grandfather paradox

American  

[grand-fah-ther par-uh-doks, gran-] / ˈgrændˌfɑ ðər ˌpær ə dɒks, ˈgræn- /

noun

1. (in science fiction) a paradox created by time travel in which a person travels back in time and changes something in their own past or the past of their own timeline, after which the resulting timeline is altered such that the future point from which the time travel began does not exist or is unrecognizable.

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Etymology

Origin of grandfather paradox

First recorded in 1970–75

Example Sentences

This is how the grandfather paradox was first explained to me: Imagine a boy whose grandfather invented a time machine.

From Los Angeles Times • Mar. 14, 2025

Discussion of the butterfly effect, the grandfather paradox, or big balls of wibbly wobbly, timey wimey stuff are scarce.

From Salon • Jul. 25, 2023

Add a few flying saucer chases, cook up a quickie solution to the grandfather paradox and this movie might have fallen at the intersection of “E.T.” and “Back to the Future.”

From New York Times • Mar. 10, 2022

Those pesky killer automatons, always time-traveling to grandfather paradox the savior of we flesh-and-blood organisms out of existence.

From The Guardian • Jan. 6, 2020

The theory neatly solves the grandfather paradox by positing separate universes in which each possible outcome exists, thereby avoiding a paradox.

From "The Sun Is Also a Star" by Nicola Yoon