The many-worlds interpretation begins with a refusal to add a special rule for measurement. That is its appeal, and also the source of its strangeness.
In ordinary quantum mechanics, an electron, atom or photon can be described by a wavefunction that contains several possible outcomes at once. When a measurement is made, we see one result. The textbook language says the wavefunction has collapsed. Many-worlds asks a sharper question: what if collapse is not a physical event at all?
On that view, the wavefunction never stops evolving as a wave. Every outcome allowed by the quantum state continues, but the observer becomes correlated with only one outcome in one branch. The wave has not vanished. We have become part of it.
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