MOUNTAIN VIEW, Calif. — For more
than a half-century, a small group of astronomers has sought intelligent company
among the stars. They’ve done so by turning large radio antennas skyward, hoping
to eavesdrop on signals from an advanced society. It’s a program known as SETI,
the Search for Extraterrestrial Intelligence.
But now some researchers propose that we should do more than simply don
headphones and await E.T.’s call: We should make serious efforts to encourage a
response from putative aliens by deliberately transmitting our own messages.
It’s a simple idea, akin to tossing a bottle into the cosmic ocean. But recent
arguments for what’s termed active SETI have loosed a storm of controversy, one
that has even washed into the halls of academe.
Why is this? Why has the sending of dispatches to worlds many trillions of miles
distant suddenly become a hot-button issue? The simple answer is that there’s
now a perception that advertising our existence could be a mortal threat to the
The reasoning is this: While no one has yet offered decisive proof for life
beyond Earth, in the past two years astronomers have learned that tens of
billions of habitable planets suffuse our galaxy. Consequently, to believe that
only Earth has spawned intelligence is to insist that our world is the site of a
miracle. That point of view rarely appeals to scientists.
The aliens could very well be out there. And that realization has spurred a call
by some for broadcasts intended to elicit a communication from at least the
nearest other star systems. But we know nothing of the aliens’ possible motives
or behavior. Therefore, it’s conceivable that betraying our existence might
prompt aggressive action from space.
Broadcasting is likened to “shouting in the jungle” — not a good idea when you
don’t know what’s out there. The British physicist Stephen Hawking alluded to
this danger by noting that on Earth, when less advanced societies drew the
attention of those more advanced, the consequences for the former were seldom
It’s a worry we never used to have. Victorian-era scientists toyed with plans to
use lanterns and burning pools of oil to contact postulated Martians. In the
1970s, NASA bolted greeting cards onto spacecraft that will leave our solar
system and wander the vast reaches between the stars. The Pioneer and Voyager
probes carry plaques and records with information about what humans look like
and where Earth is, as well as a small sampling of our culture.
Those messages move at the speed of rockets. But in 1974, a three-minute encoded
pictogram was transmitted using the large radio antenna at Arecibo, Puerto Rico.
It moves at the speed of light, 20,000 times faster. More recent radio
transmissions include a Beatles song beamed by NASA to the North Star, a Doritos
advertisement launched to a planetary system in the Big Dipper, and a series of
broadcasts sent to nearby stars using an antenna in Crimea.
When most people believed that aliens were no more than easy black hats for
Hollywood, the idiosyncratic nature of these messages could be easily dismissed.
But if cosmic company is a legitimate possibility, shouldn’t we offer up
something more edifying than pop music and snack food? A deliberate transmission
should represent all of humanity — not short-circuit the important question of
who will speak for Earth.
Consequently, recent conferences on the merits of active SETI have sought the
advice of social scientists. Among their worries is whether to be up front about
humanity’s seamy side: Should we tell the extraterrestrials about war and
Personally, I think this concern is overwrought. Any society that can pick up
our radio messages will be at a level of development at least centuries beyond
our own. They would be no more incensed by our bad behavior than historians who
learned that Babylonians attacked one another with spears. It seems naïve to
imagine that, by shielding aliens from the less flattering aspects of humanity,
we would somehow lessen any incentive to do us harm. If there’s a danger,
mincing words is unlikely to eliminate it.
A better approach is to note that the nearest intelligent extraterrestrials are
likely to be at least dozens of light-years away. Even assuming that active SETI
provokes a reply, it won’t be breezy conversation. Simple back-and-forth
exchanges would take decades. This suggests that we should abandon the “greeting
card” format of previous signaling schemes, and offer the aliens Big Data.
For example, we could transmit the contents of the Internet. Such a large corpus
— with its text, pictures, videos and sounds — would allow clever
extraterrestrials to decipher much about our society, and even formulate
questions that could be answered with the material in hand. Sending the web on
its way would take months if a radio transmitter were used. A powerful laser,
conveying bits much like an optical fiber, could launch these data in a few
Sending messages — even big ones — is technically feasible. However, there’s
still the highly controversial matter of whether to broadcast at all. Who
decides? One could simply let the public weigh in, but doing so wouldn’t address
the security issue. Even if a majority is comfortable with a transmission, how
does that mitigate the possible danger?
The inability to gauge this peril prompts some critics to argue that, given the
possibly existential threat posed by active SETI, we should choose the side of
caution. We should simply forbid powerful transmissions to the skies. Indeed, a
small consortium of academics in California has drafted a petition urging this.
It’s a wary approach. It’s also poor insurance. Any extraterrestrials with
technology advanced enough to threaten us will surely have antennas larger than
our own, instruments that can pick up the television and radio signals broadcast
willy-nilly since World War II. We are already shouting into the jungle, albeit
with less volume than a deliberate signal. But the dangerous creatures may have
Additionally, if we forbid high-powered transmitters aimed at the sky, we shut
out such obvious future technologies as better radars for aviation and tracking
dangerous asteroids. Do we really want to hamstring our descendants this way?
A decision to engage in active SETI has not been made. The benefit — learning
our place in the cosmos — is only hypothetical, and so is the danger. But I, for
one, would hesitate to let a paranoia based on nothing more than conjecture
shackle the activities of our children and our children’s children. The universe
beckons, and we can do better than to declare that future generations should
endlessly tremble at the sight of the stars.
Seth Shostak is the director of the Center for SETI Research at the SETI
Institute, and a host of the radio program “Big Picture Science.”
A version of this op-ed appears in print on March 29, 2015, on page SR3 of the
New York edition with the headline: Should We Keep a Low Profile in Space?.