Statistically speaking, it turns out that 20% of the stars form double or multiple systems and that a roughly identical percentage probably have a procession of planets which, in all probability, at least one with the minimum conditions to maintain the life. But if life does not seem to be able to evolve around all the stars, for different reasons (temperature, gravity, radiation), it is statistically demonstrated that the appearance of life is a quasi-mandatory phenomenon under the conditions of Universe, if, as is assumed, the laws of nature are universal. Since we exist, we must explain this fact without invoking a supernatural being, which in any case remains a non-falsifiable and therefore unscientific concept.
An important observation already underlies the universality of the laws of nature: the extreme precision with which the constants of nature have been determined. Many physicists and astrophysicists believe that these values are not due to chance. At the quantum level, it is as if the different forces had the right values to make it work. This is the anthropic principle that we will see in cosmology.
In a few words, in its weak version, the anthropic principle considers that if the energy of the universe had been somewhat weaker or somewhat stronger, it would have exploded or shrunk too quickly without leaving the time to constitute itself to form the first molecules of life. After all, the universe is a living laboratory in which reactions take some time to complete, depending on the properties that govern nature.
One can also ask why the world is locally organized and measure the lack of information systems irrespective of the scale of the phenomenon and our appreciation of the state of disorder. In the universe, there exists a very special quantity, entropy. As we will see in another file, this thermodynamic quantity applies to all systems, both to the evolution of the physical and chemical systems and is summed up in two words: globally order tends towards disorder. Without some energy loss, no interaction would be possible. The universe as a whole would have remained at the primordial stage and would never have succeeded in building up the complex edifice of the growing organization.
The task of biochemists, exobiologists and astrobiologists therefore consists in demonstrating that life is a common phenomenon in the universe. Starting with some ingredients and a primitive soup, they must invent the scenarios that have led to the current “breeding ground”. If only one star in the Milky Way harbors life, it is potentially billions of inhabitable worlds that fill the universe. By studying the biochemistry and behavior of prebiotic molecules, it is discovered that they survive under conditions deemed hostile or exist in unknown metastable states on Earth.
It is by using the new tools of bioastronomy and by studying the evolution of life on Earth that we can confirm or deny the existence of life elsewhere in the universe.
When we turn our gaze to the sky, among the many questions we raise in front of the infinity of stars and extent of the universe, we are naturally led to ask what is the origin and the reason for our presence down here.
The answer to “why” will sometimes be the footprint of anthropocentrism, a naive but understandable feeling, that we will try nevertheless to get rid of.
As for the question of “how” life and thought have emerged, it is better to consider that God has nothing to do with it – except for the initial state – until it is demonstrated that the universe could have developed independently of any outside influence.
One can question the determinism of the world or the reality of the anthropic principle, but the theological problem will have no place in this scientific context. Since the total comprehension of the Universe is now beyond our understanding, we must address only the more limited problem: the origin of life and the possibilities of existence of another form of life in the universe in light of the latest discoveries.
Teams of researchers have sought to understand the mechanisms that govern the living world, but no one will tell you that he has succeeded in synthesizing even a single-celled being. Life is an assortment of chemical and physical conditions which in our case has arrived at such a stage of organizational complexity that one may wonder if a similar situation can occur somewhere in the universe. In any case, our generation will not know the answer. True astronomy has existed for less than half a century, what does it represent for the existence of the world? Very little …
Before detecting other signs of life in the universe, it is prudent to ask whether the process we have known on Earth can reproduce elsewhere in space.