Written by Isla Madden

If you counted one galaxy per second, it would take somewhere around 63,000 years to count them all. In 1950, physicist Enrico Fermi asked a question which would reverberate through scientific and philosophical schools of thought: if extraterrestrial civilizations are likely, then where is everybody? The contradiction of the Fermi paradox lies in that despite the probability of extraterrestrial civilizations existing in the vast Universe, there is a complete absence of any evidence or contact with them. Part of the difficulty in answering this question lies in defining what we’re even looking for. 

Biological life refers to entities that exhibit characteristics such as organization, metabolism, growth, response to stimuli, reproduction, and evolution. This life is typically composed of cells, utilizes DNA or RNA as a genetic blueprint, and maintains homeostasis. The biochemical model underpins our search for extraterrestrial life—we look for water, Earth-like temperatures, and atmospheres that resemble our own. Intelligent life refers to organisms that demonstrate our version of advanced cognitive abilities such as reasoning, problem-solving, abstract thinking, communication, and self-awareness.  Our criteria in the search for life is anthropic, built upon observations of the only life we’ve ever encountered.

With the increasing advancement of scientific instrumentation and a growing understanding of planetary science, the absence of any detectable sign of intelligent life becomes more conspicuous and increasingly unsettling. In 1961, astronomer Frank Drake introduced his equation to estimate the number of intelligent, communicative civilizations in the Milky Way. The equation multiplies factors such as the rate of star formation, the fraction of stars with planets, and the likelihood of life, intelligence, and technology. The Drake equation is not an answer, but a framework for estimation—if we apply this method to the Milky Way, between 1 and 10,000 intelligent and communicative lifeforms could hypothetically exist in our galaxy alone.

In 1974, the Arecibo Observatory transmitted a message toward the star cluster M13, encoded with basic information about humanity: our numbering system, DNA, a human figure, and our solar system. Several years later, Voyager 1 and 2 were launched into space, each carrying a Golden Record etched with music, images, greetings in dozens of languages, and sounds of life on Earth. Despite the 2020 collapse of Arecibo’s dish, the search continues with the SETI Institute. 

Perhaps in our search for extraterrestrial life, we are trying to satisfy a deep need for our existence to have a witness. George Berkeley famously asserted, “Esse est percipi”—to be is to be perceived—arguing that objects exist only insofar as they are observed by a mind. Humanity’s messages sent into space resemble our way of saying, “life was here.” Despite all efforts, the question might remain suspended in eternity: is there anybody out there?