canto_1980_back_of_the_envelope_1

import sympy
R = sympy.Symbol('R')
t = sympy.Function('t')
Vs = sympy.Symbol('V_*')
c = sympy.Symbol('c')
Rs = sympy.Symbol('R_s')
M = sympy.Symbol('M')
sympy.dsolve(t(R).diff(R)-(1+M*R/Rs)/Vs,t(R))