Aliens haven't contacted Earth because there's no sign of intelligence here, new answer to the Fermi paradox suggests

According to a recent article, intelligent extraterrestrials would only be interested in making contact with the technologically most developed worlds, and Earth doesn't make the cut.

Why haven't we heard from aliens? Perhaps they find Earth uninteresting.

According to a recent preprint study uploaded to the arXiv website, intelligent extraterrestrials may not find planets that support life to be very fascinating. Amri Wandel, an astronomer at The Hebrew University of Jerusalem and one of the study's authors, noted in the report that if life has developed on numerous planets around the galaxy, extraterrestrials are likely more interested in those where there are traces of both biology and technology. Peer review of the paper has not yet occurred.

The research examines the Fermi paradox, which contends that given the age of the universe, intelligent extraterrestrial life would have most certainly achieved long-distance space travel by now and would have visited Earth as a result. The lack of them (as far as we are aware) may indicate that no other sentient species exists in the Milky Way galaxy.

Nonetheless, specialists have provided further theories for the missing aliens: Maybe they came here in the past, before humans developed or had the technology to document their presence. Or perhaps long-distance space flight is more challenging than thought. Perhaps sophisticated civilizations have evolved too recently for them to reach Earth. Maybe they have consciously chosen not to investigate the universe. They could have even exterminated themselves.

Another reason, according to Wandel's latest article, is that life is actually rather prevalent in the Milky Way. Aliens wouldn't likely spend their time sending signals to every rocky planet in the habitable zone of a star if many of them are home to life; instead, they would probably try to communicate with alien amoebas or algae.

Intelligent aliens are probably far more interested in technological signals if life is widespread. Yet it can be difficult to pick up on tech indications. Since the 1930s, Earth has only been emitting radio waves as observable signals from space. Theoretically, these signals have already covered around 15,000 stars and the planets that orbit them, but that only represents a small portion of the Milky Way's 400 billion or more stars. Additionally, Wandel noted that only stars within 50 light-years of Earth have had a chance to answer since Earth began broadcasting off-planet since it takes time for any return communication from extraterrestrials to travel back.

Even worse, since Earth's first radio transmissions were not intentionally sent into space, after around one light-year they are probably so jumbled that aliens would be unable to recognize them, according to Universe Today . (In 1974, Earthlings launched the Arecibo message, aimed at the globular star cluster M13, as the first purposeful high-power transmission to extraterrestrials. It's time to send another, according to some scientists.)

Wandel discovered that it's unlikely that Earth's transmissions have reached any other sentient species, unless intelligent civilizations are extremely numerous, with more than 100 million technologically sophisticated planets in the Milky Way. Wandel suggested that it becomes more possible that intelligent listeners would stumble across Earth's technology signals over time and as our planet emits an increasing amount of radio noise.

According to the research, there may not be any advanced civilizations within 50 light-years of Earth. Yet, intelligent life may still exist in the universe and be simply waiting for our call.