Could an advanced alien race prevent the death of the universe?

We all know that the universe is going to die one day: all the stars will die, all the black holes will evaporate and life will be gone. But hypothetically speaking, if a super advanced alien race (let's say a few billion years more advanced than us) wanted to prevent this from happening, and protect all life within the universe, would they be able to do it? Or is the death of the universe inevitable and it doesn't matter how advanced you are?

• How are aliens involved? We will be more than a few billion years more advanced than us before the heatdeath is the immediate problem. – user25818 Jul 18 '18 at 18:29
• I HIGHLY recommend you read this by Isaac Asimov multivax.com/last_question.html – Andrey Jul 18 '18 at 19:40
• @Andrey Thanks for the tip on that story! I almost saw the ending coming. Great read. – BrettFromLA Jul 18 '18 at 20:28
• Not a single mention of Block Transfer Computation yet? – VBartilucci Jul 18 '18 at 20:30
• @Andrey There's also Sam Hughes' The Last-But-One Question – Ray Jul 19 '18 at 15:58

Going a bit more out there, say the aliens have discovered undeniable proof that the simulation theory is actually true.

And they have figured out how to get access to some of the API from inside the simulation.
They can't get out, because you have to have a body to exist on the outside, but they do have a bit of control over the default parameters, so long as they don't do something really crazy and draw attention to the fact that they've figured it out, they can tweak things in small ways.
Like change the rate of universe decay from 1 to -1, so that the universe starts getting younger instead of older.

They just have to remember to switch it back every few billion years so that the universe doesn't get too young and hot.

Edit:
All this depends on the point of the simulation being to study life, not the universe.

Another fun possibility that it allows is for the creator(s) to be able to take up an avatar in the simulation, which could lead to things like the greek gods.

• @TylerS.Loeper certainly by our physics, but not certainly by all physics able to host a simulation of our physics. – user25818 Jul 18 '18 at 18:24
• @TylerS.Loeper You are assuming that a billion years in the simulation is also a billion years on the outside... Apparently you've never played The Sims. From the view of the user time in the simulation can be sped up, slowed down, paused, whatever, and from the point of view of the characters (us) time is running at a constant pace. And all this is assuming that time on the outside even works remotely like it does on the inside. In here the "arrow of time" only points one direction. Out there it could be like one of those crazy sign posts with arrows pointing in every direction. – AndyD273 Jul 18 '18 at 18:43
• Though heat death could be what happens when the CPU cooler fails... – AndyD273 Jul 18 '18 at 18:46
• "...tweak things in small ways." "...the universe starts getting younger instead of older." That is not a small tweak that would go unnoticed. If anything, someone monitoring the simulation would probably kill it and try to debug the problem. Then while studying the logs, that person will discover, "Oh, whoops, it created sentient life. Let me just tweak this parameter so that won't happen again." – jpmc26 Jul 19 '18 at 0:43
• Also, the simulation would die when the universe containing it did. ;) – jpmc26 Jul 19 '18 at 0:45

We can't answer this question as we do not know how any of those things work.

Since we know the universe exists, there must be some way to create it in the first place but whether that can be accessed from within is completely unknown.

There's an old and famous sci-fi short story that explores this question: The Last Question by Isaac Asimov.

http://www.multivax.com/last_question.html

At the point we are at in the story Multivac answers your question with:

• THERE IS AS YET INSUFFICIENT DATA FOR A MEANINGFUL ANSWER – Sydney Sleeper Jul 19 '18 at 1:20
• I'm an Asimov fan, but I had never read that story until now. That was deep. – ironduke97 Jul 19 '18 at 2:46
• +1 for the pointer to The Last Question. It's a deeply profound story and it perfectly answers the question. – Tom Jul 19 '18 at 7:50
• @ironduke It was one of Asimov's favorites among his stories. Imo the best of the lot. – Voo Jul 19 '18 at 14:49
• ^_^ Also the one which he immediately gave as the answer the moment someone said, "I'm trying to remember one of your stories..." because it came up so often. – Sean Duggan Jul 19 '18 at 16:27

You can achieve trillions of years of power beyond the point where the universe goes dark, by harvesting matter.

