Certainty about our scientific statements seems to be something we can depend on, if we believe popular scientific journals. It might be more accurate to say, however, that science is always certain at the moment; certainty is not something solid and continuous. We move from being certain about one thing to being certain about another and put our faith in what the moment holds; we adapt our beliefs as theories evolve. The fact that we do this calls the objectivity of science into question in a very serious way. Even as we see on television or in magazines that a new theory answers the mystery of "x" in an indisputable manner, we forget that one hundred years in the past, our progenitors were saying and believing the same thing about another theory. So, certainty through scientific method becomes sketchy at best, there is always a new discovery around the corner that will throw us for a loop and change our minds.
I think that certainty can be achieved just as well through spirituality or other methods outside scientific ones. It is because most mainstream science relies on falsification that it can never be entirely certain. Indeed, its focus is on what is uncertain and anomalous. Science seems to be more about making statements that seem to be the most reasonable given what it has to work with than it is about making (true) essentialist declarations. Prescientific experience, on the other hand, affords us more certainty about the world, because it does not continually prescribe new theories to us (take two Bohr's atoms and call me in the morning). It allows us to develop our own epistemological framework, one which is consistent and satisfying to us as individuals. We know that the sun rises and the sun sets, and that rain helps plants grow, and so on. As science develops, we expand our theories to say that, for instance, the sun revolves around the earth, and then that the earth revolves around the sun. This shows that science can reach a point at which we are certain enough to leave research in that area at a standstill; however, the more we try to figure out, the more we are left with questions.
Paul Feyerabend attacks the certainty of the scientific method, saying that it is more or less tyrannical and appoints legitimacy to itself because it says it is legitimate! The propositions we make about the natural world are only as certain as we are about our methodology. If we have constructed a way of looking at the world that demands uncertainty to achieve truth, then our statements are always subject to change. If, on the other hand, our perspective is complete and satisfying to us, then we can be certain. In other words, certainty is not an objective thing. Truth only becomes truth when we take measures to show that it is true! When we rank science as an ideology alongside other ideologies, one that is not priveliged over any other, we can see that this is not an entirely off-the-wall statement to make. Even though it is given considerable credibility in our society the scientific world view is one we can choose to take up or keep at a distance. Science is not the only path to certainty about our world*.
*That certainly sounds like a dogmatic assertion - but I'm telling you it's not!
As my partner in noding indicated, some philosophers of science to check out include Paul Feyerabend, Imre Lakatos, and guys like that. Also, Bruno Latour is the man.