Our universe does host life, but another one might be even better suited for life.

Here’s what you’ll learn when you read this story:

• Researchers are studying how hospitable our universe is to creating life. It’s related to the density of dark energy, which impacts star formation and the chances of life forming.
• The idea is that very few universes with intelligent life would have limited dark energy density. But ours is less than optimal.
• So, it’s puzzling that we exist, researchers said.

Published in 1962 by American astronomer Frank Drake, Ph.D., the eponymous Drake equation sought to estimate the number of detectable alien civilizations in the Milky Way galaxy. This equation takes into account the average rate of star formation in the galaxy, the fraction of those stars that have orbiting planets, and the average number of those planets per star that can support life. It gets hairier: This formula also considers what fraction of those planets could support intelligent organisms, and whether those organisms can develop technology capable of contacting others.

Now, researchers in Switzerland and the U.K. have homed in on one particular aspect of this equation to contemplate how a crucial component of our universe affects star formation and, by extension, the possibility of intelligent life. Their paper studies the relationship between the density of a mysterious force in the universe, called dark energy, and the overall number of stars formed in the universe’s history. Published in November 2024 in the journal Monthly Notices of the Royal Astronomical Society, this work describes a new theoretical model of cosmic star formation applied to our universe as well as other possible ones with varying dark energy densities. In other words, it ponders the likelihood of intelligent life existing in the multiverse.

To approach this question, the team tackled anthropic reasoning. This line of thinking is the idea that we can derive fundamental properties of the universe based on the fact that we exist. There’s so much we don’t know about the universe, but one thing we know for certain is that, at least in one tiny corner, it allows humans to exist. That starting point guides the way for understanding other characteristics of the universe.Anthropic reasoning can offer explanations for the amount of dark energy in our universe. In the late 1980s, physics Nobel laureate Steven Weinberg used this idea to propose that the observed density of dark energy observed density of dark energy in the universe informs the existence of intelligent life within it. He contemplated that larger densities of dark energy would cause the universe to expand faster, negating gravity’s effort to clump matter together into galaxies, which would discourage star formation, and therefore, life.

Dark energy is an enigmatic force that may be causing the universe to expand at an accelerated rate. While it doesn’t explicitly factor into the Drake equation, dark energy does relate to star formation, which is key to the formula. In the same way that life on Earth wouldn’t exist without our sun, stars are a prerequisite for the formation of intelligent life. So, contemplating how varying amounts of dark energy in the universe impact star formation could tell us about other possible universes, too.

“Since stars are a precondition for the emergence of life as we know it, we then ask whether it would be easier for intelligent life to spawn in our Universe, or in a hypothetical universe with a different dark energy content,” the paper’s first author Daniele Sorini, PhD, a postdoctoral research associate in cosmology and astrophysics at Durham University’s Institute for Computational Cosmology in the U.K., says in an email.

Dark energy is baffling. According to Sorini, “while we can measure the density of dark energy, we do not really know what it is.” Still, measuring it is useful. For example, in the paper, Sorini and his team plot the efficiency of star formation throughout the cosmos in relation to varying amounts of dark energy density. The team found that the amount of stars formed in the universe’s history is maximized if dark energy density is about one-tenth its observed value. That means, hypothetically, the ideal universe for forming life—because the formation of life comes from the formation of stars—would have less dark energy than our universe. Assuming that this amount is proportional to stars formed, this would make for the ideal universe to create intelligent life. In this optimal scenario, 27 percent of ordinary matter in the universe converts to stars, while in our universe, it’s only 23 percent. This gap demonstrates that while our universe is close to hosting the optimal conditions for life, it’s still not the most ideal. Cosmic star formation continues to decrease with higher dark energy densities. Hypothetically, a universe with increasing dark energy density is less hospitable to the formation of intelligent life. Likewise, Weinberg posited that very few universes with intelligent life in the multiverse would have limited dark energy density.

As Weinberg had done, Sorini and his co-authors pondered what might change if a universe contained a different density of dark energy. But, considering a multiverse wherein each universe contains a different dark energy density—observed by one intelligent observer—the team found that 99.5 percent of these universes boasted a higher dark energy density than our own universe’s.

“This might seem at odds with the fact that higher dark energy abundance leads to lower likelihood of generating intelligent life,” Sorini says. “But there is no contradiction.” He explains that, individually, universes with higher dark energy densities contain fewer intelligent observers, though there are many more such universes. The paper’s calculations show that, taken collectively, these universes contain intelligent observers.

However, Sorini emphasizes that this paper doesn’t aim to prove the existence of the multiverse or locate extraterrestrial life. Rather, it’s a novel way of considering how dark energy density in the universe could impact star formation, which serves as a proxy for the development of intelligent life.

“Whether the multiverse scenario is real or not is beside the point of our paper,” Sorini says. “It is a thought experiment to understand whether we can provide a suitable explanation of the puzzling observed value of the dark energy density in our universe, based on the fact that we exist.”

Source: https://www.popularmechanics.com/science/a70226846/aliens-from-parallel-universe/?utm_source=firefox-newtab-en-gb