From New Scientist: Dark flow: Proof of another universe?
First off: did you know 45 billion light years is the furthest we can observe from Earth? I did not, and I don't quite understand how considering the universe is only supposed to be a little less than 14 billion years old. (I've heard of inflation and all that, but I'm still boggled.)
Anyway, this is a pretty interesting article about something called dark flow. Apparently, a team from NASA led by Dr. Sasha Kashlinsky noticed that there are a lot of galaxy clusters (they were studying almost 800) "racing at up to 1000 kilometres per second" "toward a small patch of sky between the constellations of Centaurus and Vela." (They're southern constellations; take a look at this map around -40˚.) This is strange because galaxies and galaxies clusters should be moving along with the expansion of space. Kashlinsky thinks something on the "cosmic horizon" is causing this, where conditions could be totally different from what they are in the observable universe, where matter and energy are fairly evenly distributed.
Other theories: "the dark flow is caused by other universes exerting a gravitational pull on galaxy clusters in our universe[;]" "dark flow could be a sign that our bubble universe crashed into another bubble just after the big bang[;]" or that the current cosmological model is wrong, matter is not evenly distributed, and "that at large scales matter is like a fractal."
It makes me a little sad that we might never know.