O universo estático de Einstein

einstein's static model is the first relativistic cosmological model. the model is static, finite and of spherical spatial symmetry. i use the solution of einstein's field equations in a homogeneous and isotropic universe friedmann's equation -to calculate the radius of curvature of the model (also known as einstein's universe). furthermore, i show, using a newtonian analogy, the model's mostly known feature, namely, its instability under small perturbations on the state of equilibrium.