The discovery that planets are actually typical in the universe is one of the great achievements of modern astronomy. From an understanding of how solar systems form, it follows that in our galaxy there could be on average at least one planet for each of more than a hundred billion stars. Most of these would not resemble the Earth and could not foster the development of life. But with such staggering numbers, the odds are that life in some form should actually be abundant in the galaxy. Somewhere there must be civilizations capable of space travel or sending trans-galactic messages. This raises the question of why ours is, so far, the only planet we know of that works to support life. Unless you are one of those folks who believe the aliens are already here, walking disguised among us, the question then also arises, where are they? If aliens are so probable, why have they not made their presence known to us? Named after a famous physicist of the 1950s, this question is known as the Fermi paradox and has stimulated many creative answers. I will focus on some that seem most relevant to our time.

One sobering explanation is that technological civilization is doomed to self-destruct, or is inherently self-limiting to the degree that it cannot penetrate the great distances between stars. Of course, any such thinking presumes a great deal about the possible manifestations of intelligence. For example, a “technological civilization” would be a form of biological life—and thus is a product of ruthless natural selection—or derived from such a form (robots). Like us, aliens would not be angels but craven animals who exploit other life forms. We need only look at slaughterhouses and how ideals of progress are regularly thwarted by human nature.

We owe our civilization to our great numbers and to fossil fuels, which are the remnants of past organisms. We have nearly used up this resource in ways not directly connected to the goal of space travel, in the process polluting and changing our world in ways that may limit future efforts to enter space. The sheer success of our species at dominating this planet has created living conditions which favor the spread of diseases that may ultimately cripple our civilization to such extent that space travel is not feasible. SpaceX notwithstanding, we may already be experiencing the beginning of this with the corona virus epidemic. We still live under the shadow of nuclear annihilation, not to mention biological warfare. Climate change may disrupt society with migrations and armed conflicts to such an extent that it cannot afford space exploration. Rampant nationalism and factionalism may preclude the cooperative global effort required. The violent and competitive nature at the base of our existence, reflected in the notion of conquering space, may be the very thing that prevents it. Our counterparts on other planets could face similar obstacles.

Another possible explanation is that aliens might simply not be interested in space travel. They could even lose interest in the external world altogether. This could happen if, like modern humans, they became too self-absorbed in entertainment, or decided to migrate to cyberspace, where consciousness can dwell in a virtual world. We have long had spiritual and meditative traditions that focus inward rather than outward, as well as myths and narratives of non-physical realms. Especially in a circumstance of limited or dwindling resources, and in the face of mortality, an alien civilization might choose some form of mental life over physical participation in the material world. Already our own civilization is moving in this direction, with digital entertainments and communication devices, not to mention the perennial resurgence of religion.

There is also the possibility that we have simply not been searching for extra-terrestrial signals long enough. We have only been able to receive and transmit radio emissions for little more than a century, and optical signals not much longer. Even the telltale heat signature of civilization has existed for but a few millennia. Technological development has been exponential, with most rapid change in the past couple of centuries. We can expect the change in the next couple of centuries to be far greater. Extrapolating, some people predict an imminent “singularity,” a point of no return when automation takes technology beyond human control. Perhaps the forms of AI that will control this world (or others) will have no interest in space travel and may even make the planet inhospitable to biological life. Some transhumanists foresee artificial life as an advancement over humanity. Equally likely seems the prospect that a post-human world could be dominated by artificial versions of viruses, bacteria and insects, rather than high-level artificial intelligence capable of space travel.

The fanciful vision of inter-galactic space travel, which fired our imaginations in Star Trek and Star Wars, projects characteristic human ambitions, values, and social dynamics on a cosmological scale. There is no sound reason to expect aliens to have a humanoid form, however, much less to gather in saloons at galactic outposts. Yet, if alien intelligence is a product of natural selection, as on this planet, there would be every reason to expect it to follow the fundamentally opportunistic patterns we see on Earth. Civilized aliens could only develop on other planets in the context of their biosphere, upon which they would be as dependent as we are here. Granted that we humans attempt to set ourselves apart from our biosphere, we might expect space-faring civilizations to have developed ideals and codes of behavior that facilitate cooperation, and a science that facilitates control of nature. And, of course, mathematics.

There is an understanding among scientists and science-fiction writers that the math glorified on this planet would be a lingua franca among galactic civilizations—not the same symbols, of course, but similar concepts deemed universal. However, the biological basis and parochial nature of our mathematics is even less recognized than that of our physics. The basis of our math is the natural numbers, which abstract the integrity of discrete “objects” such as human beings perceive in their physical or mental environment, and which they themselves exemplify as individuals. The finite steps of a proof, calculation, or verification exemplify discrete acts of an agent upon a world of objects it can manipulate. This corresponds to primate experience and action in an environment consisting of countable things, whether tangible or abstract. What if, at some level perceivable to aliens, the world does not consist of discrete objects and actions? Would another concept of mathematics and of computation be more suitable? What about an alien whose body does not amount to a discrete object? Of course, the technology of space travel may require manipulating and assembling what we take to be countable objects. Yet, an amorphous or non-localized creature might have ways to change its environment analogically—for example, through chemical emissions. (Indeed, this is how most self-regulation works within the organisms we know.) Computation for such an alien would not be digital processing, but direct covariance with environmental changes. What need or use could such a being have for natural “laws” as algorithmic compressions of an input? Would such a math, and the biology and mentality behind it, lend itself to space travel?

I had an epiphany while watching the original Star Wars movie. I realized that this planet—our home in space­—is an alien world and that we are the bizarre aliens that inhabit it! Whether or not any of those fancied other interstellar watering holes exist, the vision of them was created here, modelled on what is familiar to us. Just as children are attached to their mothers, we naturally find beautiful the place of our origins, without which we could not have come forth into existence. That first Star Wars film was released when the Province of Quebec still issued license plates with the motto: “La Belle Province.” Just to let all that alien traffic know how we feel about home, perhaps one day our missions to the stars will bear license plates that read “The Beautiful Planet,” in whatever language then prevails.