A SETI Blog Feature

On November 16th, 1974, the giant Arecibo radio telescope in Puerto Rico transmitted Earth’s first message to the stars. The target was M13, a globular cluster 25,000 light years away. The message, no longer than a typical tweet, disclosed the location of Earth and basic information about the nature of life on this planet.

While the transmission was heralded as the first serious attempt to make contact with alien life, it was just a clever way to publicize the power of the recently upgraded telescope. In reality, the chances of an alien civilization ever receiving the message lie somewhere between zero and non-existent.

Nonetheless, the event raised an important question still being hotly debated today–should we be actively trying to make contact with intelligent life elsewhere in the Milky Way?

Such luminaries as physicist Stephen Hawking, and science fiction author David Brin, have urged caution, while others, including astronomers Neil Degrasse Tyson and Seth Shostak, believe we have nothing to fear. Indeed, they encourage it, saying we have much to gain from being part of the wider galactic community, should one exist.

Active attempts to make contact with aliens, collectively called Active SETI or METI (Messaging to ExtraTerrestrial Intelligence), have been controversial for decades. The argument against them straightforward. Opponents claim that broadcasting the location of Earth to the entire galaxy leaves us open to predatory and perhaps even genocidal acts by anyone who detects our transmissions:

“We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet,” [Stephen] Hawking said. “I imagine they might exist in massive ships … having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach.”

David Brin’s main objection is less about METI’s existence, and more that its main proponents have been unwilling to delay the program until a worldwide consensus on the merits and nature of the METI program can be reached. He argues we should at least understand all the risks involved before proceeding any further.

Brin’s position is reflected in a 2006 editorial published by the prestigious science journal, Nature:

[T]he risk posed by active SETI is real. It is not obvious that all extraterrestrial civilizations will be benign — or that contact with even a benign one would not have serious repercussions for people here on Earth. There is already an agreement within the SETI community that, should a signal from beyond be picked up, various bodies will discuss what response, if any, should be sent. Yet the Valencia meeting voted against trying to set up any processes for deliberating over the style or content of any spontaneous outgoing messages. In effect, anyone with a big enough dish can appoint themselves ambassador for Earth.

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These small risks should nonetheless be taken seriously. When technologies offer radical new possibilities, the people who have the privilege of playing with them also have a duty to consult widely about what those possibilities might mean. The SETI community should assess them in a discussion that is open and transparent enough for outsiders to listen to and, if so moved, to actively participate. Of course, consensus may not always be possible—but the sort of debate out of which consensus has a chance to emerge must now take place.

Curiously, when searching the Internet for arguments in favor of METI, I found precious few. Proponents of METI spend far more time rebutting arguments against their efforts than they do presenting a positive case for the program.

An article titled “Making a Case for METI” looks promising, but it spends most of its energy refuting claims that METI is unscientific, too risky, and ultimately futile.

Perhaps this should be expected since the odds of METI ever succeeding are extremely low. Indeed, they are far lower than the odds of SETI detecting an alien signal. If by some miracle one of our METI broadcasts is detected by an alien civilization, it would take decades for any reply to reach Earth, and that’s assuming the aliens are capable of replying and choose to do so.

Even if the METI program wasn’t a long shot, it would still be hard to make a strong enough case for blindly broadcasting to the Universe to overcome our intrinsic fear of the unknown. It’s true, we simply do not know what’s out there waiting to be alerted to our presence.

The SETI League’s guest editorial (linked above) does eventually get around to making one positive argument in favor of METI, but I can’t help feeling they’re grasping at straws:

In conclusion, we subscribe to one possible solution to the Fermi Paradox: Suppose each extraterrestrial civilization in the Milky Way has been frightened by its own SETI leaders into believing that sending messages to other stars is just too risky. Then it is possible we live in a galaxy where everyone is listening and no one is speaking. In order to learn of each others’ existence – and science – someone has to make the first move.

My own position on the wisdom of the METI program is that it doesn’t matter one way or the other. Any effort to pursue contact with extraterrestrials in the absence of likely targets–life-bearing planets or signals detected by SETI–is futile, but I also believe that the risks associated with revealing our location to an unknown alien civilization are hopelessly overblown.

