Why don't we see any other civilizations in the universe? This is the Fermi Paradox. Physicist Brian Cox says the answer may be the Great Filter — a deadly barrier that almost no civilization survives. It could be ahead of us right now: technology, war, or destroying our own planet. Are we about to hit it… or have we already passed it? What do you think? #FermiParadox #BrianCox #GreatFilter #Aliens #space