User:ScienceNerd99

If building a functional time machine were possible, you could not change the past with it. According to Xander Eades's time travel hypothesis, one could theoretically go back and change an event only to return to the present to realize it didn't work. This is because going back to change or prevent something means the 'present you' never would have thought to go back and change or prevent it and it still would have happened. An example of this would be going back to kill Adolf Hitler. If you built a time machine (currently fiction and not possible according to physics) and used it to go back to 1939 and assassinate Hitler, the '2023+ you' never would have known about Hitler and you could not have had the idea to assassinate him in the first place meaning he was never killed by you. can't be done because you changed it which means it never happened and if it never happened you never went back to change it. The efforts cancel each other out.

This is similar to the "Grandfather Paradox"

"What's done is done and cannot be undone without also undoing your efforts to undo it, meaning it was never undone and still happened. You can't have thought to undo something that was never done" - Xander Eades