Stephen Hawking has said it before and hell say it again: If extraterrestrials call, do not answer at least, not without careful consideration.

The renowned theoretical physicists hosts Stephen Hawkings Favorite Places, a new short film available on the streaming service Curiosity Stream. The film follows Hawking around the universe as he travels in a computer-generated imagery spacecraft, giving the audience a peek into simulations of a black hole and Gliese 832c , an earth-like planet outside our solar system that scientists believe may be able to support life.

And Gliese 832c isnt even the closet possible second-Earth. In August, scientists announced that Proxima b , a planet orbiting Proxima Centauri the nearest known star to our sun has a temperature that could allow liquid water and is possibly habitable.

But if we ever get a signal from any of these places, Hawking warns that we shouldnt be too eager to say hello.

We should be wary of answering back, he says in the film, according to USAToday. Meeting an advanced civilization could be like Native Americans encountering Columbus that didnt turn out so well.

Its an idea Hawking has expressed numerous times before typically using human beings as an example of why we shouldnt trust other intelligent life.

We only have to look at ourselves to see how intelligent life might develop into something we wouldnt want to meet, he told The Times of London in 2010. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach.

Well, were convinced. NASA, we really hope youre listening.