Actually this was the argument that bothered Newton, but about gravity. In an infitely old but finitely large universe, why wouldn&#x27;t gravity pull everything together? Unless in all directions gravity canceled out.<p>Similarly, we can ask why the universe isn&#x27;t filled with light. If the universe was infinitely old then indeed the light would eventually heat up all the matter and penetrate everywhere. But if it&#x27;s expanding, then the light didn&#x27;t have time to fill the space-time before it expanded further.