General relativity without tensors in a central field

For static and spherically symmetric gravitational fields in the general theory of relativity, it is found possible completely to avoid tensor analysis. The principle of equivalence, illustrated by Einstein's elevator, is used to obtain Schwarzschild's equation, on which the three well-known tests of the general theory are usually based. The derivation is guided, as with Einstein, by Poisson's (Laplace's, in empty space) equation, which here can be solved by simple calculus.