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.
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They discovered that the clusters were moving nearly 2 million mph (3.2 million kph) toward a region in the sky between the constellations of Centaurus and Vela. This motion is different from the outward expansion of the universe (which is accelerated by the force called dark energy).

“We found a very significant velocity, and furthermore, this velocity does not decrease with distance, as far as we can measure,” Kashlinsky told SPACE.com. “The matter in the observable universe just cannot produce the flow we measure.”