In response to Adam Kirsch's long read on the absence of hard evidence for extraterrestrial civilisations, readers have offered a range of explanations, from the role of fossil fuels in technological development to the possibility that advanced societies are deliberately keeping their distance.
Fossil fuels as a barrier to alien technology
Ian Simmons from Westcliff-on-Sea, Essex, argues that a crucial factor is often overlooked: fossil fuels. He suggests that while alien life could develop intelligence on many planets, achieving advanced technology capable of off-world travel requires an industrial revolution equivalent, which on Earth depended on coal, oil, and gas. Without easily accessible fossil fuel equivalents, alien civilisations might never progress beyond a 17th-century level of development.
Simmons adds that even if we detect life on exoplanets, such civilisations would be indistinguishable from planets with only plant-like life and a fire ecology. He concludes that most alien races, if they exist, might be living in an eternal equivalent of Game of Thrones' Westeros rather than Iain M. Banks's Culture, remaining undetected from afar.
Deliberate distance and cosmic timing
Miland Joshi from Birmingham suggests that advanced civilisations might simply be keeping their distance. He cites the Kayapó people of Brazil, who tell of Bep Kororoti, a visitor who shared knowledge and helped build a stable society. Joshi imagines distant observers debating whether humans will destroy themselves with atomic weapons or rebuild sustainably, possibly waiting to see if we can maintain our civilisation before making contact.
David Walker from Sheffield points to the universe's estimated age of 13.8 billion years, suggesting that many life forms and civilisations have likely risen and fallen. He argues that two such phenomena occurring simultaneously to allow communication would be a cosmic coincidence, offering responses to Fermi's question: 'they all left before we got here' or 'they haven't arrived yet, and we'll be gone by the time they do.'
Small-scale arrivals and the search for evidence
Sheila Preston from Shoreham-by-Sea, West Sussex, offers a lighter theory: maybe aliens have arrived but were too small to notice, possibly falling down drains, being eaten by seagulls, or ending up in ants' nests.
The letters, published in response to Kirsch's article, reflect a spectrum of scientific and speculative thinking about the Fermi paradox, with no single explanation yet resolving the question of why we have not encountered intelligent alien life.
