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Cosmologist Stephen Hawking says it is too risky to try to talk to
space aliens.
Oops. Too late.
NASA and others already have beamed several messages into deep space,
trying to phone extraterrestrials.
The U.S. space agency, which two years ago broadcast the Beatles song
"Across the Universe" into the cosmos, on Wednesday discussed its
latest search strategy for life beyond Earth.
"The search for life is really central to what we should be doing
next in the exploration of the solar system," said Cornell University
planetary scientist Steve Squyres, chairman of a special National
Academy of Sciences panel advising NASA on future missions.
The academy panel is looking at 28 possible missions, from Mars to
the moons of Jupiter and Saturn. And NASA is focused mostly on looking
for simple life like bacteria in Earth's solar system rather than
fretting about potential alien overlords coming here.
Just days ago, Hawking said on his new TV show that a visit by
extraterrestrials to Earth would be like Christopher Columbus arriving
in the Americas, "which didn't turn out very well for the Native
Americans."
The famous British physicist speculated that while most
extraterrestrial life will be similar to microbes, advanced life forms
would likely be "nomads, looking to conquer and colonize."
The comment reinvigorated a three-year debate roiling behind the
scenes in the small community of astronomers who look for
extraterrestrial life, said Seth Shostak, a senior astronomer at the
SETI Institute, which looks for aliens. Should astronomers ban
purposeful messages into the universe for fear of attracting dangerous
aliens?
Shostak maintains it really does not matter, saying that approach is
unnecessarily fearful.
While some people think broadcasting into the universe is "like
shouting in a jungle, not necessarily a good idea," Shostak asked, "Are
we to forever hide under a rock? That to me seems like no way to live."
There is a big difference of opinion in astronomy about the issue,
said Mary Voytek, a senior astrobiology scientist at NASA headquarters.
"We're prepared to make discoveries of any type of life, of any
form," Voytek said in a NASA teleconference. Much of the search for
intelligent life is privately funded, by groups like SETI, she said.
About 20 years ago, NASA held a conference on this issue. Back then,
most of the experts were worried about attracting the wrong type of
aliens, said Christopher Kraft, the former NASA Johnson Space Center
director who created Mission Control.
But Kraft, a NASA legend who received a lifetime achievement award
Wednesday from the Smithsonian Institution, said he would welcome
aliens. "I might just learn something," he said.
The SETI Institute in Mountain View, California, takes a passive
approach, listening for any signals from aliens.
For more than a quarter of a century, however, various groups have
been purposely sending out signals to other worlds. The most famous was a
three-minute broadcast from the Arecibo Observatory in Puerto Rico in
1974, Shostak said.
The Canadians made a series of broadcasts using a Ukrainian antenna in
the 1990s. The now-defunct Team Encounter of Houston and a prominent
Russian astronomer made public and distinct "cosmic calls" out to the
universe, including one just from teenagers.
NASA beamed "Across the Universe" to the star Polaris in 2008 to promote
the space agency's 50th anniversary, the 45th anniversary of the Deep
Space Network and the 40th anniversary of the Beatles song. And the same
year, as part of the publicity for the remake of "The Day the Earth
Stood Still," the movie was broadcast to the stars, Shostak said.
Four NASA deep space probes — Pioneer 10 and 11 and Voyager 1 and 2 —
carry plaques and recordings that say hello from Earth and give
directions on how to get here. Those probes launched in the 1970s are at
the edges of the solar system.
And that is on top of the broadcasts Earth inadvertently sends into the
cosmos as part of daily life: radio and TV signals, airport and other
radar communications.
"That horse left the barn a long time ago," Squyres said, speaking from
an astrobiology conference in Houston. "Whether you do it intentionally
or not, the signals are out there."
Massachusetts Institute of Technology planetary scientist Sara Seager
does not think much of the broadcasts to space, because so far they are
pointed at random, not toward potential Earth-like planets.
"We wouldn't even know where to send our message, it's so vast out
there," Seager said. That will change in a few years when new telescopes
will be able to find terrestrial planets that could support life.
Even then, Seager said any aliens coming to Earth probably would be so
advanced they would not need to hear our message to find us. It would
not be like Columbus stumbling upon on the New World, she said.
"If they have the capability to come here, they're probably to us as we
are to ants on Manhattan," said former NASA sciences chief Alan Stern.
The closest any aliens could be is a few tens of light years away. With
one light year equaling about 5.9 trillion miles, that means it would
take them generations to get here travelling at the speed of light,
Shostak said. And even that would be unlikely, he added.
Frank Drake, who did the first modern experiment looking for
extraterrestrial intelligence, estimated there are about 10,000
intelligent civilizations in the universe, while the late Carl Sagan
figured it was closer to a million, Shostak said.
Given how big the universe is, our nearest intelligent neighbour is more
likely about 5,900 trillion miles away, he said.
"God has nicely buffered us," he said."
Your thoughts?
Modifié par Colesslawz, 02 mai 2010 - 05:27 .
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