Have you ever thought about traveling back in time?

Well, you are not the only one. The first thing that comes to mind when the topic of traveling back in time is discussed is the time traveling paradoxes that come with the package.

The main paradox is the "Grandfather Paradox" in which a traveler goes back in time and kills his grandfather, not sure why anyone would want to do that, but let's assume our traveler wants to do exactly that.

The obvious problem with this is, if you go back in time and kill your grandfather before one of your parents is conceived you will never be born so you could not go back in time to kill your grandfather... BAM! Paradox!

The grandfather paradox was described as early as 1931, and even then it was described as "the age-old argument of preventing your birth by killing your grandparents". Early science fiction stories dealing with the paradox are the short story Ancestral Voices by Nathaniel Schachner, published in 1933, and the 1943 book by René Barjavel Future Times Three.
Nathaniel Schachner

Now the main accepted theory is that traveling back in time is impossible, but if you manage to do it anyway, then here are a two theories that prevent you from actualy causing a paradox.

The Novikov self-consistency principle expresses one view on how backward time travel would be possible without the generation of paradoxes. According to this hypothesis, physics in or near closed timelike curves (time machines) can only be consistent with the universal laws of physics, and thus only self-consistent events can occur. Anything a time traveler does in the past must have been part of history all along, and the time traveler can never do anything to prevent the trip back in time from happening since this would represent an inconsistency.

This means anything you do to change the past will fail. Try to shoot your grandfather and your gun will not work. Try to stab him the blade will brake. Throw him off a building and a pillow delivery truck will come by at just the right moment to soften his landing.

The parallel universe approach. When the time traveler kills their grandfather, they are actually killing a parallel universe version of their grandfather, and the time traveler's original universe is unaltered; it's been argued that since the traveler arrives in a different universe's history and not their own history, this is not "genuine" time travel.

Thanks for making it this far!

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Also check out the youtube video where the graphics were taken from: