# Killing a star safely

A messenger from the stars just arrived in peace but has brought horrible news. A vast swarm of planet devouring phototropic insects are approaching from deep space and our only hope is to obscure or snuff out our sun until they pass by.

The messenger provided a copy of the galactic encyclopedia which includes all of the scientific knowledge of the Kardashev Type II civilization she comes from, but she has since returned to space, heading off to warn other civilizations of the approaching threat.

We have enough time to prepare Earth for the cold darkness. The encyclopedia includes several different techniques for generating enough energy to keep us warm and techniques for synthesizing nutritious food without the need for plant life. We also have time and the new knowledge to build enormous opaque enclosures to serve as green houses, zoos and gardens, so none of our world's bio-diversity will be lost. We won't have to live in complete darkness but we will need to keep our light hidden behind solid windowless walls.

So my challenge as an author and world builder is that I don't have my own copy of that encyclopedia. So I can't read the chapter on how to safely snuff out our sun without making it go nova or expand to consume the Earth. I would also prefer to keep it's corpse in one piece so that the arrangement of the solar system can continue, relatively unchanged.

My question is...

Given unlimited resources, nearly magical scientific knowledge and enough time, how do we snuff out or obscure the light and heat of our Sun?

I'm looking for an alternative to building a complete Dyson sphere because my goal as an author is to write stories about the dark cold earth. Sort of an homage to the old Space 1999 TV series, only with a more ominous, grittier, darker theme.

Bonus points if the process is reversible once the swarm has flown by.

• Comments are not for extended discussion; this conversation has been moved to chat. – L.Dutch - Reinstate Monica Jul 22 at 18:52
• "The messenger provided a copy of the galactic encyclopedia " - there are huge problems with this premise. Imagine going back to cavemen in the stone age, and giving them an USB flash drive, saying that "on this you can find schematics of tanks and jet fighters, build them because an invasion is coming, goodbye!". There is at least that much difference between a Kardashev II civilization and us, probably more. – vsz Jul 23 at 6:09
• @vsz, Good point, and I'm considering having the Messenger's friends take care of darkening the sun (haven't decided how yet but lots of good options) but with the Earth's atmosphere about to freeze and blow around on the lifeless ground, I need to do something or all the insects will find when they arrive are a bunch of freeze dried human corpses. Maybe I'll have the messenger leave a robot behind as sort of a white hat version of Klaatu who can build the domes and dig the caves. No, that's not a good fit. Gotta keep thinking. – Henry Taylor Jul 23 at 6:17
• Don't cover the sun, freeze it in time. A decent-sized bobble ought to do it. – John Wu Jul 23 at 9:27
• I would say to envelop our entire solar system with a UV-blocking bubble which keeps the light and heat inside. However, it does make me wonder if that would just bake us alive. – MonkeyZeus Jul 23 at 19:46

If you slow time down for the sun the emitted energy will drop proportional to the time dilation factor and light will redshift off into obscurity.

No idea how you'd do it (something akin to a localized distortion of the curvature of spacetime), but that's half the point of technomagic. And should be easily reversible, or at least as easy as getting it to happen in the first place. Semi-bonus: an argument can be made that the mass of the sun is still there, so orbits and the like stay the same.

Nice bonus is the sun is still there, and probably still visible as a black spot in the sky (or dim spot... not entirely clear on what might be redshifted into the visible spectrum), but something about slowing down the nuclear processes of the sun has a nice sense of wrongness to it.

• Thanks. I really like this. It has a creepy greater power feel to it. Like the K2's who pulled it off are so far beyond us that they are dangerous to us even in peace cooperation. Just so I am sure I understand, by encapsulating the sun in a bubble of slower moving time we are extending its lifespan relative to our own but also lowering the speed of the light it is emitting relative to us. This makes its light (which is affected by time) lower frequency and thus invisible while leaving its gravity (which is unaffected by time) unchanged. Great Answer! +1 – Henry Taylor Jul 24 at 19:51

Problem: even if you could just stick a blanket over the sun, it is probably already too late. The solar system formed more than 4 billion years ago, and for all that time anyone who was watching and had suitably acute vision would have been able to see Sol, and almost certainly the protoplanetary disc around it and later the planets themselves. Certainly, anyone or anything with K2-level technology will know where the sun is, and have a pretty good guess at what sort of planetary system it harbours.

Stars don't just poof out of existence without a trace. Even being eaten by a black hole is a pretty drawn-out and violent event. Those planet eaters? They'll see, and they'll know. You can't pull the wool over their eyes. They'll see that little yellow dot fade away, the little yellow dot that is making unscheduled departure from the main sequence and clearly isn't behaving like a natural star should. They'll come and take a look at the clear and unambiguous evidence of intelligent agency, because intelligence generally comes from planetary systems and that means more food.

So give up on your plan. You gonna get ate.

Instead, read up on mechanisms of planetary relocation, preferably with reactionless drives, and boost the Earth out of Sol's gravity well as soon as you possibly can. They might notice the absense of the earth, but given the rest of the solar system to snack upon, and assuming suitable stealthiness of the fleeing world, maybe, just maybe, they won't find you.

Good luck, cos you're gonna need it.

As an aside, given that you have the potential power to snuff out a sun, you will certainly have the power to do simpler things. I'd see about building a giant "blackhouse" roof covering the earth (or as much of it as seemed practical), in a technique sometimes called paraterraforming or a worldhouse. Life might not able to be as thermodynamically exciting as it used to be, absent energy input from the sun, but you've got access to a lot of fusion fuel in the seas and you can build and run a lot of grow lights with that.

