Why haven't aliens gotten in touch? Maybe they think Earth is boring. 

A new preprint paper published to the arXiv (opens in new tab) database suggests that intelligent extraterrestrials might not find planets that host life particularly interesting. If life has evolved on many planets in the galaxy, then aliens are probably more interested in the ones where there are signs not just of biology but technology, study author Amri Wandel, an astrophysicist at The Hebrew University of Jerusalem, wrote in the paper. The paper is yet to be peer-reviewed.

The study explores the Fermi paradox, which holds that given the age of the universe, it's likely that intelligent aliens would have developed long-distance space travel by now, and thus it’s likely that they would have visited Earth. The fact that they haven't (as far as we know) may be evidence that there is no other intelligent life in the Milky Way galaxy. 

But experts have offered  other explanations for the missing aliens: Perhaps they visited Earth in the past, before humans evolved or were capable of recording the visit. Or maybe long-distance space travel is more difficult than believed. Perhaps aliens evolved advanced civilization too recently to make it to Earth. Or they've deliberately decided not to explore the cosmos. It’s even possible that they’ve killed themselves off.

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