I recently got a starter home learning course on quantum mechanics and well its basically at the stage of explaining the simplistic basics of it. Now one part of the lecture video mentions that if a photon has two possible pathways it can take. They cancel each other out and there for it takes neither path ? The video failed to explain why it won't pick either given i thought everything was based on probability, therefore it must take at least one of them? Or the other theory i was told was it takes all of them simultaneously and creates branches in the universe. But if the pathways cancel out - then wouldn't they have to have some kind of energy in the positive and negative to eliminate each other =/ It didn't go into depth on it but i've not heard of this before. I've only heard of the "it takes all possible paths".