Is a scientific fact something that is a absolute and unchanging?

No, a scientific fact is something that can be verified by other people by following a described procedure. If the fact is more closely examined or the conditions change, the fact may be reformatted. Largest and clearest example is Newton's Laws of Motion which are still perfectly good if you stay within the limits of his times. It is when you add large long term accelerations, great speeds, etc., that they breakdown and Relativity is required to explain the motion.