Evolution isn't something you have to believe in, in fact as a scientific theory it's rigorously tested constantly to check it's model fits what we observe in the real world. Understanding what it describes and what in allows you to predict would be a leap for most people.
I suppose you can use the word belief, but you wouldn't say you "believe in gravity" would you? Well you might, but it would be odd.
And "theory" in science is as good as it gets in science, it doesn't mean "might be true" as in the everyday use of theory.
I was gonna say something similar...when people say they don't believe in evolution I ask them if they believe in the colour red. It exists, as does evolution, it's not a case of believing in or not. And clearly we are not desended from monkeys, but share a common ancestor.
An interesting fact is that, so far, in space exploration we have not found a single element in space, that is also not found here on earth.
