Episode 78 of SfS — Where is Everybody? The Percolation Hypothesis — is now Live!

Matt Williams
2 min readAug 28, 2024

This week’s episode was one of the last installments in my series exploring the Fermi Paradox (i.e., “Where are all the aliens?”). This episode was special in that it dealt with a proposed resolution that is one of my favorites and the one that I believe is the most likely explanation for the “Great Silence” — the Percolation Hypothesis. The theory was proposed by famed NASA scientist and science fiction author Geoffrey A. Landis in 1993.

To break it down, the Percolation Hypothesis takes its name from Percolation Theory, a concept in mathematics and statistics that describes the behavior of a network when links are added or taken away. In the latter case, the theory states that a large network will break down into smaller clusters if enough links are removed. When applied to the Fermi Paradox, the theory argues the challenges of interstellar space exploration impose constraints on how far a civilization can settle.

Among these are the hazards of cosmic radiation and microgravity and the unknown dangers of exploring “alien” worlds. But perhaps the most important is General Relativity, which rules out FTL travel and communications (to the best of our knowledge). This makes the entire premise of a “galactic empire” impractical and means that large portions of our galaxy would remain unsettled. This theory is not only consistent with known physics, but it doesn’t suffer from the “it only takes one” rule.

With other proposed resolutions, there is a tendency to assume a uniformity of motivation. Such theories tend to break down if just one civilization doesn’t share these motivations. Instead, this theory incorporates the idea that civilizations will be motivated by a plurality of motivations. As I said, this theory is the most plausible (IMHO) and is consistent with what the late and great Carl Sagan argued. Follow the links below to learn more.

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Originally published at http://storiesbywilliams.com on August 28, 2024.

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Matt Williams

Space/astronomy journalist for Universe Today, SF author, and all around family man!