Even after all the black holes are gone there will still be asteroids, planets, and all kinds of other cosmic junk that has mass. This mass can be converted via E=mc^2 to energy. Using antimatter, for example, would be one way to achieve very high efficiency conversion of mass to energy.

The energy generated from these reactions, and the incomprehensible amount of matter in a single galaxy, let alone the universe guarantees a near infinite amount of energy for any galactic civilization that can harvest it. While this amount of energy will eventually run out, after for example 10^50 years, the time frame is so long that the galaxy will have "died", as we know it now, a trillion times over by the time our selected galactic civilization runs out of a means to survive.

By that time one would assume that they would have found a way to create a new universe, or to hop between them.

The universe might die, but the species that live within it don't necessarily have to.

Edit:

A Kugelblitz is another way to harvest energy from mass efficiently, via hawking radiation: https://en.wikipedia.org/wiki/Kugelblitz_(astrophysics)

Thank you @Ryan_L for bringing up the idea of using a blackhole instead of antimatter:

You are best off slowly dumping these planets and asteroids into the black holes and living off the Hawking radiation. This is because many systems are most efficient at very low temperatures; particularly computation. en.wikipedia.org/wiki/Landauer%27s_principle

Also of interest:

The universe could possibly avoid eternal heat death through random quantum tunnelling and quantum fluctuations, given the non-zero probability of producing a new Big Bang in roughly 10^10^10^56 years.[41] https://en.wikipedia.org/wiki/Future_of_an_expanding_universe#Dark_Era_and_Photon_Age

• You are best off slowly dumping these planets and asteroids into the black holes and living off the Hawking radiation. This is because many systems are most efficient at very low temperatures; particularly computation. en.wikipedia.org/wiki/Landauer%27s_principle – Ryan_L Jul 18 '18 at 18:46
• This depends on whether or not protons are stable. If they are not, they will "all" have decayed by the time the black holes have evaporated, and the universe is reduced to a soup of photons, neutrinos, and other primary particles. en.wikipedia.org/wiki/… – Suppen Jul 19 '18 at 8:59
• @ Ryan_L, Taking this idea further, we can dump the mass into man-made blackholes like a Kugelblitz. This can be better regulated than a cosmic blackhole : en.wikipedia.org/wiki/Kugelblitz_(astrophysics) – Tyler S. Loeper Jul 19 '18 at 13:12
• Would I be correct that his is more accurately "Delaying the heat death" as opposed to "living beyond it"? – IronSean Jul 19 '18 at 14:36
• This is neither delaying nor living beyond heat death. "Heat Death" refers to the point where all such energy stores are exhausted. If anything, it would speed heat death up slightly (though only by a negligible amount), as it exhausts these resources faster than they would run out by natural processes. Also note that we do not run on energy, which is conserved. We run on the flow of energy from high concentrations to lower concentrations. – Paul Sinclair Jul 19 '18 at 17:05

We don't know: possibly not

First, I want to say that we are nothing compared to that super advanced civilization, so how you dare to think we could actually have any kind of idea of how to prevent the Heat Death of the universe? Actually, we have some ideas, possibles or not is another matter:

Turn matter into energy

Even if starts die and everything gets frozen, the matter will be there -at least for a while (we aren't sure if the matter is unstable)- and we could convert it into energy. Mass energy equivalence! $$\text{E} = \text{mc}^2$$ Each gram of matter has 89,875,517,873,681,764 Joules of energy, that is, 90 petajoules.
We could use matter as ultimate fuel for some time.

Escape from the universe

If our universe is dying we should make portal/spaceships and travel to another young universe in order to escape from death.

I strongly don't recommend this idea because it could be really dangerous, since we don't know how physical laws work on other universes. With a minimal change in some physical constant, we could stop existing.

So I have another idea:

Drain energy from other universes

Heat death means all the suns will die by inability to continue fusion and all the entropy will reach its maximum level, meaning all the universe will have a constant of 2.7 kelvins everywhere.
So we just need a new energy source to draw from it: another universe. Draining energy from a younger universe, making our universe an open system, is safer than travel there because we aren't exposed to their laws.

That will let us buy more time until death again, but again we have problems. If our entropy is increasing and we still keep draining more energy from other universes, our universe will start inflating like a balloon of energy until something bad happens.

