In human quest for life beyond Earth, distance acts as a barrier

Caballero has looked at wars and invasions since 1915 to figure out how likely it is that an alien civilisation would be malicious

A recent paper, “Estimating the prevalence of malicious extraterrestrial civilisations”, from Alberto Caballero of Vigo University (Spain) has generated interest across social media. The paper estimates there may be four “malicious extraterrestrial civilisations” in the Milky Way.

Caballero is doing a PhD in Conflict Resolution at Vigo and calls himself a criminologist. The paper, which he calls a thought experiment, hasn’t been peer-reviewed. It’s a follow-up on a paper (peer-reviewed), which he published in Cambridge’s International Journal of Astrobiology: “An approximation to determine the source of the WOW! Signal.”

A patents clerk called Albert Einstein based the Theory of Relativity