Great Silence Theory Or Why Are Aliens Hiding From Us?
26th Jan 2025
Since ancient times, mankind has assumed the existence of many worlds beyond the Earth. With the development of science and technology, this idea is no longer purely philosophical. We have learned to catch radio signals from distant galaxies, send messages into space, and find exoplanets potentially suitable for life. But all this has not helped us to solve the famous Paradox formulated by physicist Enrico Fermi 75 years ago: ‘If the Universe is so old and vast, where is anybody but us?’ No reports, no aliens’ spacecraft, no traces of astro-engineering activity. Only some conspiracy theories around mysterious alien abductions and the notorious Area 51. And the absolute silence of the Universe.
This disturbing silence, fuelled by the Fermi paradox, gave rise to another theory called the Great Silence theory. What is the main idea of the Great Silence theory and how science tries to explain it? Let’s get to the bottom of it.
What Is The Great Silence Theory?

Imagine that you live in a large apartment building, but you have never seen or heard any of your nneighbours No one rings your doorbell, plays loud music, or comes out on the landing. Is that possible? Hardly.
Now, extrapolate this to the Universe scale. You will get a contradiction between the high probability of the existence of alien civilizations and the obvious lack of any evidence for this. That’s the main idea of the Great Silence theory, explained as a set of hypotheses designed to resolve this contradiction.
And this is not about silence in the literal sense (after all, as we know, it’s impossible to hear sound in space) but about the absence of obvious signs of intelligent activity that we might expect from technologically advanced civilizations.
This silence gets especially loud considering that the Universe is nearly 13.8 billion years old, and our galaxy, the Milky Way, alone contains hundreds of billions of stars. Even if the probability of intelligent life on any planet is extremely low, the sheer number of stars and planetary systems in the Universe, multiplied by the enormous timespan, should have resulted in the emergence of many civilizations. And at least some of them should have evolved enough to make their presence known at the interstellar level. But this is not happening.
“So, where is everybody?” Fermi asked, and the Great Silence theory covers all possible explanations for this unique phenomenon.
Drake Equation

In 1961, astronomer Francis Drake proposed an equation aimed at estimating the number of civilizations in our galaxy that could potentially come into contact with us. Here’s how it looks:
N = R* * fp * ne * fl * fi * fc * L
Where:
- N: number of communicating civilizations in the Milky Way galaxy.
- R*: rate of star formation in the Milky Way.
- fp: fraction of stars that have planetary systems.
- ne: average number of habitable planets in the Solar System (where water can exist in the liquid form).
- fl: fraction of planets where life actually emerges.
- fi: fraction of habitable planets where intelligent life appears.
- fc: fraction of intelligent civilizations that develop technologies allowing them to declare their existence (e.g., radiocommunication).
- L: average lifetime of a communicative civilization.
If we substitute optimistic values into the equation (many stars, many planets, high probability of life’s emergence), it turns out that there should be many civilizations (N). The Drake equation seems to say: “Look, by all calculations, there should definitely be someone.” So why is there nobody?
The thing is that we actually do not know the values of most of the variables very well. This is especially true for the probability of life’s emergence (fl), development of intelligence (fi), and the lifetime of civilizations (L). And it’s this imperfection of the Drake equation that makes the Great Silence theory of Fermi paradox so intriguing – we simply do not know how rare or common we are in the Universe. Still, the Drake equation helps us visualize the factors that assess the probability of other civilizations, and finding more precise values for each variable can bring us closer to understanding the possible reasons for their silence.
Great Silence Theory: So Why Is Space Silent?

