Much Ado About METI

To transmit, or not to transmit, that is the question.

The Arecibo Radio Telescope in Puerto Rico. Image Source: NAIC

There has been quite a bit of brouhaha in the Search for Extra-Terrestrial Intelligence (SETI) community recently about Messaging Extra-Terrestrial Intelligence (METI), also know as ‘active SETI’. On the one hand, members of the SETI Institute (or at least a few) in Mountain View, California, advocate actively transmitting signals into space to advertise our intelligence to prospective listeners. On the other hand, various people and groups, spearheaded by the Berkeley SETI Research Center (BSRC) in Berkeley, California — best known to the public for their SETI@home program — oppose the idea, and have issued a statement in support of their stance.

The question of the existence of other intelligent civilizations is extremely interesting, and unimaginably challenging to answer. Answering this question requires answering a number of questions about the astrophysics of star and planet formation, the physics and chemistry conducive to the creation of self-replicating molecules, the evolutionary biology behind the emergence of complexity and intelligence, and the biological, social and technological dynamics that result in the establishment of civilization. Answering most of these questions is impossible with our current state of knowledge, so the only way to answer the original question is to search the skies for electromagnetic signs of alien technology in action. This is what SETI astronomers have been doing for decades. With the detection of a large number of extrasolar planets, the searches have become more sophisticated, such as observing Kepler planetary systems during conjunctions to look for interplanetary radar/communications. Observations with upcoming facilities such as the Square Kilometre Array will expand the boundaries of SETI and allow us to put better constraints on the search parameter space. A true detection, however, will most likely continue to elude us in the near future.

This is where METI comes in. The crux of METI is that it is not enough to passively listen, but that humans should actively radiate a strong signal (a ‘beacon’) into space that will enable prospective listeners to detect us. The hope is that this detection will prompt a strong, directed response that we can pick up relatively easily with our technology. The idea does make logical sense. After all, we have been listening for decades without transmitting a beacon. If every civilization in the Galaxy is doing the same, the chances of anybody detecting anybody else is abysmal. Sure, our radio communication signals have been steadily leaking into space, but these signals are difficult to detect light years from Earth, and even if detected, their coded nature makes it unlikely to be decoded. There have been a handful of symbolic transmissions, such as the famous ‘Arecibo message’, but these were all transmitted to some far away star or globular cluster such that they serve no purpose other than as a publicity stunt. The closest thing to a beacon that we have been sending out is the Arecibo planetary radar that is used to study asteroids, the Moon, comets, and nearby planets in the Solar System. This signal can be detected by large radio telescopes on planets within a few hundred light years from us. But since the Arecibo radar tracks Solar System bodies, there is no fixed cadence with which a receiver on an extrasolar planet might receive the signal. They may not receive the signal more than once, making a conclusive detection on their part unlikely.

So what is wrong with METI? The main argument of those opposed to METI is that we cannot possibly know how the extra-terrestrial civilization would react to the discovery of intelligent life in their neighbourhood. They argue that it is likely that the civilization that picks up our signal may be millions of years ahead of us in development, and can pose a threat to our existence. The first statement is obviously true — we possess no information that will enable us to judge how an intelligent civilization would respond. Assuming that they are near enough that communication and close-to-light-speed-travel can happen within a few decades, without the technological capability of either civilization changing dramatically in that time frame, I can think of the following scenarios:

1. They are about as technologically developed as we are, or less so: In this scenario there is no problem — just as we cannot possibly go and kill them, they cannot possibly come here and kill us.
2. They are a few hundred years ahead of us: In my mind, this is potentially the most dangerous scenario, assuming that the trajectories of their biological, cultural, and technological development are akin to ours. We are a technologically advanced civilization, but biologically we are still brutes, and culturally we are still backward. This makes us vulnerable to emotions that cloud our judgement and cause us to lose sight of the larger goals of civilization. I do not expect this nature to change in a few hundred years’ time, so we will be as dangerous then as we are today. If they are in the same boat, and are close enough to travel the distance between us within a few decades, an invasion might be a possibility, and what ensues can possibly be similar to what happened to the first inhabitants of Australia and the Americas following the arrival of Europeans. But for this to happen, the civilization needs to be within a few tens of light years of us. Anything farther than that renders a protracted military campaign sub-optimal due to the travel time involved. It is unlikely that a civilization that is a few hundred years ahead of us exists within a few tens of light years from us, so this scenario does not seem plausible.
3. They are thousands to millions of years ahead of us: In thousands to millions of years, we will cease to be human. We would have taken our evolution into our own hands, away from the vagaries of biology. We would be so advanced that when our automated telescopes detect the blip of a distant intelligence, they would automatically classify it and save it in a database, along with all the other blips from all the other civilizations that they detect. If the characteristics of the blip pass follow-up criteria, autonomous space probes would automatically be launched to study that planet. We would be so technologically advanced that we would not need to invade them to preserve our way of life, and we would be so culturally advanced that we would not destroy that termite mound of a planet for fun. In other words, I doubt if we have anything to fear from a civilization a million years more advanced than us. Given the age of the universe, it is more likely that any civilization we encounter is millions of years ahead of us than hundreds, and hence, any threat that METI poses to our existence is negligible.

That is not to say that METI is practicable. To be worthwhile, METI has to be comprehensive in that every single star within a certain distance from us be periodically signalled with a trivial-to-decode message, for a time span of decades to centuries. Given that the nearest stars are a few light years away, a few years from the moment transmission starts, we should begin to exhaustively monitor all the stars that we have transmitted to, for decades to centuries, searching for a response. This is patently infeasible. The following are a few reasons why this will not and probably should not be done:

1. Mainstream astronomy — of which SETI does not form a part — survives with barely enough funding, so SETI embarking on such an expensive venture is certainly not a possibility.
2. As mentioned above, since the first civilizations we encounter are likely to be much more advanced than us, we should be able to detect their existence by looking for waste heat, signs of large-scale astro-engineering, etc., without having to send them a costly message.
3. METI fails a cost-benefit analysis. METI assumes that the extra-terrestrial civilization will respond, but there is no reason to assume that they will. Therefore, the amount of money spent on building and operating a METI program as outlined above is better spent building and operating highly sensitive radio, optical, and infrared telescopes that would enable us to spy on our Galactic neighbourhood more effectively.

The bottom line is that the whole argument about active versus passive SETI is moot, given the perpetual funding crunch. But in case funding appears magically, we are certainly better off just listening — not for fear, but for reason.

Disclosure: I am a BSRC collaborator.