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 planet.
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 agreeable.
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 injustice?
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 days.
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 good hearing.
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.”
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