is it not possible that a man made system could be completely wrong?
Completely wrong? Possible, but fairly unlikely.
Science is interesting because it progresses as new information is discovered. If a fact is found to be wrong, it becomes part of science's history (e.g. the Ptolemaic model of the cosmos) but is not used in current practice. In this way, science tends to move towards more accuracy and a better understanding of the physical universe.
Religion eschews this kind of corrective mechanism in favour of tradition, so religions become less wrong by spawning new sects (but the parent sect usually keeps going). The new sect can even go the other way, towards Even More Wrong Than Its Predecessor.