The analysis of the Sloan Digital and DEEP2 sky surveys data has uncovered a redshift-dependent anisotropy in the distribution of apparent (i.e, redshift-space) relative angles of galaxy pairs with respect to the line of sight. Such a dependence could have been predicted and can be considered as an example of the Alcock-Paczynski effect, where the redshift-space anisotropy of an otherwise spherically symmetric distribution is due to the cosmological expansion. Therefore at least in principle such observations could be used to set constraints on the energy content of the Universe in general and on the dark energy in particular.
