When creationists denounce Carl Sagan for calling evolution a proven fact, they are actually attacking all physical scientists, because no scientist can prove any physical law or theory will be eternally true. Creationists want absolutes, which science will never generate. Science does not provide the kind of eternal verities creationists seek. Every law or theory in science is a temporary truth, a relative truth. But that is not to say it will never be enhanced.
Scientists gather data and formulate theories based on what they have.
As new information is collected, the theory is modified and improved, to take account of new facts. Creationists, on the other hand, formulated theories based on the book of Genesis, gathered data to corroborate them, and discarded all information to the contrary. Facts were made to fit beliefs, rather than vice versa. Secondly, there are always going to be questions in the physical sciences for which current theories or laws have no provable explanation. That is inherent to the nature of science.