Based on our previous observations, it seems that our Earth is unique in having intelligent life. However, there are several reasons that may prevent us from detecting the light of civilization elsewhere in the Milky Way, as well as factors that could influence whether it even appears at all.
Revisiting the Drake Equation
More than half a century ago, these variables were compiled into a tool known as the Drake Equation, which allows scientists to ponder and reflect.
However, one variable was missing from the Drake Equation. Recently, a team led by physicist Daniele Sorini from Durham University in the UK has added a variable to the Drake Equation as the basis for a new calculation: the impact of dark energy on the star formation rate in the universe.
The Drake Equation needs additional variables.
Sorini explains: “Understanding dark energy and its effects on our universe is one of the greatest challenges in cosmology and fundamental physics. The parameters that govern our universe, including the density of dark energy, may explain our very existence.”
Dark energy is an unidentified force that accelerates the expansion of the universe, rather than slowing it down due to the gravitational pull between galaxies. While we do not know what it is made of, we can estimate how much dark energy exists. It is significant, comprising about 71.4% of the total matter-energy content of the universe.
Another 24% is dark matter; only the remaining 4.6% is ordinary baryonic matter, which includes all stars, planets, black holes, dust, humans, and everything else we can theoretically see and touch.
One of our assumptions about life is that it requires a star. It may not necessarily need one, but the likelihood of life emerging on an object far from a source of energy is so remote that it is unhelpful in determining the Drake Equation.
Therefore, assuming that life requires a star, knowing the star formation rate in the universe we inhabit can provide insights into the chances of finding life within it.
Stars form from clouds of dust and gas collapsing into dense clumps. As mass accumulates to the point where the density and temperature in their cores trigger nuclear fusion reactions, the outward pull of dark energy plays a role in how quickly these reactions can occur. Dark energy counteracts the inward pull of gravity; otherwise, all matter in the universe would condense into clumps too dense to form stars.
The researchers calculated this conversion rate of matter for different dark energy densities using a cosmological simulation software to determine the most efficient rate at which stars could form. They discovered that the most efficient rate occurs when 27% of the universe’s matter is converted into stars.
We Are in an Unideal Universe
What makes this interesting is that the optimal rate of 27% is not present in the universe we inhabit. Our universe has a conversion rate of 23%. This is not the first time we have found evidence suggesting that humanity does not exist under the most optimal conditions for life. This indicates that the possibility of intelligent life may arise elsewhere in the universe.
Sorini notes: “It is surprising that we found even significantly higher dark energy densities are still compatible with life. This suggests that we may not be in the universe most conducive to life formation.”
There are many other factors that can influence the emergence of intelligent life. The star formation rate is just one of them. Other factors include the number of stars with planets and the number of planets capable of sustaining life. Additionally, there are variables we do not yet understand, such as how the building blocks of life are distributed and combined into an evolving system.
However, each study contributes valuable insights that may someday allow us to see a broader picture than what we currently observe in the universe. In turn, this will help us narrow down how and where to search for other civilizations that may be scattered throughout our galaxy.
Theoretical physicist Lucas Lombriser from the University of Geneva in Switzerland commented: “It will be very interesting to use this model to explore the emergence of life in different universes and see whether some fundamental questions we ask about our current universe need to be reinterpreted.”
