Readers have offered their own explanations for why humanity has not yet encountered intelligent alien life, responding to an article by Adam Kirsch that explored the lack of hard evidence for extraterrestrial civilisations.
Fossil fuels as a barrier
Ian Simmons from Westcliff-on-Sea, Essex, argues that fossil fuels are a neglected factor. He suggests that alien life could develop intelligence on many planets, but to create advanced technology enabling travel off-world, they would need an equivalent of the Industrial Revolution, which required coal, oil, and gas.
Simmons notes that many intelligent alien races could exist, but on planets without easily accessible fossil fuels, they would never progress beyond a 17th-century level of development. Even if life were detected on planets outside our solar system, these civilisations would remain invisible, as their signature would be indistinguishable from a planet with plant-like life and a fire ecology.
He concludes that almost all alien races, if they exist, might live in an eternal equivalent of Game of Thrones's Westeros, not Iain M Banks's Culture, and would never be detected from afar.
Keeping 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 their ancestors build a stable society. Joshi imagines distant observers debating whether humans will destroy themselves with atomic weapons or rebuild, and choosing to wait before attempting contact.
David Walker from Sheffield points to the universe's age of 13.8bn years, arguing that many forms of life and civilisations have likely arisen, flourished, and disappeared. He suggests that two such phenomena occurring at the same time would be a cosmic coincidence, and answers Fermi's question "Where is everybody?" with "they all left before we got here" or "they haven't arrived yet, and we'll be gone by the time they do."
Sheila Preston from Shoreham-by-Sea, West Sussex, offers a lighter take, wondering if aliens have arrived but were too small to notice, perhaps falling down a drain, being eaten by seagulls, or ending up in an ants' nest.
