The Science Book

284

EVERYTHING

THAT CAN

HAPPEN HAPPENS

HUGH EVERETT III (1930–1982)

H

ugh Everett III is a cult

figure to sci-fi enthusiasts

because his many-worlds

interpretation (MWI) of quantum

mechanics changed scientists’

ideas about the nature of reality.

Everett’s work was inspired by

the embarrassing flaw at the heart

of quantum mechanics. Although

it can explain interactions at the

most fundamental level of matter,

quantum mechanics also produces

IN CONTEXT

BRANCH

Physics and cosmology

BEFORE

1600 Italian philosopher

Giordano Bruno is burned at

the stake for his belief in an

infinity of inhabited worlds.

1924–27 Niels Bohr and

Werner Heisenberg seek to

resolve the measurement

paradox of wave-particle

duality by invoking a wave

function collapse.

AFTER

1980s A principle known

as decoherence attempts to

provide a mechanism by

which the many-worlds

interpretation may work.

2000s Swedish cosmologist

Max Tegmark describes an

infinity of universes.

2000s In quantum computer

theory, computational power is

sourced from superpositions

that are not in our universe.

bizarre results that seem to

be at odds with experiment,

a dichotomy at the heart of the

measurement paradox (pp.232–33).

In the quantum world,

subatomic particles are allowed

to exist in any number of possible

states of location, velocity, and

spin, or “superpositions,” as

described by Erwin Schrödinger’s

wave function, but the phenomenon

of many possibilities disappears as

A quantum theory in

which nature does not

decide between outcomes

is consistent with

observation.

Repeat the experiment

four times and we have

created 16 parallel worlds

(2 × 2 × 2 × 2).

A card finely balanced on

its edge will fall faceup

or facedown.

Quantum theory allows

both outcomes to happen.

So each card fall results in

its own possible world.

Everything that can happen happens.