December has been a crazy month for extraterrestrial life, from a New York Times article exposing secret alien research programs, to Elon Musk’s SpaceX missile launch over Los Angeles that sent the city into alien-hysteria for a few hours. It seems unreasonable, from a scientific perspective, to think that we’re alone in this universe, or even this galaxy. But if there are aliens, why haven’t we met them yet? The answer may be complicated.

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One popular theory to explain why aliens have not made open contact with humans is the “Zoo Theory.” John A. Ball, an MIT radio astronomer, proposed the theory in 1973, suggesting that aliens may purposely be avoiding contact with humans so they don't interfere with our activity, similar to zookeepers at a zoo or nature preserve, Science Alert reported.

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“ETI (extraterrestrial intelligence) may be discreetly and inconspicuously watching us but not dabbling," Ball wrote in his paper on the subject.

According to this theory, we are too unevolved and uncivilized to be a threat or burden to alien life, but rather than interfere with our natural evolution, they monitor us from afar. Of course, they aren’t completely perfect in their effort to stay out of human affairs, which is why we have several thousand alleged sightings each year.

This is only one of several theories on why we haven't made official contact yet. Other theories suggest that there may be alien life out there, but it's not advanced enough to reach out to its cousins in other neighborhoods. Much research has been done to support this idea, particularly surrounding Saturn’s moon, Enceladus. This moon has a salty ocean beneath its icy crust, but, according to David Brown, a researcher at Warwick University’s Center for Exoplanets and Habitability who focuses on studying this moon, any life that might exist here would likely be microbial, Newsweek previously reported.

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Furthermore, even if life were more advanced, if it did reside in an ocean rather than on the planet’s surface, space travel would likely not be a top priority. Alan Stern, a planetary scientist at the Southwest Research Institute, previously told Newsweek.

Then again, some argue there's the possibility that we have made contact with aliens but the government is keeping it hush to prevent hysteria and fear. According to a New York Times article this month on the topic, the U.S. government has been tracking aliens for years. The main source in the Times article was Luis Elizondo, a former Pentagon worker who ran a program called Advanced Aerospace Threat Identification from 2007 to 2012, NY Magazine reported. According to Elizondo, aliens are real and the government knows it.

This article was first written by Newsweek

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