Probably would be insufficiently gritty for your narrative needs, but, y'know, the category of "things easier to do than surreptitiously turn off an entire main sequence star" includes a lot of stuff like this.

• Comments are not for extended discussion; this conversation has been moved to chat. – L.Dutch - Reinstate Monica Jul 22 at 18:52
• Good frame challenge, wrong reasoning. Modern insects fly into light bulbs over and over because their brains are too simple to account for any light source behaving differently than the light sources in their ancestral environment. Life evolves to be as stupid as possible while remaining competitive: Unless these space "insects" have been co-evolving with star-hiding super-civilizations long enough, their brain will be limited to a dumb "point at light source that will be viable when we get there and go" algorithm. But that might mean they don't change course even if the light goes out... – mtraceur Jul 23 at 21:11
• Elaboration (part 1): Unless they can aim perfectly from astronomical distances, they will have a course-correction algorithm (as simple as possible while still working in the common case) built into their brain. Based on existing "designs" of such algorithms in real brains in nature, we know that algorithm can be very stupid simple in practice - human baseball outfielders run into stadium walls (and in other situations, humans will in fact run off cliffs when trying to catch a falling object, etc) because the human brain does not even bother predicting where a falling object will land. – mtraceur Jul 23 at 21:26
• Elaboration (part 2): So then the question becomes - what algorithm for final course correction is the simplest, or most energy efficient, or otherwise advantageous for these insects to persist and duplicate? And the answer could be "point at the brightest light source and aim at where it seems it will be", but it might also be "orient by the gravity well once close enough", and it might also be "fly dormant, get caught by the gravity well, and just let it pull you in". And the latter two would ignore the light source going out. – mtraceur Jul 23 at 21:27
• But having thought through all that, I have decided to -1 this... I like where this frame challenge went, but the question takes as given that these insects can be tricked by the light going out, and dismissing that premise should be done on the basis of there being no good conceivable way for it to work, which is a higher, more rigorous bar than us individually not finding it most likely. – mtraceur Jul 23 at 21:35

# A star shines because it has mass...

You put enough mass together, it gets a dense core, heats up, and voila, solar fusion. Yes, that's an oversimplification, but, fundamentally, making a star not shine would require removing its mass.

# So let's figure out how to remove mass...

But you said you want the mass to stay at the center so that orbital mechanics doesn't shift for the planets. That suggests a delicate surgery -- divide the sun into N parts where each part is less than the minimum stellar mass, and let the masses orbit around the original gravitational center of the sun (because gravity works as if all of an object's or system's mass were at the center of gravity for everything in orbit around it). The smallest theoretical mass for a star with same metallicity of Sol to support nuclear fusion is 75 x mass of Jupiter. Sol is ~1000x mass of Jupiter. So we'll need to cut Sol into 14 chunks.

14 is an awkward number, so let's make it 20, and make each one drift away so that we get an icosahedron of chunks. A, that'll make it easier for our imaginary thrust system to arrange things geometrically, and B, that'll make a great book jacket cover. It might also keep the star's mass well-balanced, so, again, we don't have to worry about the planets feeling the effect. I did mention this was a delicate surgery, right? Yes? Good. Moving on...

Having divided the star, the core should cool down, fusion stops: Good night, starshine! (Gonna need a new musical number when future humans perform the stage play Hair.)

You want your Giant Space Scissors to push the chunks apart at just the right speed so that they eventually drift back together when the threat is passed.

# Design of Giant Space Scissors

You have a problem of scale. Stars are BIG. Really big. Like hurling-Earth-into-Sol-won't-break-it big. That means we are NOT talking about any sort of mechanical scissors.

You're going to need a chemistry solution -- something that you can seed into 20 sides of Sol that starts some sort of repulsive reaction. I think you're going to invent handwavium or unobtanium for this. Here's my attempt...

Each seed must be a little thing that will pull Sol's mass to itself and overcome the gravity that is holding Sol together. As it does this, it needs to generate either positive or negative charge such that it pushes away from the seeds around it. ALAS -- there is no way to color an icosahedron with only two colors such that no two adjacent edges have the same color. You can only do that with an octagon. So you can't just rely on alternating positive and negative electrical charge to do the push back (i.e., have some "positive seeds" and some "negative seeds"). So, more handwaving: we'll assume that the act of the seed pulling in mass somehow imparts momentum to the chunks along the vector from which they are pulling the most mass (i.e. away from star's core). That's nice because it means that momentum will eventually be overcome by gravity and the chunks will drift back together.

Note: Having the seeds become uniformly positively (or negatively) charged would cause them to push away from each other, but if that pushback was strong enough to overcome gravity, they'd never drift back together. The momentum solution is better in my opinion.

# Problems:

1. It'll require a lot of set up to get the seeds arranged around the sun. We're talking years of construction and travel, not weeks.
2. The process of dividing the sun won't be fast. Sure, you can posit a geometric expansion of speed as the seed grows and acquires mass, but we are still talking SOLAR MASS. It takes a while for that much mass to move, even if the impulse is given atom by atom in some sort of known-physics-defying tractor beam that the seed is emitting.
3. It'll take a while for the core chunks to cool. Possibly as long as tens or hundreds of thousands of years. Not a lot of ways to accelerate the cooling. (Thanks to user @MikeScott for the link.)

