Great Filters: the Limits of Future Life

The concept of the Great Filter was introduced by Robin Hanson. According to it, the Fermi-paradox can be explained by the existence of a barrier that usually prevents the dead matter to become living and/or intelligent and albeit we were able to overcome it, the other candidates for either life or thinking wasn’t lucky/smart enough to get over it. In short: there are some factors that work against the living/intelligent beings.
Of course, it is only a theory and there are other, possible explanations for the “Great Silence” (=our missing “companion intelligences” in the Universe). For example: a low probability of life; or our inability to detect their signs; or we are the first intelligent races so it is not a surprise not to observe other intelligences in our light cone.
But we could adapt this Great Filter hypothesis for the future. Fred C. Adams (Long-term astrophysical processes, in: Global Catastrophic Risks, 2008) draws up our Universe’s very distant future up to 10^100 ears and regarding the survival of life, there are some fundamental turning points in the distant future of the Universe.
The first one is about the survuval of the earthly life. Our planet will be uninhabitable for an intelligent being within a 0.9 – 1.5 billion year and the biosphere will be “essentially sterilized in about 5.5 billion years” by the Sun. Notice that our environment in the Planetary System is not too life-friendly: a smaller start with 10% mass of the Sun would shine for trillion years (p. 44–46.). Regarding our actual knowledge about the pace of our human races’ technological developments, it seems to be possible to circumvent these problems–e.g. by migrating to another star.
The second barrier is more problematic. About 10^40 years later, because of the proton decay the matter in its traditional form will disappear and it means the “life as we know it”. (p. 47.)
It seems to be a serious “Great Filter” regarding the future of life and it would be a real challenge to find a solution which would be able to guarantee the survival of the life in this radically different physical environment. Of course, 10^40 year seem to be an unimaginably long time–but notice that it is not the end of the history of our Universe. The remains of the earlier era: the last black holes will be evaporated within a 10^100 years and only after it begins that epoch when “predictions of the physical universe begin to lose focus”. (p. 49.)
In other worlds: the living period (its end will be caused by the baryon decay) is like a phenomenon disappearing after the first trillionth – trillionth – trillionth… second of the Big Bang.  A 10^40 years are simply negligible to the remaining period of time.
So it isn’t evident to argue that the “aim” of our whole Universe is that momentary phenomenon of life. However, the final conclusion of the Strong Anthropic Principle is that the appearance of life is a necessity. But why not, for example, the black holes?
So we have two choices. We can either refuse the Strong Anthropic Principle as a ridiculous and flawed theory (and I tend to do it) or we can ask how it would be possible for the future life to survive these two Great Filters: the baryon and the black hole barriers–and it is a really exciting question.

Living in an extremely big Universe

Fred Adams and Greg Laughlin distinguish (in their book entitled Five Age of the Universe) four “windows” from an astronomical point of view which are opened to observe the physically existing Universe.

• The first level is the planets;
• the second is the solar systems;
• the third one is the level of the galaxies and
• the last one is the Universe itself.

One can question why the level of galaxy clusters ignored and it is unquestionable that this scale is influenced by our special circumstances. An intelligent being living in the interstellar space probably would not regard either the planets’ or the solar systems’ level as important (although she could recognize their existence.)

Another example for the observer-dependent nature of scales/taxonomies is the megatrajectory theory. It is based on the evolutionary mile stones and

• the emergence of life is the first so-called megatrajectory;
• the second is the prokaryote diversification;
• then eukaryotic cells appear;
• it is followed by the rise of the multicellular life forms;
• the “invasion of the land” is the 5th and
• the rise of intelligence is the 6th megatrajectory that gave an opportunity for the invasion of every possible environment

–perhaps including the outer space (A.H. Knoll, R.K. Bambach: Directionality in the history of life: diffusion from the left wall or repeated scaling of the right. Paleobiology, 2000).
The post biological intelligence can be interpreted as the 7th megatrajectory (Cirkovic, Dragicevic and Beric-Bjedov 2005).
This taxonomy is focuses at least partly on parochial details of earthly evolution, since its aim is to give a description of the history of life on earth: I.e. the fifth megatrajectory would never occur on a water covered planet.
We can reinterpret this megatrajectory concept focusing on those factors that are presumably universal. Freeman Dyson distinguishes three classes of phenomena which can occur in our universe: “normal physical processes”; “biological processes” and radio (or another forms of) “communication between life forms existing in different parts of the universe.”(Disturbing the Universe, 1979) These factors can be interpreted as “gigatrajectiores,” because they–opposite to megatrajectories–can be typical in any universe which is populated with intelligent observers.

