Einstein's Spooky Action at a Distance (Paperback) (ISBN-13: 9781643545288)

Entanglement is what Einstein referred to as "spooky action at a distance." It's a phenomenon by which one particle can effectively "know" something about another particle instantaneously, even if those two particles are separated by a great distance. It appears to go against the idea that nothing, not even information, can travel faster than the speed of light.