Asked by: Steve Grantham, Preston
Although astronomers often discuss the expansion of the Universe in terms of a two-dimensional plane, the Universe is, of course, three-dimensional (at least in our spatial experience of it). The expansion of the Universe is the same in all directions, so it is just as ‘tall’ (or ‘deep’) as it is ‘wide’.
Unfortunately, though, we cannot know the size of the Universe. This is because light takes time to reach us from the furthest depths of space: we’re currently unable to see beyond around 46 billion light-years (the boundary of the ‘observable Universe’). We have no idea how much of the Universe lies beyond that.