Broadly, science is an intellectual loop or maybe a circuit. It starts with observation; it starts with that which can be seen, touched, smelt, heard or measured with instrumentation. These inputs, are then made sense of with a theoretical assumption about why these things are the way they are. But it can work in the other direction; a scientist can have a theoretical assumption that is validated or invalidated by empirical observation. It works both ways. You can not have science with just observation and you can not have science with just theories. Observation and theory COMBINED are what make this intellectual process as powerful as it is.