The improbability of life

By: Marllory Fuentes Salazar and Franco López Flores / departamento.astronomia@gmail.com

Photographs: Courtesy of Communications and Outreach, UdeC Department of Astronomy

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Where is everyone and everything? The question posed in the summer of 1950 by the Italian physicist Enrico Fermi during a conversation between scientists, became the great paradox that still looms over one of the great questions afflicting humanity: despite the vastness of the universe and the fact that there are billions of planetary systems like ours, we have still not found evidence of other advanced civilizations. 

This is how the so-called Fermi Paradox was born, which has found solutions such as the famous Drake Equation that calculates the possibility of finding intelligent life considering several factors, including estimates on the number of habitable planets in our Milky Way, which could exceed 300 million. But inexplicably we have only found silence.

Research by astronomers from the University of Concepción and the Center for Astrophysics and Related Technologies (CATA), offers a new answer to this paradox, reducing the possibility of the existence of advanced civilizations in the universe by half. The work was published in the Journal of Astrobiology. The analysis takes into account the time required for the colonization of planetary systems and dramatic astrophysical events, such as supernova explosions and supermassive black holes, elements not considered by previous research.

Colonizing the Milky Way

The study was carried out by Dr. Dominik Schleicher and Dr. Stefano Bovino, who clarify that the actual number of possible civilizations is still unknown and can be very variable. From the scenario of a ”Rare Earth” (where our planet is the only one in our galaxy with an advanced civilization), to what the Fermi Paradox poses, in the sense that there should already be many colonized planetary systems.

Dr. Schleicher explains that, based on the size of our galaxy and the typical distance between the stars, it can be calculated that it would take about 400 years to reach the nearest star, Proxima Centauri. “Assuming that we have a method of transport that moves at 1% of the speed of light, this would be the time required to reach that planetary system, located approximately 4 light-years away from our planet,” the astronomer points out.

But how long would it take to colonize our entire galaxy? Given the necessary technology, Schleicher continues, one could estimate that the time required for colonization would be short, cosmologically speaking. “An advanced civilization could colonize the Milky Way in a period of one hundred thousand to one million years, considering the distance between stars and the estimated times for extraterrestrial travel,” he says.

The evidence proposed by the new research suggests that the possibility of such civilizations reaching development would be reduced by half. The Fermi paradox already considered the possibility that we do not know other advanced civilizations because they would only manage to exist for a short period of time before self-destructing, due to wars or the depletion of their resources, with threats like climate change affecting our planet today. 

“To this, we add the destructive effect of astrophysical phenomena, which are relatively common and, in principle, could affect any system. Although they will not completely suppress the development of advanced civilizations, very energetic events, such as gamma-ray bursts, or differing types of supernova explosions, contribute to reducing their number significantly,” says Professor Stefano Bovino.

Rare earth?

The research explains that a very significant parameter to understand this uncertainty is the lifetime of an advanced civilization, which determines global abundance. ”If an advanced civilization can survive for about a thousand years, we could have about ten thousand civilizations in our galaxy, but there is a lot of uncertainty and the number decreases by almost 50% if we consider the astrophysical effects that we have incorporated into the research,” says Dominik Schleicher.

We are still talking about a lot of civilizations, but we have not been able to detect intelligent life yet. Stefano Bovino clarifies that the main limitation is their ability to exist long enough. “The absolute numbers proposed by different models could be quite small, if we consider the instabilities capable of affecting these societies, such as nuclear wars or other reasons that prevent them from thriving long enough. Astrophysical effects are going to reduce this further still, but the main limitation is the stability of the civilizations themselves,” he concludes.