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=                     Expansion of the universe                      =
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                             Introduction
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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
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 spacetime itself that changes in scale.
Although light and objects within spacetime 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.