A Thought Experiment Relevant to the Fermi Paradox

Saturday

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Knowledge relevant to the Fermi paradox will expand if human knowledge continues to expand, and we can expect human knowledge to continue to expand for as long as civilization in its contemporary form endures. Thus the development of scientific knowledge, once the threshold of modern scientific method is attained (which, in terrestrial history, was the scientific revolution), is a function of “L” in the Drake equation, i.e., a function of the longevity of civilization. It is possible that there could be a qualitative change in the nature of civilization that would mean the continuation the civilization but without the continuing expansion of scientific knowledge. However, if we take “L” in the big picture, a civilization may undergo qualitative changes throughout its history, some of which would be favorable to the expansion of scientific knowledge, and some of which would be unfavorable to the same. Under these conditions, scientific knowledge will tend to increase over the long term up to the limit of possible scientific knowledge (if there is such a limit).

At least part of the paradox of the the Fermi paradox is due to our limited knowledge of the universe of which we are a part. With the expansion of our scientific knowledge the “solution” to the Fermi paradox may be slowly revealed to us (which could include the “no paradox” solution to the paradox, i.e., the idea that the Fermi paradox isn’t really paradoxical at all if we properly understand it, which is an understanding that may dawn on us gradually), or it may hit us all at once if we have a major breakthrough that touches upon the Fermi paradox. For example, a robust SETI signal confirmed to emanate from an extraterrestrial source might open up the floodgates of scientific knowledge through interstellar idea diffusion from a more advanced civilization. This isn’t a likely scenario, but it is a scenario in which we not only confirm that we are not alone in the universe, but also in which we learn enough to formulate a scientific explanation of our place in the universe.

The growth of scientific knowledge could push our understanding of the Fermi paradox in several different directions, which again points to our relative paucity of knowledge of our place in the universe. In what follows I want to construct one possible direction of the growth of scientific knowledge and how it might inform our ongoing understanding of the Fermi paradox and its future formulations.

At the present stage of the acquisition of scientific knowledge and the methodological development of science (which includes the development of technologies that expand the scope of scientific research), we are aware of ourselves as the only known instance of life, of consciousness, of intelligence, of technology, and of civilization in the observable universe. These emergent complexities may be represented elsewhere in the universe, but we do not have any empirical evidence of these emergent complexities beyond Earth.

Suppose, then, that scientific knowledge expands along with human civilization. Suppose we arrive at the geologically complex moons of Jupiter and Saturn, whether in the form of human explorers or in the form of automated spacecraft, and despite sampling several subsurface oceans and finding them relatively clement toward life, they are all nevertheless sterile. And suppose that we extensively research Mars and find no subsurface, deep-dwelling microorganisms on the Red Planet. Suppose we search our entire solar system high and low and there is no trace of life anywhere except on Earth. The solar system, in this scenario, is utterly sterile except for Earth and the microbes that may float into space from the upper atmosphere.

Further suppose that, even after we discover a thoroughly sterile solar system, all of the growth of scientific knowledge either confirms or is consistent with the present body of scientific knowledge. That is to say, we add to our scientific knowledge throughout the process of exploring the solar system, but we don’t discover anything that overturns our scientific knowledge in a major way. There may be “revolutionary” expansions of knowledge, but no revolutionary paradigm shifts that force us to rethink science from the ground up.

At this stage, what are we to think? The science that brought to to see the potential problem represented by the Fermi paradox is confirmed, meaning that our understanding of biology, the origins of life, and the development of planets in our solar system is refined but not changed, but we don’t find any other life even in environments in which we would expect to find life, as in clement subsurface oceans. I think this would sharpen the feeling of the paradoxicalness of the Fermi paradox still without shedding much light on an improved formulation of the problem that would seem less paradoxical, but it wouldn’t sharpen the paradox to a degree that would force a paradigm shift and a reassessment of our place in the universe, i.e., it wouldn’t force us to rethink the astrobiology of the human condition.

Let us take this a step further. Suppose our technology improves to the point that we can visit a number of nearby planetary systems, again, whether by human exploration or by automated spacecraft. Supposed we visit a dozen nearby stars in our galactic neighborhood and we find a few planets that would be perfect candidates for living worlds with a biosphere — in the habitable zone of their star, geologically complex with active plate tectonics, liquid surface water, appropriate levels of stellar insolation without deadly levels of radiation or sterilizing flares, etc. — and these worlds are utterly sterile, without even so much as a microbe to be found. No sign of life. And no sign of life in any other nooks and crannies of these other planetary systems, which will no doubt also have subsurface oceans beyond the frost line, and other planets that might give rise to other forms of life.

