For a project I'm working on, a pair of "immortal" characters end up crossing from their dimension (a fantasy world) into what could be described as the "real" world, and I'm considering aging them back a bit when it happens. (Think "The Devil is a Part Timer" for that.) This would be because the 2 dimensions' timelines are moving at different speeds, instead of them being completely parallel. For example, Point A could be where they converge and are close enough to parallel that a portal could be opened and characters could cross over, while Point B could be 5 years later in one dimension and 50 years later in the other.

The characters are half vampire, so they'd age extremely slowly after reaching maturity, but they can still die under the right circumstances. For the story, I want to have them revert back to just before reaching maturity as humans when they cross into the other dimension. I'm trying to decide what would happen if they brought a human back with them into the fantasy dimension. I could explain some bits and pieces with the fact that there's no magic in the "real" world, but I feel like it would need something a bit extra to it.

Would the human age forward? Would they stay the same? Would they become a demi-god of some sort because 5 years for them is 50 years in the new dimension they're in?

Edit: looks like a lot of confusion is as to why their ages would be rolled back and I'm gonna chalk that up to them having magic in their blood or something and the other dimension they're entering having no magic, therefore their magic would've been removed upon entering the portal. The age change wouldn't be severe, it would probably be 5 year difference in appearance, or Something like that.Fantasy vs. reality timeline graph


closed as unclear what you're asking by StephenG, Separatrix, L.Dutch, Rekesoft, Renan May 3 '18 at 12:12

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    $\begingroup$ I don't get how this is a question. In 5 years, the protagonist would either age 5 years or because insert fantasy element he wouldn't. How fast time passes elsewhere is kind of irrelevant, isn't it? You have not given any reason why the human would age at a different speed in another dimension $\endgroup$ – Raditz_35 May 3 '18 at 9:12
  • $\begingroup$ I edited your edit as it might effect people's willingness to reopen or answer. Feel free to rollback if you wish (click on the "last edited" by my name, and then view the edit#3 and click the rollback option on the edit bar). WB is still good to get opinions. They catch those logical nightmares which could become plotholes faster than anyone :) hope you stick around and ask more questions. $\endgroup$ – EveryBitHelps May 5 '18 at 14:40

If you want the characters to age or de-age, then it is purely fantasy under most circumstances.

People age based on the time that they have experienced. If I have been raised in universe A where time travels (for me) normally, and then I visit universe B where time travels 50 times faster, nothing should happen to me upon my entrance to B (assuming that I survive - I expect the time difference might cause problems with the gateway, but that can be handwaved away in a fantasy). Then I spend one year in universe B (at my subjective time) and then go back to A.

Now it is 50 years later in A, but I am only one year older. And this was gained through the normal one-second-per-second aging rules.

For the story, I want to have them revert back to just before reaching maturity as humans when they cross into the other dimension.

This is even worse. You are having character go back in age. The only way this makes even a little sense to me is if they truly go back to that age. This means that they have no memories of anything beyond their younger days and don't realize anything has happened because for them it hasn't.

In other words, why should their bodies be extremely selectively changed merely because they've go to a universe with a different rate of time?


from the description time in the two dimensions is passing at different rates. Time is passing ten times in one dimension compared to the other. However, this should have not effect whatsoever on their ages or rates of ageing when they pass from one dimension to another.

However, it will have an influence on how much is spent on one dimension to compared to the other. if character A spends one day in the slower dimension she will find ten days have gone in the faster dimension on her return there. Conversely, someone spending a day in the faster dimension will find only 2.4 hours have passed in the slow dimension.

The characters will effectively age at different rates compared to how much time has been spent in the alternative dimension. Ten years in the fast dimension will be only one year in the slow, so a character who has spent that ten years in the fast lane will seem to have aged ten years in one year for people in the slow dimension.

It seems as if you have assumed that a person in one timeline will be aged as they pass from one dimension to another to somehow compensate the time differences between the timelines. There is a no scientific or logical basis for this happening. The way it could happen is if there is a magical property that operates, independently of the actual passage of time, but causes the characters' ages to be 'adjusted' to the time in the dimension they travelled to.

For example, if a character has lived twenty years after the two timelines have diverged at Point A, in the faster dimension and then travels to the slow one. In the slow dimension only two years will have passed. if the magic age adjusting power operates that character will revert in age to eighteen years younger. So they will now be at the age they would have been had they lived in the slow dimension for the equivalent period of time they had spent in the fast dimension. Twenty years in the fast dimension equals two years in the slow dimension.

Also, if the character spends another year in the slow dimension when they return to the fast timeline they will revert to their old age plus additional ten years. One year in slow being the equivalent of ten years in the fast dimension.

But, remember this age adjusting only works by magic.


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