Or the Universe is neither infinite or as old as it's assumed to be. Although there's strong evidence for it being as old as we (me included as a figure of speech) currently believe it, our belief is based on some fundamental assumptions that can only be strengthen but not proven. At least for the sake of honesty, one must be aware of the nature of this kind of opinions. Science is part of the larger discipline called epistemology, so all the rules valid there, are valid in science too.