Basically, these space bugs better be a long way away. Centuries. Millennia. Long enough for humans to have developed multiple spacefaring civilizations, collapsed back to bronze age, and rebuilt again. So you may want to posit FTL travel because FTL MUST grant time travel, so humanity can launch the probes toward the sun and backward in time. Just be aware that once you allow for violations of causality, forever will it dominate your destiny. (Yoda lives in a galaxy that has FTL, so he knows this problem. Or will know it. Hard to say with relativity + FTL.)

Or you could NOT violate known physics and just put the whole of humanity on a space ship that gets up close to speed of light (C) and then let relativity and time dilation do the work for you, so humanity is only gone a few weeks and comes back to a much changed Earth, but no space bugs. You get to solve the acceleration and deceleration problems yourself if you choose this solution!

1. Something has to tell the seeds to shut off. When the chunks drift back together, stellar fusion won't ignite if the seeds keep the chunks isolated enough that the "swiss cheese" of the chunk spheres provide enough venting for the heat. Ok... let's just assume that there isn't enough venting for the heat, stellar fusion reignites, and the seeds get pulled toward the core where it eventually becomes too hot and they lose whatever tractor beam powers they had. Ok, so not a problem. Nothing is a problem with enough handwavium. :-)
2. That star will be cranky when it comes back online. Expect a lot of solar flares while it settles back into its mainline again. That may cook the Earth, but you'll be used to living underground by then, so just add a few thousand years to the underground time. Unless you pick that time dilation solution. Or you could have everyone upload their minds into a computer or... yeah, we've all read sci-fi... pick your solution here.

Seriously... we are talking STARS here. Anything you do involving space blows human lifespans out of the water. You're going to need to deal with that in any story that has even a passing acquaintance with science. That's the saddest part of modern physics: The Stars Are Not For Humanity. (Thank you, Arthur C. Clarke, for summing up the crushing of geek dreams.)

PS: Book title: "Divisions of the Sol" -- the dividing of the sun set against the divisions in a young protagonist's heart as he/she longs for a partner against family wishes. It'll sell like hotcakes to the folks who like their sci-fi soft and their romance hard. :-)

• It takes tens or hundreds of thousands of years for energy created in the sun’s core to emerge as visible light. Even if you break it up into chunks and turn off the fusion reactions, the fragments will be emitting light for a very long time. – Mike Scott Jul 21 at 17:25
• @MikeScott Got a citation I can add to Problem #3 discussion? I knew it would be a long time. – SRM Jul 21 at 17:27
• sunearthday.nasa.gov/2007/locations/ttt_sunlight.php – Mike Scott Jul 21 at 17:29
• I really like this, but I think with the issues of scale and time, it will fit into my stories as part of the back story. Perhaps the messenger's civilization used this approach for their suns, (which will let me keep the cover graphics and cool "Divided Star" series name) while leaving the humans to find a more mundane solution such as what AlexP offered in a comment on one of the other answers. Thanks! This is really great work! +1 – Henry Taylor Jul 21 at 17:30
• @MikeScott Thanks. Edit made. – SRM Jul 21 at 18:07

I'm looking for an alternative to building a complete Dyson sphere because my goal as an author is to write stories about the dark cold earth.

There isn't sufficient matter in the solar system to build a Dyson sphere or swarm at one astronomical unit or farther (i.e. with the Earth inside the sphere) more than four meters thick. So you'd have to build it much closer to the sun, perhaps inside Mercury's orbit, to get it thick enough to obscure the Sun. That would still give you your dark cold Earth (presuming you didn't take apart the Earth to make the Dyson sphere).

Surface area is proportional to the square of the radius. So a quarter of the radius (which is about where Mercury is) would give sixteen times the thickness. I'm not sure how much farther in you can make the Dyson sphere before it would get too hot.

You may also find that it makes more sense to build two spheres. The inner one catches the light but reradiates a significant portion. The outer one catches that light and reradiates it with a different wavelength as already suggested. In between the spheres might be the gaseous portion of the mass, soaking up some of the energy output.

• Great Answer. I am probably going with something like this for my story. A comparatively small Dyson sphere (built by the Messenger's people and with Earth's consent to save time and address the easier-options issue) . Not a habitable sphere, just a power capture and concealment device. Maybe two layers of spheres as you and others have suggested. I like the idea of having an iris to vent off accumulated energy periodically to keep the whole thing from melting. I will be asking more questions to iron out the dyson sphere details. Thanks! +1 – Henry Taylor Jul 22 at 13:56
• @HenryTaylor: If you know which direction is safe to radiate without attracting the swarm (because they're coming from the other direction), you can build a permanent opening on that side. Unless that makes it unbalanced? Maybe need a thruster to keep it centred on the Sun. – Peter Cordes Jul 22 at 15:28
• @PeterCordes, Yep. That is the plan. I'm actually planning to have two vents, one that is pointing at the swarm but is closed as they approach and the other pointing in the exact opposite direction and open as they approach. As they arrive, I will close both vents then after they have passed open the one that is pointing at where they came from. The tension will be based on whether the swarm can all pass by before the vent opening mechanisms fuse shut under the unvented energy. Should be an interesting series of scenes. – Henry Taylor Jul 22 at 15:35
• Also, the energy you collect from the Dyson sphere can actually solve your energy requirements for Earth once it's in the shade. I know you were planning on just handwaving them, but I think it's cooler if you tie problems and solutions into a grand plan, something like 'we still get energy from the Sun, but now it comes in a concentrated beam'. Just don't use a long cable, the mass would wreck your orbit. – Blueriver Jul 22 at 18:43
• Just how tightly could you focus the energy vented by this solution? Could you focus it towards a stellar sized solar sail? If I were a phototropic space insect and the star on my path got dimmer while another object some distance off my path got brighter, i would head towards the new object, even if it keeps moving away from me – Alchymist Jul 23 at 15:56

how do we snuff out or obscure the light and heat of our Sun?

