Deafening Silence

The race to the stars

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In a universe that we now understand to be both unimaginably vast and ancient, the question becomes, where are the aliens? Surely, with modern technology, we would see signs of intelligent life everywhere we look, but we don’t. This apparent contradiction, known as the Fermi Paradox, has many theorized solutions. Some potential answers are encouraging, others are frightful, but all embody the importance of continued human progress on the pale blue dot.

The Paradox

The Big Bang, the first moments of the creation of the universe, set into motion the immutable laws of physics. Chief among these laws was the Second Law of Thermodynamics, which lays out what we know as “entropy.” Under the second law, the universe will naturally trend from order to disorder, or more specifically, toward energy dispersion. As we will see, life on Earth, paradoxically, conforms to the second law and accelerates the process of entropy on the universe’s behalf. Indeed, the emergence of life may have been a natural and inescapable consequence of physics.

To be fair, the precise temperature and chemical conditions that allowed for the formation of life on Earth are probably not common, but there is no requirement that life be so constrained to these parameters. Earth’s oceans, for example, harbor life that survives harsh acidic, high-temperature environments… and in complete darkness. There is also no inherent reason that life must be “carbon-based” either. Scientists believe silicon-based life is possible, if less probable, and this greatly broadens the environments where life could survive and thrive. Surely, in the vastness of the universe, there are many others. The universe is incomprehensibly large, with trillions upon trillions of planets.

This begs the question, why do we not find a universe teeming with life? This question was first raised in 1950 by Enrico Fermi, in what became known as Fermi’s Paradox. The paradox has only grown more mysterious with time. Our telescopes can now analyze the atmospheric composition of some distant planets, which could detect the presence of bacterial life via chemical fingerprints. We have found nothing. Intelligent life would probably be even easier to spot. As we do, advanced civilizations would use radio communication. We should be able to “hear” some of them, or otherwise “see” their activity as they terraform planets or harvest energy from stars. Yet, our telescopes have scanned the skies for decades, hearing only silence. This silence, however, speaks volumes.

Many solutions to Fermi’s question have been proposed. Among the more unique was posited by John Allen Ball in 1973, known as the “Zoo Hypothesis.” This theory holds that intelligent life exists and knows that we are here, but is hiding from us, preferring to observe from afar. Not unlike a nature reserve or a zoo, observing our development serves a scientific purpose for them. Should our civilization become sufficiently advanced, they may one day contact us. If you ask me, this seems far-fetched. Not actively making contact is one thing, but hiding their entire civilization (and others), including their radio transmissions, spacecraft, laser communications…etc is another.

The approx. the small red dot on the right represents human radio broadcasts' reach.

Others have more plausibly suggested that the universe is simply too vast. Travel and communication are limited by the speed of light or nearly 300,000,000 meters a second. That’s fast, but our galaxy is some 150,000 light-years across. This means radio transmissions leaking from Earth would take tens of thousands of years to reach the ends of our galaxy. Since humans invented radio only <150 years ago, even our earliest signals have barely touched the smallest fraction of our galactic home (see image above). The same applies to “them;” we don’t hear them because their signals haven’t reached us yet. But in a universe that is 14 billion years old, that too seems unlikely. It took only ~300,000 years for humans to invent radio, 14 billion years is plenty of time for many civilizations to have done the same.

The Great Filter

In the 1990s, another possible explanation for the universal silence was formulated by Robin Hanson, in what became known as the “Great Filter” theory. This theory holds that while the universe’s vastness creates countless opportunities for life to emerge, one or more rungs on the “ladder” between chemical evolution and the emergence of civilized life must be highly improbable. This rung, or rungs, is called the Great Filter since it appears to block the advancement of life beyond a certain point.

What could the Great Filter be? Is the emergence of life itself extremely unlikely? Or perhaps the universe is filled with life, but the development of intelligent, multi-cellular organisms is rare? Or maybe intelligent life emerges but fails to develop and sustain progress as we have? Or maybe, most ominously, civilized life has emerged many times, but like the stars themselves, their efflorescences quickly burn out. Perhaps they, like us, become hopelessly dependent on fossil fuels and never find a viable workaround. Maybe they never overcome their biological limitations and eventually and inevitably wage wars between them that extinguish the light of their civilization.

