You've been tricked! Due to [backstory] and [events related] you have found yourself immortal, with total control over the natural world around you (think Earth bending and stuff) and it's not all it's cracked up to be. You rocked around the world for a few hundred years performing miracles and being awesome until you realised that everyone you knew has grown old and died. People think you're a legend, like Bigfoot or Shania Twain, and you give up the spotlight and try to find some peace. But you're immortal too...

Cut to 43,000 years later and the world is unrecognisable, but you're still there. Looking... stretched but still youthful.

How much could you possibly remember about your past? How little would you care about current events knowing that you'd still be there no matter how it turned out? How can I motivate this character to help the hero?

Assume that anything goes, but no modern technology (I know 43,000 years and still stuck with High-Fantasy technology, get your act together imaginary world.)

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    $\begingroup$ Unfortunatly, this question is too broad. The real answer as to whether an immortal person could remember everything is completely and utterly tied to the metaphysical/magical process that causes the immortality. I have seen everything from a bored 43k year old who has seen it all to immortals that choose to forget their immortal past so they can live multiple short "mortal" lives. $\endgroup$ – Cort Ammon May 28 '15 at 4:10
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    $\begingroup$ Does his brain deteriorate like aging normal humans? $\endgroup$ – Jimmy360 May 28 '15 at 4:10
  • $\begingroup$ @Jimmy360 Let's assume that it doesn't deteriorate, but that it's not magically powerful like his body. (He can create fire, but not read minds, etc.) $\endgroup$ – Wompguinea May 28 '15 at 4:11
  • $\begingroup$ The movie "The man from Earth" touches on this. $\endgroup$ – MichaelHouse May 28 '15 at 6:18
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    $\begingroup$ unlike rain man our memory not only fade with time they can be "photoshop" as new connections form with new experiences, Toph will be very jealous of your sight and your scratch resistant! $\endgroup$ – user6760 May 28 '15 at 8:23

You could of course remember everything, but what would be the point?

Everyone I know has some sort of selective memory. If you are living in the here and now only a small percentage would be actively present: The really useful long-term stuff (probably very little) and all that was put recently on top, just like any other person.

For motivation to help the hero, anything would serve; amusement to battle boredom, a chance conversation late at night, a link to the past. How they would meet at all is a bigger problem, likely our immortal is an oddball withdrawn from society.


An immortal man could not remember everything even if he doesn't forget things. This is because the human brain contains about 1 billion neurons. Each neuron makes about 1000 connections with other neurons, leading to about 1 trillion connections. If each neuron could store a whole memory (which is VERY generous), one could only have 1 trillion memories. However, the brain is very efficient. The neurons help each other, making the final capacity for human memory about 2.5 petabytes. That's a LOT. If you are on your computer, there is a good chance you have a 500 gigabyte hard drive. To add this up to the human memory maximum we would need 5000 FULL computers. One would not exceed this in a lifetime, but given infinite time and ignoring forgetting things, one can reach a maximum.

  • $\begingroup$ $ 500 GB = 5 \times 10^{11} bytes $, $ 2.5 PB = 2.5 \times 10^{15} bytes $, meaning you need 5000 hard drives. $\endgroup$ – Jim2B May 28 '15 at 4:58
  • $\begingroup$ @Jim2B Opps, that was a mistype. Thanks. $\endgroup$ – Jimmy360 May 28 '15 at 5:08
  • $\begingroup$ Do you have a reliable source to the brains storage capacity ? $\endgroup$ – Magic-Mouse May 28 '15 at 7:58
  • $\begingroup$ @Magic-Mouse Scientific American $\endgroup$ – Jimmy360 May 28 '15 at 16:15

When you grow older you realize that the days and weeks and even years are getting shorter - well it is not really but your brain records exceptions, when you go to work every day you are doing the same stuff, you are getting in to routines and the brain does not save that information. Thus making the days, months and years seems shorter.

A man living 43 000 years would experience the same effect. He would remember the first space flight, the first Holographic TV the first organic computer, the first cyborg so on and so forth but not every single day since the brain is working in that fashion.

Conclusion: No the brain will not remember everything unless you suffer from Hyperthymesia, because of the way the brain is constructed.


No, he could not remember everything, unless the magic involved lets him.

The human memory is not a very reliable thing. Our memories get re-invented over and over again.

You may want to have a look at whitness reports from a crime scene. While some of them are simply fakes, a lot of whitnesses will be very sure about what they saw, and still their reports will often directly contradict each other.

Or, think about a family get-together. Telling stories from the past: how often have you encountered a situation where someone said: "no, that's not how it happened. it was like this". Or "no, that was not uncle Willy, it was grandpa John who did that, and the situation was that".

Human memory does not nearly work like a hard-drive or a picture taken with a camera. It gets re-written all the time.

So: No, he would forget things, mix up things, sometimes more or less deliberately "fine-tuning" his own memories.

Yet: for anywone talking to him, his memories would still be so broad as to create the impression that he would in fact remember everything.

And for why he should help your hero: For one of two reasons: Either he thinks your hero deserves help because he wants to support the heroe's cause, or he simply likes him.


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