Attacks from Extraterrestrial Civilizations are Unlikely

People have expressed concern regarding the broadcast of powerful electromagnetic signals into space and deliberate attempts to contact extraterrestrial intelligences. The reason for such concern is that extraterrestrial intelligences could be hostile to humanity as they might see Earth as an attractive exploitable resource or the growth of human technology might be perceived as a threat to their future safety. British theoretical physicist Dr. Stephen Hawking states: “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet. 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… If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans.”

In recent years, the technologies used to detect new planets and humanity’s ability to find alien life has improved dramatically. As the possibility of finding extraterrestrial life catches up with science fiction, the question of whether extraterrestrial intelligences are likely to be “friend or foe” seems increasingly pertinent. In a paper written by Janne M. Korhonen from Aalto University in Finland, the author suggests that conflicts between extraterrestrial intelligences are very unlikely and also examines a number of factors that would deter such conflicts from taking place. The author assumes that extraterrestrial intelligences are rational and have a concept of risks and benefits.

A major problem for any extraterrestrial civilization that might launch an attack involves knowing what to attack in the first place. Gathering information about another civilization over interstellar distances is going to be extremely difficult and full of uncertainty. Due to the finite speed of light, it takes many years for electromagnetic radiation to travel the enormous interstellar distances that separate individual planetary systems. As a result, whatever information that is collected by a potential aggressor is likely to be outdated by the time the attacking civilization arrives at the target civilization. If the Milky Way galaxy contains one million randomly distributed extraterrestrial civilizations, then the average minimum distance separating one civilization from another is ~200 light years. This creates an intelligence lag of at least 400 years because it takes 200 year for signals from the target civilization to arrive at the attacking civilization and another 200 years or more for the attacking civilization to travel at near the speed of light to the target civilization. The huge lag time can provide ample opportunity for the target civilization to develop some retaliatory capabilities and also allows the target civilization to establish contacts with other civilizations.

The rise of human civilization is only a very recent phenomenon in Earth’s history. Given that the galaxy is billions of years old and considering how much human civilization has progressed in just the last century alone, any extraterrestrial civilization is very unlikely to be at the same level of technology as human civilization. Instead, any extraterrestrial civilization is going to be significantly more advance. Assuming an exponential growth of technology, it is hard to imagine a civilization that is a billion, a million or even a thousand years ahead. A civilization that is technologically able to detect signs of another civilization for the first time will deduce that the detected civilization is already far ahead of theirs.

Detectable signs of an extraterrestrial civilization such as electromagnetic transmissions and signatures of mega-scale engineering projects cannot be reliably used to gauge that civilization’s level of technological development. This is because a hyper-advanced civilization can still use old and obsolete technologies simply for recreational or educational purposes. Furthermore, if a hyper-advanced civilization believes that hostile civilizations can develop, it can create “baits” that mimic less advance civilizations to lure out hostile civilizations and pre-emptively attack them.

If an aggressive civilization were to launch an attack on another civilization, it will be nearly impossible for the aggressor to be certain that it will not face retaliation. Survival of some form of the victim civilization is very likely, especially if the victim civilization has self-sustaining off-world colonies that can easily evaded detection. Just a few survivors from the victim civilization can grow to billions of individuals in a few hundred years assuming a growth rate of one percent per year by human standards. It is uncertain if survivors from the victim civilization will subsequently launch a retaliatory strike. Nevertheless, as long as there are survivors, the attacking civilization cannot completely discount the possibility of a subsequent retaliatory strike.

Even if the attacking civilization completely eliminates the victim civilization, there is always a possibility that the attack may be noticed by other extraterrestrial civilizations. These other civilizations can also include off-shoot colonies of the victim civilization and even the attacking civilization itself. A civilization that launches an unprovoked attack on another civilization is likely to be seen as a danger by other civilizations as well. One or more of these other civilizations may launch a pre-emptive strike on the attacking civilization to eliminate the danger it poses.

Attacking another extraterrestrial civilization for the purpose of resource exploitation is also very unlikely to occur. The reason is that distances involved in interstellar spaceflight are so enormous that the resources required to travel to another planetary system is likely to vastly outweigh any returns. For example, transporting a 1000 ton payload across interstellar space at just 10 percent the speed of light would require at least as much energy as the current annual energy consumption of the entire human civilization. Long before achieving the overwhelmingly more difficult feat of interstellar spaceflight, an extraterrestrial civilization is likely to already have technologies that allow full recycling of its resources which alleviates the need for any further exploitation. As a result, an extraterrestrial civilization with a mastery of interstellar spaceflight is unlikely to attack another civilization since the gain of all resources from a single planet would be trivial. The risk of future retaliation from survivors or witnesses is also expected to greatly outweigh any benefit.

It seems that any attack launched by an extraterrestrial civilization on another is a dangerous gamble for the attacker. An extraterrestrial civilization is unlikely to attack another civilization because the benefit of not attacking is expected to outweigh any benefit derived from an attack. Studies also show that “pacifistic” civilizations tend to perform better than aggressive ones in the long run. Unfortunately, the arguments put forth here are obviously limited since humanity’s own history serves as the only source of reasoning. Any extraterrestrial intelligence is going to have a reasoning process which differs from ours. Besides, extraterrestrial intelligences that are far ahead of human civilization may be entirely incomprehensible.

Even though the threat of an attack by an extraterrestrial civilization appears irrational and very unlikely, a certain amount of caution should still be taken. The design and operation of an interstellar spacecraft can potentially be seen as a threat by another extraterrestrial civilization. For example, a planetary system can be home to an advance civilization and still appear uninhabited because the civilization chooses to remain undetectable. An interstellar spacecraft sent from Earth may accidentally crash into one of the civilization’s planets and cause massive damage. That is not hard to imagine because a 100 ton interstellar spacecraft travelling at just 10 percent the speed of light can release a comparable amount of energy upon impact as humanity’s entire nuclear arsenal. Such an incident can cause the extraterrestrial civilization to strike back at Earth to prevent further “attacks”. As a result, any mission which involves sending an interstellar spacecraft to explore another planetary system must ensure that the planetary system is uninhabited or that the spacecraft will not appear to pose any danger to an extraterrestrial civilization that may reside in the planetary system.

Reference:

Janne M.Korhonen, “MAD with aliens? Interstellar deterrence and its implications”, Acta Astronautica Volume 86, May-June 2013, Pages 201-210