I'm writing a science fiction story about a man who has to rebuild civilization from the ground up after all intelligent life in the galaxy is destroyed. (Using gene samples, seed banks, etc.). But I need to guarantee he's the only person left.

I can imagine any number of reasons an entire galaxy might be wiped of intelligent life, such as those in @AlexP's excellent comment below. But I'm struggling with explaining how just a single person survived.

Was he simply not there when "it" happened? If so, why wasn't anyone else wherever he was? Or maybe he was in some protective chamber. But why couldn't anyone else survive in a similar chamber? Is it just a man's consciousness in an immortal robot body? Then why aren't there other androids?

The more credibly an answer explains why just one person is left behind, the better.


closed as too broad by rek, vodolaz095, user6415, user535733, Shadowzee Oct 14 at 22:15

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ This is the broadest on-topic question that I've ever seen, it could also rate as opinion based - as you've currently not given us any way to decide what might be a "best" answer. Please edit to narrow it down considerably. Voting to put on hold as POB (primarily opinion based) to prevent unhelpful answers. $\endgroup$ – We are Monica. Oct 13 at 17:01
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    $\begingroup$ @AlexP - please expand the false vacuum collapse into an answer. I want to read more about that and Wikipedia was unrewarding. Quick, before there are too many closers! $\endgroup$ – Willk Oct 13 at 17:45
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    $\begingroup$ I stand defeated by the greater creativity of my peers. You are both right. This is opinion-based. ...and I need to go eat some fish to get my mental gears back up to full speed. $\endgroup$ – Henry Taylor Oct 13 at 17:47
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    $\begingroup$ @Willk: There's not much to write. In quantum mechanics, the vacuum has a certain energy level. It may (or, hopefully, it may not) be the case that in our part of the universe the vacuum is at a metastable energy level higher than the lowest possible level, and thus we live in a "false" vacuum. Should some random fluctuation disturb this metastable state, the false vacuum will collapse to the lower energy level, in the process destroying every single atom, electron, proton and neutron. The total destruction would propagate at the speed of light, so that we would not even see it coming. $\endgroup$ – AlexP Oct 13 at 17:56
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    $\begingroup$ He is inside one of Larry Niven's stasis fields. ("Known Space" universe.) Niven actually does something like this, but his lone survivor is not human, but a member of the Slaver species, who was in a stasis field when all other intelligent life in the galaxy was wiped out, 1.5 billion years ago. " World of Ptavvs" $\endgroup$ – jamesqf Oct 14 at 3:56

His ship made a close-approach orbit of a supermassive black hole, "frozen" in time dilation while the rest of the galaxy lived its life out.

Something similar to this happened in Larry Niven's novel, A World Out of Time. In it, the main character deliberately flies his ship close to a supermassive black hole in order to "escape", into the future, from a present that had no value for him. Something like 150 years pass from his perspective, while over 3 million years have elapsed for the rest of the galaxy.

Perhaps something like this happens, accidentally, to your single survivor. While this answer does not give you the explicit cause-of-death of your galactic civilization, what it does give you is reams of time in which galactic civilization can grow, flourish, decay, and finally die, all in a way that leaves your survivor untouched and emerging unscathed - even, if you like, in the prime of his life.

Why does the black hole need to be supermassive?

  • Small black holes are perilous to approach for many reasons, but chief among them are the violent tides caused by the sharp gradient in its gravitational field's strength. Bigger black holes, while still perilous to approach, have much softer tides; less likely to tear an orbiting ship apart.
  • The bigger the black hole, the stronger the time-dilation one can achieve while staying far away enough that the aforementioned tides won't tear your ship apart.

So perhaps, like with Larry Niven's "chrononaut", the giant black hole hypothesized to be at the center of the galaxy would be your best bet.


He cannot die. He is the Wandering Jew.

Wandering Jew



The Wandering Jew is a mythical immortal man whose legend began to spread in Europe in the 13th century.1 The original legend concerns a Jew who taunted Jesus on the way to the Crucifixion and was then cursed to walk the earth until the Second Coming.

Your character is immortal for reasons not immediately relevant to your story, although the fact that he exists means that other aspects of the legend might or might not be true. Your character himself has had time to consider these things and will definitely have opinions on that front. Those sorts of interludes as well as snippets from his long personal past history will give the story a unique perspective and help leaven your tale of an empty post-Apocalyptic world.


There have been a few suggestions which were along the lines of "Space Hitler wanted to be alone in the galaxy and so killed everyone else". That's pretty obvious to me, so how about instead...