You cannot completely hide the energy emitted by the Sun.

You can just shift it to longer wavelengths as a consequence of using the usable content of the emitted energy, but, as madam Thermodynamic states, any transition results in some form of heat being emitted by a system at a lower temperature. Once you reach 0 K, you cannot extract any more usable work, and you have reached the thermal death.

I.e. the visible light we get on Earth and warms up a car parked under the Sun comes from the surface of the Sun being at about 6000 K, while the car re-emits it in the infrared, at longer wavelength.

Even if you were able to convert the emitted energy into mass, you would have the problem of dissipating all the gravitational energy of the resulting mass plus the Sun, else the whole thing would ignite again. And dissipating that energy would give an energy emission.

• Converting the energy to a wavelength to something the insects aren't drawn to. Thanks, that is helpful. It would give me the darkness I want for my stories while keeping the mass of the sun just where it need it for orbital dynamics. If I go with this, I will need to ask another question... how to change the wavelength of the sun? +1 – Henry Taylor Jul 21 at 16:15
• @HenryTaylor: Quite obviously, put enough objects in orbit around the Sun to obscure it. The Sun will warm up the objects which will re-emit the energy as longer-wavelength photons. Basically what you are doing is providing a large surface for the Sun's energy to fall onto. – AlexP Jul 21 at 16:20
• You should be able to hide the energy as long as you do it directionally. If you know what vector the insects are coming in on you can stick a big refrigerated disc in the way. Reradiate the waste heat back towards the star and you can get the ‘insectward’ side of the disk down to any arbitrary temperature with sufficiently advanced cooling tech. Do this with enough surface area and you can turn the sun into a Shkadov thruster and bring the fight to the enemy!!! Wait... – Joe Bloggs Jul 21 at 20:12

### Basic Requirements

We are talking about disassembling a star here. While this is certainly possible within known physics, it is something that requires the infrastructure, resources, and energy of a K 2.something civilization. Therein lies the issue. Even with all the knowledge and technology, is disassembling the sun really the smartest option? You gonna have to explain why other options weren't chosen. Running away seems quite easy in comparison.

This is basically using half a Dyson sphere to accelerate the sun. The issue is that the acceleration is abysmal. This video and the Wikipedia article on the subject might be interesting.

For a star such as the Sun, with luminosity $$3.85 \cdot 10^{26}\;W$$ and mass $$1.99 \cdot 10^{30}\;kg$$, the total thrust produced by reflecting half of the solar output would be $$1.28 \cdot 10^{18}\;N$$. After a period of one million years this would yield an imparted speed of $$20\;\frac{m}{s}$$, with a displacement from the original position of 0.03 light-years. After one billion years, the speed would be $$20\;\frac{km}{s}$$ and the displacement 34 000 light-years, a little over a third of the estimated width of the Milky Way galaxy.

Fleeing with Earth

There are several ways to do this. This video discusses it in detail. While the thrust you can apply to Earth before the engines will push the continent they are on into the mantle and deform the Earth is still small, it isn´t as abysmal as the Shkadov thruster idea. Fuel will be a problem, but putting several layers of shielding and hydrogen for fuel and reaction mass around Earth will give you a dark planet theme. Putting this armored Earth in orbit around Jupiter and using fusion candles, which are discussed in the linked post. The following description is from said post.

Build a fusion candle. It's called a "candle" because you're going to burn it at both ends. The center section houses a set of intakes that slurp up gas giant atmosphere and funnel it to the fusion reactors at each end. Shove one end deep down inside the gas giant, and light it up. It keeps the candle aloft, hovering on a pillar of flame. Light up the other end, which now spits thrusting fire to the sky. Steer with small lateral thrusters that move the candle from one place to another on the gas giant. Steer very carefully, and signal your turns well in advance. This is a big vehicle. Balance your thrusting ends with exactness. You don't want to crash your candle into the core of the giant, or send it careening off into a burningly elliptical orbit. When the giant leaves your system, it will take its moons with it. This is gravity working for you. Put your colonists on the moons.For safety's sake, the moons should orbit perpendicular to the direction of travel. Otherwise your candle burns them up.They should also rotate in the same plane, with one pole always illuminated by your candle (think "portable sunlight") The other pole absorbing the impact of whatever interstellar debris you should hit (think "don't build houses on this side")

Colonial Fleet

Just get everyone onto colony or world-ships and run for it. You wanna take the Earth with you? That's easy. Just peel it like an orange and place the crust fragments in rotating habitats on said vessels. Sounds crazy? Keep in mind that you just proposed to disassemble the sun.

Peeling earth is relatively easy given the knowledge humanity was given. There will be a ton of very advanced geo-engineering knowledge in there. Dig extensive tunnel systems under the continental crust, place engines there and keep them thrusting until the huge, domed over parts of Earth sit in prepared spin habitats.

