In our endeavour to understand reality we are somewhat like a man trying to understand the mechanism of a closed watch. He sees the face and the moving hands, even hears its ticking, but he has no way of opening the case. If he is ingenious he may form some picture of a mechanism which could be responsible for all the things he observes, but he may never be quite sure his picture is the only one which could explain his observations. He will never be able to compare his picture with the real mechanism.And so we are left with theories and models of reality that cannot be proven. And so we, even if the best of scientists, are left with faith.
In other news, check out this NPR article about the discovery of particles that may move faster than light, thus perhaps leaving E=MC^2 as an old, incorrect theory.