[University of Central Florida theoretical physics professor Costas Efthimiou] begins with the assumption that a vampire feeds only once a month. "Certainly a highly conservative assumption," the paper notes. Every time the vampire feeds, the vampire population increases by one and the human population decreases by one. Efthimiou supposed that the first vampire arrived on Jan. 1, 1600, when the human population was 536,870,911. That means there would have been two vampires and 536,870,910 humans on Feb. 1, four vampires and 536,870,908 humans on March 1, and so forth. With the vampire population increasing geometrically and the human population decreasing geometrically, by the 30th month the human race would have been wiped out.Zombies, of course, have the same problem, so stop worrying so much about the walking dead – the bad guys are apparently confined to George Romero and Dario Argento movies. And don't even get Efthimiou started on ghosts – they can't apply force, and thus there's no way they can walk like humans, as Patrick Swayze does in "Ghost." So next time you think you're being haunted, don't bother calling Ghostbusters – just look up Newton's third law of physics, and let science do its thing.