Scientists propose various hypotheses aimed to resolve the Fermi Paradox and explain the Great Silence. The versions may touch on several related concepts and ideas in the search for extraterrestrial intelligence (SETI), but each has its own unique features.
Great Filter Theory
Probably, every civilization at a certain stage of its development faces an insurmountable obstacle that causes its development to stop. For example, it could be the complexity of intelligent life evolution since the transition from the simplest organisms to creatures capable of producing technologies and exploring space may be an incredibly long and complex process full of evolutionary dead ends.
Another possible “filter” is technological barriers: perhaps there are certain limits to technological development that civilizations are unable to overcome.
And finally, we cannot exclude the possibility of self-destruction: having reached a certain level of development, civilizations may destroy themselves through wars, environmental or space disasters, and other causes.
Zoo Hypothesis
Aliens are aware of our existence, but deliberately do not come into contact, observing us from afar as if we were animals in a zoo. Perhaps they consider us too primitive or do not want to interfere with our development, like anthropologists who study tribes in remote corners of the planet without interfering with their lives. Perhaps the aliens are simply waiting for us to reach a certain level of development before making contact.
Rare Earth Hypothesis
The conditions for the emergence of life and intelligence development are so rare that the Earth is the only such place in the Universe. Perhaps a unique combination of many factors is required to make this possible: liquid water, the optimal distance from the star, magnetic field, tectonic activity, a large satellite to stabilize the axis of rotation, etc.
This hypothesis is partially consistent with the term “carbon chauvinism”, which suggests that all life in the Universe must be constructed from carbon, like the Earth. This limits our imagination when searching for extraterrestrial life, forcing us to look only for “Earth-like” planets and biological signatures familiar to us.
Anthropocentrism VS. The Concept Of Incomprehensible Aliens
We may think that aliens are similar to us in their thinking, motivation, communication, and even appearance, but in reality, alien intelligence may be so different from our own that we not only cannot understand it but may not even recognize it as intelligent life. Their biology, psychology, culture, motivations, and ways of interacting with the world may be beyond our understanding.
Simulation Hypothesis
We live in a computer simulation created by some super-civilization. In this simulation, like in the Matrix movie, we ourselves are constructs, while other civilizations are absent. Although it seems fantastic, this hypothesis makes us think about the nature of reality and what is actually true. If we live in a simulation, then who created it, and what are their goals?
Technological Limitations And The Problem of Distance
We cannot detect signals from other civilizations due to the insufficient level of development of our technologies. Aliens may use communication methods we do not yet understand, such as neutrino-based communication or quantum teleportation.
Or maybe the distances between the stars are so great that even with advanced technology, communication between civilizations is extremely difficult. Imagine trying to send a message to a friend on another continent using a carrier pigeon. Chances are that your message will never reach the recipient. The same happens with the search for extraterrestrial civilizations: perhaps our “carrier pigeons” simply cannot reach them.
Dark Forest Hypothesis
Because of the vast space distances and the impossibility of rapid information exchange, civilizations cannot reliably assess each other’s intentions. Even if one civilization seems benevolent, there is no guarantee that it will not change its behavior in the future or that another, more aggressive civilization will not conquer it. Therefore, advanced civilizations, like hunters in a dark forest, prefer to either attack first or behave as covertly as possible to avoid detection.
Galactic Club Hypothesis
This variation on the Zoo Hypothesis implies the existence of a “club” of advanced civilizations that communicate with each other but do not interact with less advanced civilizations until they reach a certain level of technological and social development. We simply have not yet been accepted into this “club,” and we still have much to learn before we can take our place in the galactic community.
When The Universe Defies

The Great Silence theory, woven from many hypotheses and assumptions, is not just an attempt to answer Fermi’s famous question “Where is everybody?” It’s a dive into the very depths of our space solitude and an attempt to understand our place and role in the Universe. None of the Great Silence theory explanations gives us either comprehensive answers or ready solutions, but it poses us a challenge that we simply cannot but accept by our nature. Perhaps this is the main message from highly developed alien civilizations to humanity: seek, and you shall find.
References And Additional Information:
- The Great Silence – the Controversy Concerning Extraterrestrial Intelligent Life https://adsabs.harvard.edu/full/1983QJRAS..24..283B
- Drake equation https://www.seti.org/drake-equation-index
- The great filter https://www.aao.org/lifetime-engaged-ophthalmologist/perspective/article/great-filter
- How Incomprehensible Could Extraterrestrials Be? https://www.psychologytoday.com/intl/blog/world-wide-mind/201208/how-incomprehensible-could-extraterrestrials-be
- Are we living in a computer simulation? Many people think so https://www.earth.com/news/simulation-hypothesis-are-we-living-in-a-computer-simulation/
- Life in the Cosmos: Paradox of Silence and Self-Awareness https://www.researchgate.net/publication/372737424_Life_in_the_Cosmos_Paradox_of_Silence_and_Self-Awareness
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