How does the many-worlds interpretation account for every possible outcome of a quantum measurement?

The many-worlds interpretation, proposed by Hugh Everett III, accounts for every possible outcome of a quantum measurement by suggesting that the universe branches into a series of noninteracting, parallel realities.1

In standard quantum mechanics, a system exists in a superposition of states before measurement, and the act of measurement is often described as an unpredictable, discontinuous "collapse" of the wave function into a single outcome. The many-worlds interpretation rejects the idea of this collapse. Instead, it posits that when a measurement occurs, the measuring apparatus—and any observers involved—interact with the quantum system to "enlarge" the superposition.12

Consequently, the measurement does not force a single result; rather, the superposition extends to include macroscopic states where each possible experimental outcome occurs. Every potential result of a quantum measurement is realized, but each takes place in a different, separate universe. Because these universes are mathematically unified but decohered, they remain essentially impossible to interact with, effectively branching the history of the world into multiple, equally real paths.21