I´ll calculate in a moment why I believe that fleeing is the superior choice. Several of the options will still give you decent dark Earth setting.

The Logistics

Whatever you attempt the only way to do it in any reasonable time frame are self replicating machines. Say goodbye to Mercury, Mars, the asteroid belt and probably more of the planets, as they´ll be needed for construction materials. Beyond that, you´ll need a lot of time. With all of that out of the way.

### Starlifting

Starlifting is discussed in detail in this video. The issue with starlifting is that it takes a long time. A very long time. Using 100% of the energy output of the sun will allow you to remove 0.000003% of the Sun's total mass per year. After only 334 million years the sun will have been disassembled. (it will be even longer if you intend to collect the material for later use) The swarm would have to be out past the Andromeda galaxy assuming they can move with a speed near light speed. Fortifying the entire Milky Way galaxy and turning every star into a Nicoll-Dyson Laser (the satellites of a Dyson swarm act as a phased array laser emitter capable of delivering their energy to a planet-sized target at a range of millions of light years) to fry the bastards out of the sky seems easier and more practical. That said, there are three main methods suggested in the Wikipedia article:

Thermal-driven outflow

The simplest system for star lifting would increase the rate of solar wind outflow by directly heating small regions of the star's atmosphere. This would produce a large and sustained eruption similar to a solar flare at the target location, feeding the solar wind. The resulting outflow would be collected by using a ring current around the star's equator to generate a powerful toroidal magnetic field with its dipoles over the star's rotational poles. This would deflect the star's solar wind into a pair of jets aligned along its rotational axis passing through a pair of magnetic rocket nozzles. The magnetic nozzles would convert some of the plasma's thermal energy into outward velocity, helping cool the outflow.

"Huff-n-Puff"

In this system the ring of particle accelerators would not be in orbit, instead depending on the outward force of the magnetic field itself for support against the star's gravity. To inject energy into the star's atmosphere the ring current would first be temporarily shut down, allowing the particle accelerator stations to begin falling freely toward the star's surface. Once the stations had developed sufficient inward velocity the ring current would be reactivated and the resulting magnetic field would be used to reverse the stations' fall. This would "squeeze" the star, propelling stellar atmosphere through the polar magnetic nozzles. The ring current would be shut down again before the ring stations achieved enough outward velocity to throw them too far away from the star, and the star's gravity would be allowed to pull them back inward to repeat the cycle. A single set of ring stations would result in a very intermittent flow. It is possible to smooth this flow out by using multiple sets of ring stations, with each set operating in a different stage of the Huff-n-Puff cycle at any given moment so that there is always one ring "squeezing". This would also smooth out the power requirements of the system over time.

Centrifugal acceleration

The two magnetic nozzles would then be located on the star's equator. To increase the rate of outflow through these two equatorial jets, the ring system would be rotated around the star at a rate significantly faster than the star's natural rotation. This would cause the stellar atmosphere swept up by the magnetic field to be flung outward. This method suffers from a number of significant complications compared to the others. Rotating the ring in this manner would require the ring stations to use powerful rocket thrust, requiring both large rocket systems and a large amount of reaction mass.

Deathsinger

This method is a bit more speculative than the others. Science-fiction author Alastair Reynolds proposed to use a gravity laser (Gwaser, Gaser, Graser, or Glaser) to "sing" a hole down to the core of a star. This would create a beam of stellar material powered by the internal pressure of the star, which would slowly deplete the star. In the novel Redemption Ark this happens on a timeline of a few years. This might be the option that would fit your purposes best.

• Thank you for several great answers! I will definitely be using the colonial fleet idea. I'm seeing at least three distinct stories emerging from this world-building effort and the third will involve the return of a fleet which was launched as a backup plan to the mainline story of hiding the sun. Thanks for introducing me to Star Lifting. There is a place for that idea in here somewhere but I don't know exactly where yet. In every way, this was a really great set of responses! Thanks! +1 – Henry Taylor Jul 22 at 13:50

Forget the Sun. Flee the solar system

If you add more mass to Jupiter, you could potentially create a second star. Binary star systems create unstable orbits in the planets that orbit them and will often eject planets from the system into deep space as rogue planets.

This is making the assumption you have enough time, but trying to put out the sun isn't going to be quick and if you remove too much mass it could explode.

Personally I'd have gone with the Dyson sphere and the people on Earth are the ones that refused to leave and are now stuck in the dark.

• There's no magic threshold in physics that suddenly makes a system into a binary system that rapidly ejects other planetary bodies. Jupiter already is massive enough that it could eject Earth, but it is vanishingly unlikely. Even if you could double that chance by adding some mass (and where would you get it?), that chance would still remain too low. – MSalters Jul 22 at 10:01
• I considered turning Earth into a rogue but figured that I had enough challenges to my stories believability without messing with orbits. I am very close to going with a dyson sphere of a sort. A comparatively small one which is not habitable but does server to capture most of the suns energy, venting just enough away from the approaching swarm so that the sphere doesn't accumulate heat and melt. Thanks Again! +1 – Henry Taylor Jul 22 at 13:37
• @PeterCordes A rouge dwarf? – CJ Dennis Jul 23 at 2:56
• @CJDennis: oh, I didn't get your Red Dwarf joke until after I deleted my comment about the typo that's since been fixed. Yes. :P Except this time all of humanity is cast adrift from the solar system, not just Rimmer and Lister. – Peter Cordes Jul 23 at 3:09

A solution requiring only one unknown technology: Precision gravity control (think tractor beam) on a very large scale.