• Either we die cooked because of that 2.7 K of passive heat increase into something so hot that even with thermal pumps (AKA: AC) we can't survive.
• Or we adapt to the heat and then the universe blows up or cracks due to massive energy because that "2.7 k" of passive heat ends reaching the Plank temperature... a bit worried...
• Or the expansion of the universe is forced and accelerated even more: in order to increase the universe volume ($\text{V} = \frac{3}{4}\pi\text{r}^3$) and that decrease the energy density.
• Or, our passive heat (2.7 k) becomes so hot that we are not more able to drain energy from other universes because the heat flows becomes the opposite ($\text{T}_{\text{our}} > \text{T}_{\text{their}}$).

To prevent this we have another solution, which is to artificially provoke the last alternative. If we keep draining energy from other younger universes, our universe will keep inflating in energy, so we just need to transfer it passively to another older universe already in its Heat Death.

Now the matter would be if there is an infinite or finite amount of universe to gather and expel energy.

Quantum tunnelling and Heisenberg uncertainty principle

I've already explained quantum tunneling today in this answer, so I don't want to explain it again. Easy: particles are able to teleport to anyplace where it doesn't consume more energy than they have, even if in order to do that they must move through a barrier which in classical physic they wouldn't be able.

Combining the Quantum tunnelling and the Heisenberg uncertainty principle we could archive it. We just need to learn how to do manipulate them at will artificially. If that is possible, we could reverse Heat Death at the cost of statistics, it will be just a matter of time reverse it.

Big Bounce

Artificially or maybe naturally if gravity is stronger than the universe expansion, in some time all the mass of the universe will fall into a huge supermassive black hole (that would provoke a big crunch), and if that happened, we could have the "hope" of that will produce a big bang, effectively resetting the universe.

Now it will be a matter of how to produce the big bounce and how to survive it (we will need to escape from the explosion zone and the gravitational well), maybe they could use wormhole technology, FTL drives, Warping space around themselves, etc.

Dark energy generator

If we get deeper into science fiction, we could develop a way to convert dark energy into normal energy.

If that is true, we are saved because dark energy is infinite.

If we could gather this high amount of energy (around $68.63\text{%}$ of the universe) from its low but constant density ($~7\times10^{−30}\text{ g/cm}3$) and turn into energy we would archive endless energy.

Dark energy is quite peculiar because it is born from space itself and also produce more space. Dark energy produces a negative pressure in the container its hold -the universe-, that means that dark energy is pushing the "boundaries" of the universe making it bigger. And also, we already know that the universe expansion is accelerating, so the dark energy is being produced from somewhere. We just need to gather it!

Vacuum energy

Without the need to get close to science fiction we could try to gather vacuum energy which has a density between $10^{-9}\text{ j/m}^3$ and $10^{113}\text{ j/m}^3$... scientist still aren't agree and have a problem.

Do you remember that above I said dark energy births from space? Well, I lie, because vacuum energy births from space itself and this produce dark energy. Vacuum energy could be said that its the mother or dark energy.

But it's even better. Vacuum energy isn't a normal energy, it's an intrinsical property of space itself. Space has the magical property to produce more space, everywhere, always, all the time. That is why the expansion is getting faster, because each time there is more space, which is producing more space, which that is producing more space..., per second, per second... per second. The vacuum energy is how scientists explain this space replication property

Virtual Particle Generator

Do you what is a virtual particle? It's again another way to interpret vacuum energy.
This way of thinking states that void isn't vacuum, it has particles. Not exactly normal particles but virtual particles.
These particles are always spawning in pairs of two: a virtual particle and a virtual anti-particle. They spawn and almost instantly they collide disintegrating themselves into a net 0 energy profit.

But, what happens if we capture one of this particles? Well, black holes already do that in the way os Hawking radiation. A pair of particles spawns one of them inside the even of the horizon while the other outside. That particle escape producing energy, so in order to not break the conservation law, the black hole pays the energy price. That is the explanation of why black holes evaporate over time.

If we could artificially create virtual particles without a black hole, something inside our universe must be obligated to pay the energy price disintegrating itself. If we are lucky and that victim isn't us we could generate energy even after the Heat Death of the universe. Just pray to not be the next victim of energy price.