Either way, if there are any alien civilizations out there within hailing distance of Earth, they already know we are here, or will do soon enough, without any assistance from us.

How so? Well, let’s consider our own situation for a moment. Though we have barely begun to venture beyond the bounds of Earth, we already know an incredible amount about our small corner of the Universe. We have cataloged over 200 million individual stars, and in the 25 years since the first extrasolar planet was detected, we have confirmed the existence of over four thousand planets orbiting nearby stars, with many more candidates in the pipeline. That number will only continue to grow apace as better equipment and detection techniques come online.

Our search for other worlds has barely begun, so imagine where we’ll be when we’re finally ready to dip our toes into interstellar space, say, five hundred years from now. With fleets of deep space telescopes using advanced techniques like optical interferometry and gravitational lensing, we could easily have found a million or more extrasolar planets by then, a good number of which may be suitable for life, perhaps even intelligent life.

Naturally, this type of remote exploration will always be orders of magnitude cheaper than sending spacecraft across the interstellar void. Not only that, but the payback is far more immediate. Unless we find a way to extend the human lifespan indefinitely, nobody present at the launch of the first interstellar mission will be alive by the time the spacecraft sends back the first closeup images of another star system. The scientists and engineers building the next generation of exoplanet-hunting telescopes have no such issues.

What is true for us is almost certainly true for any other intelligent species out there. It simply makes sense for technological civilizations–even ones capable of interstellar travel–to be heavily invested in remote sensing, since it allows them to monitor thousands, perhaps even millions of planets simultaneously. Given the relative costs, it seems reasonable to assume that any advanced civilization would want to tease out every last bit of information from the exoplanet-skimming photons entering their telescopes.

So, when an advanced alien civilization turns its powerful telescopes toward Earth, what will they find? Even at the very edge of detectability, they will see a planet eminently suitable for hosting life. It’s rocky, not too big, not too small, in the middle of its star’s habitable zone, warm, and has vast oceans and an oxygen-rich atmosphere.

That alone should be enough to single Earth out for special attention. If life in the Milky Way is rare, Earth is a beacon shining bright against the dark background of space. Even if living worlds are commonplace, Earth would still make the short-list of planets worthy of continuous observation, just in case something out of the ordinary happens there, like the advent of intelligent life.

Earth’s atmosphere will receive close scrutiny. They’ll look for pollutants that might hint at some kind of industrial activity. Perhaps the atmosphere is changing in a way that suggests planet-wide activity, like an increase in greenhouse gases or the sudden onset of nuclear winter. Rapid changes in Earth’s albedo may indicate widespread changes to the landscape, like wholesale deforestation, and the dark side of the planet could reveal the faint sodium signature of a web of city lights draped across the globe.

Naturally, there will be a limit to how much can be detected from many light years away, but the cost and time advantages of mass long-distance surveillance over interstellar travel are so great there is every incentive to continue developing the observational technology and processing power needed for such a program. Our own astronomers and planetary scientists are certainly banking on this being the case.

Realistically, anything METI can broadcast pales in comparison to the brilliant blue omnidirectional beacon we know as Earth. Absent some astoundingly fortunate confluence of extremely rare circumstances, the best METI can realistically hope for is to confirm to an alien civilization that Earth is the home of an intelligent species of some kind. In all likelihood, aliens will spot a METI signal only because they have already detected signs of life on Earth.

Therefore, in all likelihood, sending messages to the stars does nothing to increase the chances of contacting aliens, but nor does it increase the risks associated with making contact. There is no hiding place. Earth itself singles us out as a place of special interest to any alien observers out there, even if we are just one of millions of life-bearing worlds throughout the Milky Way.

Does that mean we should make ready for extraterrestrial visitors, or be on the lookout for attempts to contact us from afar? Perhaps, though detectable evidence of our global industrial prowess is only a few decades old, so unless our nearest neighbors are only a few dozen light years away, it will be decades before they are alerted to our presence as a technologically capable society.

But what if they are already heading our way? Should we fear their impending arrival? Should we be preparing for the worst or looking forward to the day we finally join the galactic community of civilized worlds?

Find out in part two, Facing the Unknown.