Surround the sun with stations whose job is to pick up basically the whole mass of the sun. You will need many, many stations as the material has to be separated so it will cool.

Note that so long as this whole operation takes place within the orbit of Mercury the effects on the planets will be trivial.

Once you have all the star-stuff separated and cooled you gently reassemble the sun. The material must be carefully lowered to the surface, not allowed to fall. Since it's far below fusion temperature the star doesn't relight, once you have put everything back together the result is a very unusual black dwarf.

If the threat was intelligent they would immediately realize something was up but you're talking about insects. They're not going to realize no black dwarf should yet exist, nor are they going to realize that a black dwarf shouldn't be mostly hydrogen.

Once the threat is passed you pick the material back up but this time you let it fall back down, the gravitational heating will reignite the star. Ensure you have picked up enough mass that the core is no longer degenerate before you allow ignition, fusion in degenerate matter does not regulate itself properly and the result would be cataclysmic.

Note that this process requires more energy that a K-2 civilization has access to!

• Thanks! I like the visuals of the K-2 Messenger's society attempting this in desperation then while coming up short on the energy needed, have the insects attack. If the sun sections were dropped during the panic, the star might nova, taking out the colony worlds that were trying it. If the insects somehow survive the nova and continue approaching, that might be the moment when the Messenger's society decides that hiding is the only option. Thanks for giving me even more back story! You can never have too much of that! +1 – Henry Taylor Jul 22 at 14:05
• @HenryTaylor Nova? When a white dwarf initiates carbon burning you get a supernova. Here you have mostly hydrogen, though, which yields 12x the energy per gram. See why I said "cataclysmic"? – Loren Pechtel Jul 22 at 16:39
• So even at their most distant colony, such an event would turn into a bigger problem than the insects. Got it. Thanks for helping me understand the scale. – Henry Taylor Jul 22 at 16:50

Push the Earth into a very highly eccentric orbit (maybe even push it into a high inclination as well to make it even harder to find), such that when the swarm arrives the Earth is in the Oort cloud. Then hope the swarm doesn't notice it. Eventually the Earth will return to the inner solar system on its own where you can then push it back into a circular orbit, but in the mean time it will get very cold and dark on Earth at that distance.

• Interesting new angle on addressing the problem. If the insects instinctively approach a solar system on the plane of its planetary rotations and if it relies on the swarm's size to catch the vast majority of its food (planets) which would usually be found on that plane, then a planet in high inclination might escape as long as the swarm passes before the planet returns to cross its original plan. Not bad at all. +1 – Henry Taylor Jul 22 at 14:15

Create a stranglet and drop it in to the sun, it will convert the whole thing into a quark star (https://en.m.wikipedia.org/wiki/Quark_star), which will also halt all fusion, or any other currently understood reactions. It would still be quite hot so you would have to deal with that somehow, but it’s a start. Downside, you can’t undo that via any process we could even imagine from current physics.

We don’t really know much about the properties of what you would end up with, so you would have to come up with your own physics here and there. It would be easy to claim that quark matter doesn’t emit black body radiation so it would still be highly energetic but also entirely dark.

• Thanks for the amazing wiki link. That is all brand new to me and will undoubtedly influence the story. Perhaps as something the Messenger's civilization tried on one of their colony worlds prior to vivisecting the home star as described in one of the other answers. I can imagine that initiating a process with an unpredictable result on such a large scale is a very desperate act. Maybe the colony closest to the approaching swarm tried it because they didn't have time for anything else. The resulting quark star might not have behaved as they hoped it would. Very Good Stuff! +1 – Henry Taylor Jul 22 at 13:31

If you have a means to divert the light of the sun to specific locations, you can use a network of dyson spheres (or regular polyhedrons, e.g. icosahedrons) containing artificial black holes to absorb the energy.

Around the black hole you can install "filters" which use part of the gravitational energy of the incoming mass and energy to maintain the structure, to balance the black hole inside of it and for propulsion.

Later on you would want technologies to speed up the dissipation of the black holes - especially as an emergency hatch. If the suggestion that all energy of a black hole is encoded on its surface is correct, it would seem likely that sending very small but precisely programmed packets of energy could be used to control the kind and amount of Hawking radiation emitted.

• Diverting the light seems to be an emerging trend among the answers and I'm beginning to like the consequences in terms of what it offers to the plots of later stories. I really like the idea of controlling the rate of black hole evaporation. That is exactly the kind of knowledge that I want my characters to find in the encyclopedia. I will need to research it deeply if I hope to be able to describe your idea to readers. Thanks! +1 – Henry Taylor Jul 22 at 13:11
• @HenryTaylor if you need inspiration for the black hole tech in your book, check out the Tree of Life (10 Sefirot) and Metatron's Cube. Or for a profane source, this YouTube video: youtube.com/watch?v=XTIe114FFyM – Willem Jul 28 at 1:02
• @HenryTaylor According to this article throwing "negative energy" (and perhaps antimatter? or particles with negative mass generated by particle accelerators?) into black holes would be the way to speed up the dissipation of black holes: vox.com/science-and-health/2018/3/14/17119320/… – Willem Jul 28 at 12:44

Honestly if your just concern about the heat and light from our sun it shouldn't be a huge problem.

