  In the end, it was the Belgian astronomer Georges LeMaître’s theory of an expanding universe that came to be accepted. LeMaître’s model was publicly proclaimed as appropriate and generally correct during a special session of the British Association for the Advancement of Science, 31 Oct 1931. Modern scientific cosmology had been officially born; because of its birth within the context of Einstein’s theory of relativity, the new cosmology became quickly and broadly known as Relativistic Cosmology. The model of this cosmology is most famously that of the blowing up of a balloon painted with dots to represent galaxies. Over time, the radius of the model’s spherical space (the balloon) increases, thereby decreasing the curvature of the space (the balloon’s skin), and increasing the distance between the dots.