The Great Filter is one possible solution to the famous Fermi Paradox, also known as the "Where Are They" problem. If you don't recall what that is, the famous physicist Enrico Fermi purportedly posed the question "Where are all the aliens?" on the way to lunch with his colleagues in 1950. Michael Hart formalized the Paradox further in 1975, and it goes something like this.
There are hundreds of billions of stars in the Milky Way. Many of them are much older than our sun.
Earth isn't unique - mathematically there must be many earth like planets in the galaxy, some of which have spawned intelligent life.
Some of those advanced enough to develop interstellar travel.
Several millions of years should be enough time to traverse the entire galaxy, yet we find no artifacts or evidence of 'them'.
Like any proposed scientific model, the Paradox raises more questions than it puts to rest. The Paradox asks both "why is there no evidence of extraterrestrials on earth", and "why are there no artifacts of extraterrestrials that we can observe" relying on a probability model given the massive scale of the Milky Way. Among the artifacts that scientists are looking for include stars with odd spectral signatures as clues to civilizations that have invented Dyson Spheres (apparatus for large scale harnessing of the main star's energy). The likely forms of advanced space travel have been contemplated since von Neumann riffed his idea that self replicating probes are plausible.
“Any sufficiently advanced technology is indistinguishable from magic“ - Arthur C. Clarke
The idea of the Great Filter was hatched by economist Robin Hanson in the mid 1990s as a response to the Fermi Paradox. The Great Filter is a probability barrier. It states that the reason we observe no evidence of interstellar visitors is because there are a number of existential tipping points that must be passed through successfully to achieve interstellar capabilities. It's our only concrete data point on existential risk. Hanson lists nine conditions:
The right star system (including organics)
Reproductive something (e.g. RNA)
Simple (prokaryotic) single-cell life
Complex (archaeatic & eukaryotic) single-cell life
Tool-using animals with big brains
Where we are now
He makes clear that this list is incomplete. The claim is that the Great Silence has happened because one or many of these conditions is very difficult to satisfy. Other scientists have identified more specific sub-filters at length. For instance, between numbers 7 and 8, one could talk about splitting the atom as a filter for a civilization that has a high amount of improbability of passing through. It has been 74 odd years after developing the first fission bomb, has it been long enough to mean we are through that specific filter? Or should we be grouping all nuclear technology development into one larger category that would include past achievements, current applications and future new technologies and development?
Philosopher and futurist Nick Bostrom makes the case that the worst thing that could happen to mankind is that we find evidence in our backyard of past intelligent life. If we found evidence of life on say, Mars, it would suggest that the emergence of life is not very improbable, that lots of star systems would have gotten to this point, and yet we still have the Great Silence. It implies that the weight of the Great Filter is ahead of us. However, even finding a Great Filter behind us does not rule out another ahead of us. If the artifacts we discover indicate an advanced level of biological and technological development, even worse for us. If humankind did make such a Martian discovery, it would be heralded by the press and state as a positive event, yet it would be completely the opposite.
The Great Filter is a nice heuristic - very much like the models and explanations humans like to throw around to explain incredibly complex phenomena where the complex causal loops and variables are not properly understood. To go from Hanson's #8 to #9 is the most crucial step, if only because it would be the step necessary to allow us to see the evidence of extraterrestrial life. And as complexity increases, the dependent variable relationships increase superlinearly. Complex systems often result in 2nd and nth order effects that are very hard to see. This would mean that passing through this stage of the filter is not a single-key problem. It is not a dual key problem. It is more complex that we can imagine.
Hanson has written a long piece entitled "Beware General Visible Prey" which aside from being a fun (and long) read, he postulates an idea about how a late stage Great Filter plays out. He coins the term "General Non Diminishing Prey"
So, bottom line, the future great filter scenario that most concerns me is one where our solar-system-bound descendants have killed most of nature, can’t yet colonize other stars, are general predators and prey of each other, and have fallen into a short-term-predatory-focus equilibrium where predators can easily see and travel to most all prey.
He explains why that scenario could be plausible in his piece. To me, this sounds more like "Everything Goes Wrong at Once" as a filter. "Killed most of nature" implies resource scarcity, predator/prey equilibrium becomes impossible.
The more different are the methods that prey use to create and store value, the smaller the fraction of that value a predator can obtain via a simple hostile takeover.
Typically predators face a diminishing return in a particular predator/prey scenario. At some point in the equilibrium game it gets harder and harder for the Arctic wolf pack to pursue the local hare population. That doesn't mean that they won't sometimes spend an non-rational amount of calories on a kill, it just means in aggregate the returns are diminishing, and the pack must pursue a different prey or one in a different geography. In nature, the more ways or interfaces available to prey for protecting themselves and their resources, the more prevalent the diminishing returns to the predator.
