According to a poll at a Quantum Mechanics workshop in 1997 ,< ref > the Copenhagen interpretation is the most widely-accepted specific interpretation of quantum mechanics, followed by the many-worlds interpretation.

The quantum-mechanical " Schrödinger's cat " paradox according to the many-worlds interpretation.

The many-worlds interpretation is an interpretation of quantum mechanics that asserts the objective reality of the universal wavefunction, but denies the actuality of wavefunction collapse.

It is also referred to as MWI, the relative state formulation, the Everett interpretation, the theory of the universal wavefunction, many-universes interpretation, or just many-worlds.

Although several versions of many-worlds have been proposed since Hugh Everett's original work, they all contain one key idea: the equations of physics that model the time evolution of systems without embedded observers are sufficient for modelling systems which do contain observers ; in particular there is no observation-triggered wave function collapse which the Copenhagen interpretation proposes.

The many-worlds interpretation shares many similarities with later, other " post-Everett " interpretations of quantum mechanics which also use decoherence to explain the process of measurement or wavefunction collapse.

Many-worlds is often referred to as a theory, rather than just an interpretation, by those who propose that many-worlds can make testable predictions ( such as David Deutsch ) or is falsifiable ( such as Everett ) or by those who propose that all the other, non-MW interpretations, are inconsistent, illogical or unscientific in their handling of measurements ; Hugh Everett argued that his formulation was a metatheory, since it made statements about other interpretations of quantum theory ; that it was the " only completely coherent approach to explaining both the contents of quantum mechanics and the appearance of the world.

In the many-worlds interpretation locality is strictly preserved, since the effects of operations such as measurement affect only the state of the particle that is measured.

Hugh Everett's many-worlds interpretation ( MWI ) is one of several mainstream interpretations of quantum mechanics.

Related to the many-worlds idea are Richard Feynman's multiple histories interpretation and H. Dieter Zeh's many-minds interpretation.

The Everett many-worlds interpretation, formulated in 1956, holds that all the possibilities described by quantum theory simultaneously occur in a multiverse composed of mostly independent parallel universes.

The quantum-mechanical " Schrödinger's cat " paradox according to the many-worlds interpretation.

In 1957, Hugh Everett formulated the many-worlds interpretation of quantum mechanics, which does not single out observation as a special process.

It examines the Schrödinger's Cat experiment from the point of view of the cat, and argues that by using this approach, one may be able to distinguish between the Copenhagen interpretation and many-worlds.

The many-worlds interpretation ( MWI ) is sometimes presented as a waves-only theory, including by its originator, Hugh Everett who referred to MWI as " the wave interpretation ".

A possible resolution to the paradoxes resulting from wormhole-enabled time travel rests on the many-worlds interpretation of quantum mechanics.

Specifically, it assumes either that there is only one timeline, or that any alternative timelines ( such as those postulated by the many-worlds interpretation of quantum mechanics ) are not accessible.

In the many-worlds interpretation ( MWI ), one of the mainstream interpretations of quantum mechanics, there are an infinite number of universes and every possible quantum outcome occurs in at least one universe.

DeWitt's phrase " many-worlds " has become so much more popular than Everett's " Universal Wavefunction " or Everett-Wheeler's " Relative State Formulation " that many forget that this is only a difference of terminology ; the content of both of Everett's papers and DeWitt's popular article is the same.

Thus, the many-worlds quantum model is proved to be both real, and accessible, a fantastic achievement.

In the many-worlds interpretation both realism and locality are retained, but counterfactual definiteness is rejected by the extension of the notion of reality to allow the existence of parallel universes.

Decoherent interpretations of many-worlds using einselection to explain how a small number of classical pointer states can emerge from the enormous Hilbert space of superpositions have been proposed by Wojciech H. Zurek.

Like the many-worlds interpretation ( MWI ), TI is a ‘ pure ’ interpretation in that it does not add anything ad hoc but provides a physical referent for a part of the formalism that has lacked one ( the advanced states implicitly appearing in the Born Rule ).

In many-worlds, the subjective appearance of wavefunction collapse is explained by the mechanism of quantum decoherence, which resolves all of the correlation paradoxes of quantum theory, such as the EPR paradox and Schrödinger's cat, since every possible outcome of every event defines or exists in its own " history " or " world ".

It attempts to distinguish between the Copenhagen interpretation of quantum mechanics and the Everett many-worlds interpretation by means of a variation of the Schrödinger's cat thought experiment, from the cat's point of view.

The phrase " many-worlds " is due to Bryce DeWitt, who was responsible for the wider popularisation of Everett's theory, which had been largely ignored for the first decade after publication.

However, the mainstream view ( without necessarily endorsing many-worlds ) is that decoherence is the mechanism that forbids such simultaneous perception.

* In quantum mechanics, the many-worlds interpretation suggests that every seemingly random quantum event with a non-zero probability actually occurs in all possible ways in different " worlds ", so that history is constantly branching into different alternatives.

However, there is currently no argument from physics that there would be one brane for each physically possible version of history as in the many-worlds interpretation, nor is there any argument that time travel would take one to a different brane.

Lynch said " Everett firmly believed that his many-worlds theory guaranteed him immortality: His consciousness, he argued, is bound at each branching to follow whatever path does not lead to death ", Tegmark explains, however, that life and death situations don't normally hinge upon a sequence of binary quantum events like those in the thought experiment.

However, if the many-worlds interpretation is true, a superposition of the live experimenter necessarily exists, regardless of how many iterations or how improbable the outcome.

Decades later John Bell proved Bell's theorem ( see p. 14 in Bell ), in which he showed that, if they are to agree with the empirical predictions of quantum mechanics, all such " hidden-variable " completions of quantum mechanics must either be nonlocal ( as the Bohm interpretation is ) or give up the assumption that experiments produce unique results ( see counterfactual definiteness and many-worlds interpretation ).

Everett's many-worlds interpretation is an attempt to demonstrate that the wavefunction alone is sufficient to account for all our observations.

A universe in which changes are possible may be indistinguishable from the fully deterministic many-worlds interpretation of quantum mechanics in which there are multiple " growing block universes.

Confusion of causality and determinism is particularly acute in quantum mechanics, this theory being acausal in the sense that it is unable in many cases to identify the causes of actually observed effects or to predict the effects of identical causes, but arguably deterministic in some interpretations ( e. g. if the wave function is presumed not to actually collapse as in the many-worlds interpretation, or if its collapse is due to hidden variables, or simply redefining determinism as meaning that probabilities rather than specific effects are determined ).

Because the differences between the different interpretations are mostly philosophical ones ( except for the Bohm and many-worlds interpretations ), physicists usually employ language in which the important statements are neutral with regard to all of the interpretations.

More recently he has also argued TIQM to be consistent with the Afshar experiment, while claiming that the Copenhagen interpretation and the many-worlds interpretation are not.

However, according to Everett and DeWitt the many-worlds interpretation can be derived from the formalism alone, in which case no extra interpretational layer is required.

Although invoking the many-worlds interpretation of quantum mechanics, whereby events from his own timeline may differ from our own, Titor also expressed assurance that the differences were minimal.

Because Titor claimed the many-worlds interpretation of quantum physics was correct, effectively meaning that his travel was from a parallel universe and that things could occur differently than he had predicted, the details he presented were unfalsifiable.

Modern day physics-oriented philosophers have sometimes tried to answer the question of free will using the many-worlds interpretation, according to which every time there is quantum indeterminacy each possibility occurs and new universes branch off.

However the story is more closely related to the many-worlds interpretation of quantum mechanics where all possible outcomes of an event occur, each in its own parallel universe.