Mytch answered well, science is a logical system that is based on the obvious principles and these principles give us the ability of defining new things. for example euclidean geometry is a science, it derives from 5 principles founded by euclid, if you change one of these principles it'll result to create a new geometry, for instance if you change the 5th principle about the parallel lines the result is the creation of a new geometry called "non euclidean geometry".
god is a whole different story, i don't like to talk about him cuz i'm exhausted from telling the repetitive things over and over