In this paper, it is proposed that the size of the classical electron, which is a stable elemental particle with the smallest concentration of matter in Nature, can be used to explain the very big size of the Universe. In order to reach that objective, the apparent size of heavenly bodies as seemed each other at very big distances in space, is used as a fundamental concept. Also, it is proved that the size, shape, mass, and future of the Universe are ruled by the speed of light, and the range of gravitational interactions.