Asked by: Chris Hunt, Manchester
When astronomers refer to the ‘expansion’ of the Universe they are referring to the abstract concept of space-time. Space-time is the ‘fabric’ of the Universe, consisting of three physical dimensions and the additional ‘dimension’ of time. When an object is in motion, it changes its position within this ‘grid’ of space-time.
The speed of light is only a limit for objects within space-time, not actual space-time itself. So, there is no conundrum in space-time expanding at (or greater than) the speed of light.