Fermi's Paradox resolved: a new theory explains the whereabouts of all the extraterrestrials.

In recent decades, scientists have discovered a vast number of new planets, stars, and galaxies, and have been able to peek into the farthest corners of the Universe. Yet, the question remains: where are all the aliens? The famous Fermi Paradox states that if extraterrestrial beings exist, then why have humans not yet found them? The authors of a study published on the preprint server arXiv offer their explanation, as reported by IFLScience.

No Aliens in the Milky Way?

Back in the 1970s, astrophysicist Michael Hart suggested that if extraterrestrial civilizations exist in our galaxy, they could colonize many planets relatively quickly by cosmic standards. According to his hypothesis, aliens that began to spread throughout the galaxy approximately 2 million years ago should have already made contact with humanity. However, since this has not occurred, Hart concluded that aliens do not exist in our galaxy.

In the 1980s and 1990s, scientists proposed that the lack of contact with aliens could be attributed to the complexities of interstellar travel, as well as the fact that not all planets are suitable for colonization. This means that extraterrestrial civilizations have limited space for expansion. Four years ago, NASA researchers published a paper stating that there are constraints on how far any intelligent civilization can spread within the Milky Way.

Modeling the Spread of Extraterrestrial Civilizations

The authors of the new study aimed to determine how quickly a potential extraterrestrial civilization could populate planets within its reach. To do this, they created a model of the Universe consisting of habitable planets. They assumed that extraterrestrial civilizations could move from one planet to another, utilizing their resources for further expansion into space at a constant speed.

Next, the scientists used three different models of the Universe: static, matter-dominated, and dark energy-dominated.

• In a static Universe, there is no expansion or contraction, making it infinite in space and time.
• According to the standard cosmological model, for the first 9.8 billion years after the Big Bang, matter dominated the Universe. At that time, the energy density of matter exceeded that of radiation and vacuum energy.
• The dominance of dark energy in the Universe began approximately 9.8 billion years ago, leading to the accelerated expansion of space.

The modeling indicated that in a static Universe, the spread of extraterrestrial civilizations starts slowly due to the scarcity of habitable planets. However, colonization accelerates as new planets are discovered and continues until the number of habitable worlds is exhausted. Interestingly, a similar scenario was observed in the other two models of the Universe.

The scientists found that in an expanding Universe dominated by dark energy, planets are receding faster than civilizations can reach them, which slows down the colonization process. In a matter-dominated Universe, extraterrestrial civilizations would still find it easier to achieve faster cosmic colonization.

Solving the Fermi Paradox

The authors of the study believe that in our Universe, where dark energy predominates, extraterrestrial civilizations could indeed colonize the accessible regions of the Milky Way within reasonable timeframes.

The researchers contend that if intelligent aliens exist, they have initiated a slow spread across our galaxy and are currently in the early stages of their expansion into space. The rates of galaxy colonization will only increase after millions, or perhaps billions, of years. Therefore, it is only at that point that humanity might discover extraterrestrial civilizations, according to the scientists.

In this case, the solution to the Fermi Paradox is that extraterrestrial civilizations are still in the early stages of their expansion into space, which explains why we have not yet found them.