Accounting for time dilation in timelines


I have a story which has one character experience time dilation while she is traveling at 99% the speed of light. A year for her is ~22 years for the rest of the universe. I have characters and events that I want to keep track of both within and out of the time dilation. Does anyone have any advice for dealing with this?


As far as I know, you can’t use multiple different timelines in one Aeon Timeline project.
I would create two Aeon Timeline projects in this case, one for the local date/time onboard the spacecraft, and one for the local date/time e.g. on Earth.
Then I would create some events in both timelines, which mark events in the other reference system, for visual synchronization. This could be departures and arrivals, for instance.
A little cumbersome maybe, but I think it would work.

I would assume that during the travel, most of the incidents in the two temporal frames of reference take place independently of each other; that is, outside the perceptual possibilities in the other frame of reference.
Actually quite interesting: Would a person switch back and forth between the two time lines, i.e. disappear from one and appear in the other? However, there are phases in which both timelines run synchronously, e.g. during the spacecraft’s stay on Earth.

I cannot swear that this actually corresponds to the “real” relativistic effects; there would be some literary freedom anyway.

By the way, I ask myself whether there can be a reference time for the rest of the universe at all, if the universe itself is continuously expanding …

That makes sense. I will try two timelines. Thank you.

The character in question is not always on the ship and does have impact on the planetary(?) timeline. I think I will just document the events in the correct project.

I suppose the the entry in and out of the accelerated timeline would be just about instantaneous. Hmm.

One of my worries was about the character’s age being accurate. I’m thinking I will have to manually adjust. In fact, I did think about just having the time in the ship have an accurate duration and work around it that way. So the year long voyage has a timeline duration of ~22 years. It would look like she is far older, but I can keep track of that manually.

I am already taking some literary license as I have not tried to calculate what the dilation is when speeding up and slowing down. It would be a pain for me to figure out and, honestly, I’m not sure the average reader would think about it.

I guess it would be more accurate to say the time around a particular planet.

Thank you again for responding. I have some ideas now as to how to proceed.

That’s not really a problem, just keep in mind that the “accelerated timeline” remains nearly synchronous with the planetary reference timeline for a long time after departure, assuming the spacecraft doesn’t abruptly change speed.
Significant deviations occur only when the travel speed comes close to the speed of light.
From my studies, I still have this formula; if you want to get an idea, you could enter it into a spreadsheet and get the changed time duration for different velocities, or for different distances from the home planet. Also, remember that the spacecraft does not stop abruptly at the end of the trip; halfway through, it would have to start decelerating.


However, this would not be “hard science fiction” yet, because you probably disregard all other relativistic effects (also the mass and the geometry of the space would change).

That’s actually the most appealing aspect of it. Your protagonist has after her journey a “calendar” age corresponding to the time of the home planet, and a biological age corresponding to the course of the journey. Provided that the relativistic effects mentioned above do not influence the biological condition of her body unfavorably, she is biologically younger after her return than her age-mates left behind. Therefore, I would not change anything about her age as shown on the planetary timeline.

I’m sure you’ve already considered all of this, I’m just restating the expectations of the average science fiction reader. :nerd_face:

Good luck!


By the way, this reminds me of a classic science fiction story by the Strugatzki brothers:
Family and friends of a daring astronaut crew meet at the spaceport for the expedition’s farewell. After the departure, everyone is very sad because they think they have seen their loved ones for the last time. While they are still trying to console each other, the spaceship lands again and the loved ones disembark as old men.
“It’s really just the other way around than we had assumed.”

True, but if I recall my college physics correctly, “decelerating” is really acceleration, which is equivalent to gravity per relativity theory; which means time slows for the character who is “decelerating” relative to the observers not “decelerating.” It’s been a long time since I used to calculate these things, but it’s fun to unexpectedly bump into this kind of thing in this forum!

I was trying to think how I would try to do this. Assuming the main character is the one traveling and whose time is passing slowly compared to the other characters, I think I would place the events of the other characters along a non-dilating timeline – in the context of Aeon Timeline, they would be on whatever “normal” date/time calendar I have for them. Then I would calculate (or guestimate, more likely) how old my MC would be at each event where my MC interacts with my other non-time-dilating characters. Since I’m a nerd, I’d probably waste way too much time with formulas and Excel to do this. :0

Yeah it’s been awhile since college physics. :slight_smile: I figured the decelerating would reduce the dilation. I had read about accelerating/decelerating had to be ‘slowly’ so that our puny human bodies didn’t get crushed. Depending on how long that process took… I can’t remember the reference, but could it be months(?), that could change the over all 1 year == 22 years translation. I guess if we assume the beginning and the ending of the trip had the same acceleration/deceleration, it probably washes out in the math.

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Yup! This is what I am trying to avoid. Right now my math is on a scratch pad based on a cool link that calculates the dilation effect and events. My issue is I have four story arcs that takes place that are overlapping timelines and the dork in me wants the timing to work between all of the lines.

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Huh, I will have to see if I can find that one. :slight_smile:

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That is a good point. I was keeping track of her biological age so she could look appropriate for her age.

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Any chance you could share that “cool link”? I need to waste some time checking it out!

Time Dilation Calculator :slight_smile:

How cool! It’s way more fun than writing! :0