This article was automatically translated from the original Turkish version.
The Fermi Paradox addresses the question of why, despite the presence of billions of stars and planets in the universe or even just within the Milky Way Galaxy, no evidence of extraterrestrial intelligent life has ever been observed. The paradox was brought to the attention of the scientific community in 1950 when physicist Enrico Fermi posed the question “Where is everybody?” during a lunch with his colleagues. Fermi argued that, given the size of the galaxy its age and the relatively short time required for interstellar travel, numerous civilizations should have emerged and colonized the galaxy by now.
Alien Image Representation (Generated by Artificial Intelligence)
The Milky Way Galaxy is known to be approximately 13 billion years old and about 100,000 light years in diameter. It is estimated to contain between 100 and 400 billion stars, many of which are thought to host planets in habitable zones. If even a small fraction of these planets developed life and some of them evolved intelligent civilizations capable of technological advancement, we would expect these civilizations to have left detectable traces. Such traces could include radio signals artificial structures or interstellar travel activity. Yet no observational evidence for extraterrestrial intelligent life has been found to date.
To evaluate the Fermi Paradox numerically, astrophysicist Frank Drake developed the Drake Equation in 1961. This equation incorporates various variables to estimate the number of communicative civilizations in a galaxy:
N = R* × fₚ × nₑ × fₗ × fᵢ × f꜀ × L
In this equation:
Commonly used numerical values for these factors reduce the equation to this simplified form:
N = L / 10
According to this simplification, if a civilization remains detectable for 100 years after beginning to transmit signals, approximately 10 civilizations should exist in the Milky Way alone. However, if this duration is assumed to be only 10 years, the equation yields N = 1; meaning only one communicative civilization — our own — might exist.
One explanation proposed for the Fermi Paradox is the Dark Forest Theory. According to this theory, other intelligent civilizations may exist deep within the galaxy, but they deliberately avoid revealing their presence. The theory is based on the fear that unknown civilizations could be perceived as potential threats and that revealing one’s existence might lead to catastrophic consequences. Therefore, each civilization chooses silence to ensure survival. However, this theory assumes that all civilizations adopt the same defensive strategy, and this assumption has not been verified.
In a statement by the SETI Institute (Search for Extraterrestrial Intelligence), Enrico Fermi’s insight is emphasized: “Any civilization with modest rocket technology and a modest amount of imperial drive could rapidly colonize the entire galaxy.” Calculations suggest that a civilization traveling at just one percent of the speed of light could encompass the entire galaxy within tens of millions of years. This timescale is extremely short compared to the age of the galaxy.
Nevertheless, no trace of extraterrestrial intelligent life has yet been detected. This has led some scientists to propose alternative explanations, including:
Another significant explanation is the Great Filter Hypothesis. This hypothesis posits the existence of an extremely difficult barrier in the evolutionary process. This barrier could occur at any stage, from the emergence of life to the development of multicellular organisms, the evolution of intelligence, or the sustainability of technological civilizations. If the filter occurred in the past, humanity may be one of the rare civilizations that have already overcome it. However, if the filter lies in the future, it may indicate that technological civilizations cannot survive long-term and that humanity too will eventually face this obstacle.
