In Stephen Hawking’s Favorite Places, the iconic science superstar notes in recent years, scientists found thousands of planets outside our solar system.

“Some are burning hells, gates of fire and lava, others are solid diamond made in deadly x-rays from a dying star, but some are more like home,” he said.

In the film, Hawking takes viewers on a trip around the universe in his own CGI spaceship. He stops on Gliese 832c, a planet that could be one of the closest habitable world candidates discovered so far.

“It’s a breathtaking sight, a super-Earth five times more massive than ours,” he said.

Hawking notes scientists have no way to know if the planet is habitable. In the film, he said it's possible the atmosphere is so thick that it smothers the surface in super heat and smog, or the gravity of its nearby sun could lock the planet's spin. So, one side is always facing the sun.

“But if the planet escapes such fates, the planet could have Earth-like temperatures with an abundant liquid water, and where there is water, there is very often life,” Hawking notes.

Hawking said his Breakthrough Listen Initiative, which uses sensitive radio telescopes to pick up potential signals from planets, is in the range of Gliese 832c.

He said one day we might receive a signal back from a planet like Gliese 832c.

“We should be wary of answering back,” he said.  “Meeting an advanced civilization could be like Native Americans encountering Columbus — that didn’t turn out so well.”

According to Hawking, the discovery of intelligent life would be the greatest scientific discovery in history.

“It would force us to change,” he said. “We would have to give up the idea that we are unique and start acting with more compassion and humility.”

Top Reddit comment:

It is times like this I am always reminded by the wisdom of Gene Roddenberry's perspective on alien non-interference with humans, and I'll simply use a quote from Jean Luc Picard when referring to the Prime Directive:

"The Prime Directive is not just a set of rules. It is a philosophy, and a very correct one. History has proven again and again that whenever mankind interferes with a less developed civilization, no matter how well intention-ed that interference may be, the results are invariably disastrous."

So let us be objective here, and assume for the sake of argument at least, that aliens do exist and they are unequivocally observing us at this moment. So why aren't they making their presence known? Well, if you had to take a wider lens and judge human society as a whole, for as much as science and technology has exponentially increased in the last century, but also the standard of living has immensely progressed, we still cling to outdated and outmoded religious institutions. Our greed and willingness to exploit each other for the sake of profit has led to the over consumption of finite resources has destabilized the balance of our fragile eco-system. This has resulted with mans present instability and tensions with other countries for the control of these precious resources. Hell, as long as writing has existed, we've been perpetually at war with each other. As advanced as we think we are, the comparative difference between us and a species which have perhaps a thousand years advanced knowledge ahead us, we must seem like primitive apes to them, unable to fathom the awe of infinite space and the dangers it brings.

It is hubris to assume that if an alien ship suddenly landed on the White House lawn, the governments of the world would open up with wide arms in friendship. No... market currencies would crash, global unrest and violence would ensue due to fear and panic. There are so many unknown variables to consider if such a thing were to happen: Are they benevolent or are they here to control us? What are their intentions? Have they been living among us in the past? Are there more than one alien species? What if they said Jesus and Muhammad was a lie? Should I even go to work today? The list goes on and on and on. It is a humbling and scary thing to suddenly realize that you are no longer the top of the food chain, and that fear and uncertainty tends to led to violence. Human history has consistently told us this we fear what we don't understand. SImply look back at history and look what happens when a more advanced civilization encounters a less advanced one. It never ends good. The chain reaction of aliens making contact as of right now in our development could possibly destroy our planet because the ones in power don't want to relinquish control. They've been too accustomed of control through fiat currencies and global institutions, and the reality that of aliens existence and it's outcomes undermines their psychological control over their citizens.

So simply looking at the last decade alone I'd say we're still not ready to be welcomed to the galactic community. We're still at least 50-100 years (optimistically speaking) before we're mature and advanced enough to handle this kind of information. And I'm sure aliens understand this. Their presence alone even if peaceful and sincere could have severe unintended consequences if the species they're interacting with are fearful, mistrustful, and have access to atomic weapons. I'm not concerned what the US or Russia might do, but I'd be damn concerned what Pakistan or India might do. Or worse, what would North Korea do with their peaceful dictator. And it is this reason alone why I bring up the Star Trek reference because Gene was brilliant in his forward thinking when concerning the ramifications of First Contact, and I encourage anyone to watch that episode because it beautifully depicts what happens when a civilization is on the cusp of interplanetary exploration but not prepared to handle the truth that, "we are not alone."

2500+ Reddit comments:

https://reddit.com/r/Futurology/comments/545o78/stephen_hawking_if_aliens_call_we_should_be_wary/

Be good to each other, because aliens.

http://pandawhale.com/post/49855/be-good-to-each-other-because-aliens-web-comic-by-nate-swinehart