• The way you explained hawking radiation and black hole evaporation didn't sound quite right. The way you put it, the black hole is constantly increasing in mass from these events and is doing the opposite of evaporating; the net result would be an increase in mass. – Loduwijk Jul 19 '18 at 18:41
• @Aaron I think you are right... I have heard it better explained as due to the uncertainty principle around a virtual particle at the event horizon in different reference frames. If it was really particle/anti-particle pairs, then why would only the anti-particles fall into the hole? (This would provide a convenient explanation for why the universe doesn't contain appreciable amounts of anti-matter, however...) – Michael Jul 19 '18 at 19:25
• @Aaron, I am sorry but isn't the idea this?: A pair of virtual particles spawns, one of both falls into the black hole, the other one escape from it. In order to prevent breaking the conservation law because they didn't collide and disintegrate, the black hole must pay the energy of both particles. – Ender Look Jul 19 '18 at 20:29
• @Michael, please read the comment I've left to Aaron. – Ender Look Jul 19 '18 at 20:29
• @EnderLook What do you mean by "pay the energy of both particles"? How does it do that? It has been a long time since I have read anything on black holes, so what you are saying sounds familiar but I think you might be missing a step. I am not completely sure, but it just looks odd reading about a black hole taking a particle in but losing mass. – Loduwijk Jul 19 '18 at 20:48

Maybe

Assuming all mass and energy don't collapse back in on themselves due to gravity and the universe resets with a big bang. (Leading to the separate question of how do you survive the Big Bang)

The entropy and disorder of any closed system is always going to increase. The universe will eventually degrade to a random jumble on neutrinos and photons of progressively lower energies that spread away from each other occupying a larger and larger space.

The hyper-advanced life that you posit might be able to make the cold scatter universe livable by changing the fundamental assumption of closedness. Opening the bottle as it were to another universe would allow for the importation of yummy highly structured and ordered matter and energy. This would decrease the entropy to the hyper-advanced life's universe and increase the entropy of the other universe by a greater amount so everything is cool physics wise. The owners of pilfered stars and galaxies would probably disagree though.

• Hello, MongoTheGeek, and welcome to Worldbuilding.SE! Please take our tour and visit the help center to learn more about the site. Have a nice day! – Gryphon Jul 18 '18 at 19:59

I offer as an answer, this quote from Daniel Moynihan: "everyone is entitled to his own opinion, but not his own Facts..."

To suppose that a Type III (Or greater ) Civilization has an understanding of Physical Laws superior to ours is a given, however they are the same laws we have. Entropy flows in a single direction, only, therefore, No, they could not.

For an interesting side read ( only 13 pages) see Isaac Asimov's brilliant short story " The Last Question" - it addresses a nearly identical question as you have posed.

• This assumes that our current understanding of entropy is correct and that in general the laws of physics we have inferred so far are correct and will stay correct. Occam's razor and many experiments suggests that's the case but on the other hand from the point of galactic time scales we are laughably young and stupid. If it is actually possible for sentient life to survive for galactic time scales it's anybody's guess. – DRF Jul 18 '18 at 18:36
• Agreed, it's not really possible for us to understand the intelligence, science or power required, we can only work within our scope. – Joe Jul 18 '18 at 19:10
• A small correction: "Entropy flows in a single direction" ... with high probability. In a maximally entropic system, for instance, entropy can no longer increase, and there does exist a minuscule probability that it will decrease. It's small enough that we can usually just ignore it, but for this question, the distinction is potentially important. – Ray Jul 18 '18 at 19:26
• The laws of thermodynamics are the real kicker here. Nobody truly understands where they come from yet (they appear to be almost a 'meta-law'). But I think I read an article where a scientist posited the possibility that, assuming a slow heat death is the final state, living entities with enough know-how could keep mining energy from temperature difference almost indefinitely if they kept slowing down their metabolism/thinking processes (to the extent it would take years, then hundreds of years, then thousands of years etc for a single thought!). – PJRZ Jul 19 '18 at 9:05
• @PJRZ The current understanding is that the second law arises from statistical mechanics. Large aggregates of particles tend to enter high entropy states because there are so many more of them. – timuzhti Jul 22 '18 at 7:02

Maybe

We currently think that entropy is inexorable. That the universe will certainly continue expanding and cooling, and eventually all that will remain is an incredibly sparse expanse of fundamental particles a fraction of a degree above absolute zero, no matter what we do.

