This is still an open question, and a really good one. The predictive power of quantum theory is amazing; it gives excellent numerical predictions as to the ou

This is still an open question, and a really good one. The predictive power of quantum theory is amazing; it gives excellent numerical predictions as to the outcome of experiments. But as to how we interpret that, especially the question of what a measurement is, is not at all addressed by the theory, and remains a point of intense discussion and study.