Einstein never agreed with bohr on his interpretation of quantum mechanics, but it was Hugh Everette who paved the way to a realistic opposing theory in 1957.

Many Worlds Interpretation (MWI)

The various paradoxes that the Copenhagen Interpretation gave rise to (famously Schroedinger's cat, and Einstein's dislike of "spooky action at a distance") led others to keep on trying to find a better interpretation.

The simplest was put forward by a student, Hugh Everett, in 1957. He simply said that the Schroedinger equation does not collapse. Of course, everyone laughed at him, because they could see that the photon, for example, was in just one place when they looked, not in all possible places. But after a couple of decades, this issue was resolved with the concept of decoherence - the idea that different universes can very quickly branch apart, so that there is very little relationship between them after a tiny fraction of a second.

This has led to what should strictly be called the 'post-Everett' Interpretation, but is still usually called Many worlds interpretation or MWI. It is now one of the most popular interpretations and has received a lot of attention at physics conferences. Unfortunately it means that billions of you are splitting off every fraction of a second into discrete universes and it implies that everything possible exists in one universe or another. This comes up with its own set of hard-to-digest concepts, such as the fact that a 500-year-old you exists in some universes, whereas in others you died at birth.

In 1997, Max Tegmark at Princeton University proposed an experiment to prove that the many worlds interpretation (MWI) was correct. It involved pointing a loaded gun at your head and pulling the trigger. Of course, you will only survive in those universes where the gun, for whatever reason, fails to go off. If you get a misfire every time, you can satisfy yourself -- with an arbitrarily high level of confidence -- that MWI is true. Of course, in most universes your family will be weeping at your funeral (or possibly just shaking their heads and muttering).