Adding to the for dummies.
The real spherical harmonics are orthonormal basis functions on the surface of a sphere.
I'd like to fully understand that sentence and what it means.
Still grappling with
- Orthonormal basis functions (I believe this is like Fourier Transform's basis functions are sines and cosines, and sin is orthogonal to cos, and so the components can have a zero inner product..)
- ".. are orthonormal basis functions ..on the surface of a sphere".
- What sphere? Where does the sphere come from? Do you mean for each position on the sphere, we have a value? Is the periodicity in space on the sphere exploited? Is that how we get the higher order terms?