why is learning quantum mechanics hard?

why is learning quantum mechanics hard?

There are, I think, three reasons.

 First, we grew up in and now inhabit a macroscopic world. Our intuition-our sense of how things ought to behave-has been reinforced every waking minute by experiences in a world that abides by classical physics. Moreover, as students of physics, our intuition has been deepened and further reinforced by our study of classical physics. Quantum physics is an affront to that intuition. To understand it, to use it effectively, we must develop a new way of thinking about the way things work, because, as Richard P. Feynman has written:

Things on a very small scale behave like nothing you have any direct experience about. They do not behave like waves, they do not behave like particles, they do not behave like clouds, or billiard balls, or weights on springs, or like anything that you have ever seen.

Second, quantum physics operates at a level that is one step removed from reality. It is more abstract than classical physics. While classical physicists can deal with well defined trajectories that describe particles they can visualize, quantum physicists must forever wander through a haze of uncertainty, probabilities, and indeterminacy, trying to understand a universe they cannot directly observe. The microcosm can be understood, but it cannot be seen.

Third, quantum mechanics is inherently mathematical. There is an important distinction here between classical and quantum physics. In classical physics we use mathematical methods to implement the ideas of the theory, but we can discuss those ideas without recourse to mathematics. This is not possible with quantum mechanics. Notwithstanding the achievements of writers who have recently tried to popularize quantum theory-several of whose books  believe it is impossible to fully grasp the principles of quantum theory without seeing them expressed mathematically. Math is more than a tool for solving quantum mechanics problems: mathematics is the language of quantum physics. As we move deeper into quantum theory, we'll see physics and math become inextricably intertwined. Thus quantum physics demands that we think in a new, abstract, inherently mathematical way-no easy task.

Finally, we must re-think and redefine many familiar words and concepts, and when we use these words to discuss quantum concepts, we must do so with great care and precision. Familiar terms such as "particle" and "motion" assume in the quantum domain subtle overtones and shades of meaning that we ignore at our peril. The "position" of a quantum particle prior to its measurement is not a single, well-defined number, such as IO.7m. Rather it must be specified as a collection of several-maybe an infinity of-values, none of which represent the position of the particle. Instead, each value represents a possibility, a location at which the particle might be found.

represents a possibility, a location at which the particle might be found. In spite of these roadblocks-our classical intuition, the inherently abstract, mathematical nature of quantum mechanics, and the need to use old words in new ways-I believe that you can understand quantum physics. Even if you cannot visualize what goes on in the micro world of atoms and molecules, you can grasp the beautiful and powerful physical laws that govern that world. After all, countless physicists have done it.

The source:

Michael A. Morrison - Understanding Quantum Physics.

By. Fady Tarek