Your survivor was a soldier who was supposed to stop Space Hitler. They were just a moment too late.

Space Hitler (SH from here on) comes up with a genius plan to eradicate all life in the galaxy, for reasons that we may never comprehend. He engineers not one, but several deadly plagues for each of the inhabited worlds in our galaxy, and to ensure no survivors, the plagues are delivered from orbit by robots that will descend on the few survivors the plague cocktails leave behind.

Our survivor to be, let's call them Anne, is a part of the strike team that's sent to stop SH in his secret base, hidden inside of one of the moons of a gas giant. Her team is the best, led by amazing strategists, armed to the teeth, but SH expected this strike team so the moon base's defenses are just as devastating. Each line of defense claims 2-5 soldiers, but they manage to make progress.

There are multiple possible entry points to SH's control room, where he waits for all of his death machines to be in position to commence the galactic devastation he's spent years planning. It just so happens that Anne's air vent was the only entry point that turned out to be breachable. She lands on the floor just as SH presses his big red button, and shoots her laser blaster through his skull... But it's too late. The plagues have been deployed, and there's no going back now.

SH had planned to rebuild society as he wanted, so he already has a lot of equipment in his moon base for this, and plans of where to start. But first comes the waiting. With deadly plagues ravaging all inhabited worlds, the only solution is to quarantine them, waiting for the pathogens to die out by themselves.

Ten, twenty, fifty years pass. The once young and lively soldier Anne is now slow and wise. Over these decades, she's had time to investigate each planet's seed banks and genetic samples and now has a plan to rebuild the galaxy as they once were. The robots, once full of death and pain, now carry hope. The only hope for the future of the galaxy. Now, all Anne needs to do is to press that big red button...

  • $\begingroup$ Actually, your survivor is more likely to be Space Hitler. $\endgroup$ – Spencer Oct 14 at 23:48
  • $\begingroup$ @Spencer did you read the first line of my answer? $\endgroup$ – Whitehot Oct 15 at 6:07

The key here is not in understanding how a person can survive through an apocalypse, but in how exactly 1 person would survive an apocalypse at that scale.

In every war, plague, or natural disaster, there are almost always those lucky few who are left behind. When you increase the scale to that of a galaxy, even the most destructive natural disasters in the universe such a supernova would fail to come close to wiping out such life on that scale. A False Vacuum collapse or other infinite matter destroying event COULD kill everyone in a galaxy, but would not leave a galaxy left to re-seed; so, those don't really work. You need something deadly enough to kill everyone whether they be in their deep space station tucked away in a dense nebula outside of all sensor contact, or in underground bunkers 100s of feet underground or in colonies build at the floor of the ocean, but still leaving stuff to rebuild on.

This leads to the conclusion that this is not a natural disaster, this is an insidious and intentional extermination of life by something that can find people wherever they go without exception, and when it finds you, it will need an absolute 100% kill rate such that no act of luck or resistance could possibly, even maybe save your life. Even the slightest random chance of 1 person's survival at that scale means many people should survive given the same circumstances happening in more than 1 place. This significantly reduces the likelihood of many other answers such hiding in an event horizon, time-travel, leaving the galaxy, etc. because if the science is there for one person to do that, chances are many other people will do it too.

I'm not sure how many ways there are to kill everyone spread across such a large area, but I'm picturing a grey-goo or tyranid swarm type scenario, where the goo/swarm is capable of FTL travel, and sets up a continuous, uninterpreted surveillance grid of deep space recon stations that can simultaneously monitor every square inch of the galaxy for intelligent life.

This leads to the single inescapable conclusion that the survivor designed the extermination to kill everyone expect for himself. This is the only factor that would believably only happen to one person out all the quadrillions of people on all the millions of worlds you would expect to see in a galactic civilization. This also explains why he just so happens to have all the genes and seed banks he needs to repopulate the galaxy since this was part of his plan all along, and how he is able to simply get rid of whatever horrible killing mechanism that ended all life to prevent it from happening again once he tries starting to rebuild.


I'm writing a science fiction story about a man who has to rebuild civilization from the ground up after all intelligent life in the galaxy is destroyed. (Using gene samples, seed banks, etc.). But I need to guarantee he's the only person left.

(...) after all intelligent life in the galaxy is destroyed (...)

(...) life in the galaxy (...)

(...) in the galaxy (...)

Dude was out of the galaxy when whatever happened.

