(Also not a physicist). GR works and has been tested experimentally on a large scale, but it doesn't always work on a small scale. QM works, has been tested exp

(Also not a physicist). GR works and has been tested experimentally on a large scale, but it doesn't always work on a small scale. QM works, has been tested experimentally on a small scale, but it doesn't always work on a large scale. They just give different predictions in some very small or very large cases. Obviously they can't both be right: if one theory predicts A and the other theory predicts B then we can just do the experiment and one of them will turn out to be wrong. Unfortunately, they only differ in extreme circumstances that are hard to recreate, and we were not able to perform an experiment that will tell us which is right (or how to tweak them to make them compatible with each other). Fun fact: There is a thing called a cosmological constant problem. It's the disagreement between the observed values of the cosmological constant (using GR) and a theoretical value suggested by QM. The observed value is... 10**120 times smaller than QM predicts it should be [1]. Now this is what I call a fundamental incongruence :). [1] This is also called "probably the worst theoretical prediction in the history of physics".