What is Pulling the Milky Way Towards It at 14-Million MPH? (Today's Most Popular)

What is Pulling the Milky Way Towards It at 14-Million MPH? (Today's Most Popular): "Astronomers have known for years that something unknown apears to be 'pulling' our Milky Way and tens of thousands of other galaxies toward itself at a breakneck 22 million kilometers (14 million miles) per hour. But they can't pinpoint exactly what, or where it is."