90 seconds to midnight: From Doomsday Clock to 'The Last of Us,' our demise is always near

My first nuclear nightmare shook me awake one night when I was in elementary school in the 1970s. Five decades later, I still recall an image from that dream – I'm running in terror with other children on the school playground after we've been told of our imminent doom.

My last atomic dream was scorched into my memory as an adult – I am driving away from my college campus when a mushroom cloud erupts in the eastern sky.