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These are excerpts and elaborations from my book "The Nature of Consciousness"
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The Indivisible Universe Albert Einstein was so unhappy with the uncertainty principle that he accepted
Quantum Mechanics only as an incomplete description of the universe. He thought
that Quantum Mechanics had neglected some "hidden variables". Once
those hidden variables were found, we would have a complete theory without
Quantum Theorys oddities but with all of Quantum Theorys results. Quantum Theory
is a practical tool to calculate probabilities for sets of particles, but no
prescription is provided for calculating quantities of individual particles.
Einstein thought that there is an underlying reality
where determinism rules and the behavior of the individual particle can be
predicted. It is just that Quantum Mechanics is incomplete and has not found
out that underlying reality yet. Einstein was particularly unhappy about the "nonlocality" of
Quantum Physics, which he thought constituted a paradox.
"Nonlocality" means "action at a distance". In Quantum
Physics one can prove that, if they were once part of the same state, two
particles will always be connected: once we measure the position of the first
one, we instantaneously determine the position of the other one, even if, in
the meantime, it has traveled to the other end of the universe. Since no
information can travel faster than light, it is impossible for the second
particle to react instantaneously to a measurement that occurs so far from it.
The only possible explanation for this "paradox" was, to Einstein,
that the second particle must have properties which are not described by
Quantum Mechanics. Einstein thought that Quantum Physics provides a fuzzy picture of a sharp
reality, whereas for Bohr it provides a complete picture of a fuzzy
reality. Einstein was proven wrong in 1964 by the Irish physicist John Bell (On the Problem of Hidden Variables in Quantum Mechanics,
published two years later), whose theorem basically ruled out "local
hidden variables", precisely the type that Einstein invoked. Bell's
conclusion is that, on the contrary, there are objective, non-local connections
in the universe. In other words, two particles, once they have interacted, will
keep interacting forever (their wave functions get entangled forever). Einstein
believed in the law of locality, i.e. that two objects can interact only if
they touch each other or if their interaction is mediated by some other object;
but Bell proved that the "wave" is enough to provide
interaction. Two measurements can be
related instantaneously even if they are located in regions too far apart for a
light signal to travel between them. Non-locality, or inseparability, is a fact
of nature. Objects are not only affected by forces. They are also affected by
what happens to other objects. (More precisely,
Bell showed how to test whether a world of properties that are not due to
observation and of separated objects is possible. In 1972 John Clauser carried out an actual experiment to perform the test, and its
result proved Einstein wrong: either properties are due to
observation, or objects are forever connected, or both. Our world cannot
possibly have both an observer-independent reality and entanglement-free
objects. To be fair to Einstein, Bell assumed that induction is a valid logical
method to prove theorems. And, as Nick Herbert has noted, Bell's theorem is metaphysical, not physical, and
ultimately relies on the metaphysical assumption that the world behaves in a
classical deterministic manner). This shattered
another belief of classical Physics. Newton believed that objects interact through forces that somehow have to
travel from one to the other. A cannonball has to travel from the cannon to the
walls before the walls explode; and nothing else in the universe is affected.
The sun attracts the earth into an orbit, but it doesn't have any effect on the
other stars. These are "local" interactions. Einstein added that forces can only travel as fast as light. Therefore, the
impact of a force on an object is delayed by the time it takes for the force to
reach that object at a speed which cannot exceed the speed of light.
"Locality" became a distance: there is only so much in the universe
that can exert a force on me, because only so much of the universe can send its
force to me during my lifetime. If I live 80 years, an event that occurs more
than 80 light-years away from here will never cause any disturbance on my life.
Bell proved that this is not the case, because Quantum Theory prescribes the
existence of a non-local "force": once two waves have interacted,
they are forever entangled. Note that
Heisenberg's
"knowledge interpretation" never had a problem with non-locality:
obviously, a change in the observer's knowledge does change the observer's
knowledge about the entire system, regardless of how "extended" in
space the system is. For example, if I observed the two particles at the
beginning, when they were in the same place, and noticed that one is black and
the other white, and later I observe the white one, I will "know"
that the other one is black even if the other one is light-years away from me. Ensemble Interpretation Back to the beginning of the chapter "The New Physics" | Back to the index of all chapters |
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