Humans have always wondered about life beyond the stars. The curiosity doesn't only stem from popular culture and the advent of film and television, but even before then. Books, oral stories and painting depicted "evidence" of aliens. People have always thought about extraterrestrial life, what aliens would look like, and if the creatures would come in peace, if they exist. But what are the nation's scientists and researchers saying about the potential existence of aliens?

NASA's administrator believes we are not alone. In 2015, the head of the NASA confirmed the existence of life on other planets. "I do believe that we will someday find other forms of life or a form of life, if not in our solar system then in some of the other solar systems — the billions of solar systems in the universe," Charles Bolden, who has been NASA Administrator since 2009, told British students, according to the Telegraph.

Read more: Why 7 Experts Are Convinced Alien Life Might Really Exist

"Today we know that there are literally thousands, if not millions of other planets, many of which may be very similar to our own earth," the 69-year-old former astronaut continued. "So some of us, many of us believe that we're going to find ... evidence that there is life elsewhere in the universe."

According to the History Channel, Frank Drake, a notable astronomer, created an equation that was able to "estimate the likelihood of the existence of alien life, taking into account a number of factors including the average number of planets able to support life and the fraction that could go on to support intelligent life." The equation found that "hundreds of thousands" of planets that could support extraterrestrial beings could (and should) exist.

So why haven't they contacted us? There are several hypotheses that try to explain why aliens haven't reached out to Earthlings. One theory, titled the "Zoo hypothesis," posits that aliens are actually preventing us from contacting them, so that the extraterrestrial beings don't interrupt our natural development. In short, Earth might be a "zoo" for aliens, to watch our growth as a species.

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The Fermi Paradox is multi-layered, but a branch of the theory known as the Rare Earth Hypothesis essentially posits that humanity is the only species to have made it through the "Great Filter," a set of circumstances that make life possible, such as living on a planet that is just close enough to the Sun, or having just the right set of evolutionary events occur to create life. The Rare Earth Hypothesis believes that these set of circumstances are so infinitesimally small, that no other life in the universe is able to replicate it. Humanity won the cosmic lottery!

But there is no way to know for sure if aliens exist or not, that is until we are contacted. This could be dangerous and we should be cautious of alien life, Stephen Hawking, one of the world's leading minds on the cosmos, warns.

"Primitive life is very common and intelligent life is fairly rare," the 74-year-old physicist said at the 50th anniversary celebration of NASA in 2008, according to the Daily Galaxy. "Some would say it has yet to occur on earth. We should be careful if we ever happen upon extraterrestrial life. Watch out if you would meet an alien. You could be infected with a disease with which you have no resistance."

But finding alien life would be a monumental step for science. Finding out that we aren't alone out there, and there are extraterrestrial beings attempting to contact humanity, opens a world of possibilities and a variety of questions. What do aliens know? What can aliens teach us? How would we interact with beings from space?

"Just imagine the moment, when we find potential signatures of life," Matt Mountain, director and James Webb telescope scientist at the Space Telescope Science Institute, said at a seminar in NASA's headquarters in 2014. "Imagine the moment when the world wakes up and the human race realizes that its long loneliness in time and space may be over — the possibility we're no longer alone in the universe."