probably artificial. But allow me to engage. We all know – or assume – that our planet is quite old in comparison with mankind, and we can compare its age with the time it took us to go from the deserts to the cities, so to say. Barely a hundred thousand years, a glimpse if we compare it with the time the dinosaurs rule the Earth. The dinosaurs time itself is also not spectacular in cosmic terms. So here’s the thing. We could divide the age of the Earth, 4.54 × 109 years, on intervals of 100.000 years. To be fair, let’s start counting after the multicellular life is supposed to appear, which leaves us “only” with 1.5 × 109 years. That will be 15000 civilisation intervals. Don’t forget I’m here being quite rough, so I’ll divide the number by two – extending de facto mankind history to 200.000 years. We have now 7500 civilisation intervals. There’s no civilisation after civilisation, so now we need to add, a la Drake, some probability factors. Drake’s equation is like this:
We want to know N, the number of cryptoterrestrial civilisations. Let’s “map” the other values
- R∗ = is going to be the number of civilisation intervals = 75000
- fp = the probability of having moving life (no tree civilisation) = 0.5
- ne = the probability of having the right challenge (no challenge, no evolution) = 0.2
- fl = the fraction of consecutive life changes (so that we end on intelligence) = 0.1
- fi = the fraction of intelligent societies = 0.1
- fc = the fraction of civilisations with technology = 0.1
- L = the length of time for which such civilisations lasted (one for simplicity) = 1 [
After my above leaps of faith (sorry, no science here) my final number is N = 7,5. Which is a big one, if you ask me. So hello, lizard people! Hope you enjoyed watching us…
Bonus: link to An Astrobiology Introductory Course. PhD level needed.
Bits and Dragons 
Fascinating thought! I think. Sorry, numbers are not my strength, and I certainly don’t have a PhD, but the idea of so many civilizations is quite thought provoking. I sometimes find myself wondering what might come after us.
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If we believe what Lovecraft says, there will be giant smart scarabs. Or something like that 😛
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