Science fiction is whatever we're worried about now, spray painted silver. Our monsters are metaphors for what scares us most. RUR was about industrial class struggle, Flash Gordon fought World War II in advance, 1984 was about 1948, and we knew all those crappy '50s flying saucers were piloted by godless commies. So what are we afraid of now? Zombies. They stay scary, year after year, because, what if somehow you yourself became a mindless shambling thing, just a blind hunger groping around wanting more more more for no good reason? What if the brains you ate were your own?