What is the EPR paradox?
Q: What is the EPR paradox?
A: The EPR paradox is an early and strong criticism of quantum mechanics put forward by Albert Einstein, Boris Podolsky, and Nathan Rosen. They argued that Niels Bohr, Werner Heisenberg, and other scientists in Copenhagen were wrong about uncertainty.
Q: What did Heisenberg claim?
A: Heisenberg claimed that you could never know for any one time both the position and momentum (or velocity or trajectory) of any atom-sized or smaller particle. It was thought that measuring one would cause a change to occur in the other so they couldn't be measured at the same time.
Q: How did Einstein respond to this claim?
A: Einstein said that if two very small particles were stuck together after having their weights measured and then given a push before being broken apart again, they should have positions and velocities related to each other. Therefore if you measure the position of one particle, even if it messes up its velocity in doing so, it still must have had a definite velocity before measurement.
Q: What explanation did Erwin Schrödinger suggest for this paradox?
A: Erwin Schrödinger suggested that maybe the relationship between position and velocity would gradually go away somehow; he called this connection between two particles "entanglement". This phenomenon was referred to by Einstein as "spooky action at a distance".
Q: Did Einstein believe entanglement existed?
A: No, Einstein had no way of knowing that future experiments would show entanglement exists.
Q: Who mathematically proved entanglement exists?
A: John Stewart Bell showed mathematically that there is no way hidden variables could account for experimental results showing entanglement exists.
