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Curated by RSF Research Staff

Dark Flow – Large-scale Cosmic Structure and Evidence of the Multiverse

Conventional cosmological models stipulate two primary principles: the universe is isotropic (the same in all directions, or without preferred orientation); and the universe is homogeneous, which is to say that the universe has a roughly equal consistency and density everywhere so different places should appear similar to one another. This is the cosmological principle: isotropy and homogeneity -- and it has some important consequences for physics. For instance, the laws of physics are the same no matter where you are located in the universe, and importantly, if it is indeed homogeneous, then sufficiently large-scale structures cannot exist.

While these stipulations are taken as axiomatic, the cosmological principle has encountered discrepancies in observational data that throw its basic assumptions into question – observations that suggest possible anisotropy, or preferred orientation, as well as inhomogeneity at large scales, a topic we cover in our article The Rotating Universe.

For example, data from the Planck Mission shows hemispheric bias in 2 respects: one with respect to average temperature (i.e. temperature fluctuations), the second with respect to larger variations in the degree of perturbations (i.e. densities). As such, the European Space Agency (the governing body of the Planck Mission) has concluded that these anisotropies are statistically significant and can no longer be ignored.

In addition to anisotropies, possible large-scale inhomogeneity has been observed as well, as evidenced by a number of observations that conflict with predictions of maximal structure sizes:

  • The Clowes–Campusano LQG, discovered in 1991, has a length of 580 Mpc, and is marginally larger than the consistent scale.
  • The Sloan Great Wall, discovered in 2003, has a length of 423 Mpc, which is only just consistent with the cosmological principle.
  • U1.11, a large quasar group discovered in 2011, has a length of 780 Mpc, and is two times larger than the upper limit of the homogeneity scale.
  • The Huge-LQG, discovered in 2012, is three times longer than, and twice as wide as is predicted possible according to these current models, and so challenges our understanding of the universe on large scales
  • In November 2013, a new structure 10 billion light years away measuring 2000-3000 Mpc (more than seven times that of the SGW) has been discovered, the Hercules–Corona Borealis Great Wall, putting further doubt on the validity of the cosmological principle (The largest structure of the universe, defined by gamma-ray bursts).

Perhaps one of the most interesting and controversial of the anomalous findings is Dark Flow. Dark Flow is the observation, based on analysis of data on the cosmic microwave background interaction with large-scale galaxies clusters, that there appears to be a non-random directional motion of galaxies – which means the universe appears to be moving in a preferred direction. If Dark Flow holds up against continued scrutiny and does in fact become an observational fact, it would be another important observation that gives us insight into the non-uniform structure at the largest scales, perhaps even structures beyond the cosmic horizon of the observable universe. Like the CMB cold spot, which seems to suggest interaction with a universe parallel to our own, Dark Flow may be the result of residual galactic flow following the inflationary Big Bang towards a region of the multiverse with higher mass than average, or as physicist Nassim Haramein has suggested, a torus geometry of the universe in which it is rotating and has directional toroidal flow.

Check out the video by PBS spacetime for more information on Dark Flow and large-scale multiverse structure:


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