Einstein called this idea "spooky action at a distance." And he dismissed it, arguing that nothing could move faster than light, so entanglement couldn't be real. Instead, he proposed that unknown "local factors" must determine the strange properties of these so-called entangled particles.
So how has Hanson proven him wrong? He separated a pair of entangled particles far enough apart that local forces could not act on both at the same time, measured their properties, and found that the particle properties correlated.