Enrico Fermi once posed a question we now call the Fermi Paradox: where are all the aliens and why haven’t they contacted us?
People have tried to answer this question by looking for things familiar to them. Because we were currently doing these things (transmitting radio signals into the cosmos, searching for radio signals) we assumed that other civilizations were doing this too.
Other people have tried to answer the Fermi paradox by various means: the dark forest hypothesis (any space faring civilization would immediately kill its neighbors) or the great filter theorem (there are obstacles we don’t know about).
I’d like to throw out my own hypothesis: industrial civilization is not sustainable in the long term. And in order to actually be seen, you have to put out radio signal for tens of thousands of years. Perhaps even hundreds of thousands of years.
We are assuming that once people achieve the level of civilization necessary to make ourselves visible, we stay that way, and do not regress into barbarism, or do not lose our technology or knowledge. Academics assume that once we achieve the state necessary to sustain this level, we will always stay there.
Any student of history will know that this is not the case. The average life span for any sophisticated civilization is about 350–400 years. At some point, they collapse into anarchy, often for a variety of reasons: the political system rots, or there’s a climate disaster, or plague, or famine. And then the massive system sustaining higher education and industry collapses and the population reverts to subsistence agriculture in order to keep themselves alive.
Sending signals into space is a massive endeavor. It requires the mobilized resources of an entire continent to achieve it. And whether that signal continues to spread or persist largely depends on whether or not the political system supporting it can continue, as well as the scientific system.
Most do not. The survival rate for any thing, be it a country or an animal, or person, always drops to zero over the passage of time.
And when you think about the fragility of most countries, it’s not surprising that we don’t hear anything. In about 12,000 years of civilization (we might have records for about half that), we have only been able to achieve our current state of visibility in the last 100 years. That’s only .0083 percent of all of human history.
We have been able to achieve this by using cheap, abundant energy (oil) as a substitute for enslaving large portions of the population. That won’t last — and once oil is gone the cheap energy we’ve been using to ship food and feed ourselves will be gone. And even if we do come up with a viable replacement (solar) there’s no guarantee that we’ll keep the technology necessary to keep making it.
The silence is not surprising. It is expected.