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Redshift space is a concept of cosmological space based on spherical coordinates (with us at the center), taking the redshift of distant objects, as found in redshift surveys, as the radial dimension. A collection of data over three dimensions, such as throughout some redshift space, can be stored in a data cube. Comparing object's position within redshift space against other means of determining their distance yields information on the geometry of the universe over time, such as acceleration of its expansion, i.e., the phenomenon that suggests dark energy. Data stored as redshift space has undergone less interpretation, and distances can be determined in the future as needed, taking advantage of future determinations of the relation between redshift and distance. However, some types of analysis can be carried out without converting from redshift space.
Hubble's law gives a means of converting between redshift space and "normal" space, but can yield errors due to redshift space distortion or RSD, the effect of the peculiar velocity of galaxies on their redshift, e.g., in a region where galaxies have high random peculiar velocities (appearing stretched toward and away from us, i.e., the finger of God distortion) or a pattern of high peculiar velocities (e.g., when they are attracted toward the center of a larger structure, the Kaiser distortion). The Alcock-Paczyński effect also presents complications.