Einstein's static universe
arXiv:1203.4513
Abstract
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.
9 pages, 1 figure. Portuguese version published by Revista Brasileira de Ensino de Fisica (Brazilian Journal of Physics Teaching) at http://www.sbfisica.org.br/rbef/pdf/341302.pdf - Minor revision on text, added 1 reference