Life exists only on Earth?


The debate about the existence of life elsewhere in the universe is akin to the controversy over the existence of God. Some believe in it as hard as iron, others consider it impossible. Surprising! The hypothesis of a life elsewhere is however more accessible to the scientific approach. We now understand better the formation of celestial bodies and then the steps that made it possible to move from inert to living. This makes the border indistinct. A simple reasoning is this: take the initial conditions necessary to cross each step; calculate their frequency; let’s multiply all these probabilities together and we get that of having another Gaia somewhere.

This is the reasoning followed by Jean-Pierre Bibring in his recent book Alone in the Universe. With this method of calculation, the final probability is so tiny that we can turn off our radio transmitter to other species. No listener will come to say hello. You might as well go back to painting in the caves. The probability is higher to contact our distant descendants, who will be as strange as aliens imagined today.

Major bias

But this reasoning is based on a major cognitive bias. It uses exclusively the downward look, the one worn by the observer, already aware of the result, at the end of the complex chain of the process. The downward look consists of reconstructing the whole sequence in such a way as to obtain this result and no other. The intention is not at the origin of the sequence but at its end. The reasoning is done a posteriori. It takes the direction which I call ‘descending’ in the complex dimension. Philosophers use a similar term: teleological. This is the intention of the observer who seeks herself in her own constitution.

Another story

The upward look shows a completely different story. It consists in questioning the initial constituent elements, questioning them about their “projects”. The intention is given back to the ascending direction, called ontological. It does not yet know anything about the result it can achieve. Many are possible. But not an infinity, as Bibring thinks, who calculates the probability of “his” result among an infinity and declares it impossible. The starting elements do not interact randomly. They create their own laws together, eventually meeting stable organizations on which they maintain themselves. The immeasurable number of configurations of fundamental particles thus stabilizes on atomic organizations, with an incredibly long duration.

The universe is not chaos. It explores, it still explores the multitude of its possible organizations. When one of them is relatively stable, the entities created immediately generate a new context that can lead to additional organizations. The Universe is never at rest. There is always free energy on top of the already bound energy, which forms new systems, higher in the complexity scale.

Life is a detailed exploration

Life is that: a remarkable elevation in the complex dimension. Certainly this elevation is local. It has not taken place on other planets in the solar system. These have not yet met with the successive stabilities that have allowed life to appear. Perhaps they never will. But elsewhere? The solar system and the Earth are not particularly ancient systems. Others have had an infinitely longer time than ours to increase their complexity. Seeing the speed of our recent technological evolution, we might even be surprised that we don’t already live in a neighborhood overcrowded by alien civilizations.

Why this apparent desert?

The reason is that complexity can go in the direction of collapse as well as elevation. The higher it is, the more fragile it is. You have to keep the organization stable in the midst of a host of random events. Let us note that our technological progress is not accompanied by such substantial social advances. Major weapons are in the hands of tribal humans. The collapse of civilization is possible. Maintaining complexity requires a collective “up to the task”.

It is also possible that the principle of residual free energy, the engine of complexity, operates at the mental level. The motivation to reproduce and expand would then decrease in the most complex aliens. Why continue to satisfy a primal instinct, when much more abstract concerns have come to replace it?

The Gods, if they exist, have probably become wise enough not to show themselves.


Life exists only on Earth, Science & Life HS 80 2022
Alone in the Universe, Jean-Pierre Bibring, 2022

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