The debate over whether there’s a malicious space-faring civilisation out there humanity needs to avoid is heating up like the Enterprise’s shields under bombardment from a Romulan phaser attack. 

A paper earlier this year used back-of-the-envelope maths to work out there was probably a one-in-five chance of a hostile race out there capable of space travel. But if unfortunate human traits like the need for revenge, dehumanisation of the enemy and so on are considered, there could be more than four.

“An extraterrestrial civilization may have a brain with a different chemical composition and they might not have our empathy or they might have more psychopathological behaviours,” author Alberto Caballero of the University of Vigo in Spain told Vice in May.

He based his calculations on recent invasions on Earth and how they’ve typically become more rare as technology advances, concluding it was extremely unlikely – about 100 times less likely than the apocalypse being delivered via planet-destroying asteroid. 

Caballero suggests as a result, we shouldn’t fear making our presence known to potentially life-bearing exoplanets. This contrasts with the view of world-famous physicist Stephen Hawking, which is that we should stay quiet.

“If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans,” he said in 2010.

Faulty assumptions?

But a new paper argues Caballero’s conclusion is based on faulty assumptions and fails to take into account the possibility we might be destroyed by interstellar civilisations that aren’t malicious, but just acting rationally. 

“Caballero used three unstated but implied hypotheses,” wrote Emory Taylor, whose website describes him as an “amateur astronomer, writer, and artist”. They are that:

alien civilisations will “behave toward an exoplanet alien civilization in the same way human communities have behaved towards each other, particularly in the 20th century”;

that the Kardashev Scale (which supposedly measures a civilisation’s technological ability) is correct and applicable;

and that humans themselves will, sometime between now and when the original Star Trek show is set, will achieve interstellar travel. 

Taylor disputes all of these in his paper, and brings up the possibility a mass extinction event could drive an otherwise peaceful race to war.

“An important extinction event is stars die, and when they die the habitable zone is not a safe place to be living. Eventually, both the human civilisation and an exoplanet alien civilisation must find a new planet to call home. 

“What will happen when the Sun is dying and the only habitable zone exoplanet the human civilisation can reach is already occupied? Does the human civilisation go prepared to exterminate the occupiers if they refuse to share their planet? 

“It would be wise to assume an exoplanet alien civilization has also asked and answered this question.”

Any civilisation fleeing a supernova “must harbour malicious intentions or be willing to succumb to extinction”, Taylor argues.

Shock and awe

Caballero also left out the possibility an alien race might launch a preemptive strike before as we start to develop achieved interstellar capabilities as that might be “seen as a threat”, citing a previous paper from 2013

That paper says if a preemptive strike is to happen, it will likely need to happen this century “or they will likely have to confront a civilization that already has a sizable presence in space and is building its first interstellar spacecraft”.

It’s safe to say none of these papers have been peer-reviewed, uploaded straight to the internet for our amusement/consideration. Interesting stuff, nonetheless.