The universe might be splitting every time you make a measurement
In short: In the quantum world, objects exist in multiple states at once. For decades, scientists debated whether these possibilities vanish the moment we look at them, or if every single outcome actually happens in its own distinct reality. The Many Worlds interpretation suggests the latter.
The Many Worlds interpretation (MWI) was first proposed in 1957 by Hugh Everett. While it was initially dismissed as preposterous, it has gained mainstream traction as a viable way to understand quantum mechanics without the logical hurdles of its primary rival, the Copenhagen interpretation.
During the 1920s, Niels Bohr advocated for the Copenhagen interpretation, which posits that reality lacks objectivity prior to observation. In this view, a wave function—a set of probabilities governed by the Schrödinger equation—collapses into a single value the moment a measurement occurs. This creates a 'measurement problem' because it requires two different sets of rules: one for the quantum system before observation and another for the world after.
MWI removes this duality by proposing that there is only one set of rules: the Schrödinger equation applies to everything, including the observer. Instead of a wave function collapsing, the universe undergoes 'decoherence.' When a measuring device interacts with a quantum system, like an electron's spin, they become entangled. This causes the universe to branch. In one branch, the device measures 'spin up'; in another, it measures 'spin down.' Both outcomes exist simultaneously in different branches of the universe.
Decoherence can be defined as the process where information escapes into the surroundings. By engaging with nearby molecules or photons, an isolated quantum system undergoes decoherence as these particles establish its spatial characteristics. While MWI elegantly solves the measurement problem and allows quantum mechanics to be applied to the entire universe, it faces significant theoretical hurdles, such as explaining exactly how branching occurs, how energy is conserved across worlds, and why we only perceive a single timeline.
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Sources
- Summary by Intellect · source: MWI: Many Worlds interpretation of quantum mechanics explained | featuring Sean Carroll
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