It’s one of those unanswerable questions of the modern age. With so many stars in the Milky Way (not to mention all the stars in nearby galaxies) with the potential for tens of billions of planets, the odds of intelligent life existing somewhere are pretty high. Yet in all recorded history, no confirmed contact with an alien civilization has ever been recorded. So where is all this life? Or as physicist Enrico Fermi was quoted as saying in 1950, “But where is everybody?” Good question, so good scientists still call this Fermi’s Paradox.

There are several possible explanations. The first is that distances are so vast contact isn’t really practical. Star Trek’s warp drive notwithstanding, there is no easy way to explore the neighborhood. And when you consider our planet’s location is more in the Milky Way’s suburbs rather than being centrally located, such lack of contact is easier to comprehend.

But now NASA has theorized a more sobering possibility. Perhaps eventually each civilization ultimately confronts some barrier to its own survival? This barrier might be an external threat, such as a direct strike from a huge asteroid or a lethal burst of radiation from a nearby star. Or it could possibly be internal, like all-out nuclear war. Called the Great Filter, it basically means if you hang around long enough, something will eventually get you, probably before anyone else even realizes you exist.

So should we be worried? Absolutely! We need to be aware of what’s happening in the Solar System around us, and what we are doing to ourselves. Our main reason for hope is that life on this planet has already survived several mass extinctions, the most notable being the Permian-Triassic extinction (the Great Dying) of 250 million years ago which wiped out about 96% of marine life and 70% of land species. The problem is we still don’t understand exactly how this happened.

So until we better understand all the threats to our planet, we need to make sure we don’t get filtered out — or filter ourselves.