In 1964, John Bell became fascinated by the EPR paradox, an idea that Einstein had dreamt up to highlight what he saw as a major flaw in quantum mechanics.
The paradox (called EPR after Einstein and his mates Boris Podolsky and Nathan Rosen) is a thought experiment involving two particles that share the same quantum state. The particles become separated. Then a measurement is made on one particle which immediately determines the state of the other, regardless of the distance between them. This, said Einstein, violates special relativity and is in an act of “spooky action-at-a-distance”.
For thirty years or so, physicists ignored this paradox, all that is, except Bell, a physicist at CERN, the European particle physics laboratory near Geneva.
Bell developed a set of inequalities that could be tested against experiment. If violated, Bell’s inequalities would prove that quantum mechanics and relativity really were at odds.
At first everbody ignored Bell’s ideas but in 1984, a French team succeeded in showing that quantum mechanics did violate the inequalities. Today Bell’s inequalities are routinely violated in quantum laboratories all over the world, leaving little doubt over the issue.
Except for Joy Christian at the University of Oxford, who says that Bell’s inequalities ought to be violated on a macroscopic scale as well as the quantum level.
His assertion is based on an argument about the topology of space. In particular, he relies on a bizarre property of space that, like the EPR paradox, physicists have tended to ignore. It is this: turn an object through 360 degrees and it returns to its starting position, right? Actually, no. Not if you’re dealing with fermions such as protons and electrons which have a 720 degree symmetry. To get back to the start, you actually need to rotate them through two full turns.
Christian’s argument is that Bell’s inequalities take no account of this property, which he likens to taking an image apart pixel by pixel but without numbering them and then trying to put them back together again. He says this is the reason why Bell’s inequalities are violated, because they do not take account of the toplogy of space, not because of any spooky action-at-a-distance (although this doesn’t rule that out).
He suggests a somewhat tricky experiment that could be done on the macroscopic scale which would also violate Bell’s inequalities as strongly as on the microscopic scale. It involves measuring how balls pop apart when they’re heated, like popcorn (this is not a joke, see the paper for full details).
So is Christian implying that there’s nothing strange about the quantum world that isn’t also strange about the macroscopic world? And that perhaps Einstein was onto something after all?
Obviously, we need to take a closer look at this “macroscopic world” everybody is talking about.
Ref: arxiv.org/abs/0806.3078: Can Bell’s Prescription for Physical Reality Be Considered Complete?
His says that a macroscopic test of Bell’s inequalities and today he explains why.