Our operators are standing byToronto Star
23 July 2006
By Kurt Kleiner
a wooded ridge in Harvard, Mass., a specially built telescope has spent
the last month scanning the skies for laser signals from alien
civilizations. No luck yet.
But the Oak Ridge Observatory
telescope is a sign that the Search for Extraterrestrial Intelligence
(SETI) is alive and well. Despite official indifference — neither the
Canadian nor the United States government funds SETI research —
scientists around the world continue to scan the skies, looking for
proof that we are not alone in the universe.
In addition to the
Oak Ridge Observatory telescope, the Allen Telescope Array this summer
will begin an in-depth survey of the skies, listening for radio signals
from a million different stars in a search that will take until at
least 2025. By the time it's done, we should have a better idea of
whether or not anyone out there is trying to get in touch.
remains a fringe discipline, partly because of what people in the field
refer to as the "giggle factor." To a lot of observers, the idea that
aliens are beaming us messages seems too ridiculous to take seriously.
was certainly the case in 1993, when the U.S. Congress cut a $12
million NASA SETI program. Sen. Richard Bryan, the Nevada Democrat who
led the fight to kill the program, joked at the time that after
spending millions of dollars, "we have yet to bag a single little green
fellow." For Bryan and many others, SETI gets tossed into the same
mental box where they keep UFOs, Bigfoot, and Star Trek conventioneers.
fact, the search for extraterrestrial intelligence has been a
legitimate scientific enterprise from the start. In 1960, Frank Drake,
at the time an astronomer at the National Radio Astronomy Observatory
in Green Bank, W. Va., pointed a radio telescope at two nearby stars
and listened for signals that could have been generated by intelligent
beings. He didn't find anything, but he did launch the modern search
for extraterrestrial intelligence.
"It is difficult to think of
another enterprise within our capability and at relatively modest cost
which holds as much promise for the future of humanity," wrote Carl
Sagan, the famous astronomer and SETI enthusiast who died almost 10
Sagan thought that technologically advanced
civilizations might send important advice that would help humans to
survive our technological "adolescence" without destroying the planet.
also has its legitimate scientific skeptics, who think that the
conditions for life are so unlikely that they must occur only rarely,
or else that intelligent life is a fluke.
But for optimists,
SETI has one big thing going for it: the size of the universe. With 100
billion stars in our galaxy alone, and more than 100 billion other
galaxies in the universe, optimists think that life has probably
developed countless times, and that some of that life is intelligent.
formalized this line of thought when he came up with the Drake
Equation, which calculates the number of civilizations in our galaxy
that could be trying to communicate with us right now.
with 100 billion stars in our galaxy. Assume that 50 per cent of those
have planets around them, and each of those has at least one planet
capable of sustaining life. Assume that any planet that could sustain
life has a 50 per cent chance of developing it, and that once life
develops there is a 20 per cent chance of intelligent life evolving.
that only 20 per cent of intelligent beings are interested in
communicating. Then assume that those who are interested in
communicating are capable of sending out signals for 10,000 years
before their civilizations collapse. Using those numbers, our galaxy
should contain about 1,000 alien civilizations busily beaming messages
around right now.
Of course, you can monkey with those numbers
any way you want; credible estimates of civilizations interested in
communicating range anywhere from millions to only one: us. But working
through the numbers this way convinces a lot of people that the idea
isn't totally absurd.
Most of the SETI work so far has involved
listening for radio signals. One idea is that aliens would transmit
their signal at or around a frequency of 1.420 gigahertz, which is the
frequency emitted by hydrogen. Hydrogen is the most abundant element in
the universe, and radio astronomers are often tuned in to that
frequency in order to map hydrogen clouds.
they used, aliens would need to make sure we recognized the signal. It
seems likely that they would transmit some sort of basic mathematical
information; for instance, a list of the first dozen or so prime
numbers, repeated again and again.
In fact, though, almost any
non-random pattern would be likely to catch our attention. It's even
possible that we've detected one or more of these signals already.
The most famous is the "Wow!" signal recorded by the "Big Ear" radio telescope at Ohio State University in 1977.
72-second signal was so startling that statistics professor Jerry R.
Ehman wrote "Wow!" on the printout. But the signal was never repeated.
Many other signals have gotten attention over the years but have also
`It is difficult to think of another
enterprise within our capability and at relatively modest cost which
holds as much promise for the future of humanity'
researchers are still listening for radio signals. For instance, the
University of California at Berkeley runs the SERENDIP (Search for
Extraterrestrial Radio Emissions from Nearby Developed Intelligent
Populations) project, which piggybacks observations off of the Arecibo
Observatory in Puerto Rico.
Some of the raw data are seen by
millions of volunteers, who download it to their home computers and
analyze it using spare computing cycles. So far about five million home
users have participated.
Meanwhile, the Optical SETI telescope
at Oak Ridge Observatory is part of a relatively new approach to the
search for extraterrestrial intelligence.
scientists assumed that visible light would be useless for
communicating, since it would be too difficult to see against the
background light of the transmitting planet's nearby star.
it turns out that by using extremely brief pulses of laser light, a
beacon could outshine its nearby sun by thousands of times. The
drawback is that the beacon would have to be pointed straight at us to
The idea is that anyone setting up a beacon like
this would choose hundreds or thousands of likely stars, and send
messages to each in turn, maybe for just a few seconds at a time.
of the most stinging criticisms of SETI has always been the Fermi
Paradox, named after physicist Enrico Fermi, who once asked the simple
question, "Where are they?"
If there really are thousands or
millions of civilizations out there, why haven't we picked up any
signals, despite 45 years of looking?
The answer is that we
haven't been looking hard enough, says Seth Shostak, an astronomer at
the non-profit SETI Institute in Mountain View, Calif.
now, SETI projects have had to make do with telescopes they could
borrow for a few days or weeks at a time, or else been forced to make
their observations at the same time that other astronomers were looking
for other things.
That means we've only taken a good look at a
few thousand stars. But even if there were 10,000 civilizations beaming
signals straight at us, with 100 billion stars in the galaxy we would
have to look at a million stars before we could reasonably expect to
see even one of the signals.
The new privately funded, dedicated
SETI telescopes like the Allen Telescope Array and the SETI optical
telescope will have the time to look at a lot of stars in the next few
decades and make it much more likely that we'll be able to detect any
But that brings up the biggest question of all: Why would anyone bother sending a message in the first place?
universe is such a big place that light takes years to reach us even
from the nearest stars. If we do detect a signal, it's likely to be
hundreds, thousands, or even tens of thousands of years old. Why would
anyone go to the time, trouble and expense of sending a signal that
couldn't be answered for thousands of years?
For one thing, an
advanced civilization might not think it's very much trouble. Shostak
points out that humans have had radio for only about 100 years. We've
had lasers for only about 50 years. Older, more advanced civilizations
with better technology would find it cheap and easy to send
interstellar signals. "It might be a high school science fair project
for them," he says.
And if they're anything like us, the urge to
advertise their existence will be strong. From the Egyptian pyramids to
the graffiti on the wall of a downtown building, we humans seem to have
a deep need to announce our existence.
We've even sent a few of
our own signals into space. In 1974, the Arecibo radio telescope
broadcasted a message to a star cluster 25,000 light years away. We've
also packed written information and sound recordings in some of our
space probes, on the off chance they'll be picked up by other beings
Although it's hard to guess about alien psychology,
this need to announce our existence might be an impulse common to
intelligent beings. Like us, they might want to shout out to the
Universe, "We're here — is anyone there?"