- Quantum mechanics is, with relativity, the essence of the big conceptual revolution of the physics of the 20th century.
- Now, do we really understand quantum mechanics?
- It is probably safe to say that we understand its machinery pretty well; in other words, we know how to use its formalism to make predictions in an extremely large number of situations, even in cases that may be very intricate.
- Heinrich Hertz, who played such a crucial role in the understanding of electromagnetic waves in the 19th century (Hertzian waves), remarked that, sometimes, the equations in physics are “more intelligent than the person who invented them” .
- The remark certainly applies to the equations of quantum mechanics, in particular to the Schrödinger equation, or to the superposition principle: they contain probably much more substance that any of their inventors thought, for instance in terms of unexpected types of correlations, entanglement, etc.
- It is astonishing to see that, in all known cases, the equations have always predicted exactly the correct results, even when they looked completely counter-intuitive.
- Conceptually, the situation is less clear.
- Nevertheless, among all intellectual constructions of the human mind, quantum mechanics may be the most successful of all theories since, despite all efforts of physicists to find its limits of validity (as they do for all physical theories), and many sorts of speculation, no one for the moment has yet been able to obtain clear evidence that they even exist. Future will tell us if this is the case; surprises are always possible!
But it is hard to understand that an equation that cannot be solved, always predicts exactly the correct results! It is more easy to believe that any observation made can be claimed to fit exactly with the equation, since checking is impossible. It would be more convincing if observation was somewhat different from theory.