1. ## A terminology problem

I was wondering why the series below is called a harmonic series? Thanks.

2. I wondered about that too. But I used the internet to find the answer just now.

Originally Posted by Wikipedia
Its name derives from the concept of overtones, or harmonics, in music: the wavelengths of the overtones of a vibrating string are 1/2, 1/3, 1/4, etc. of the string's fundamental wavelength.
It turns out the harmonic series is very closely related to music (harmonics) even more so than a redneck and his wife. Here.

3. On the same note (get the pun ), why are "harmonic functions" called "harmonic".

Somebody asked me this a long time ago. I made a guess that the Laplacian equation describes the motion of a wave, hence the name harmonic. But now I know that I was wrong. Because the Laplacaian equation appears everywhere in mathematical physics. Both the heat and wave equations have contain this del-squared operator in the PDE along with over equations, so my initial explanation is totally wrong.