describes progress of search for extraterrestrial intelligence
TV images of Star Trek's U.S.S. Enterprise flitting about the
universe, tracking interstellar radio waves is a much better bet
than traveling in spaceships for finding intelligent life somewhere
out in space.
would take 100,000 years in a rocket going 36,000 miles per hour
to reach the nearest star, and 200 times that to reach the nearest
potential civilization; the chance of picking the right star is
about one in 10 million, said Frank Drake, an astronomer at the
University of California-Santa Cruz and president of the SETI
Institute. SETI stands for the Search for Extraterrestrial Intelligence.
about 900 people at the Charlottesville Center for the Performing
Arts last week, Drake described the progress of monitoring radio
wave emissions from outer space, whether deliberately or incidentally
beamed from another planet.
"We know that one day there will be a signal. There is life
out there that's the easy question,² Drake said. "The hard
question is what it will take to find it."
certainty that other civilizations exist derives from a theory
of cosmic evolution scientists have developed over the last 50
years, predicting that life is likely to have developed on planets
orbiting sun-like stars, he said. Drake developed an equation
in 1961, known as the Drake Equation, to estimate the number of
possible intelligent civilizations in the universe.
technology has come a long way since the late 1950s, when scientists
at the National Radio Astronomy Observatory (NRAO) in Green Bank,
W. Va., used an 85-foot telescope with one channel to search for
radio signals, said Drake, whose talk was the NRAO's 34th Janksy
Lecture. The event is named for physicist Karl Jansky, who discovered
radio emissions in space in 1933.
through Project Phoenix, a privately funded program that succeeded
the one at NASA, SETI is using a 1,000-foot telescope in Arecibo,
Puerto Rico, that sits 500 feet in the air and can detect a billion
frequency channels. It also transmits a signal in the form of
a 20-million-watt, highly focused beam that outshines the sun
by a factor of 10 million and could be detected from anywhere
within the Milky Way.
"Given our own capabilities, it seems reasonable to search
for signals from anywhere," he said.
need to search a wide range of channels. We have computer chips
now that are made to perform as a multi-channel radio receiver"
and can monitor 200 million channels, generating 56 million numbers
per second, he said.
A signal would appear as a diagonal line (because the earth is
rotating). Even a six-watt signal from the Pioneer spacecraft
close to Pluto can be detected, he said. A notable signal received
by the Arecibo telescope is verified by a 250-foot telescope in
"If the second telescope sees the signal, we compare it to
the first one and can tell if it's local or from outer space,"
he said. "So far, we've never found a signal that's passed
signal that appeared to be a candidate -- it looked like a zipper,
unlike the straight lines generated by satellites -- was received
by both telescopes, but they discovered it was a Japanese spacecraft
out beyond the moon, signaling for help because it was lost, he
said. Another promising signal resembling a double helix turned
out to be a tumbling Russian spacecraft with two antennae.
permission to use the Arecibo telescope only 20 days per year,
SETI has been planning for the past several years to build its
own radio telescope, developing a new paradigm. Rather than building
one huge dish, they will place about 1,000 3.6 meter dishes (like
those used for cable television reception) adjacent to one another
and operating as a single system, creating a one-hectare telescope.
funding for SETI is challenging because "we can't make any
promises," he said.
new system "will give us a telescope dedicated to SETI 365
days a year," said, adding that using numerous small dishes
will make it easy to expand the telescope.