Parallel universes
Branching timelines offer a way to avoid contradictions: altering the past would create or achieve another history, without erasing the one that gave rise to the traveler.
Three different concepts
“Parallel universes” can refer to the many-world interpretation of quantum mechanics, to disconnected cosmological regions, or to branching histories created to model time travel. They are not interchangeable ideas and none are confirmed as a means of transportation.
The way out of the paradox
If the traveler arrives at a different branch, he can prevent an event without eliminating the starting point from which he came. The grandfather paradox disappears because cause and effect belong to different stories. The price is to introduce a physical rule that connects branches, something that the standard quantum interpretation does not provide as a technology.
Many worlds does not mean portals
Everett's interpretation describes a universal wave function and decoherence. The branches stop interfering in a practical way; it offers no known mechanism for choosing another branch, sending matter to it, and returning.
Time curve models
Some quantum proposals represent interactions with acausal regions through multiple states. They are mathematical laboratories for studying information and computation, not demonstrations of visitable universes.
Consistency or branching
The Novikov conjecture preserves a single self-consistent history. Multiple stories allow for incompatible results by separating them. Science fiction usually mixes both models and generates contradictory narrative rules; Distinguishing them improves any analysis.
Reference
THE NEXT JOURNEY BEGINS WITH A QUESTION
You cannot return to the past. But you can change how you inhabit time.
Go beyond equations and explore what time reveals about your identity, your freedom and the responsibility of every choice. Five lessons connecting philosophy, consciousness, paradoxes and ethics.
Online course in Spanish and English · External access at TimeTravelers.cc