At this stage in the expansion of our scientific knowledge, we would probably begin to think that the Fermi paradox was to be resolved by the rarity of the origins of life. In other words, the origins of life is the great filter. We know that there is a lot of organic chemistry in the universe, but what doesn’t take place very often is the integration of organic molecules into self-replicating macro-molecules. This would be a reasonable conclusion, and might prove to be an additional spur to studying the origins of life on Earth. Again, our deep dive both into other planets and into the life sciences, confirms what we know about science and finds no other life (in the present thought experiment).

While there would be a certain satisfaction in narrowing the focus of the Fermi paradox to the origins of life, if the growth of scientific knowledge continues to confirm the basic outlines of what we know about the life sciences, it would still be a bit paradoxical that the life sciences understood in a completely naturalistic manner would render the transition from organic molecules to self-replicating macro-molecules so rare. In addition to prompting a deep dive into origins of life research, there would probably also be a lot of number-crunching in order to attempt to nail down the probability of an origins of life event taking place given all the right elements are available (and in this thought experiment we are stipulating that all the right elements and all the right conditions are in place).

Suppose, now, that human civilization becomes a spacefaring supercivilization, in possession of technologies so advanced that we are more-or-less empowered to explore the universe at will. In our continued exploration of the universe and the continued growth of scientific knowledge, the same scenario as previously described continues to obtain: our scientific knowledge is refined and improved but not greatly upset, but we find that the universe is utterly and completely sterile except for ourselves and other life derived from the terrestrial biosphere. This would be “proof” of a definitive kind that terrestrial life is unique in the universe, but would this finding resolve the Fermi paradox? Wouldn’t it be a lot like cutting the Gordian knot to assert that the Fermi paradox was resolved because only a single origins of life event occurred in the universe? Wouldn’t we want to know why the origins of life was such a hurdle? We would, and I suspect that origins of life research would be pervasively informed by a desire to understand the rarity of the event.

Suppose that we ran the numbers on the kind of supercomputers that a supercivilization would have available to it, and we found that, even though our application of probability to the life sciences indicated the origins of life events should, strictly speaking, be very rare, they shouldn’t be so rare that there was only a single, unique origins of life event in the history of the universe. Say, given the age and the extent of the universe, which is very old and vast beyond human comprehension, life should have originated, say, a half dozen times. However, at this point we are a spacefaring supercivilization, we can can empirically confirm that there is no other life in the universe. We would not have missed another half dozen instances of life, and yet our science points to this. However, a half dozen compared to no other instances of life isn’t yet even an order of magnitude difference, so it doesn’t bother us much.

We can ratchet up this scenario as we have ratcheted up the previous scenarios: probability and biology might converge upon a likelihood of a dozen instances of other origins of life events, or a hundred such instances, and so on, until the orders of magnitude pile up and we have a paradox on our hands again, despite having exhaustive empirical evidence of the universe and its sterility.

At what point in the escalation of this scenario do we begin to question ourselves and our scientific understanding in a more radical way? At what point does the strangeness of the universe begin to point beyond itself, and we begin to consider non-naturalistic solutions to the Fermi paradox, when, by some ways of understanding the paradox, it has been fully resolved, and should be regarded as such by any reasonable person? At what point should a rational person consider as a possibility that a universe empty of life except for ourselves might be the result of supernatural creation? At what point would we seriously consider the naturalistic equivalent of supernatural creation, say, in a scenario such as the simulation hypothesis? It might make more sense to suppose that we are an experiment in cosmic isolation conducted by some greater intelligence, than to suppose that the universe entire is sterile except for ourselves.

I should be clear that I am not advocating a non-naturalistic solution to the Fermi paradox. However, I find it an interesting philosophical question that there might come a point at which the resolution of a paradox requires that we look beyond naturalistic explanations, and perhaps we may have to, in extremis, reconsider the boundary between the naturalistic and the non-naturalistic. I have been thinking about this problem a lot lately, and it seems to me that the farther we depart from the ordinary business of life, when we attempt to think about scales of space and time inaccessible to human experience (whether the very large or the very small), the line between the naturalistic and the non-naturalistic becomes blurred, and perhaps it ultimately ceases to be meaningful. In order to solve the problem of the universe and our place within the universe (if it is a problem), we may have to consider a solution set that is larger than that dictated by the naturalism of science on a human scale. This is not a call for supernaturalistic explanations for scientific problems, but rather a call to expand the scope of science beyond the bounds with which we are currently comfortable.

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