[2006/06/30] Paper View: Why SETI Hears Only a “Great Silence”
Paper View: Why SETI Hears Only a “Great
Silence” 06/30/2006 Enrico Fermi posed a curious question in 1950: “Where is
everybody?” If life emerges on planets as a consequence of
evolution, there should be other intelligent civilizations out there, and
some of them must have colonized other worlds. He thought there must
have been plenty of time for galactic colonizers to achieve technologies
far beyond our own by billions of years, and therefore to have reached
every corner of the Galaxy by now, including Earth. Where are
they? This innocuous question, named “Fermi’s Paradox” (though
others had asked it, too) has troubled advocates of the Search for
Extraterrestrial Intelligence (SETI) ever since. Though SETI
technicians patiently eavesdrop on more and more stars each year in the
half-century since SETI began, the Great Silence seems ominous.
Milan M. Cirkovic and Robert J. Bradbury think they know why.
Their ideas, published in New Astronomy July 2006,1 call
for nothing less than a complete overhaul of SETI thinking:
Hereby, we would like to propose a novel
solution, based on the astrophysical properties of our
Galactic environment on large scales, as well as some economic and
informational aspects of the presumed advanced technological
civilizations (henceforth ATCs). In doing so, we will suggest a
radically new perspective on the entire SETI endeavor.
Traditional SETI, listening for radio signals from
biological life, is “fundamentally flawed,” they claim. Think
post-biological. Life will not remain content with the
limitations of flesh, they reason. Borrowing from the speculations
of science historian Steven J. Dick, they believe biology will eventually
give way to technology. Advanced technical civilizations will be
composed of machines. They quote Dick:
In sorting priorities, I adopt what I term
the central principle of cultural evolution, which I refer to as
the Intelligence Principle: the maintenance, improvement and
perpetuation of knowledge and intelligence is the central driving
force of cultural evolution, and that to the extent intelligence can be
improved, it will be improved.
Not “whatever can go
wrong, will go wrong,” in other words. At least until the universe
runs down, the Intelligence Principle will triumph over Murphy’s
Law. This is the foundational principle of their proposal.
Life will gravitate toward maximum information processing, subject to the
constraints of physical laws.
A natural extension of the Intelligence
Principle is what can be called the digital perspective on
astrobiology: After a particular threshold complexity is
reached, the relevant relations between existent entities are
characterized by requirements of computation and information
processing. It is related to the emergent computational
concepts not only in biology, but in other fields such as
fundamental physics, cosmology, neuroscience, and social sciences.
Here’s a brief synopsis of their scenario. Life
emerges on a planet, evolves to a state of intelligence, then gravitates
toward more efficient information processing and computation, till it
transcends the biological and becomes strictly technological. A
machine civilization is not going to care about communicating with beings
like us. Its priority will be to maximize information
processing. To do this, the entities will have to have to migrate
from the places where they first evolved as biological life forms.
This is due to simple constraints of physics. The warmth of a summer
sun may be valuable to biological organisms like us, but heat is an enemy
of computation. Galaxies have a galactic temperature gradient: hot
at the center, cooler at the edges. It’s at the outskirts of the
galaxy, therefore, where a machine civilization would migrate. That,
however, is not where traditional SETI is looking, and that is the reason
for the Great Silence. In their scenario, we need to
drastically modify our search strategy. Whether artifacts of
technology would be detectable at the edges of the Milky Way or external
galaxies, they are not sure. Perhaps aliens would send inscriptions
(see 09/01/2004).
They are quite certain, though, that radio is not on the broadcast
schedule:
We conclude that the conventional radio
SETI assuming beamed broadcasts from targets – selected exclusively on
the basis of the old-fashioned biological paradigm – within the
vicinity of our Solar System ... is ill-founded and has minuscule
chances of success on the present hypothesis. It is a clear
and testable prediction of the present hypothesis that the
undergoing SETI experiments using this conservative approach will yield
only negative results.