But we've only been really studying the universe for a few hundred years. I think it's far too early to say with any certainty that the end of the universe is actually truly unavoidable. We have trillions of years left until the stars burn out, and even that isn't the end. We could have civilizations around black holes, living on the Hawking Radiation, which would also last for trillions of years. And during all this time, we could be searching for a way to reverse entropy. Sure, we haven't found a way to do that given ~400 years of study. But how about after 10^12 years?

We don't really know.

Our current models of how the universe works say the answer is a definite NO. As Joe points out entropy is one directional.

The trouble is all we know about the universe are models. Even if we ignore the pure philosophical questions of a Plato's cave, the thing we call Laws in physics, Conservation Laws, Law of Entropy etc. are really "just" models/theories. (Got rid of gertruding here)

The models we currently have we've been developing for, very optimistically, 4000 ($4*10^3$) years. We have at least 400 ($4*10^8$) million years before the sun becomes a problem for us in terms of it's own decay (it won't decay for much longer but that's an order of magnitude guess at when we start having trouble).

We are talking about 5 orders of magnitude difference here. Given the knowledge we had of the universe even 400 years ago vs. now, the answer to "Will the models we have now still hold after another 40000 years?" seems completely unknowable much less 400 million years in the future when we must confront our sun or the couple billion years when we start having to confront deaths of many stars.

• @L.Dutch Of course sorry. Apparently I can't add. I will claim I was trying to figure out the best choice (sun's death is still billions of years away but it will become an issue much earlier then that.) and got confused. Why downwards though I can not say,. – DRF Jul 18 '18 at 19:31

Yes, and there's two or three ways that require finagling.

The first is to let it happen and become a spontaneously occurring omnipotent brain that decides the heat death never happened. This, although pretty dumb, is based on an actually theory in physics. Essentially, since time scales will be infinite after the heat death of the universe, everything can and will happen so this is plausible. Perhaps a sufficiently advanced civilization would be able to figure out how to do this intentionally, and how exactly the heat death didn't occur.

The second is to simply find another universe or dimension, and use that universe to get rid of the entropy in our universe. Entropy is always generated by everything. That means that in a closed system like our universe it always rises. Finding another universe or dimension would give the aliens a way to make our universe an open system. That means, like with all other open systems, that the total entropy can be lowered even though entropy is always generated. Functionally, this is literally just lowering our univers's entropy by putting it somewhere else.

A "or third way" would be limiting the amount of entropy created by unreasonable levels of micromanaging followed by handing the issue to some other hyper advanced civilization. This would be the universal equivalent of the "Kicking the can" approach. Certain governments consider this a solution, while individuals usually see this as an easy cop out.

• For the first idea, see Boltzmann brain. – Alchymist Jul 20 '18 at 14:43
• @Alchymist Thanks! I forgot what that was called and that documentation was really needed. – user32463 Jul 20 '18 at 14:53

The real answer is, we dont know. But if it is possible. Vacuüm energy is a likely candidate:

https://en.m.wikipedia.org/wiki/Vacuum_energy

One theory about the universe is that it first started as a quantum fluctuation. If you read "implication" of the wiki page it may be that Black holes are theoretically creating matter on its event horizon by sucking up either the particle or antiparticle before they can annihilate eachother back into nothingness. This wouldnt stop entropy, but it would be a way for matter and energy to enter the universe and keep it going.

Everybody so far has focused on the universe-scale problem. I will try to talk about smaller scale: solar system-level

For life on Earth to continue to exist, theoretically there is no need for any other star to be still burning other than the Sun. If all the stars in Universe are dead but the Sun is still running strong, we're fine. The night sky will be dark, but that will not be much of a change from what a city dweller sees today because of the light pollution.

So the problem is smaller: keeping one star running. The Sun produces energy by using a fusion reaction: it fuses two atoms of hydrogen to produce one atom of helium and a ton of energy. When most of the hydrogen in the Sun is gone, the Sun will start fusing helium and it will start growing large enough that it will engulf Earth, and turn into a red giant.

To keep life going on Earth, the alien race would have to have a technology that restores the hydrogen in the Sun, without any catastrophic side effects (exploding Sun, or massive gamma radiation, or anything like that.)

