belief and knowledge are not equals
belief doesn't require knowledge even if belief is part of the knowledge process
Well, in philosophy knowledge is called "justified true belief", which is a phrase I personally don't like, but there it is.
Belief itself has a huge range. It can include belief in ideas that are contrary to fact, thus irrational, so impossible, into the improbable range, through a range where belief is based on varying degrees of evidence. So belief can be highly probable, but not conclusive. For example we cannot say we know OJ did it, but the evidence is so overwhelming that our belief is well justified and his guilt is highly likely.
As far as knowledge in science there is a probability in results, and they seldom come out to be 100%. So this knowledge it highly likely true, thus justified belief. Now we can be certain about many things. We are certain that the poisons chlorine and sodium will become harmless table salt when combined.
So really belief versus knowledge is a misleading and vague question.