The "Predestined Timeline" Sci-fi Trope, Explained

gamerant.com:

Time travel is a tricky business that can turn reality on its head or leave all life on Earth in a new worst-case scenario. However, a lot of sci-fi stories take place in a world where it doesn't matter what anyone does at any time. In these predestined timelines, the ending is already decided.

The multiverse concept has taken off in the past few years. Between Marvel's ongoing antics across multiple universes and indie takes on the concept, the idea of multiple converging timelines has become very popular. The idea of a single timeline with hard rules is not as common, but much more simple.

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A predestined universe is one in which all events are set in stone and the path will always reach the same end. The grand prophecy has already written out every event that will occur, and nothing anyone does can stop it. The heroes might travel back in time to solve whatever apocalypse they're up against, only to discover that the end will come regardless of the changes made. Sometimes the heroes can change everything except for the one thing they went back in time to fix. This is, in many ways, a horrific concept that erases the idea of free will. Even when mankind can change anything and everything without the linear flow of time as a barrier, their choices still don't matter. This is typically cynical, but sometimes the predestined timeline sees happy days ahead. In these cases, all hope is lost for a while, but things will come around eventually.

In the days long before sci-fi, this idea was explored through prophecy. Ancient myth seemed to have a tablet or scroll that could accurately predict the beginning, middle, and end of every known series of events. These prophecies almost