"ER = EPR" or "What's Behind the Horizons of Black Holes?" - Leonard Susskind (Lecture 1)

ER = EPR is a shorthand that joins two ideas proposed by Einstein in 1935. One involved the paradox implied by what he called “spooky action at a distance” between quantum particles (the EPR paradox, named for its authors, Einstein, Boris Podolsky and Nathan Rosen). The other showed how two black holes could be connected through far reaches of space through “wormholes” (ER, for Einstein-Rosen bridges). At the time that Einstein put forth these ideas — and for most of the eight decades since — they were thought to be entirely unrelated.  But if ER = EPR is correct, the ideas aren’t disconnected — they’re two manifestations of the same thing. And this underlying connectedness would form the foundation of all space-time. Quantum entanglement — the action at a distance that so troubled Einstein — could be creating the “spatial connectivity” that “sews space together." (Source: Quanta Magazine)