Is the reason we haven’t yet found aliens anywhere in the universe because they can’t start fires?

That’s the idea put forward by researchers in a new paper, suggesting life on low-oxygen exoplanets would not be able to generate combustion – a vital step in the development of human technology.

Fire is a natural phenomenon on Earth, but evidence suggests humans first discovered how to control it between 300,000 and 400,000 years ago. In time, this enabled early civilisations to smelt and mould metals, leading first to the Bronze Age, then the Iron age. Over millennia, this resulted in the invention of the internal combustion engine, a revolution in our history.

Some also argue that cooking food led to an expansion in our brains, further enabling humans’ incredible development.

However, laboratory experiments have shown that atmospheres with oxygen levels below about 18% do not allow combustion to fully occur. This suggests that even if life did proliferate on such a planet, they would never be able to develop technology advanced enough to either find us, or help us find them.

‘You may have enough oxygen in the atmosphere of an exoplanet to have complex multicellular life, but you may not have enough oxygen to start combustion,’ said co-author Professor Amedeo Blabi, speaking to New Scientist.

The University of Rome scientist, alongside co-author Professor Adam Frank from New York’s University of Rochester, suggests this ‘bottleneck’ for creating advanced civilisations may explain why we have yet to find life beyond Earth – potentially solving the Fermi paradox.

The Fermi paradox is the discrepancy between the lack of evidence for advanced extraterrestrial life and the likelihood of its existence, given the sheer scale of the universe.

It is named after Italian-American physicist Enrico Fermi, who apparently over lunch one day in 1950 asked the question ‘where is everybody?’.

Without the ability to create fire everybody else could well be out here, but we may never know.

How these exoplanets come to have an atmosphere containing oxygen is also up for debate, because both geological and biological processes lead to its formation.

Astronomers suggest the ‘Goldilocks’ zone of atmospheric oxygen may be between 18.5% and 21%. When the concentration rises above 30%, the opposite problem arises – the chance of widespread fires destroying life would be very high as combustion would be so easy, warned Professor Frank.

Few telescopes observing exoplanets have the ability to detect atmospheric oxygen levels at present. 

However, the James Webb Space Telescope is beginning to monitor atmospheric oxygen levels on exoplanets by measuring changes in infrared light as O2 molecules collide.

‘We’re just getting started looking for the atmospheres of terrestrial planets,’ said Professor Frank. ‘This is the exciting thing – we’re at the frontier now.’

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