[ExI] Drake Equation Musings
pharos at gmail.com
Sun May 15 08:38:44 UTC 2016
A Less Bleak Lesson from the Silent Universe
May 7, 2016 by Rick Searle
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
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.
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.
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