(Italics theirs.) How
can their prediction indeed be tested? If conventional SETI does get
a radio signal, the prediction might fail; otherwise, how long would they
have to wait in silence to feel vindicated? Traditional SETI
researchers would probably argue this point. But Cirkovic and
Bradley also put forth a falsification test: look for evidence of
technological artifacts at the outer fringes of nearby galaxies.
That, unfortunately, will probably be very difficult without more advanced
technology. Nonetheless, they are quite adamant that traditional
SETI thinking is parochial. It’s oblivious to the physical
constraints that would drive life toward information processing. “In
a sense the problem has nothing to do with the universe itself, and
everything to do with our ignorance and prejudices,” they state
accusingly. “In this special sense, the flaws in the currently
prevailing views on SETI are much less excusable.” In
their paper, the authors acknowledged the contribution of Guillermo
Gonzalez (along with Peter Ward and Donald Brownlee) to the extension of
ideas about planetary “habitable zones” to galactic scales: the
Galactic Habitable Zone (GHZ).2 They extended this
concept further to a Galactic Technological Zone (GTZ), where
machines could optimize their computational power. This zone would
be the outer reaches of a spiral galaxy – but not so far out that heavy
elements would be lacking. They were also honest about their
assumptions:
There is no meaningful scientific
hypothesis for resolving Fermi’s Paradox – or, indeed, any problem of
importance in science – without a set of assumptions. In
building of the migrational solution to Fermi’s puzzle, we have relied
on the following set of assumptions:
The Copernican principle continues to hold in astrobiology,
i.e. there is nothing special about the Earth and the Solar
System when considerations of life, intelligent observers or ATCs are
made.2
Laws of physics (as applied to the classical computation theory
and astrophysics) are universally valid.
Naturalistic explanations for the origin of life, intelligence
and ATCs are valid.
The Milky Way galaxy exhibits well-established gradients of both
baryonic matter density and equilibrium radiation field temperature.
Habitable planets occur naturally only within the GHZ (which
evolves in a manner roughly understood), but ATCs are not in any way
limited to this region.
We assume local influences both of and on ATCs. Thus, we
disregard overly speculative ideas about such concepts as cosmic
wormholes or “basement universes”. Interstellar travel is
feasible, but it is bound to be slow and expensive (for anything
larger than nanomachines) at all epochs.
Astroengineering on the scales significantly larger than the scale
of a typical planetary system (on the pc-scale and above) will remain
difficult and expensive at all epochs and for all ATCs.
ATCs will tend to maximize the efficiency of
information-processing, no matter how heterogeneous their biological
and cultural structures and evolutionary pathways are.
These
assumptions are naturally of varying validity and importance.
Items 1 through 3 are essential methodological guidelines of
the entire scientific endeavor. Although item 1 has recently
become controversial with “rare Earth” theorists, there is still no
compelling reasons for relinquishing it. Assumption 4 is an
empirical fact, and 5 is quite close to it. Assumptions 6 and 7
are conservative extrapolations of our limited scientific and
technological perspective, but in our view should be retained until the
contrary positions can be verified. In particular, absence of the
Galaxy-size astroengineering effects in external galaxies ... strongly
supports the assumption 7.
The most speculative
assumption was #8, they acknowledged, but they reasoned this way: whether
a civilization evolves toward hedonism (like the Romans) or toward
accomplishment (like the Greeks), both would need to maximize their
information processing. “In either situation,” they rationalized,
“they will seek the greatest computational capacity and efficiency
possible to support these activities.” So there you have
it. The drive toward the ultimate CPU governs the fate of life and
intelligence. Geeks will someday rule the universe.
1Milan M. Cirkovic and Robert J. Bradbury,
“Galactic gradients, postbiological evolution and the apparent failure of
SETI,” New
Astronomy, Volume 11, Issue 8, July 2006, Pages 628-639,
doi:10.1016/j.newast.2006.04.003. 2See also the film The Privileged
Planet. In this film Gonzales discusses the GHZ, and
Brownlee gives reasons for his “rare earth” hypothesis. The film
also argues against the assumed Copernican Principle.
