Dear Fabien
Thanks for reading my essay, I am glad you enjoyed it. Indeed science has been unraveling the truth progressively, and I think that we made a lot of progress in this direction: understanding nuclear energy, electromagnetic radiation, life, evolution, gravity, matter, consciousness, etc. is astonishing. Certainly, due to space limitations it is difficult to express ideas with precision. What I mean is that the main goal of science is to find the best description of how the world works, not merely an absolute truth. For me, science would be meaningless if it were an aesthetic activity, such as art, if it were not about understanding the world. Philosophers claim that philosophy has no utility for human life, they said that it is just an aesthetic human activity, the art of reflecting about the world, human nature, etc. If science were like this, it would be meaningless to me.
You say: But I thought that the way it was phrased was somehow unfair to the practice of mathematics.
Here is where we have to draw a line between physics and mathematics. If we deal this problem in the realm of pure mathematics, negative and imaginary solutions would be legitimate; and nobody would complain about it. However, we are using algebraic rules to find an answer to a physical problem and for this reason we are forced to rule out some mathematical aspects. This is the thesis I defend that physical understanding is crucial to make sense of mathematics. My argument is that sometimes physicists, based on mathematical rules, grant physical meaning to some mathematical results. Here is where the problem arises; because many times there are physical criteria to tell if the mathematical result is meaningless or not.
This is a similar argument for the case of the electron in a box. The initial assumption is that THERE IS an electron inside the box and accordingly the electron MUST HAVE an associated wavenumber k DIFFERENT from zero. If this wavenumber were zero, that would mean that there were no electron in the box. Now, you say that the wave function has to satisfy the time-independent Schrodinger equation, hard boundary conditions at the walls and the normalization condition. All of these are physical criteria. The last condition is just another way of saying that the particle IS IN THE BOX that is why the volume integral of the square of the wave function is equal to ONE (it is the sum of all probabilities in that space). If the integral were zero, the particle would not be in the box. So, n=0 implies k=0 and k=0 means that THERE IS NO WAVE associated to the particle or that THERE IS NO PARTICLE in the box.
Regards
Israel