A new theory suggests that intelligent life forms may have a limited time window to colonize the cosmos before the expansion of the universe makes it impossible.
One of the most intriguing questions in science is whether we are alone in the universe or not. The Fermi Paradox, named after the physicist Enrico Fermi, poses this question by asking why we have not detected any signs of extraterrestrial civilizations (ETCs) despite the vastness and age of the universe.
One possible answer is that interstellar travel and colonization are not easy or feasible for any civilization, due to the physical and biological constraints imposed by the nature of the universe. This idea is based on Percolation Theory, which describes how networks break down into smaller clusters when nodes or links are removed.
In the context of ETCs, Percolation Theory implies that there is a critical threshold for the density and connectivity of habitable planets in the galaxy, below which interstellar diffusion becomes impossible. This threshold may depend on various factors, such as the speed of light, the rate of star formation, the availability of resources, and the lifespan of civilizations.
A New Model for Galactic Expansion
However, a recent study by Allan L. Alinea and Cedrix Jake C. Jadrin from the University of the Philippines Los Banos challenges this view by proposing a new model for how civilizations can grow and spread in different types of universes. Their paper, titled “Percolation of ‘Civilization’ in a Homogeneous Isotropic Universe”, was published online as a preprint.
The authors used a Logistic Growth Function (LGF) to describe how the population of ETCs increases over time, taking into account the carrying capacity of their environment. They then applied this function to three scenarios: a static universe, a dark energy-dominated universe, and a matter-dominated universe.
They found that in a static universe, where space does not expand or contract, ETCs can reach a steady state where their population growth is balanced by their resource consumption. In this case, Percolation Theory holds true and interstellar diffusion is limited by the density and connectivity of habitable planets.
However, in a dark energy-dominated universe, where space expands at an accelerating rate due to a mysterious force called dark energy, ETCs face a different challenge. As space expands faster than light, distant regions become inaccessible and isolated from each other. This means that ETCs have a finite amount of time to colonize other planets before they are forever out of reach.
In this case, Percolation Theory breaks down and interstellar diffusion is limited by the speed of expansion and the time window available for colonization. The authors calculated that in our current universe, which is dominated by dark energy, ETCs have about 10 billion years to spread across the cosmos before it becomes impossible.
Finally, in a matter-dominated universe, where space expands at a decelerating rate due to the gravitational attraction of matter, ETCs have an advantage over the other scenarios. As space expands slower than light, distant regions remain accessible and connected for longer periods of time. This means that ETCs have an infinite amount of time to colonize other planets as long as they can overcome the physical and biological constraints.
Implications for SETI and Humanity
The study by Alinea and Jadrin has several implications for the Search for Extraterrestrial Intelligence (SETI) and humanity’s future in space. First, it suggests that ETCs may be more common and widespread in universes that are dominated by matter rather than dark energy. Second, it implies that ETCs may have different strategies and motivations for interstellar exploration and colonization depending on the type of universe they live in.
Third, it indicates that ETCs may face different challenges and opportunities for communication and cooperation with other civilizations depending on the type of universe they live in. Fourth, it shows that ETCs may have different impacts and influences on their environment depending on the type of universe they live in.
Finally, it reveals that humanity may have a limited time window to explore and colonize other planets before they become unreachable due to the expansion of space. This may motivate us to accelerate our efforts to develop advanced technologies for interstellar travel and settlement. Alternatively, it may inspire us to cherish our home planet and focus on preserving its habitability and biodiversity.