Today we have a material called vanta black which is the blackest black ever. So if your encyclopedia has an even blacker black you can use that to make a blanket or wall to surround the sun. It can easily be disassemble afterwards.

Now the heat issue, the heat from the sun really only makes it to Mars at best. That is the outer edge of the habitable zone. All the other planets are cold dead rocks or balls of gas, so that shouldn't even be an issue.

If the bad guys get that close to our solar system to feel the heat they will see through almost any deception.

2. Using a wormhole to swap the sun for an appropriately sized blackhole. (Matching our suns gravity as exactly as possible.) Downside lack of solar winds will have an unpredictable effect. Powering the wormhole with said blackhole should make getting the power necessary an easy task.

As long as they can't detect the solar winds it shouldn't be too hard.

You might be able to shift the light out of there visible spectrum.

• I like the idea of a cloaking field. Some field effect beyond our current understanding which warps all of the sunlight around to shine away from the bugs current location. Thanks! +1 – Henry Taylor Jul 22 at 18:21
• @HenryTaylor Actually I just had another brilliant thought. We don't need to darken the sun at all. We just need to deploy a filter which shift the light of our sun, out beyond Mars, into a spectrum they can't see. We can't see every spectrum of light so neither can they. – cybernard Jul 22 at 19:33

# Matrioska Shield

If you build a Dyson sphere around the Sun, what you get is a hot shell that reradiates in the near infrared. So you build a second shell a few centimeters out, which will reradiate half of the energy. And then a third shell. In the end, provided there is nonconducting vacuum between the shells, you can radiate as little as you want.

# but it won't be enough

because the Sun has already radiated lots of energy away, and if the swarm is at (say) 200 years out and is approaching at one tenth of the speed of light, they'll see the Sun as it was 20 years before. If they have good memories, and set out towards the Sun a long time ago, the Sun's disappearance would mean nothing. They will still come.

# ...or not?

Blacking out the Sun is only part of the plan. The obvious thing that anyone would have attempted (and the Galactics surely did) would have been to investigate the swarm, using heavily defended probes (probes cooled to next to absolute zero, or equipped with plasma sheaths fit to vaporize anything, or very precise, ultrafast captive needle point defenses and so on. Probes floating inside a liquid bubble of carboranes. And so on).

So they discovered another very likely thing: that the insects actually sleep away their travel, with one swarm "aiming" its child swarm towards a likely star, and the "child" drifting for millennia until the heat of the target star thaws the drones, the Queen and the eggs for the cycle to repeat itself.

The plan is therefore to light up the path of the incoming swarm using the Matrioska reflectors, to intermittently revive as many drones as possible, as far away as possible, getting them to waste precious energy. When they come closer, the heat ray will be so intense as to do actual damage to the insects, that they'll have to repair. Then it will vanish, forcing them to hibernate again to save precious resources (and hibernation requires more energy). And when they're frozen again, the cycle will repeat.

Long before the tired, depleted swarm reaches the Kuiper belt, the Sun will have been completely shielded, its heat locked in or redirected far away from the swarm. Statite shields of the stablest materials available, or smaller Dyson spheres, will both supply artificial sunlight to the planets and/or deflect the incoming swarm safely away. Again, munching through hardened ice XI requires horrendous quantities of energy, gives the insects no sustenance whatsoever, and the little that will get melted will rob them of still more thermal energy.

The whole time, humanity will have to hide in darkness, looking worriedly at the black statite disk that blots out the stars.

• Thank you for the idea that the swarm sleeps in transit and the related idea of spawning unhatched child swarms. I really enjoy answers which start with the underlying premise of the question but then build upon the question's universe beyond just answer it specifically. I try to do that with my answers and I am happy when I find other members doing the same. Your war of attrition against the bugs is great stuff and may go into a later story in the series. I want the early books to be use the insect threat and impending danger as a back drop. – Henry Taylor Jul 22 at 21:21
• ...exploring the noir potential of the darkened, fear-filled world. Later, as the story evolves, I can have spin off novels which explore the more sci-fi aspects such as the returning fleet of generation ships which were launched as a plan B, and your reflector-armed planetary defense forces. I have gotten a lot more great stuff out of this question than I ever expected. Thanks! +1 – Henry Taylor Jul 22 at 21:25
• The Matrioska Shield won't work: All energy that you cannot convert to storeable forms of energy (like oil and coal) will be radiated away from the Dyson sphere eventually. If you add another layer of insulation, all you achieve is raising the temperature of the inner layers so far that the outer layer radiates the same amount of energy away in the long run. The only way to make a cooler Dyson sphere, is to build a bigger Dyson sphere that spreads the emissions to a larger surface. – cmaster Jul 22 at 22:02
• With regards to the Matrioska Shield still radiating energy... Turn it into a Matrioshka Brain. If the energy is used, even if just for factoring primes and brute forcing 256 bit keys, then the outermost layer could be colder than the cosmic microwave background. – Ghedipunk Jul 23 at 18:45

Convert it into a Black-hole: If you had unlimited resources/energy, and "near magical" tech, then you might be able to manipulate gravity, making a black-hole out of the star, while not affecting it's gravitational field so you don't throw orbiting bodies off into space. The lack of light might be a new problem though, but ideas for theoretical technology that could utilize black-holes for energy production exist, which could allow for artificial lighting...albeit on a massive scale.

