Archives - Physics: Page 21
Author: amparo enriquez (Wed Jan 11, 2006 4:36 pm)
Title: Physics
In a 1935 paper that Einstein and his colleagues, usually referred to as E.P.R., they argued that the uncertainty principle could not be the final word about nature. They thought there must be a deeper theory behind the quantum veil.
Imagine that a pair of electrons are shot out from the disintegration of some other particle, like fragments from an explosion. By law certain properties of these two fragments should be correlated. If one goes left, the velocity goes right; if one spins clockwise, the other spins counterclockwise.
That means, Einstein said, that by measuring the velocity of, say, the left hand electron, we would know the velocity of the right hand electron without ever touching it.
Conversely, by measuring the position of the left electron, we would know the position of the right hand one.
Since neither of these operations would have involved touching or disturbing, the right hand electron in any way, Einstein, Podolsky and Rosen argued that the right hand electron must have had those properties of both velocity and position all along. That left only two possibilities, they concluded. Either quantum mechanics was “incomplete”, or measuring the left hand particles somehow disturbed the right hand one.
But the latter alternative violated common sense. Such an influence, or disturbance, would have to travel faster than the speed of light. “My physical instincts bristle at that suggestion”, Einstein later wrote.
Bohr responded with a six-page essay in physical review that contained but one simple equation, Heisenberg’s uncertainty relation. In essence, he said, it all depends on what you mean by “reality”.
Most physicists agreed with Bohr, and they went off to use quantum mechanics to build the atomic bomb and reinvented the world.
The consensus was that Einstein was a stubborn old man who “didn’t get” quantum physics. All this began to change in 1964 when John S. Bell, a particle physicist at the European center for Nuclear research near Geneva, who had his own doubts about quantum theory, took up the 1935 E.P.R. argument. Somewhat to his dismay, Bell who died in 1990, wound up proving that no deeper theory could reproduce the predictions of quantum mechanism, in spite of it’s challenge to reality as we know it.