Metric expansion of space
![Full-sky image derived from nine years' WMAP data](/Images/godic/202502/05/Ilc_9yr_moll40965514.png")
![When an object is receding, its light gets stretched (redshifted)](/Images/godic/202502/05/Redshift_blueshift.svg5514.png")
![Two views of an isometric embedding of part of the visible universe over most of its history, showing how a light ray (red line) can travel an effective distance of 28 billion light years (orange line) in just 13 billion years of cosmological time. (Mathematical details)](/Images/godic/202502/05/Embedded_LambdaCDM_geometry5514.png")
5514.png")
The metric expansion of space is the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion whereby the scale of space itself changes. This is different from other examples of expansions and explosions in that, as far as observations can ascertain, it is a property of the entirety of the universe rather than a phenomenon that can be contained and observed from the outside.