For the tiny cadre of scientists probing the cosmos for signs of alien
life, the most difficult question isn't always, "Are we alone?"
Sometimes it's the shopworn, "What do you do?" from a fellow airline
passenger. Jill Tarter generally doesn't like to answer that question when she
first meets someone. She's director of the Centre for SETI Research, as in
Search for Extraterrestrial Intelligence.
But after four decades of frequent ridicule, the astronomers seeking signs
of life in the heavens are gaining some respect. Since 1960, when Tarter's
colleague Frank Drake first pointed a radio telescope at a pair of nearby
stars in hopes of dialing in an alien broadcast, there have been about 100
searches for ET signals.
No aliens have been found. But new planets have, more than 100 outside our
solar system since the first was discovered in 1995.
Whether those distant worlds teem with life, let alone intelligent life,
remains unknown. But each new discovery further energizes the search for ET.
Some scientists are beginning to talk in terms of when, not if, they'll be
able to answer a question that's vexed humankind probably since we first
peered upward at the stars that pierce the dark.
For Martin Rees, Britain's astronomer royal, finding that answer represents
the main exploratory challenge of the next half-century.
"Our cosmic importance depends on whether we are alone or not," Rees said
from Cambridge, England.
It's also worth answering simply because it is such a big question, Rees
added: "The main aim of science is to take steps toward answering the big
questions."
It's that sentiment that keeps the hunt going, even without positive
results.
"It's a great goal. That is a lot of what sustains you - the payoff," said
Kent Cullers, director of research and development for the Centre for SETI
Research. "That's why we keep the champagne on ice."
Even SETI skeptics, like Ben Zuckerman from the University of California at
Los Angeles, concede it's three things - cosmology, black holes and the search
for life in the universe - that drive public support for his field.
"And a substantial fraction of the funding comes from the third of those,"
Zuckerman said from atop Mauna Kea, where he was using the Keck Observatory to
investigate the formation of planets around young stars in the Milky Way.
So how do you carry out such a search?
Directly listening for a signal has by far been the most popular approach,
at least judging from its appeal to the general public.
As of early August, 4.6 million people have signed on to one SETI project
alone, run by the University of California, Berkeley. The Web-based project
enlists idle computer time and processing power to scan packets of data
collected by the mammoth radio dish at Arecibo, Puerto Rico, for traces of
alien signals.
That level of interest is not matched by employment in the field or the
modest private funding, which is merely in the millions of dollars.
The SETI Institute's Drake estimates that just 20 people work full-time on
the hunt for extraterrestrial intelligence, with maybe 40 more working
part-time.
"It's tiny," Drake said, quickly adding that the field has never been
larger.
SETI's not likely to grow much bigger any time soon, but it is about to get
a whole lot stronger, faster and cheaper.
When he started out in 1960, Drake used a 26-metre diameter dish in West
Virginia to check out just two stars.
This fall and coming spring, SETI hopes to wrap up a survey of 1,000 nearby
stars similar to our sun, listening to each for five minutes for a trace of an
alien signal.
The survey's completion would mark the finale of a project initially funded
by NASA but dropped after a year.
The SETI Institute picked up the search. It uses equipment at Arecibo and
Britain that is one quadrillion times more powerful than the operation Drake
cobbled together 43 years ago.
Further advances in computing power and a drop in price should allow for
searching even more stars over a greater number of frequencies and with vastly
improved sensitivity, Drake said. He estimates SETI's power doubles every 250
days.
To capitalize on that, the SETI Institute and Berkeley together are
building an array of six-metre diameter radio telescopes in northern
California that should be capable of surveying one million stars over a
decade.
Three of the dishes are in place now; it should bristle with 350 by 2006.
Microsoft co-founder Paul Allen is bankrolling much of the cost.
And a slew of teams around the world are proposing building an array of
telescopes 100 times larger. Tarter predicts that such advances will allow
SETI to canvass much, if not all, the Milky Way and its 100 billion-plus stars
within several decades' time.
Drake, using an equation he devised and which now bears his name, estimates
there could be 10,000 technologically sophisticated civilizations in the
galaxy. The implications of contact with just one are hard, if not impossible,
to gauge.
"I think science fiction is our best guide," Rees says.
But there really isn't too much to fear about physical contact, much less
dialogue, with an alien civilization should a signal be detected. Bridging
interstellar space takes lots of time. Even a simple conversation, across
distances measured in light years, would be tedious at best.
Answers to questions could come thousands of years after they were posed.
The 1974 message, sent from Arecibo, still has 25,000 years to go before it
hits anyone's inbox.
"It's more like the dialogue you have right now with Shakespeare or the
ancient Romans," Tarter said of the possibility of receiving an alien signal.
"You can't necessarily ask them questions. You have to infer the knowledge
that you want to gain from what it is they have told you."
For UCLA's Zuckerman the fact that no civilizations have come calling
during the several billion years since life arose on Earth is strong evidence
that there are no such creatures beyond Earth.
Any technologically sophisticated civilization, he reasons, would have
surveyed the galaxy and spotted the telltale chemical signatures of life,
including oxygen. Such aliens would be hard-pressed not to come visit,
Zuckerman believes.
Critics of such views say that merely anthropomorphizes the issue: what if
aliens are nothing like, say, curious astronomers, but more like sullen teens
- or meditative swamis?
"You could have intelligent life living a contemplative life on the bottom
of the ocean and not wanting to communicate," Rees suggested.
For those undaunted by the quest, like Jill Tarter, there is no time like
the present to keep asking the fundamental question of our cosmic uniqueness.
"I realized I lived in the very first generation of all human beings that
had ever lived that could try and answer this question that humans have been
asking themselves forever - and by doing an experiment, rather than asking the
priests and the philosophers and having a belief system give you an answer,"
Tarter said. "There's only one time in history that that's going to happen,
and I happen to be living at that time."
That sort of reasoning has drawn NASA back into the game. The types of
searches SETI is undertaking and those NASA is about to undertake are
different, yet complementary - and are likely to grow even more so, said
Charles Beichman, chief scientist for astronomy and physics at NASA's Jet
Propulsion Laboratory.
The space agency has a trio of space telescopes on the drawing board that
would seek out planets like our own. Such planets presumably would become
SETI's No. 1 targets, drawing the programs even closer. The first of the NASA
missions is expected to launch in 2006.
SETI efforts also could be bolstered by the discovery of life - even
microbial life - much closer to home. Scientists believe Mars and Europa, a
moon of Jupiter, could harbour life deep in the dust and ice, respectively,
covering each. A British mission is also en route to the Red Planet, where
beginning in December it will scratch the surface and sniff the air for
evidence.
While such microbes are unlikely to be proficient radio operators, their
discovery inside the bounds of our solar system would open up the hunt for
intelligent life forms within the greater galaxy, said Rees, the British
astronomer.
"If you could say life arose twice, independently, in one solar system," he
said, "that would tell you straight away the origin of life didn't involve a
rare fluke and there must be some sort of life on millions of other planets."
