With so many stars that contain Earth-like planets out there, why haven’t we encountered any extraterrestrial life?
This is the Fermi paradox. It essentially asks if we are alone in our vast and relatively old universe. Given the huge number of solar systems and planets, it is reasonable to assume that a good number of them contain life, possibly intelligent beings, and, more optimistically, advanced civilizations capable of space travel.
But why haven’t we found any signs of alien life yet?
A study conducted by two faculty members from the Institute of Mathematical Sciences and Physics (IMSP) of UPLB explored the future of human colonization in the universe.
Dr. Allan Alinea and Cedrix Jadrin, both from the Physics Division of IMSP, considered how civilizations might grow in three different types of universes: static, dark energy-dominated, and matter-dominated.
In their study, they applied concepts from Percolation theory to examine how civilization spreads as they occupy the nearest planets over time, starting from one ‘mother’ planet that initially solely contains advanced civilization.
Dr. Alinea explained that the universe is expanding faster than we can travel, so we can only reach a limited number of planets for colonization. If there is a mechanism to drive the universe into a state such that its expansion rate is the same or similar to that of a matter-dominated universe, then we will be lucky enough to have a universe that can, in principle, be colonized up to any distance from us.
“Our work is based on an ideal framework, but there are fragments in our study and references thereto that may be helpful in a quest for space colonization, possibly for the survival and development of our species,” according to Dr. Alinea.
Under the assumptions in their paper, they found that even in this dark energy-dominated setting (according to the model they used), colonization follows the Logistic Growth model.
This is similar to the behavior of the spread of communicable diseases (like COVID-19), which is slow in the beginning due to the few carriers. However, as the number of carriers increases, so does the rate of disease spread.
“This model is marked by a three-phase pattern: (I.) slow colonization rate, (II.) fast colonization rate, and (III.) slow colonization rate.
We are probably in phase I: slow colonization rate due to the small number of spreading civilizations (few intelligent and advanced civilizations). This slow phase can be exacerbated by large distances between ‘living’ planets. But once some number of traveling civilizations is reached, we may enter phase II characterized by a fast colonization rate. Given enough time upon entering this phase, we may finally say hello to aliens out there,” he added. Their research can be accessed here: https://iopscience.iop.org/article/10.1088/1361-6404/acfbc5 (Jessa Camille Duero)