SOMETHING big is out there beyond the visible edge of our universe. That's the conclusion of the largest analysis to date of over 1000 galaxy clusters streaming in one direction at blistering speeds. Some researchers say this so-called "dark flow" is a sign that other universes nestle next door.
Last year, Sasha Kashlinsky of the Goddard Space Flight Center in Greenbelt, Maryland, and colleagues identified an unusual pattern in the motion of around 800 galaxy clusters. They studied the clusters' motion in the "afterglow" of the big bang, as measured by the Wilkinson Microwave Anisotropy Probe (WMAP). The photons of this afterglow collide with electrons in galaxy clusters as they travel across space to the Earth, and this subtly changes the afterglow's temperature.