What is dark flow?

Dark flow is a term used in cosmology to describe an observed phenomenon where galaxy clusters appear to be moving in a direction that cannot be explained by the known distribution of mass in the universe. This movement seems to be aligned with large-scale cosmic structures, such as the cosmic microwave background (CMB), suggesting that these clusters are influenced by gravitational forces from regions beyond the observable universe. The idea of dark flow emerged from studies that indicated certain clusters of galaxies are moving at unexpected velocities and in a specific direction, possibly towards a supercluster or some other significant mass. While this has led to hypothesize about structures beyond the observable universe, the concept remains controversial. If confirmed, dark flow could imply that our understanding of the universe's large-scale structure is incomplete and may hint at features or phenomena that lie beyond the observable limits of our cosmos. Further observations and studies are needed to clarify the nature of this phenomenon and its implications for cosmology.