If the universe is a 3 dimensional (plus time) space expanding into something, what is that something? Am I correct in stating that the universe is an infinite eternal space in which the Big Bang happened 13.5 billion years ago, and that the observable cosmos is expanding into this space? Or, did all of space begin at the Big Bang as well as all the matter and energy that arose from that event? If the latter is correct and there is no space beyond the expanding bubble of matter and energy that resulted from the Big Bang then will somebody kindly tell me what does lie beyond the extent of the observable Cosmos please? Thanks.