Problem : The Foundational Problems of Quantum Mechanics

One issue with understanding quantum physics is what the underlying physical mechanism involved is. There are many interpretations in quantum physics - the classic Copenhagen interpretation, Hugh Everette II's controversial Many Worlds Interpretation, and even more controversial ones such as the Participatory Anthropic Principle. The question that comes up in these interpretations revolves around what actually causes the collapse of the quantum wavefunction. (The puzzle of the curious aspect of human consciousness's role in resolving these questions is related in Quantum enigma.)

Most modern physicists who work with quantum field theory no longer consider these questions of interpretation to be relevant. The principle of decoherence is, to many, the explanation - interaction with the environment causes the quantum collapse. Even more significantly, physicists are able to solve the equations, perform experiments, and practice physics without resolving the questions of what exactly is happening at a fundamental level, and so most physicists don't want to get near these bizarre questions with a20 foot pole.