In 1962, American astronomer Dr. Frank Drake published the eponymous Drake Equation, which was designed to estimate the number of detectable extraterrestrial civilizations in the Milky Way galaxy, as reported by Popular Mechanics.
This equation takes into account data such as:
However, this formula also considers what portion of those planets might support the existence of intelligent organisms, as well as whether those organisms could develop technologies that allow them to communicate with others.
In a new study, a team from Switzerland and the UK focused on one specific aspect of the equation—how a crucial component of our universe influences star formation and, consequently, the potential for intelligent life. The scientists examined the relationship between the density of the mysterious force in the universe known as dark energy and the total number of stars that have formed throughout the universe's history. As a result, the team described a new theoretical model of cosmic star formation applicable to the universe, as well as other possible models with varying densities of dark energy. In simple terms, the model considers the likelihood of intelligent life existing in the multiverse.
In their work, the researchers turned to anthropic reasoning—a line of thought based on the idea that we can derive fundamental properties of the universe from the fact of humanity's existence. Humanity knows little about the universe, but one thing is certain: in at least one tiny corner of it, life does exist. Scientists view this as a starting point that points the way to understanding other characteristics of the universe.
It is believed that anthropic reasoning can explain the quantity of dark energy in our universe. As early as the late 1980s, Nobel Prize-winning physicist Steven Weinberg used this idea to suggest that the observed density of dark energy in the universe indicates the presence of intelligent life within it.
Dark energy is a mysterious force that may be responsible for the accelerated expansion of the universe. However, it is clearly not factored into the Drake Equation, even though it is related to star formation, which is a key element of the formula. Just as life on Earth could not exist without our Sun, stars are a necessary condition for the emergence of intelligent life. Scientists believe that contemplating how varying amounts of dark energy in the universe affect star formation could provide insights into other possible universes.
According to the first author of the paper, Dr. Daniel Sorini, a Ph.D. and researcher in cosmology and astrophysics at the Institute for Computational Cosmology at Durham University, stars are a prerequisite for the emergence of life as we know it. But the question arises: is it easier for intelligent life to emerge in our universe or in a hypothetical universe with different dark energy content?
Sorini states, "While we can measure the density of dark energy, we actually don’t know what it is." In their study, the researchers modeled a graph of star formation efficiency throughout the cosmos based on various values of dark energy density.
The team found that the number of stars formed in the history of the universe peaks when the density of dark energy is about one-tenth of the observed value. In simple terms, a hypothetically ideal universe for life formation would have less dark energy than our universe.
If we assume that this quantity is proportional to the number of stars formed, then it would represent an ideal universe for the emergence of intelligent life. In this optimal scenario, 27% of ordinary matter in the universe transforms into stars, whereas in our universe, only 23% does. According to the team, this suggests that our universe is close to ideal conditions, but still not perfect.
Next, the scientists examined what might change if the universe contained a different energy density. The team considered a multiverse where each universe has a different density of dark energy and found that 99.5% of all considered universes boast a higher density of dark energy than ours.
The researchers' findings may seem contradictory, but they assert that this is not the case: individually, universes with higher dark energy densities contain fewer intelligent observers, although there are many more of such universes. The results of the study also indicate that collectively, these multiverses contain intelligent observers.
At the same time, the researchers emphasize that their work is not aimed at proving the existence of a multiverse but rather discovering extraterrestrial life. The authors of the study believe that their work is more a way to explore how dark energy density in the universe might influence star formation, which serves as an indicator of the development of intelligent life.