• The first gigatrajectory is characterized by the domination of lifeless matter;
• the appearance of life was the second gigatrajectory and
• finally intelligence rose.

Robert Batterman mentions in his article about “The Tiranny of scales” (in the Oxford Handbook of Philosophy of Physics) that it is a reductionist approach to believe that “whatever the fundamental theory is at the smallest, basic scale, it will be sufficient in principle to tell us about the behavior of the systems at all scales.” Regarding the second gigatrajectory, after its appearance life was able to conquer our whole planet and, what is more, thanks to the relative small size of the earth, we can visit any point of it–even on foot. It is imaginable a bigger planet where its habitants too small and/or too short lived to do it individually, but it is questionable whether it is imaginable a so big planet that there isn’t enough time for life to occupy every part of it, since their sun goes out before the end of it. In short: the size of our earth is consistent with life’s abilities.
What is more, if you accept one or other form of panspermia hypothesis, then it seems to be possible that life which appeared on the surface of a planet can spread in our Galaxy. But it seems to be impossible even to the microbial life to sail to the closest galaxy, since it would take billions of years. So the spread of life is localized for ridiculously small parts of the Universe. In other word: to believe that other galaxies inhabited with intelligent beings, we should believe that both life and intelligence arose independently from us somewhere in in the Universe.
Similarly, technology seems to be provide an opportunity (theoretically, at least) to conquer not only our planet, but both our solar system and our galaxy–after all, even the Fermi Paradox is based on the presumption of its possibility (if we are able to, then they should be able to visit any stars, including the sun, as well). But notice that even the SETI is mainly about the search for alien intelligence within the Milky Way. Although we have a theoretical chance to observe a super civilization’s energy emission from another galaxy, it is impossible to visit even the M31, since it would take million years even with 0.9 c. And although the time dilatation would make slower the aging on the board of the spaceship, its construction should survive an unimaginably long period of time (notice that the Homo sapiens itself didn’t existed a million year ago). This long travel seems to be not theoretically, but technically impossible. So unless we invent a revolutionary new form of travel (i.e. a warp driver, but it is only an unfounded dream today without a chance to build it), we will never leave the Milky Way and it means that the Universe is extremely huge compared to our possibilities.
In short: the spatial structure of the Universe limits the possibilities the spread of life and intelligence. It raises a question whether it would be possible a universe which can be conquerable by its habitants.

The tree of cosmological natural selection

According to Lee Smolin, it is not a well-founded idea to apply Newton’s paradigm about the nature of physical laws without an approximation to the whole Universe, since it is based on a local observation and it suggests the existence of timeless laws which can be applied to a timeless space.
What is more, the Newtonian interpretation is unable to explain why the observed laws exist instead of others. Similarly, both our Universe’s high homogeneity and that this Universe is so far from thermal equilibrium are in question. Boltzmann answered the second problem arguing that it was a result of the fact that our world was born in an incredibly low-entropy state (it is the “past hypothesis”). But he simply replaced the original problem with a new one, since it is not known why was so low the entropy originally.
Generalizing this problem, the Newtonian paradigm is “a theory [which] has infinite of solutions,” but we observe only one Universe.
To solve this problem, one can introduce the multiverse hypothesis without changing the Newtonian paradigm. According to this logic, our Universe is a part of a bigger ensemble and we live in a biofil cosmic environment, because all of the possible universe-variations are realized, and we are simply lucky enough to find ourselves in a world of life-friendly conditions. But there is no testable predictions to falsify the multiverse proposal.
Smolin’s answer is the “cosmological natural selection”. It states that “the laws of nature have evolved over time” and he “decided to copy the formal structure of population biology by which populations of genes or phenotypes evolve on so called fitness landscapes.” The reproduction happens via black holes and the result is the birth of new baby-universes which inherit the physical laws of their parent universes’ laws in a slightly changed form (thanks to small, random changes). This process selects the more successful (=more back hole reproductive) universes and we presumably live in a successful universe which laws offers favorable conditions for black hole creation. And it is not a surprise, since life seems to be improbable without long-lived stars and carbon – which are necessary to the formation of black holes.
But this coincidence seems to be strange. Why the preconditions of black holes and life are the same?

