PARALLEL UNIVERSES 245
So does there exist the wave function of an evil Federation of Planets that plunders weaker planets and slaughters its enemies? Perhaps,
but if so, we have decohered from that universe.
QUANTUM
UNIVERSES
When Hugh Everett discussed his "many worlds" theory with other
physicists, he received puzzled or indifferent reactions. One physicist,
Bryce DeWitt of the University of Texas, objected to the theory because
"I just can't feel myself split." But this, Everett said, is similar to the way
Galileo answered his critics who said that they could not feel the Earth
moving. (Eventually DeWitt was won over to Everett's side and became
a leading proponent of the theory.)
For decades the "many worlds" theory languished in obscurity. It
was simply too fantastic to be true. John Wheeler, Everett's adviser at
Princeton, finally concluded that there was too much "excess baggage"
associated with the theory. But one reason that Everett's theory is suddenly in vogue right now is because physicists are attempting to apply
the quantum theory to the last domain that has resisted being quantized: the universe itself. Applying the uncertainty principle to the entire universe naturally leads to a multiverse.
The concept of "quantum cosmology" at first seems like a contradiction in terms: the quantum theory refers to the infinitesimally tiny
world of the atom, while cosmology refers to the entire universe. But
consider this: at the instant of the big bang, the universe was much
smaller than an electron. Every physicist agrees that electrons must be
quantized; that is, they are described by a probabilistic wave equation
(the Dirac equation) and can exist in parallel states. Hence if electrons
must be quantized, and if the universe was once smaller than an electron, then the universe must also exist in parallel states-a theory that
naturally leads to a "many worlds" approach.
The Copenhagen interpretation of Niels Bohr, however, encounters problems when applied to the entire universe. The Copenhagen
interpretation, although it is taught in every Ph.D.-level quantum me-
So does there exist the wave function of an evil Federation of Planets that plunders weaker planets and slaughters its enemies? Perhaps,
but if so, we have decohered from that universe.
QUANTUM
UNIVERSES
When Hugh Everett discussed his "many worlds" theory with other
physicists, he received puzzled or indifferent reactions. One physicist,
Bryce DeWitt of the University of Texas, objected to the theory because
"I just can't feel myself split." But this, Everett said, is similar to the way
Galileo answered his critics who said that they could not feel the Earth
moving. (Eventually DeWitt was won over to Everett's side and became
a leading proponent of the theory.)
For decades the "many worlds" theory languished in obscurity. It
was simply too fantastic to be true. John Wheeler, Everett's adviser at
Princeton, finally concluded that there was too much "excess baggage"
associated with the theory. But one reason that Everett's theory is suddenly in vogue right now is because physicists are attempting to apply
the quantum theory to the last domain that has resisted being quantized: the universe itself. Applying the uncertainty principle to the entire universe naturally leads to a multiverse.
The concept of "quantum cosmology" at first seems like a contradiction in terms: the quantum theory refers to the infinitesimally tiny
world of the atom, while cosmology refers to the entire universe. But
consider this: at the instant of the big bang, the universe was much
smaller than an electron. Every physicist agrees that electrons must be
quantized; that is, they are described by a probabilistic wave equation
(the Dirac equation) and can exist in parallel states. Hence if electrons
must be quantized, and if the universe was once smaller than an electron, then the universe must also exist in parallel states-a theory that
naturally leads to a "many worlds" approach.
The Copenhagen interpretation of Niels Bohr, however, encounters problems when applied to the entire universe. The Copenhagen
interpretation, although it is taught in every Ph.D.-level quantum me-