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.
cosmology; Friedmann equation; Einstein model