• Perhaps it is only an observational bias and the physics of stars and the appearance of life are different phenomena without real connection, but there are other hidden, but cruical factors  – although we still didn’t realized them. Obviously, this explanation cannot be excluded, although it seems to be improbable.
• Perhaps the presence of long-lived stars, back holes and carbon are necessary preconditions of life, and these and only these preconditions lead to life.
• Or – and it seems to me the most probable – life can appear not only in carbon based universes, but our laws which leads to the creation of heavier elements allows its appearance. In other words: there are other, biofil universes without carbon, and it is another question whether there are another universes with different physics and different physical processes to reproduce themselves – perhaps even via more efficient solutions than the black holes. Namely: adapting Smolin's evolutionary approach, evolutionary processes are able to find only local maximums and the history of the descending baby-universes can be portrayed as an evolutionary tree. And it not sure that our branch is the most successful.

Compressibility, law and known facts to memorize

David Deutsch begins his book entitled The Fabric of Reality stating that the meaning of “to know everything is known” is equal “to understand” the world, but it doesn’t mean the knowledge of every isolated fact. We are far from a theory of everything which would be able to explain how our World works, but it “distinctly less fantastic than the idea that one person could memorize every known fact.” [p. 3]
It is not a surprise to found ourselves in a Universe which can be at least partially interpretable by laws –perhaps a primitive form of life could be able to evolve without a kind of predictability, but an intelligence able to interpret the World surely not. A kind of compressibility is the feature which allows to use shorthand to calculate the reality from certain pieces of information (i.e. a planetary orbits). Opposite to it, a string is random if we cannot present a representation of it which is shorter than the original sequence (Barrow: New Theories of Everything 2007, p. 11.).
Having studied a special musical instrument named lyre the Pythagoreans concluded that the reality ruled by numbers, and because of their intellectual heritage we regard self-evident that the description of the nature is compressible thanks to the numbers. It is not questionable that this mathematics based method proved to be really efficient to describe some aspects of reality.
On the other hand, there are incompressible things: i.e. it is trivial that there is no a shorter version for a poem which is equal to it, and it is a particular feature of the Universe that it can be divided into a compressible and an incompressible part.
Obviously, not “every known fact” mentioned by Deutsch is mathematically non-accessible, but our World’s another feature the proportion of the rules and the data we should memorize is unequal.
There are so few rules that some scientists hope to reduce all of them to a super formula. As it was mentioned earlier, the existence of intelligent life prescribes the existence of a very huge amount of data, since the evolution of thinking required billion years, and a long period of time means many events.
But on the one hand, why was it a so slow process? On the other hand: why do not exist many-many more laws even comparable in amount to the “every know facts?” Is it a requirement of a biofil Universe or only an accident?

And a concluding remark: we can draw up a categorization based on the relationship between "rules" (circa compressibility) and "data". Obviously the fifth subcategory is the most interesting where the efficiency of rules is determined either by a nonlinear function or changes randomly.

	efficiency	example
1.	perfect (theoretically)	compressible macro physical laws
2.	zero	poem, human society's evolution, etc.
3.	less and less efficient over time	meteorology
4.	more and more efficient	calculation by iterations
5.	different patterns determines the effectifiency in time than the third or fourth subcategory	?

Is the Universe roughly-tuned for computing?

This short paper proposes an alternative theory to Anthropic Principle. According to our interpretation, the Universe is not "fine-tuned" for life, but "roughly-tuned" for computation and its biofilness is only a phenomenon. This standpoint allows us to extend Seth Lloyd's concept about the ultimate physical limits of computing to examine the computing capabilities of any imaginable universe. In addition, I draw up a universe classification based on it.
Read more: http://arxiv.org/abs/1501.01754

Fine-tuning and evolutionary adaptation

Advocates of Anthropic Principle usually use two kinds of arguments to support their standpoint. They argue that life’s fine-tuned nature is a result either of chance/selection effect (Weak Anthropic Principle) or the explanation is our Universe “waited" for the emergence of a thinking being in a certain sense (Strong Anthropic Principle). But it is possibly that the nature of evolutionary mechanism is the answer for the“fine-tuning”.

