Where is everybody? The Fermi Paradox

The universe is old, big and filled with potentially habitable planets. Yet, despite the many chances for intelligent life to arise, so far, there is no convincing evidence of alien life or technology within our solar system (or, for that matter, in the cosmos at large). 

This contradiction is known as the Fermi Paradox––named after physicist Enrico Fermi. In 1950, Fermi was chatting with some physicist coworkers about intelligent alien life, and supposedly asked, “Where is everybody?”

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The Fermi Paradox 

Fermi’s question has not yet been answered and so far the cosmos remains eerily silent. 

Our Milky Way alone contains around 100 to 400 billion stars, many of them hosting planets in the habitable zone. Even if only a very small fraction of those planets develop life, and a small faction of these develop intelligence and technology, the galaxy should be buzzing with activity. However, humanity has been searching for signals for decades and still we have found nothing. This absence of signals, or any other signs of alien intelligence is called the “Great Silence.” 

There are numerous possible hypotheses that attempt to solve the Fermi Paradox, the most well-known being the following:

Are we not capable of detecting aliens?

Humanity has only been scanning the skies for a few decades––a blink of an eye in cosmic history. Advanced civilizations could rise and fall in cycles, missing each other in time (the cosmic timescale).

Another possible explanation for the great silence of the cosmos is that we might not be listening at the right frequencies or in the right way. Civilizations could communicate using methods that we do not understand or cannot harness, yet, like quantum entanglement (the radio silence). 

Are aliens avoiding us?

Another possible explanation is that advanced alien civilizations are out there, within the communication distance, and maybe even know that we are here, but they choose not to be found. 

According to the so-called zoo-hypothesis, aliens could be observing us like we observe animals in a nature reserve, choosing not to interfere. 

Another hypothesis––the dark forest theory––suggests that intelligent species stay silent to avoid detection by potentially hostile civilizations. According to this theory (inspired by Liu Cixin’s sci-fi novel The Dark Forest), the universe is like a dark forest, and many civilizations act like silent hunters. If you reveal your location, you risk being destroyed. The civilizations that have survived are the ones that understand that the best strategy is to stay quiet, hide, and eliminate any threats.

Is there something that prevents their expansion?

Possibly the most depressing explanation of the Fermi Paradox is that there is a nearly insurmountable barrier preventing civilizations from advancing (the great filter theory). This barrier could be at the stage of life’s emergence, intelligent life’s development, or a self-destructive phase like nuclear war or environmental collapse. 

One (probably far-out) variant of this great filter theory is that advanced societies may become so technically sophisticated that they lose interest in space expansion, opting for inward development or choosing to expand in virtual reality. 

In essence, the great filter theory suggests that our lack of contact with extraterrestrial civilizations may arise from either their absence or their inability (or unwillingness) to overcome these critical thresholds. Like us, aliens might find themselves balancing the desire to advance with the instinct to maintain the status quo for survival. 

Implications for humanity

The “great silence” of the cosmos remains one of the greatest mysteries of our time. However, attempting to understand the Fermi Paradox has real implications for the future of humankind. 

If the great filter lies behind us (e.g., intelligent life is very rare), then we may be one of the first intelligent civilizations. If the great filter lies ahead (e.g., technological civilizations inevitably destroy themselves), then our survival is far from guaranteed.

Sources

1. https://www.planetary.org/articles/fermi-paradox-drake-equation2.

2. https://www.scientificamerican.com/article/the-fermi-paradox-may-have-a-very-simple-explanation

3. https://www.planetary.org/articles/the-fermi-paradox-where-are-all-the-aliens

4. https://www.astronomy.com/science/the-great-filter-a-possible-solution-to-the-fermi-paradox/

5. https://earthsky.org/space/avoiding-the-great-filter-earth-alien-civilizations/

6. https://www.psychologytoday.com/us/blog/pop-culture-mental-health/202412/the-great-filter-and-the-fermi-paradox