While something like that would be a massive undertaking (and I have no idea what it would take to do it), it seems to me that this is a much smaller problem than keeping the entire Universe alive, and possibly achievable by a much more scientifically advanced race.

• Hello, user53241, and welcome to Worldbuilding.SE! Please take our tour and visit the help center to learn more about the way that the site works. Have a nice day! – Gryphon Jul 21 '18 at 0:43
• Nice idea. Taking all the remaining H2 and He in the universe and spreading it out thin enough to switch off all other nuclear reactions would leave a near infinite (just very large) amount of time for just one sun to burn if the one required sun was fed fuel and by products were removed.. – KalleMP Jul 21 '18 at 17:03

Maybe

See, the whole idea behind heat death is that since the universe is expanding, matter will spread out and eventually reach an equilibrium. If our super advanced aliens could somehow reverse this expansion, they could cause an artificial 'crunch', where all matter is again reduced to a single, bright point. And from there the big bang would occur, and Bing bang boom heat death delayed. How the aliens would go about this or even persevere in order to enjoy this newly re-created universe is definitely beyond me, as I have not based this portion of the answer in real scientific laws.

They could always just delay the inevitable. If these aliens found particles with negative mass and energy, as outlined in the Newsweek article, the aliens could create a wormhole connecting two different points in time, and simply travel back in time, effectively delaying heat death forever, at the cost of being stuck in this small loop of time. This is entering the territory of theoretical physics, though.

In short, without the use of theoretical physics or fantastical means, these super advanced aliens cannot stop the heat death of the universe from occurring.

Sources

Time Travel Is Possible Through Wormholes—but You Can Only Ever Go Backward

• I'm sorry but I don't believe in the time-travel wormhole. If you travel near light-speed for 40 years and stop, the rest of the universe has aged 80 years. Just because you experienced it slower doesnt mean you traveled through time. The wormhole will subsequently be connected to a wormhole that is traveling faster through time, meaning that if you look through it everything on the other end looks extremely fast (or from the other end extremely slow). But stepping through will not take you back in time (although it's likely to rip you to shreds) – Demigan Jul 19 '18 at 15:48

i once read a story with similar problem, summarizing from memory (if anyone recognizes it id appreciate the title and author)

Some billions of years ago the basic constants of the universe were different, in such a way that the universe was way smaller, and its fate was to collapse back onto itself to result in a new big-bang in not that long.

The universe was housing only one very advanced species which take an issue to that scenario and developed a way to change the universal constants in such a way that the universe would expand forever, thus not avoiding the death of the universe per-se but postponing it to way later.

A consequence of this action was that those changes also affected all of then-existing physics and basically would mean that that alien race had ceased to exist.

So the idea would be not to make the aliens save the universe from current death scenarios but to have them prevent something even worse or earlier.

What if our universe is just a pocket universe used to harvest energy from. We don't know how long until we are disposed like an empty battery. That disposal, it probably means death to our universe.

It was quite a pleasant night. Kinda hot for this time of the year but still pleasant. Suddenly the City went dark. All of it. The City never was dark. For centuries the lights didn't went out. Until now. I stood there, in awe and uncertainty. This must be a dream.

My comm device suddenly screamed at me, ordering me to report to closest emergency station. I had a faint idea that those things could turn themselves on, in cases of highest emergency, but never saw it happen. Well, i never saw the City blackout too.

Everyone at the station was clueless, some helpers even terrified. Commander appeared before us, but before he could start the breefing one of the rookies screamed

"What the hell is going on? How comes the City is dark?"

"There was an accident at the power station. One of the pocket universes become unstable and broke though the containment field" the commander responded without even lektioning the rookie. Things were way out of order to waste time on discipline.

"No-one know what exactly happened, but the universe detached itself from the stem and is rapidly expanding into our own space. The reactor core is already gone, and if the expansion rate keeps entire City will be gone in two hours." commander continue.

"How do we stop it?" i shouted

"The scientists don't know. The containment field cant stop it anymore, the pocket just ignores it. Its a lost cause. We already lost two teams in the power plant trying to set up a perimiter." He paused "Those were good people." he nodded to himself.

Raising his voice he proclaimed "Just so you all understand: this is an evacuation, we get everyone off this planet and probably out of the entire system."

