[ExI] Drake Equation Musings

Anders Sandberg anders at aleph.se
Sun May 15 09:06:06 UTC 2016


It is IMHO not a very impressive paper. Basically their argument is 
"Look, the probability per star needed to get an empty universe is 
really low, so a priori we should expect it to be higher." My own 
upcoming paper shows that if you do the probabilities right you can 
easily get empty universes given what we know.

(The quick of it: people assume some key Drake equation parameters must 
lie in a far smaller range than they are allowed to by our actual 
knowledge, and this produces over-optimistic estimates. When you update 
on the empty sky, it makes the past great filter more likely than a 
future great filter.)

On 2016-05-15 10:38, BillK wrote:
> A Less Bleak Lesson from the Silent Universe
> May 7, 2016 by Rick Searle
>
> <https://utopiaordystopia.com/2016/05/07/a-less-bleak-lesson-from-the-silent-universe/>
>
> Quotes:
>
> The astronomers Adam Frank and Woodruff Sullivan have an interesting
> paper out where they’ve essentially flipped the Drake Equation on its
> head. If that equation is meant to give us some handle on the
> probability that there are aliens out there, Frank and Sullivan have
> used the plethora of exoplanets discovered since the launch of the
> Kepler space telescope to calculate the chance that, so far, we alone
> have been the only advanced civilization in the 13.7 billion year
> history of the universe. I won’t bore you with actual numbers, but
> they estimate the chance that we’re the first and only is 1 in 10
> billion trillion. I shouldn’t have to tell you that is a really,
> really small number.
> ----
> We do have pretty good evidence of at least one thing: if there are,
> or have been, technological civilizations out there none is using the
> majority of its galaxy’s energy. As Jim Wright at Penn State who
> conceived of the recent scanning 100,000 galaxies that had been
> observed by NASA’s Wise satellite for the infrared fingerprints of a
> galactic civilization  discovered. Wright observed:
>
> Our results mean that, out of the 100,000 galaxies that WISE could see
> in sufficient detail, none of them is widely populated by an alien
> civilization using most of the starlight in its galaxy for its own
> purposes. That’s interesting because these galaxies are billions of
> years old, which should have been plenty of time for them to have been
> filled with alien civilizations, if they exist. Either they don’t
> exist, or they don’t yet use enough energy for us to recognize them.
> -----
> Yet perhaps we should conclude something different about the human
> future from this absence of galactic scale civilizations than the sad
> recognition that our species is highly unlikely to have one.  Instead,
> maybe what we’re learning is that the kind of extrapolation of the
> industrial revolution into an infinite future that has been prevalent
> in science-fiction and futurism for well over a century is itself
> deeply flawed. We might actually have very little idea of what the
> future will actually be like.
>
> Then again, maybe the silence gives us some clues. Rather than present
> us with evidence for our species probable extinction, perhaps what
> we’re witnessing is the propensity of civilizations to reach
> technological limits *before* they have grown to the extent that they
> are observable across great interstellar distances by other
> technological civilizations.
> ----
> Since the industrial revolution our ideas about both the human future
> and the nature of any alien civilization have taken the shape of being
> more of the same. Yet the evidence so far seems to point to a much
> different fate. We need to start thinking through the implications of
> the silence beyond just assuming we are either prodigies, or that, in
> something much less than the long run, we’re doomed.
> -------------------------
> End Quotes.
>
>
> To me, that seems an optimistic interpretation of the Great Silence.
> Given the billions of galaxies we see and the billions of star systems
> in each galaxy, that humans are the only intelligent species is
> really, really unlikely. The other option, that all intelligent
> species quickly become extinct (in galactic time scales) gives
> humanity a very bleak future.
>
> So that leaves a more optimistic option.
> As Searle suggests, civilisations might hit technological limits that
> force them to stabilise at a level undetectable at interstellar
> distances. Mastering nano-tech might enable very complex civilisations
> to exist in small spatial dimensions.
>
> This is an appealing solution to the Great Silence. As previous
> commentators have noted, there has been plenty of time for just one
> exponential species to have colonised the whole galaxy. So that vision
> of the future is almost certainly mistaken.
> For long-lived civilisations nano-tech and sustainable energy
> efficiency looks good.
>
>
> BillK
>
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-- 
Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University



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