I've recently come back to a story I had started some time ago and have started to develop quite a few questions about how we view time. This is likely to be the first in a small series.

The world

Our fictional creation contains humans in large numbers, but no other beings or existences. Due to the extreme time span this is likely to encompass you can consider anything +-1000 years from current humans.

Within this world also exists our special use case who just so happen to be our main cast. Let's call them Group B

Group B

Members of group B by definition live their first life as completely normal humans. They are raised in line with the beliefs and people of the time. There is absolutely no design or belief that they are any different. And, indeed, from a physical perspective they are no different.

Upon dying, from natural causes or otherwise, members of Group B wake up on the prime plane. At this point in time they are now fully awakened and functionally immortal.

Immortality Rules

  1. They cannot die from old age and do not age.
  2. They cannot die of starvation in any form, and only consume food as a consequence of enjoyment.
  3. They do not die when any subsequent life is ended
  4. They can die from having their real body killed.

Now, members of Group B can and do often (It's pretty much their purpose) create for themselves new lives on other planes. They have the ability to fabricate an existence and begin life in that existence, returning only when the pseudo life has ended. They maintain any memories from this life, including memories they created for time before they assumed the life.

The Problem

With all of the details out of the way, I find myself beginning to question a few of the constraints. With things as they are, it is completely within the range of expectations that members of Group B may go between dozens and hundreds of years between seeing each other. What I am left with now is a bit of a conundrum.

How long would a newly minted human have to live before hundreds of years seems like hardly any time at all, if it can even happen?

Note: As a baseline, I am looking for being able to remember or continue a conversation that happened ~200 years prior from their frame of reference. Never is a perfectly acceptable answer. Going into this question I realized the possibility that humanity is just not capable of keeping memories alive for that long.

  • $\begingroup$ Maybe I'm being a little picky, but if there are "no other beings or existences," then wouldn't there be no food for humans to eat? Or planets? Or stars? $\endgroup$
    – Frostfyre
    Commented Feb 28, 2017 at 13:07

3 Answers 3


Years fly by now as they never did when I was young. I am starting to speak as my father spoke of a decade as a short-term horizon. I observe this pattern in other older adults I meet. It appears to me that planning seems to occur in chuncks about the size of half your current lifespan UNTIL the point where you no longer expect to outlive your current years. So a human at 40 can reasonably think about what his/her life will be like at 60, and it doesn't seem an implausible age to be... and that seems to continue extending until the person hits the line where they don't expect to live that long, for whatever health reasons. A person at 90 would consider life at 135 (90+45) if and only if he/she expected to live to 135. So I think your immortals might do the same after they become confident in their immortality.


I think the answer really depends on your characters, instead of humanity as a whole. Though there may be an upper limit to it, I expect it quite hard to really know.
One of the members of Group B may just not have the capacity to recall everything. Every time he pops back to the prime planet and runs in to someone it may be a case of reminding him what they were talking about before.

This answer came about from reading one of the other ones

But can you really remember anything other than a vague notion of what you did? I know I can't.

I can remember details of events from ten years ago, not everything, but significant stuff is still there, dates, times, events. Some are vague, some are strong and detailed.
Recently I bumped in to a friend who I hadn't seen for 5 years and picked up a conversation we were having the last time we met. I hadn't thought about it since then, but it was tucked away and only needed that meeting to trigger it.


Never as human minds have a limited memory capacity.

Going into this question I realized the possibility that humanity is just not capable of keeping memories alive for that long.

Humans could theoretically maintain memories indefinitely. That's not the problem.

The issue is that the brain simply does not preserve memories at all. Not for long atleast. It constantly strips them away of detail, helping the individual declutter useless information. Eventually all "unused" memories fade away completely.

How long this takes depends entirely on the significance of the memory: You'll immedietely forget an insignificant thought. You'll never forget how to speak (unless you stop speaking).

Consider it this way:

Can you remember what you ate 2 months ago? How about literally anything you did 10 years ago? I know that second one sounds silly and you might be thinking "of course I can"!

But can you really remember anything other than a vague notion of what you did? I know I can't.

This is just a way to demonstrate how very limited our recollections are.

At this point it becomes hard to provide any concrete answers. We do not know how fast memories deteriorate. It depends on the memory itself and on the person's faculties. However I think it is safe to say even the most tenacious of memories would be forgotten within a few centuries.

So good news is your immortals will never become really cynical and bored like you see in movies and tv shows. Well... Not unless they just have bad attitudes.


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