1. The problem statement, all variables and given/known data A solid ball at 30 degrees C with radius a=1 is placed in a refrigerator that maintains a constant temperature of 0 degrees C. Take c (speed)=1 and determine the temperature u(r,theta,phi,t) inside the ball 2. Relevant equations partial differential heat equation in spherical coordinates 3. The attempt at a solution In this case, I started out with setting all the partials of the function u (assuming u is the solution) with respect to theta and phi as 0 since the temperature is uniform and doesn't depend on either. I then set u(r,t)=R(r)T(t), and then plugged back into the partial equation in order to separate variables, and I got T(t)=exp(mu*t). However, R turns into a bessel equation that I can't figure out how to solve, with the coefficient of R double prime equal to r^2, the coefficient of R prime being 2r, and the coefficient of R being mu. Mu is the separation constant. The book is generally unhelpful. Can anyone tell me how to solve that equation?