Alien civilizations have not yet made contact with humans because they may have been annihilated by gamma-ray bursts (GRBs), the Daily Mail reported on Tuesday, citing Frederick Walter, an astronomer from Stony Brook University in New York.
According to NASA, GRBs are short-lived outbursts of light that erupt with a quintillion times the luminosity of the Sun. Walter believes the force of an outburst would be enough to destroy any extraterrestrial civilization.
“It’s a tightly focused beam. And, if it’s directed through the plane of the galaxy, it could basically sterilize about 10% of the planets in the galaxy,” Walter explained. The astronomer noted that, according to his estimates, there is a GRB in any galaxy roughly every 100 million years.
“Over a billion years, on average, you might expect a significant number of civilizations to be eradicated, should they exist... It’s just one of many possible explanations, sort of morbid, I suppose,” he said.
According to Walter’s estimates, the Milky Way galaxy could have seen around 45 GRBs in the Earth’s 4.5-billion-year history. He stressed, however, that any potential threat to humanity from this type of event is “not worth worrying about.”
“They’re rare, and they’re directed,” he stated, noting that this makes GRBs unlikely to hit the Earth.
NASA describes GRBs as the “most powerful events in the known universe.” The phenomenon was first observed in 1967, via a pair of US Vela satellites designed to detect nuclear weapon tests. However, most researchers say GRBs are more common in distant star-forming galaxies and are less likely to happen in the Milky Way.
Walter also speculated on other reasons behind humankind’s inability to detect extraterrestrial life, suggesting that other worlds may be filled with life forms resembling aquatic species like whales and dolphins. For this type of civilization, it would be impossible to develop the technology needed for space travel or communication, he said.
He went on to say that some alien civilizations might simply choose not to take the risk that comes with contacting other potentially dangerous life forms. Another explanation, he added, which many physicists and astronomers support, is that technologically advanced life forms on other planets might have destroyed themselves.
“Just look around, you know? We’re polluting the atmosphere. We’re making it questionable as to whether we’re going to have a viable civilization in a century, unless we do something drastic. If civilizations tend to evolve in the same way that they have on our planet, then that’s going to hit everybody,” he said, warning that at our current pace “there’s a risk we’re not going to make it through another… 150 years.”