Or perhaps one of these advanced civilizations gave birth to super-intelligent AI that wiped out the mother species. One could imagine that this all-knowing AI is still out there, hidden in the darkness beyond our detection, with no need for radio communication and lacking the telltale chemical signature of life. Maybe it’s out there, harvesting energy from stars as it ceaselessly expands like cancer upon the universe, mopping up every potential threat to its survival the moment it detects competition for energy. Maybe, just maybe, this AI is coming for us and we don’t know it.

I have little doubt that our planetary conditions are fortuitous, but I do not find the Great Filter explanation sufficient. The fossil record indicates that life on Earth emerged almost instantly upon the formation of our early oceans. Knowing this, surely single-celled life cannot be that rare. The great filter theory probably limits the number of civilizations that can or will emerge in this universe, but it alone does not explain the silence of the heavens across the 14 billion-year timeframe that it has existed…unless we are early.

Auspicious Timing

Counterintuitively, despite the universe’s age, humans may be among the first intelligent organisms to emerge. Early stars were short-lived, exploding into supernovas or collapsing into black holes that sterilized much of the young universe, over and over again. The Sun was “born” at the end of this “cosmic death show.” Additionally, many of the heavier elements essential for civilization could not have been made in these earlier stellar cauldrons. In other words, our timing may have been just right. Indeed, astronomers from the Space Telescope Science Institute have estimated that the probability that the universe harbors other civilizations is an astonishing 92 percent. This estimate, however, is based on the entire lifespan of the universe, not the time that has elapsed so far. Most planets that will harbor these civilizations do not even exist yet.

There is a good chance that other civilizations are emerging around right now, we just cannot see them. Our search for intelligent life, as discussed above, is kneecapped by the universe’s size compared with the speed of light. When we look into the night sky, we do not see the universe as it is, but rather as it was. Alien civilizations could be emerging everywhere alongside us, but their light and radio waves will not reach us for generations. Think about it this way, should an alien civilization located 100,000 light-years away be able to see Earth, they would see a planet with promising oceans and reasonably intelligent mammals, but certainly no signs of a spacefaring civilization.

The fact that human civilization exists at all bolsters the notion that we are early. As humans have expanded the reach and depth of our civilization on Earth, we have molded the planet, for better or worse, in our image. We have diverted rivers, razed forests, constructed cities of steel and glass…etc. Our activity here on Earth prevents other species from doing the same. There is no threat, for instance, that chimpanzees will someday begin farming; we have already taken the land. On a cosmic scale, should intelligent life have emerged in the early universe, we humans probably couldn’t have evolved or advanced either. Like many others, our planet would have been harvested for their benefit long ago.

An interesting consequence of this theory is that there may be a “deadline” for intelligent life to emerge and thrive. If indeed other civilizations are developing right now, they are looking up to the heavens and drawing the same conclusion that we are: they must be early. They are also confronted with the same choice we are; stay confined to their home planet or expand into the heavens before someone else does. Should humanity remain confined to Earth, we risk alien domains thriving all around us, conquering the vastness of space, harvesting energy and resources, possibly including our own planet. Granted, confined to Earth, we would probably face an extinction event long before that happened anyway. These alien civilizations will conclude, as we will, that they have no choice but to progress their technology and expand outward. If they do not, the light of their consciousness will inevitably be snuffed out.

Thus, I see the pro-progress movement as the ultimate expression of philanthropy. In this race to the stars, we endeavor to be good stewards of life and preserve the light of human consciousness. Indeed, there may come a day when we hear “them” and reply. This multigenerational communiqué presents a stark choice. Should the aliens come to meet their interstellar pen pals, what will they find when they arrive thousands of years later? Will they find a prosperous and advanced civilization? Or will they find the ruins of what was and could have been? That choice is ours.

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