According to Popular Mechanics, this question goes back to what is known as the “Fermi Paradox,” which is the question posed by physicist Enrico Fermi more than half a century ago: If the universe is so vast, and if the Earth is not exceptional, why have we not seen any clear traces of alien civilizations?
The idea is simple. The age of the universe is approaching 14 billion years, and this is enough time, in theory, for intelligent life to appear in other places, and for the development of civilizations capable of traveling, communicating, or leaving technological traces in space. However, we see nothing certain.
Scientists offer several explanations for this silence.
One possibility is that alien civilizations may use communication technologies that we cannot understand or pick up. Humans have moved over the decades from radio to the Internet, fiber optics, and submarine cables, which means that the signals we search for today may not be the appropriate means of communicating with civilizations millions or billions of years older than us.
A study published in 2024 suggests that advanced civilizations may use gravitational waves to communicate. The problem is that our current tools cannot easily distinguish between natural gravitational waves and others that may be artificial.
Even if we pick up a message of this type, it is not guaranteed that we will be able to decode it. We may just know that something abnormal is happening, without understanding its meaning.
Another possibility is that alien civilizations do not live in our time. It may be very small and has not yet reached the stage of sending signals or traveling in space. Or it may be very old and gone before we could even notice it.
In a study published in 2021 in the journal Galaxies, researchers used a model to simulate the evolution of civilizations in the Milky Way, while introducing the possibility of extinction or “self-destruction.” The result is that the existence of intelligent civilizations does not necessarily mean that they will survive long enough for us to communicate with them.
A civilization may only go through a short period in which it is able to send signals or build advanced technologies, and then collapse due to war, environmental disaster, or internal failure.
There is also a simpler explanation: perhaps alien civilizations do exist, but they are not as advanced as we imagine. Hollywood depicts aliens as possessing super ships and unimaginable weapons, but the reality may be different.
In a 2025 paper, astronomer Robin Corbett put forward the idea that other civilizations may exist, perhaps more advanced than humans, but they do not have technologies massive enough for us to see them from great distances.
In other words, there may be distant civilizations, but they do not broadcast strong signals, do not build massive cosmic structures, and do not leave any traces that our current telescopes can detect.
And here the biggest problem arises: the universe is very vast. The distances between stars are enormous, and cosmic time is much longer than the lifespan of civilizations. Even a civilization that lives for a million years may only be a very short moment in the history of the universe.
Humans began building cities only a few thousand years ago, which is insignificant compared to the age of the galaxy. So many civilizations may have appeared and disappeared before we were able to listen, or they may have appeared after we disappeared.
According to the report, this global isolation has both a worrying and an encouraging aspect. The worrying aspect is that we may never meet another intelligent civilization, and may only get a fleeting glimpse in the form of a distant signal that we cannot understand.
The encouraging side is that the sky is still open. Every star we see may be an undiscovered world, and every silence in space may be an invitation to further research, not definitive proof that we are alone.
