Behold, empirical evidence of Something Out There Beyond Our Ken:
Patches of matter in the universe seem to be moving at very high speeds and in a uniform direction that can’t be explained by any of the known gravitational forces in the observable universe. Astronomers are calling the phenomenon “dark flow.”
The stuff that’s pulling this matter must be outside the observable universe, researchers conclude.
There’s a more detailed discussion of this new study at Ars Technica, where they note,
A quartet of researchers measured fluctuations in the CMB that result from the scattering of microwave photons by energetic X-ray emissions from galactic clusters, and discovered a coherent flow of matter across the universe. Dubbed “dark flow” by the team, it cannot easily be explained by the distribution of matter in the visible universe. The team postulates that this motion may be the effect of matter residing outside the CMBâ€”something beyond our ability to directly detect.
The data used in the paper came from the three year Wilkinson Microwave Anisotropy Probe (WMAP) dataset. Using the WMAP data, the researchers extracted the wavelength of scattered photons from individual galactic clusters. Since the clusters’ motion does not exactly follow the expansion of space-time, these scattering measurements allow researchers to compute the individual motions of each cluster. This is apparent in a very small change in the CMB temperature in the direction the clusters are flowing, a phenomena known as the kinematic Sunyaev-Zel’dovich effect. This technique has a drawback, in that the measurements of this effect for a single cluster have a large statistical errors; to overcome this, the researchers took measurements from over 700 distinct clusters.
The velocity of these clusters was computed to be around 2 million miles per hour. Once the part of the movement that is caused by the expansion of the universe was removed, the researchers found a coherent direction to the remaining flowâ€”matter seems to stream towards a region of space between the constellations Centaurus and Vela.
The image above shows the 700 clusters as white dots and the purple spot the general area towards which they are all headed. The autors are repeating the experiment with even more clusters using the 5-year WMAP dataset which should reduce some of the statistical uncertainty involved, but it looks like these results are robust. There really is something out there. And by out “there”, I mean not “here” but an elsewhere that is beyond anywhere that we could ever conceivably call “here”. Woah.