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Many-worlds interpretation
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<p>The many-worlds interpretation (MWI) is an <a href="/facts/Interpretation_of_quantum_mechanics/WEjlzVPl">interpretation of quantum mechanics</a> that asserts that the <a href="/facts/Universal_wavefunction/B4xMgxdn">universal wavefunction</a> is <a href="/facts/Philosophical_realism/cPo2pK16">objectively real</a>, and that there is no <a href="/facts/Wave_function_collapse/f7KvbBHK">wave function collapse</a>. This implies that all <a href="/facts/Possible_world/6jr7P8jV">possible</a> outcomes of quantum measurements are physically realized in different "worlds". The evolution of reality as a whole in MWI is rigidly <a href="/facts/Determinism/NhvNlAbe">deterministic</a>: 9 and <a href="/facts/Principle_of_locality/umaVy92L">local</a>. Many-worlds is also called the relative state formulation or the Everett interpretation, after physicist <a href="/facts/Hugh_Everett_III/yQl5Wgnj">Hugh Everett</a>, who first proposed it in 1957. <a href="/facts/Bryce_DeWitt/5qYYeaox">Bryce DeWitt</a> popularized the formulation and named it <i>many-worlds</i> in the 1970s. </p><p>In modern versions of many-worlds, the subjective appearance of wave function collapse is explained by the mechanism of <a href="/facts/Quantum_decoherence/mngM3rxy">quantum decoherence</a>. Decoherence approaches to interpreting quantum theory have been widely explored and developed since the 1970s. MWI is considered a mainstream <a href="/facts/Interpretation_of_quantum_mechanics/WEjlzVPl">interpretation of quantum mechanics</a>, along with the other decoherence interpretations, the <a href="/facts/Copenhagen_interpretation/DvMFrYJa">Copenhagen interpretation</a>, and <a href="/facts/Hidden_variable_theories/02QP5Dxp">hidden variable theories</a> such as <a href="/facts/De_Broglie%E2%80%93Bohm_theory/NysDBVeq">Bohmian mechanics</a>. </p><p>The many-worlds interpretation implies that there are many parallel, non-interacting worlds. It is one of a number of <a href="/facts/Multiverse/GUCDxvPg">multiverse</a> hypotheses in <a href="/facts/Physics/a7aH2y08">physics</a> and <a href="/facts/Philosophy/zAH5PVD6">philosophy</a>. MWI views time as a many-branched tree, wherein every possible quantum outcome is realized. This is intended to resolve the <a href="/facts/Measurement_problem/6Ux183hb">measurement problem</a> and thus some <a href="/facts/Quantum_paradox/8yIzpP7c">paradoxes</a> of <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum theory</a>, such as <a href="/facts/Wigner%27s_friend/sX26zMRo">Wigner's friend</a>,: 4–6 the <a href="/facts/EPR_paradox/rulT1oGp">EPR paradox</a>: 462 : 118 and <a href="/facts/Schr%C3%B6dinger%27s_cat/UpNp6vVu">Schrödinger's cat</a>, since every possible outcome of a quantum event exists in its own world. </p>