Scientists say that a mysterious dark cosmic flow, which is carrying along many galaxy clusters in the universe, might be the tug of another universe.

Recent research has found that the universe is not only expanding, it's being swept along in the direction of constellations Centaurus and Hydra at a steady clip of one million miles per hour, pulled, perhaps, by the gravity of another universe.

Scientists have no idea what's tugging at the known world, except to say that whatever it is likely dates back to the fraction of the second between the universe's explosive birth 13.7 billion years ago and its inflation a split second later.

"At this point, we don't have enough information to see what it is, or to constrain it. We can only say with certainty that somewhere very far away the world is very different than what we see locally. Whether it's 'another universe' or a different fabric of space-time we don't know," Alexander Kashlinsky at NASA's Goddard Space Flight Center in Greenbelt, Maryland, told Discovery News.

Kashlinsky and colleagues have spent years building up evidence for what they call "the dark flow."

They look at how the relic radiation from the Big Bang explosion scatters as it passes through gases in galaxy clusters, a process that is something akin to looking at stars through the bubble of Earth's atmosphere.

With data on more than 1,000 galaxy clusters, including some as distant as 3 billion light-years from Earth, the measurements show the universe's steady flow is clearly not a statistical fluke, according to Kashlinsky.

The force and direction of the flow holds steady across space and through time.

"It's the same flow at a distance of a hundred million light-years as it is at 2.5 billion light-years and it points in the same direction and the same amplitude. It looks like the entire matter of the universe is moving from one direction to the next," Kashlinsky said.

The observation fits theoretical models of how our universe might be impacted by sibling universes, predicted by string theory that we cannot directly detect.

It's like our universe is a box and everything that it contains is inside it like milk in a carton, physicist Laura Mersini-Houghton with University of North Carolina at Chapel Hill, told Discovery News.

"If our universe is all that's there, then the liquid in the box shouldn't be sliding. Whatever is pulling it has to be bigger than the size of the box," she said.

"There is a structure beyond the horizon of our universe and that structure is exerting a force on our universe and creating this flow," she added. (ANI)