Complexity science and biological adaptation
According to the complexity science, a hurricane is only complex, but an anthill both complex and adaptive system, since it can change itself and its operation to respond to the change of the environment. Biological evolution is a subcategory of complex adaptive systems, since it is a system which essential feature is the flexibility to adapt itself to a wild range of options. Life adapted successfully to the deep sea and the high atmosphere on our planet, and it seems to be a plausible hypothesis that it would be able to survive even on the surface of Mars. Notice that if this reasoning is true, then it is possible that the cause of other planets’ lifelessness in the Solar is not their hostile environment. Of course, they are lethal for Earthly life, since our life is adapted to our environment (inter alia, to a dangerous oxidant named oxygen). The problem is that life didn’t begin to evolve on those heavenly bodies, so it didn’t learn to adapt to those circumstances – perhaps because of the unfavorable initial conditions. All in all, it is useful to make a distinction between an environment hostile to the life, and an environment where life cannot able to begin to evolve.

Adaptation to our Universe’s physics
A complex adaptive system possibly can adapt to different circumstances. On the other hand, since this adaptation is a result of adaptive processes, the consequence will more or less strictly matches to the conditions and because of it, it is not a surprise that life seems to be “fine-tuned” for our Universe’s certain traits. Applying the complexity science’s approach to the problem of fine-tuning we can find a different solution than Anthropic Principle.
This logic raises further questions.

• First of all, it is a question whether different forms of life exist in our Universe which are either more or less fine-tuned our Universe’s conditions. It seems to me probable – but who knows.
• According to this interpretation, the rise of life seems to be possible in other universes which are characterized by other parameters (although it is not a necessity).

Life, Universe and multiverse

According to Bernard Carr, “the Multiverse picture reduces the strong anthropic principle to an aspect of a weak one” [in Universe or Multiverse, Oxford Univ. Press, 2007, p. 4], since it explains our Universe’s biofil features by hypothesizing the existence of the multiverse. If we accept the existence of (infinitely) many other universes, it is not a surprise to find ourselves in a universe fine-tuned for life. It is a consequence of the selection effect: we can live in a universe which is suitable for life, while there many, lifeless worlds (obviously, without any intelligent observer).
This reasoning based on some unspoken assumptions.
Although Abraham Loeb argues [The Habitable Epoch of the Early Universe, 2013] that there was an opportunity for the appearance of the life already 10 – 17 million years after the Big Bang, it seems to be evident that because of the physical laws, a relative huge and old universe is needed for the appearance of life. Still in Loeb’s example, the criterions of the life didn’t appear immediately after the beginning. So at least in a world governed by our laws of physics, we have to wait for some time before the first organism can be created. Obviously, it is an interesting question whether a universe with different physical laws can produce life within the first seconds. And it is a more interesting question that how long time needed for the formation of the intelligence in another Universe. Ad absurdum, one can imagine a world where the basic elements of life are cooked in the twinkle, but evolution is another story, since it based on natural selection. So a lot of steps is needed to reach a certain complexity. The appearance of the intelligence at a very, very early period of the Universe would be a powerful argument for the existence of a Creator.
Turning back to the original questions, it seems to be a well-founded argument that there are some criterion of the emergence of life and intelligence. It isn’t possible them to come into being without some physical conditions.
It is imaginable that to the emergence of a biofil universe many other universes’ existence needed. After all, life requires a relative long past with relative huge spatial extension, and ad analogiam, it cannot be excluded that a universe fine tuned for life requires the existence of other universes.
Obviously, it seems to be a not too serious concept. But Carr’s concept is based exactly on this, since he leads back the existence of our biofil environment to the existence of other universes. According to him, our Universe was chosen by chance, but I can imagine that there is a connection between our Universe and the others, and this connection isn’t based on a kind of chance, but on some kind of physical laws.
What is more, arguing that only a few (or only one) habitable universe exists, Carr suggest that life is not a general phenomenon, but an exception. But at least theoretically it is imaginable that life is necessarily associated with the presence of the matter (although not every, but) in several universes.
Or, ad absurdum, we can play with the idea of an “Ultimate Anthropic Principle” which prohibits the born of any lifeless universe. Who knows – we have only one example for a biofil world, and it isn’t enough for generalization.