Mercury,
September/October 2002 Table of Contents
Ben
Zuckerman Responds:
My
friend Seth Shostak presents a spirited defense of SETI. But of
course this was not entirely necessary since the title of my article
was "Why SETI Will Fail," not "Why SETI Should Be
Terminated." If Seth, Jill Tarter, Frank Drake, and other SETI
pundits can entice well-to-do individuals to fund their SETI efforts,
then I say great, go for it, sail on. Heck, even I contribute a
modest dollar amount each year to support the efforts of the SETI
Institute.
It
appears that Seth and I agree, albeit for different reasons, that
should SETI eventually be successful, then it will be because it
received signals from distant stars. Where we clearly disagree is
where Seth has misstated my arguments and, in so doing, has made
a subtle, but important, mistake in his own argument. In the first
sentence of "Going All the Way," Seth says that I consider
only "a first generation of interstellar expansion." But
if you re-read the first three paragraphs of my "Pessimists
are Optimists" section, you will see that this is not true.
In the first paragraph I extend what Seth calls a local "sphere
of influence" to "distant times and places." And
then, in the third paragraph, I extrapolate the argument to the
"galaxy as a whole."
A problem
with Seth's "sphere of influence" idea is that the Galaxy
is not a solid object like Earth. Different stars pursue different
sized and shaped orbits around the galactic center. Over the course
of hundreds of millions of years, planetary systems in any initial
sphere of influence will spread out over a huge volume of the Galaxy.
This natural expansion process comes in addition to any exploratory
trips between living worlds and would, over time, bring civilizations
close together. Thus, regions "untouched by aliens," if
they exist at all, will be very few and far between.
Seth
belittles my argument as a mere "special edition" of the
Fermi Paradox. Quite the contrary, the SETI literature has never
mentioned the fact that a technological civilization has the ability
to investigate in detail planets orbiting millions of stars without
ever leaving its own planetary system. This ability totally changes
the rules of the SETI game as they have been propounded until now
by SETI enthusiasts and skeptics alike (as exemplified in the papers
I cited by Newman/Sagan and Howard/Horowitz).
I have
one final thought. In Seth's section "Going All the Way,"
he refers to "colonization" because he is refighting battles
between SETI true believers and skeptics from decades past. For
example, Seth argues that colonization often is not a very compelling
motivation for large-scale expansion of a terrestrial civilization.
But I am talking about intellectual curiosity, not colonization
(which becomes an incidental consequence of intellectual curiosity).
That is, when intellectual curiosity sends explorers like Captain
Cook to far-flung places, they can easily return home if they so
choose, whereas Cook's interstellar counterparts, like Captain Kirk,
cannot. Even should most people (or aliens) be passive stay-at-home
types, just a few curious, intrepid adventurers like Columbus or
Cook can open grand new vistas from which there can be no turning
back.
The
same curiosity that motivates Seth and other SETI seekers will propel
human beings, or whatever we become, to overcome all technological
and physiological obstacles and thus to sail on and fill the Milky
Way Galaxy.
Seth
Shostak Responds:
I appreciate
Ben's support of SETI, both moral and monetary. The intention of
my article, however, as stated explicitly at the end of the first
section, was to take issue with his argument as to why SETI will
fail. It is somewhat disingenuous of Ben to strongly claim that
SETI cannot succeed, and then plead that it wasn't his intent to
suggest that SETI should be terminated. Methinks he wants it both
ways, and that bespeaks uncertainty.
Ben
is telling us that SETI experiments will come up dry because the
Galaxy can be easily and quickly occupied. Despite his disclaimers,
this really is the Fermi Paradox argument of old. It is revealing
that Ben has objected to my characterizing his argument as a "special
edition" of this scenario, implying that he does, indeed, assume
such Galaxy-wide enterprise. He prefers to think of "intellectual
curiosity" as the motive that drives advanced beings to visit
(and not return from) other suns, rather than "colonization."
But can he really argue that the former is more prevalent than the
latter given our less-than-impressive current knowledge of alien
sociology?
Still,
I'll give credit where it's due. Ben has added two ingredients to
the venerable Paradox recipe: stellar shuffling and planet-finding
telescopes. Lamentably, the former is a slow way to bring worlds
in contact. Even slow rockets could do the job much more quickly.
As
for Ben's second ingredient, planet-sniffing telescopes, it's true
that these might allow peripatetic aliens to limit their travels
to worlds with established biology. But perhaps they prefer to travel
to worlds where biology is not already under way, as a matter
of safety or ethics. We simply don't know.
Let's
add a new spice to this mix. Within a century or two, we will have
the technical capability to search for artificial signals from any
star system in the Galaxy. And just as we can assume that advanced
extraterrestrials would wield planet-finding telescopes, so too
would they have advanced SETI transmitters and receivers. If intellectual
curiosity is truly their bag, then perhaps the best course of action
is to eschew the interstellar tourism and explore the Galaxy for
intelligent signals. After all, radio antennae could tell the curious
a great deal about distant worlds, and with far less effort then
transporting themselves across hundreds of light-years.
The
bottom line is simple. While I enjoy this conceptual arm wrestling
with my buddy Ben, the facts are that no matter what you, the reader,
may think of these essays, they won't settle the question that underlies
this debate. In fact, neither argument nor experiment can prove
Ben right.
But
SETI could prove him wrong.
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