by Gabrielle Chong
We are living in a significant era in the history of mankind. As I am writing this article in late May 2012, almost 800 exoplanets (planets beyond our own solar system) have been discovered. given that exoplanet detection had only begun in earnest since the past decade and detection techniques will continue to improve greatly, we are poised to discover many more exoplanets and start investigating their habitability in the near future.
Despite advances in the search for extraterrestrial life, they aggravate one of the greatest unsolved mysteries of our times. given the age and size of the Universe, and the possibility that Earth’s habitability is not unique, it is quite likely that at least one other intelligent civilization capable of interstellar contact besides ourselves has arisen sometime in the past, and yet we have not had any evidence for its/their existence. But this question, often known as the Fermi’s Paradox, is not really contradictory at all; either extraterrestrial intelligence exists, or it does not, and the answer must lie in one of several possibilities.
The most straightforward and historically popular answer is that the intelligent life on Earth is really unique. Advocates of the Rare Earth Hypothesis and anthropic principle point out that life on Earth is a highly improbable event that arose out of a great number of favourable events, starting from the Earth’s fortunate position in the habitable zone of the solar system, the favourable geoclimatic conditions that allowed complex life to arise on earth, the fortuitous history of evolution on Earth that allowed humans to emerge and flourish as a unique species, to other conditions that led to our present capability for interstellar contact. This view, however, can only remain speculative because the absence of evidence for extraterrestrial intelligence cannot disprove the existence of extraterrestrial intelligence. Moreover, this view violates the Copernican nature of astronomical research; almost every discovery in modern astronomy has shown our world to be less and less unique.
Other views allow for the existence of extraterrestrial civilizations, but suspect that interstellar contact is constrained by matters of scale, i.e. time, distance, technology, and economy. Such views hold that given the vastness of space and the chances for cosmic accidents (gamma ray bursts, black holes, etc.) over long distances, it is difficult for even the most technologically advanced civilizations travelling at the cosmic speed limit to come into contact with each other. Moreover, they might have encountered engineering problems that we do not understand yet, or they simply do not have sufficient resources to power high energy-consuming pursuits such as interstellar transmission. These constraints, in parallel to the limiting factors in the Rare Earth Hypothesis, reinforce each other to make inter-civilizational contact a highly improbable event.
However, there are also several possible multipliers that may compensate, if not displace, these constraining factors. Firstly, it is foreseeable that a highly advanced civilization would also be a high energy-consuming civilization, and we should be able to detect the enormous energy mines, such as Dyson spheres and other gigantic artifacts which they leave behind. Secondly, it is not necessary for interstellar travel to be operated by singular probes powered by a singular energy source – an advanced civilization would be capable of building von Neumann machines that utilize resources at various checkpoints to make replicas of themselves, filling an entire region of the universe with such machines. Moreover, though most people often envision space travel and colonization to take place in a linear direction, an advanced civilization with adequate resources should be capable of sending out probes in all directions, expanding the region of colonization at a cubic growth rate and thereby significantly increasing the detectability of such civilizations.
Some other sociological speculations posit that the assumptions we make regarding the motives for interstellar travel are false. Perhaps the need for exploration and discovery is unique to humans, and advanced civilizations would simply be uninterested in expanding their colonies – for reasons unknown to us. But this, too, seems counterintuitive. Scientific inquiry, if not an evolutionary urge for colonization, would be a necessary trait of any technologically advanced society. Another sociological explanation would be that intelligent societies are predisposed to becoming unstable and self-destructing after reaching a certain threshold of technological progress. This is probable and chilling, considering that humanity currently possesses enough nuclear arms to wipe out the entire human population many times over, though it would be quite tragic and ironic that extreme intelligence – the principal enabler for the rise of intelligent civilizations – would also be the principal enabler for their extinction.
Another possible situation is that extraterrestrial intelligence exists, and may even be amongst us, but we simply cannot detect them, either because they are unrecognizable to us, or they have chosen to be invisible. For example, it is possible that an advanced society would prefer to transfer all their memories and energy into more stable depositories such as dark matter, or decentralize themselves into picobots, and that such post-biological life forms and societies would completely elude us. on the other hand, the Zoo Hypothesis postulates that extraterrestrial life would designate life on Earth as an ecological sanctuary, in the same way we create wildlife sanctuaries for purposes of conservation and observation. Under such circumstances, there would be no way for us to observe beyond the sanctuary borders that have been imposed on us. Calculations in game theory also suggest that intelligent civilizations might choose to lie low to avoid interstellar wars, given that competition for cosmic resources and/or inter-civilizational hostility are inevitable traits of advanced societies.
Last but not least, one philosophical solution that is possible but rarely discussed as a solution to Fermi’s Paradox, is that we are living in a computer simulation, and that the rest of the Universe is simply a filler to life on Earth that is the chief subject being studied in the simulation. In such a matrix, we cannot even search for ‘real life’ on Earth.
We have discussed many possible solutions to Fermi’s Paradox. The answer must lie in either one of these, or a yet unknown case. Regardless of the correct answer, the silence of the Universe is quite deafening.
The anthropic principle – The idea that the living inhabitants of a universe are able to observe it because the universe was structured to support life.
von Neumann machines – Self-replicating machines capable of interstellar travel, hypothesized by the mathematician John von Neumann.
game theory - A branch of decision theory that studies strategies in decision making when the total utility is zero-sum and participants are faced with the uncertainty of the decisions of other participants.
Dyson sphere - An energy mine that is able to harvest the total solar energy output of a sun, hypothesized by the physicist Dyson Freeman.
picobots - Extremely tiny robots, made possible with manipulation of matter on an atomic level.
About the author:
Gabrielle Chong Yong Wei is a philosophy student at Wellesley who is fond of science. Her Science Storytelling Column breaks down speculative questions at the intersection of science and philosophy into digestible bits.