Question and answer with science writer Carl Zimmer, author of ”Planet of Viruses,” who will introduce the Coolidge Corner Theatre’s showing of the science fiction film ”12 Monkeys” tonight: Q: What fascinates you about viruses? A: Viruses in a way really rule the world, we just don’t know it. They’re the most abundant form of life by far. They’re everywhere: they’re in the oceans, they’re in the soil, they’re in the air, they’re inside of us - even when we’re healthy. And they’ve been around since the beginning of life. Their existence and ours are really intertwined . . .