Interesting paper. Heavily sci-fi,
profoundly speculative, politically incorrect, and somewhat amusing,
perhaps, but thought-provoking. Is it scientific? Does its
presence in a scientific journal indicate it is worthy of more serious
consideration by rational truth-seekers than if it appeared in a
theological journal or in Mad Magazine? After all, they made
predictions and provided a falsification criterion. They talked
about baryons and physical laws and thermodynamics. And look –
they even had equations! Surely no one could accuse this kind of
sober, rigorous analysis as being equivalent to religion. What do
you think? Religion is a misleading word in this
context. It conjures up images of candles, robes, icons and prayer
wheels. World view is a more appropriate term: a way of
looking at the world, of answering the big questions: who are we?
Where did we come from? Why are we here? Where are we
going? Science cannot answer these questions, yet world-view
issues loom big in this article. They have attempted to give their
opinion about the origin and ultimate fate of the universe, dress it in
a lab coat and pass it off as science. Yet by any measure of
scientific criteria, they always left a way out. Their
prediction is hollow, because it would require proving a
universal negative. Their falsification test is hollow,
because we could all be dead before anyone finds a way to detect an
unknown kind of technology at intergalactic distances, and even if
someone did, another would find a natural explanation for it.
Predictions and falsifiability are not necessary components of science
anyway, according to some philosophers of science. And
equations – well, nice, but the ones in the paper describe
observable physical properties of temperature distribution in galaxies
and have nothing to do with the social habits of intelligent
beings. Sentient beings are notoriously resistant to obeying
equations about what they should do or will do. In short, the
scientific props of this article are distractions from the fact this is
nothing more than a world view paper. Their entire
thesis breaks down on one of their assumptions. It was nice of
them to list their assumptions, but not so nice to glibly claim that the
least plausible is one of “essential methodological guidelines of the
entire scientific endeavor,” namely, “Naturalistic explanations for
the origin of life, intelligence and ATCs are valid.” Did you
catch it? They just attempted to baptize naturalism in the waters
of science as if we wouldn’t notice. (Only Cirkovic has a PhD, but
they both attempted to doctor a philosophy.) Why should
this tactic be allowed for sci-fi speculation, but not for other kinds
of scholarly investigation? After all, theologians can make
testable predictions. A conservative Bible scholar, for instance,
could predict that evidence for King David will be found, even point to
the Tel
Dan inscription as confirming evidence. Some preachers argue
that the equation “nothing times nobody equals everything.” has been
falsified. Should sufficiently scholarly sermons be allowed in
scientific journals, then? Not a few theologians are well trained
in mathematical physics, and not a few scientists doubt the assumptions
listed by these two speculators. They should have no privilege in
this game. The quality of the reasoning and the support of
evidence, not the scientific trappings and venue, need to carry weight
in evaluating world view claims. Cirkovic and Bradbury may wish to
believe that life and intelligence are emergent properties of
matter in motion, but they cannot support this world view with
scientific evidence. In fact, the tide of evidence is
overwhelmingly against it (06/12/2006,
04/17/2006,
online
book). These sci-fi speculators pulled off a shifty
sidestep.
They merely assumed that “naturalistic explanations” for these things
are “valid,” and then hid behind an arbitrary rule that naturalism is an
essential methodological guideline for the entire scientific
endeavor. Oh yeah? It wasn’t for many of the greatest
scientists in history (see online book).
This claim is only made now by the Eugenie Scotts and Ken Millers of the
world who want to shield their philosophical speculations from critical
scrutiny. It’s a tactic not unlike the childhood ploy “King’s X”
that allows them to evade rules of the game to which the others are
bound. Cirkovic and Bradbury are as free as anyone to
speculate, but need to take their speculations out of New
Astronomy and argue them before philosophers and theologians, not
claim special privilege for things that cannot be observed or known –
indeed, things that run contrary to what we do know about the
propensities of matter in motion. What they wrote, though, is
bound to make the SETI Institute angry. A lot of investment
capital is bound up in traditional SETI strategies. These two
warring parties may make any further comments superfluous; they may end
up falsifying each other.
[2006/06/30] Paper View: Why SETI Hears Only a “Great Silence”
