[ExI] Drake Equation Musings

Rafal Smigrodzki rafal.smigrodzki at gmail.com
Mon May 16 02:16:43 UTC 2016

On Sun, May 15, 2016 at 3:35 PM, Anders Sandberg <anders at aleph.se> wrote:

> The fact that we do not see primitive aliens nearby nor supercivilizations
> far away serves to update our initial guesses in such a way that a past
> great filter (low probability of life, complex life, or intelligence) is
> more likely than a future great filter (low probability of communication
> ability or longevity).

### I find it fascinating that looking at the universe means an analysis
stretched in time. Anything outside of our galaxy supercluster is already
hundreds of millions of years back in time. If there is a time-dependent
process that has to finish before technogenesis, then looking outside
Laniakea might mean observing galaxies at the time when were still too
young to have star extinction bubbles, even if in fact all the stars there
were already eaten by aliens.

The only part of the universe which we see in close to real time is our
direct neighborhood, so we only need to explain absence of civs here, not
in the whole universe (of which we do not have current images). Our
supercluster has only 10e15 solar masses, which is 10e-7th part of the
visible universe (if the Wikipedia article is correct). So if the
likelihood of technogenesis at this time since the big bang is on the order
of 10e-15 per solar mass, then observing just one civ would not be

Is the technogenesis likelihood of 10e-15 per solar mass a reasonable

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