Future interstellar technology, if created, would mean big problems for the two mechanisms that create diminishing returns on prey: distance and diversity of hiding places. Any civilization that has the technology to colonize on an interstellar scale would most certainly have solutions to these two problems as they are fundamental to the decision to embark on the pursuit of travel in the first place. This reduces the predator/prey dynamic to fewer dimensions - less types of predator and prey, less places to hide, distance is less meaningful (technology) - leads to reduced diminishing returns to predation. This doesn't just destroy equilibrium, it increases the chance of prey population extinction.
The Great Filter concept is appealing, partly through its simplistic framework, but I suspect that focusing on descriptions of 'progress' based on science alone (multi-celled organisms, splitting the atom) becomes progressively less useful in describing how a civilization gets filtered as it progresses. Maybe the exception is some terminal theoretical physics experiment that all advanced civilizations are destined to attempt, but it's hard to optimize to prevent that type of disaster, particularly when this research might actually provide a solution to our future
If we focus on Hanson's #8 - 'Where we are Now', I suspect the likely Great Filter we are up against now is closer to "Everything Goes Wrong at the Same Time". If there was a single key problem that was responsible for the Great Filter, it would be relatively easy to think up solutions and patches, even if we could only narrow it down to say ten key problems.
The two concepts that are key here are emergence and intention.
We clearly cannot claim we are over the filter of self imposed nuclear destruction, even though Fermi created the first nuclear reaction in 1942. Emergence of technology having occurred at some point in the past has no indication as to when or if it will (if it can) be used in a way that would give it a starring role in the Great Filter. That's where intention comes into play.
Climate change, nuclear war, resource depletion - these are all legitimate problems for our brightest and best to work on. But sometimes problems build up faster than you can solve them, and so far we've been very lucky in our ability to do so. The hardest problems to solve are ones that will affect large proportions of the population and also have severe consequences for those people. Those tasked with solving these problems as well as the tools that allow them to do so are also dependent on a working economic and scientific apparatus. Task automating AI (forget about AGI for now) creates some emergent problems that society seems woefully unprepared to tackle. As it moves from the realm of unskilled labour to skilled, the problem of health of the apparatus is a real concern.
Mathematician/economist Eric Weinstein has a nice framework for describing this
Computer programs, like life itself, can be decomposed into two types of components:
Loops which repeat with small variations.
Rube Goldberg like processes which happen once.
Our skilled and unskilled labour professions look remarkably like A.
In short, what today’s flexible software is threatening is to “free” us from the drudgery of all repetitive tasks rather than those of lowest value, pushing us away from expertise (A) which we know how to impart, toward ingenious Rube Goldberg like opportunities (B) unsupported by any proven educational model. This shift in emphasis from jobs to opportunities is great news for a tiny number of creatives of today, but deeply troubling for a majority who depend on stable and cyclical work to feed families. The opportunities of the future should be many and lavishly rewarded, but it is unlikely that they will ever return in the form of stable jobs.
If you pause a piece of software while it is functioning, you probably interrupt some sort of function A loop. As foreign as the idea of ride sharing was to most people 8 years ago, in another 10 it will probably seem amazing that we had not let software entirely manage the 'Loops with small variations'. And then as software and digital products continue to replace physical economic output (MP3's) they start to resemble public goods which are both inexhaustible, fungible and easy to duplicate.
The velocity of these dynamics creates new challenges for economic stability. Machines optimize to the types of highly repetitive work the gig economy has given us. Wealth inequality partially expressed through modern culture wars have exhumed the concept of things like UBI and MMT, even as the modern version of automation has only just begun to displace the skilled labour force. How do governments replace tax revenue from skilled workers being replaced by software?
The human problems of having machines to do much of our bidding are real. With nothing that ties together the need to consume with the need to contribute, the human soul loses meaning, purpose and dignity.
Recent appeals to socialism are a result of these dynamics, and also because capitalism has become Capitalism! - the move toward corporatism, the melding of the oppressive state with the oppressive oligarchy. Modern Capitalism! doesn't currently have a real solution for the inability of a worker in an automated, financialized society to maintain dignity. This sets up political opportunists as predators with low diminishing returns to predation.
Consider the "Everything Goes Wrong at Once" scenario, specifically the balance of technology, resources and organization that allows for the maintenance of 7.5 billion people, and how quickly economic collapse could lead to a cascade of terminal events for humanity. The radical uncertainty exists that our brainiacs could have us all sucked into another dimension through some ill fated physics experiment, or a planet ending asteroid strike is obliterates all life. (Remember when scientists thought the first nuclear test could burn the entire atmosphere?) Better science and responsible science can assist there. But the potential cascade effects resulting from socio-economic collapse could unlock the tools to our own undoing that we already possess.
The emergence of potential man made Great Filter mechanisms is not new. The conditions that allow for their use have appeared here and there throughout history. It appears we are on the doorstep of another one of these periods, ushered in by both the failure of economic systems to harmonize the consumption/contribution formula, and by the emergence of software that has the potential to redefine billions of individual's roles in our Pebble in the Sky.