A Growing Universe

The expansion of the universe is the increase in distance between any two given gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion whereby the scale of space itself changes. The universe does not expand "into" anything and it does not require space to exist "outside" it. Technically neither space nor objects in space move. Instead it is the metric governing the size and geometry of space-time itself that changes in scale. Although light and objects within space-time cannot travel faster than the speed of light, this limitation does not restrict the metric itself. To an observer it appears that space is expanding and all but the nearest galaxies are receding into the distance.