"We just run and leave everything behind?!" asked the guy beside me in disbelief.

"Yes, we do. We played god and this is our punishment."

• Cool. But your short paragraph above the line appears to be the opposite of the narrative you provide below the line. – Loduwijk Jul 19 '18 at 19:22
• our universe is the pocket one in the story – Valerij Jul 21 '18 at 19:18
• Yes, and it does not discarded or dispose us resulting in the death of our universe. The way I originally read it was "Our universe dies. Now here is a narrative where it is expanding out into the 'host' universe instead of dying." Though, reading it again, I see how the death of our universe could be a future hypothetical one, and perhaps us realizing that and figuring out how to deal with it is precisely what leads to your narrative. In that case, the original point and narrative go together fine. Either way, you had gotten my +1 the first time I read it. – Loduwijk Jul 23 '18 at 14:48

If Big Rip doesn't happen long before that then the "heat death" situation could be avoided if there is a method or mechanism to regenerate hydrogen atoms from radiation, dark matter, dark energy, zero-point energy, or other sources so that star formation and heat transfer can continue to avoid a gradual running down of the universe due to the conversion of matter into energy and heavier elements in stellar processes and the absorption of matter by black holes and their subsequent evaporation as Hawking radiation.

Easy. Build a smaller universe. The heat death of the universe is only a thing at scales on the order of humans. However, as space as we know it expands, and entropy gets very large in a box the size of our galaxy - entropy in a box with an inscribed photon remains yet small. The energy contained in that box is yet orderly and compact. As the Planck Length expands along with space, who knows what will emerge from that tiny photon, and what physical constants will govern the world in which it exists? Since the photon is on the size scales of light as we know it, the speed of light as we know it is moot in photon-world, and all new interesting physical constants govern material relationships in the photoniverse. Perhaps there are even tinier particles of micro-photons within the photons that travel at the speed of micro-light. As space expands, and the heat death of our world really sets in, the size of a micro-photon might now be comparable with the size of the photons of ages past, and the speed of micro-light might be the new speed of "our" light. From the point of view of anyone living in the photoniverse, their entire reality would have originated sometime around our lifetime, when their entire universe fit into the space of a single particle....

Of course, I wouldn't bank on it being anything like the universe WE live in, or even anything at all, but this is Worldbuilding stackexchange, so some imaginative liberty is in order.

• Hello, Scott, and welcome to Worldbuilding.SE. Please take our tour and visit the help center to learn more about the way this site works. Have a nice day! – Gryphon Jul 20 '18 at 19:37
• "The Plank length expanding" makes about as much sense as "the meter expanding". Things get bigger when more of a unit of measure fit into it. If the universe is twice as large, there are twice as many meters (and Plank lengths) from one end to the other. Size is defined relative to the measuring sticks. – timuzhti Jul 22 '18 at 15:19
• @Alpha3031 the expansion of scale in our universe is a relatively well accepted theory at this point. If you are proposing an alternate theory, a citation is in order. – Scott Jul 22 '18 at 23:27
• Also, I agree that "The Planck Length expanding" (with a 'c') makes precisely as much sense as "the meter expanding". – Scott Jul 22 '18 at 23:30
• @Scott, I am proposing that something getting bigger means that there are more Planck lengths between point A and B and not "?the Planck length getting bigger". The Planck length (along with other length units like light years) is what we use to measure the expansion of the metric tensor, not what expands. – timuzhti Jul 23 '18 at 3:47

This is a very deep question and from a formal scientific basis we indeed do not have adequate information to formulate an answer.

However the Hindu philosophy (and some others) instructs us that there are various 'levels' of creation that encompass the respective level below.

The Hindu philosophy (perhaps others, I have not had occasion to investigate) also tells that at certain periods there are 'Lesser Dissolutions' and 'Greater Dissolutions' that are used to reset the levels below a certain point.

Various mystics have described these things in times past and some a bit more contemporaneously.

The time frames are long, it seems some of them are of the same order as the age of the known universe, it makes one think a bit.

Perhaps the 'Lesser Dissolution' corresponds to what we in science expect to happen to the known universe at the time of the 'Big Crunch' and this is cyclic and part of the philosophy.

