Coming at them from practical applications is one approach.
I've used spherical harmonics to model earth centric "surfaces" and fields - magnetics and gravity, etc.
You might think of them as a stacked sine and cosine waves (like a fourier transform breaking a continuous function into sin and cosine components) on a directional vector radiating outwards from the centre point of sphere.
Comments
Coming at them from practical applications is one approach.
I've used spherical harmonics to model earth centric "surfaces" and fields - magnetics and gravity, etc.
You might think of them as a stacked sine and cosine waves (like a fourier transform breaking a continuous function into sin and cosine components) on a directional vector radiating outwards from the centre point of sphere.
https://geomag.bgs.ac.uk/research/modelling/IGRF.html
https://en.wikipedia.org/wiki/International_Geomagnetic_Refe...
https://en.wikipedia.org/wiki/World_Magnetic_Model