Why would someone doggedly pursue
an objective regarded by most as quixotic? Face a probability of success that is infinitesimal? Spend a whole career doing so?
Many have asked such questions about the extraordinary
scientist Jill Tarter, director of the Center for SETI (Search for Extra-Terrestrial
Intelligence) Research. I
thought of those questions on the occasion of last weekend's SETI conference,
which celebrated her 35-year career in SETI as she steps down at 67 from the
Center's directorship.
No one is more identified with SETI than Tarter. You may have seen her in fictional form
as the young scientist played by Jodie Foster in the 1992 film Contact, which was modeled on Tarter's life and work. (It's a film worth seeing if you
haven't yet, and watching again if you have.)
What is the substance of Tarter's life work, which invites
so much skepticism? The
fundamental issue is not whether there might be life of some sort elsewhere in the universe. I think that most scientists, including
Tarter, would bet that there is.
After all, there are 200-400 billion stars in our Galaxy alone and about
100-200 billion galaxies—altogether on the order of a trillion trillion stars in the observable universe. And we now know from observations in our Galactic neighborhood by the Kepler space
telescope that planets orbiting
stars are pretty common, a few of them possibly habitable. As has been said, if there is no life
anywhere else in that enormous universe, it would be an incredible waste of
real estate!
However, extra-terrestrial life is surely preponderantly
primitive, mostly microbial, as it is on Earth. It might be successful in taking root in the most extreme places, as it has in the scalding, sulfurous vents deep in Earth's oceans. There are at least two such sites even
within our solar system—Mars and Jupiter's moon Europa—where conditions seem
right for microbes to exist in subsurface water. Space probes sent to those bodies might possibly find such
life within decades.
No, Tarter has devoted herself to an incredibly harder task:
discovering intelligent
extra-terrestrial life. Such life,
if it exists at all, is almost certainly extremely rare, even rarer if it were
technologically at a stage of exhibiting signs of its presence that we could
detect, and rarer still if it were disposed to purposefully emit a powerful
beacon announcing that presence.
For comparison, Earth has hosted life for 4.5 billion years, yet only for
the past century has one species of its intelligent life—homo sapiens—displayed extra-terrestrially detectable signs of
its existence; none of those signs is an intentional beacon. In other words, planet Earth has been
announcing the existence of its intelligent life for only a hundred-millionth
of its history, and only marginally. That small time window is but one mark of
how unlikely it would be for us to see detectable signs of intelligent life
from any given planet at any given time—and this is presupposing a prior unlikelihood, that life had already started on that planet in the first place and could evolve into
a technologically sophisticated
civilization.
To elaborate further on the long odds against SETI, look at the full
array of obstacles it still faces, even assuming that it will have what Tarter
never had: a hoped-for radio-telescope observatory that can simultaneously view
a million stars in our Galaxy over a very wide band of frequencies. (Tarter was
able to check out but a few thousand stars at limited frequencies.) First, at least one of those million
stars—say it is X light-years away—must have a very rare planet like Earth,
capable of hosting life that could eventually evolve into an advanced
civilization. Next, precisely X
years ago such a civilization must have already developed and have been in
that tiny time window, such as our current epoch on Earth, when it had the
technical sophistication to show detectable signs of its presence, hopefully an
intentional beacon. Next, SETI's
observatory must be sensitive enough and looking at the right frequencies to
detect those signs, and be able to determine that they are not random. What are the chances that all these
suppositions will simultaneously be true?
Certainly not zero, but still minute. Such are the daunting considerations that Tarter
has faced throughout her career.
So that brings me back to the questions I posed at the
outset: what keeps Tarter and her colleagues going up against such enormous
odds, with the almost-certainty that success will not come in their lifetimes
or maybe ever? Part of the answer
must surely be the intellectual satisfaction of creating tools for the hunt; in
one generation these tools have gone from single-antenna radio telescopes and
primitive computers to large radio-telescope arrays and very powerful computers. Another part of the answer must be the
thrill of the hunt itself. Yet
another is the huge payoff if the hunt is successful. But I think Tarter has said it best herself: "The great
thing about being a scientist is that you never have to grow up. You
can keep on asking 'Why?' "
Although Tarter is stepping down from the SETI Center
directorship, she is not retiring.
She has dedicated herself to raising funds for SETI, which have dried up
in these depressed economic times.
SETI's main observatory, the privately funded Allen Telescope Array
(ATA), had to be shut down for some months at the end of last year for lack of
operational funds and is now barely limping along. Tarter's new goal, she says, is to present the next
generations of SETI researchers with the planned 350-antenna ATA (it now has 42
antennas) and enough funding to keep it operating at full staffing.
Bottom line: I think we should all pay homage to this
exceptional woman. Few of us would
have the courage to spend our careers as she has, on such an other-worldly,
almost-impossible objective. I suggest that you savor her charm, vitality and
pluck by watching her 2009
presentation at TED.