# Dangerous Statement Nobody understands quantum mechanics. This is usually a quote originating from the more famous quote by Richard Feynman "I think I can safely say that nobody **understands quantum mechanics.**" # Answer / Explanation The answer to this question depends heavily on what one means by "understanding" something. The most common notion of **"understanding nature"** in the context of science, is that one can **accurately predict** the outcome of an event, usually an experiment. Particularly in theoretical physics, our goal is to describe Nature based on a set of rules which we call the laws of physics. From these laws, we construct simulations that we will solve either by hand or with the aid of computers, such that these theoretical predictions can be tested against the experimental results of our lab colleagues. An agreement between both results would usually allow one to say that they have "understood" that particular situation. Turning our attention to [[Quantum Mechanics|quantum mechanics]], we have a mathematically sound theoretical framework that we use to output experimentally testable predictions. So far, theoretical predictions and experimental results have enjoyed a phenomenal agreement, making quantum mechanics an "understood" theory of physics. There may come a day in which a disagreement is found, as it originally happened with [[Black Body Radiation| black body radiation]] for the case of [[Classical Physics| classical physics]] which led to [[Quantum Mechanics|quantum mechanics]]. When that day comes, theorists will appropriately modify our current understanding of the laws of physics to accommodate for this new development, and once again "understand" Nature. If Feynman was a scientist, what did he then **mean exactly** by his quote? Quantum mechanics becomes relevant at the level of atoms and nuclei, where our intuition from our day-to-day experience fails us. To make matters worse, quantum mechanics is also probabilistic by definition, i.e. we usually cannot predict the outcome of a single experiment, but can only predict the averages of outcomes of **many** experiments. The tension between some of the fundamental intuitive aspects of "understanding Nature" using classical laws of physics and quantum laws of physics is precisely what Feynman was alluding to with his quote. In order to reconcile this very tricky tension, several [[Interpretations of Quantum Mechanics|interpretation of quantum mechanics]] have been developed. These different interpretations place their focus on different ways of resolving the tension between classical and quantum laws. Questions like "What does it mean to measure?", "What happens exactly during the measurement process?" or "Is the [[Wave Function|wave-function]]" a physical object?" are differently resolved by each interpretation. It is important to keep in mind that these questions remain **largely open**, as they are still actively researched to this day. This is because, nowadays, an experiment that would allow us to rule out any of the interpretations has not been proposed. If one can not test their theoretical predictions to a question via experiments, perhaps the question should then be regard as a philosophical one instead of a physical one. Resolving this kind of questions is usually very hard, which is the reason why the [[Bell Nonlocality|Bell experiment]] was so important! To summarize: Quantum mechanics is a solid mathematical theory that is well "understood" and actively used by thousands of researchers and engineers every day. Your computer, smartphone and GPS rely on the fact that we "understand" quantum mechanics, even though our day-to-day experience gives us no quantum intuition whatsoever. However, many philosophical questions about the nature of Nature and quantum mechanics are still open, which pushes us scientists to deepen our knowledge of Nature even further. >[!read]- Further Reading >- [[Interpretations of Quantum Mechanics]] >[!ref]- References >- The original Feynman quote : https://www.youtube.com/watch?v=w3ZRLllWgHI&ab_channel=MohammedAlqedra