While all of this is diverting the telling point is that the souls that have reached a level that is not subject to that turn of dissolution will persist while all the souls in lower levels are in essence 'reset' and have to start their path to god realisation anew (sort of like stage extras in the play of life that are just there to help the main cast) from single cellular organisms over millennia until they incarnate into self aware beings and can strive to reach the higher levels. For this reason the Hindu philosophy places a fair amount of emphasis on spiritual advancement to achieve access to those levels that are safe from the Dissolution.

So in essence the aliens are the denizens of the higher levels and their emissaries, the various Masters, who come to visit and the technique they use to avoid the heat death of the universe is to maintain a backup copy of their soul in a fire proof safe, knowing when the fire is coming. The Masters trying to get us mere mortals to also try to prepare a backup.

Granted this is not a scientific answer unless one delves into the 'Science of the Soul' movement but is could make for a great storyline that can cover the life of a universe and still have observers.

• Not sure why someone down-voted you, as I think this answer is awesome and a great contribution. If some people have issue with this being religious while the question has technology tag, I say that many of us religious people believe that science and religion cannot be separated and they are mostly the same thing. In fact, many worlds built for fiction display magic and mysticism as merely a higher understanding of the universe (ie: science), and there is also the obvious quote "Any sufficiently advanced technology is indistinguishable from magic." – Loduwijk Jul 23 '18 at 14:58

Yes, they can prevent it for a long time, but maybe not forever.

We are barely,if even that, cave people compared to your aliens. It is highly possible that they could save, if not the universe, large portions of it given how sparsely populated it currently is.

Most of humanity major inventions have been discovered in the last 100 years, sure galieo, newton, and etc had discoveries but not at the level and rate we have achieved in the last 100 years or so.

Right now, we think "dark energy" which is a replacement for "don't know" is pushing the universe apart. Clearly the alien race will have a far better if not complete understanding of this.

Possibilities

1. Destroy dark energy
2. Move the dark energy around
3. Convert the dark energy

Converting "dark energy"/"dark matter" to real matter will cause it to again produce gravity. Thus things will start pulling themselves together. The universe has expanded a lot so, they can slowly contract it over millions of years if necessary.

Re-distribution matter will also help. For example, if you have a force you can't contain pushing the universe apart throw a black hole/sun at it. Boom, a giant source of gravity to either counter-act the forces pushing the universe apart. The sun/black hole may also be able to convert the unknown enery/matter back into real matter as a bonus.

Also the alien can probably pull energy from other universes, and possibly from the fabric of space time itself.

They can probably convert energy to mass and visa versa further extending there dominance on the universe.

So there only problems are running out of mass or energy at some point down the road.

Side note: We don't really know what is going on at the edge of our universe. We can see the light, measure the forces, and etc but all of that happened 13 billion years ago. We have no idea what its doing today.

It depends.

If multiverse is a reality then they may be able to travel from one universe to another, if instead there is only one Universe and taking into account that it is expanding at a higher pace than expected then most probably they wouldn't be able to stop that since they would need a huge amount of energy and that energy is spread at higher distances as time goes by. If creating wormholes is a posibility the amount of energy to create them would also be huge and they should be able to get more energy the place where that wormwhole takes them.

So I really don't think they could.

• Can you make more clear how this is answering the OP's question? – L.Dutch Jul 22 '18 at 15:42

If your future aliens could manipulate space-time then yes, I see no reason why not.
I'm imagining the use of technologies to fold the vast spaces between galaxies into pocket universes, then expel any energy contained within out into the Prime universe.
Essentially creating something resembling a White Hole pouring energy in the form of radiative heat in vast quantities into the now much smaller universe.
It'd be sort of like giving the universe a Nip and Tuck in its old age, or if you prefer, wringing out a towel to collect water.

An alternative is to do this to the entire universe all at once, piping all of its energy through a pinchpoint and out the other side to create a new universe with a new Big Bang. In concept like forcing a playdough sculpture through a pipe, the sculpture is destroyed but it's formless again and ready to sculpt anew.

The most important point is that this approach doesn't violate thermodynamics that I can see.

• How is such a space-time distortion different from a gravitational field? If the field does work on a particle, it will require energy in the form of work. Where are you getting the energy from? – timuzhti Jul 22 '18 at 15:30