  • $\begingroup$ From the question: "Was he simply not there when "it" happened? If so, why wasn't anyone else wherever he was?" $\endgroup$ – Muuski Oct 14 at 20:12

It is obvious that an extreme situation would cause this. There are several possibilities in this situation.

  1. The person could have been warned, given outside information to prepare/be removed for the time then brought back.

  2. The person could be overly prepared (for an apocalypse or something) and it just turned out that their preparations helped them through this.

  3. A play off of the 'chosen one' trope and make them be ignored/impervious to what happened.

  4. A mistake? Maybe they were just forgotten or lived a hermit life and not widely known originally.

  5. Maybe they are the cause of the galaxy being wiped out. Maybe this person wanted to be alone and wiped out the galaxy.

Explanations/ ways of destruction and survival:

  1. Extraterrestrial attacks/ outside forces attacking. This could lead to a mass wipe-out, but if someone wanted a specific person to survive, these forced get them before the attack.

  2. A gamma-ray burst would destroy ozone. Yet, if a person was prepared, for instance, for air to become unbreathable, they could be prepared with life support systems and oxygen tanks, etc. Prepared for the worst and end up being the only ones.

  3. Stars burning up could easily kill quite a bit. But if someone was prepared for this or was a 'chosen one', they could probably survive this.

  4. Supernova events could be caused if a person had the power to do so. Maybe said person feels it is their duty to cleanse the unclean by fire or something.

  5. Aliens. Alien life trying to take over and just missing that one person nobody knew or documented. Someone could easily be looked over in a situation like that, especially if they lived somewhere or were just somewhere extreme at the time.


  • $\begingroup$ I don't know if this is what you are looking for. This question is based on a lot more fiction than science, so it is difficult finding links for information on this sort of subject. $\endgroup$ – A Writer Oct 14 at 16:13

Being the last person in the galaxy depends what you mean by person, but assuming extra-terrestrials would count as persons the easiest way to exclude them is to ensure that there are none. Although this view point is unpopular it is entirely possible that we are alone in the galaxy. All it would take would be for the chance of biogenesis happening to be very highly improbable. If sufficiently improbable then we are likely to be alone. The same is true if it is highly improbable enough for complex organisms or intelligence to develop.

No amount of arm waving can alter the fact that we do not know how likely these events are as we only have one example to go on and being alone in our galaxy is a real possibility. It’s not likely or unlikely it’s indeterminate as we simply do not know and have very little evidence to assign a probability.

So assuming that humans haven’t reached the stars and there are no extra-terrestrials the only persons alive live in the solar system. Now imagine a spacecraft is sent to explore the outer solar system. At this point something unexpected happens to the Sun, perhaps it turns into a nova or for whatever reason its energy output becomes a lot higher. The inner solar system is fried and only a few remain alive in submarines and such like.

The question then is who can survive longest? It is possible that the crew of the spacecraft in the outer system with provisions for many years will be the final survivors. They might be able to remain in the shadow of a planet or moon, but eventually they would die. And unless they all died at once or the last few died together someone would be the last person in the galaxy. If someone in a bunker on Earth could outlive them then the people in the bunker would provide the same situation leading to a single person being alive.


It is about leaving a legacy, rather than apocalipse.

Imagine if your species has reached a technological apex and knows it can reach a state of godhood by transcending this universe into whatever is beyond, but it requires all technology they have to come along to survive there, leaving a barren universe in their wake.

The species has some sentiment and wants the universe to continue, that their old "home" might be the home for future offspring that may follow them in their footsteps. So they choose one person to stay behind with, for them, archaic tehnologies that they dont bring with them. Why one person? Because it is cruel to leave any more people behind. As a last act as they leave and transcend they re-seed much of the universe with enough resources to rebuild a society.

  • $\begingroup$ Why not use robots to re-seed? They could be biodegradable so that they aren't left over after the job is done. $\endgroup$ – Muuski Oct 14 at 21:28
  • $\begingroup$ @Muuski because sometimes humans don't think of all options, like I did just now. Perhaps the technology required to support this is in a sort of niche that would take too long. Or perhaps this "human" is simply a biological computer so that the seeds can relate to it better. $\endgroup$ – Demigan Oct 14 at 21:37

Would it be cheating to say that the life is rare in the universe, and so our galaxy happens to contain only the Earth as a source of intelligent life?

In any case, one way to implement your aim would be to have some alien race from another galaxy come along, abduct this man, and spirit him away as a specimen before the big disaster occurs. Afterwards, he might be released for whatever reason. Perhaps the aliens deliberately wanted to keep alive a member of his species.


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