• I like the idea, but black holes have a rather bad reputation. They are usually seen as bad guys, not solar system saving solutions. Sort of like that inversion of reader expectations, but I can already see the "out of the frying pan into the fire" references.from critics and fans. Might make this another of the things tried by a colony of the Messenger's civilization. An earlier experiment which was abandoned for some less severe solution. Thanks! +1 – Henry Taylor Jul 22 at 13:42
• @Henry Taylor Sooo...why not use your book to redefine the perceived nature of blackholes, and show they can be the "good guy"? It is your novel afterall, and anything goes if you make it work. Like I said, people like Isaac Arthur have speculated on ways to use blackholes for useful purposes. They only did that because they refused to look at blackholes as solely a destructive force, and sought their "charms" as well. As another example, look at how blackholes are treated in Interstellar: they do cause harm, but they also lead to the human race being saved. – SmugDoodleBug Jul 22 at 19:31
• @Henry Taylor I'm not actually arguing that you should use my solution though. My real point is this: You may want to avoid conforming to the expectations of your readers. Especially those reading scifi. I personally read scifi because I love exploration, and the sense of wonder posed by the unknown and fantastical. Whatever option you choose, it SHOULD try to subvert the expectations of your readers, so they actually feel like they themselves are exploring something foreign and new. – SmugDoodleBug Jul 22 at 19:32
• @JRFerrell +1, Almost answered this until I saw you did, but you may as well manufacture a small one by compressing mass and fly / drop it into the sun like a solar probe. "Black hole" is an obligatory answer on this site, you might get more rep if you give it an obvious heading. – theREALyumdub Jul 22 at 21:04
• Failed supernova "When the star can no longer support itself, the core collapses completely, forming a stellar-mass black hole, and consuming the nascent supernova without having the massive explosion. For a distant observer, the red supergiant star will seem to wink out of existence with little or no flare-up. The observed instances of these disappearances seem to involve supergiant stars with masses above 17 solar masses." Maybe with near magical science you could do this with 1 solar mass. – Keith McClary Jul 22 at 23:42

I am hoping that you can make it more explicit what the insects do — do they come and destroy the star and move on, or do they come because of the star and ravage the planets of some resource, or do they just block the light from the star too much… ?

I am taking it that the insects are attracted by light, but destroy, not the Sun but the Earth… and then move on. If they actually destroy the Sun, this is all inapplicable. (Equally, it might simply not fit what you want.) (Or perhaps you could have everyone working on making a star that will never go out, to keep these insects busy?) (Or, conversely, you could tweak our own Sun to last all the way through the periodic table, to buy others time… maybe. That is assuming that the insects do not actually attack the Earth, as such.)
On that theme — if the insects come because of the system’s star, but “attack” the planets, and then leave later to destroy some other solar system, there is presumably some resource that they consume to exhaustion?
Another take is to shield the Earth as described, and have the insects arrive and destroy the Sun, and then have the problem of starting it up again.

My physics is not adequate for this, but I thought the idea might be worth mentioning. As the scientist says in “Back to the Future”, you’re not thinking 4-dimensionally — or, in this case, 3-dimensionally.

I know there are problems with orbits changing and what-have-you, but…

How about moving the Earth perpendicularly to the plane of the solar system? Other people are far better qualified to flesh out the details (or point out that it is quite unworkable), but here is my starting sketch.

You will need a replacement planet where the Earth was, to keep the solar system working as it should. (Another possibility is to leave the Earth as it is, and set up somewhere else, and come back later and fix it back up again, but that sounds pretty boring compared with all this stuff about Dyson spheres and all that.) You will also need something for the Earth to revolve around — perhaps the same mass as the Sun and the same distance, but this is free to change. Conversely, with technology at such a high level, you can probably do without that.

I was originally thinking of having another body on the other side of the solar system (perpendicularly), to keep things balanced. (I had some fancy idea about segmented rings that rotate in the same or opposite directions, and bounce up and down through the plane of the solar system, but (a) there are problems with the gravitational effects within the solar system during a pass and (b) (i) either this leaves the Earth behind or (ii) the Earth has to follow, which has problems with orbit mechanics.)

This separate (part) solar system would presumably be set up (once it was already far away) to move gradually away from the actual solar system, reach a peak height and start falling down again… throughout the entire time the insects were there.

The other alternative implementation of the idea is to redirect the Sun’s energy to a similar point.

Anyway, I am distracted with the suspicion that you want the Sun darkened, either because the insects will destroy the Sun or just because that is your existing planning. I just wanted to mention the 3rd dimension.

—————

Not sure where to put this. (I am guessing that it belongs in Discussion, but I do not know “where” that is.) [Feel free to move it there, but leave me a link.]

Pardon me if I take the liberty… . [You did say that the insects were “planet-devouring”, but I am taking it that your thinking is not settled yet.]

It seems to me that you have a fundamental choice to make — do the insects do anything to the Earth directly [or indirectly — see below * ] or not (and if so what and why). Maybe it is merely that they land on it in large numbers (noting the day/night cycle). [Or possibly the survivors do not know yet… or possibly the insects’ behaviour is not yet properly understood.]

If they do not, then the Earthians do not need a shield for the Earth; they just have to survive the event… which, in this case, would be inconsequential unless the insects significantly interfere with or destroy the Sun —— they might • blot out the Sun for a time and then move on (with or without some damage of it) • blot out the Sun, and later destroy it, • destroy it immediately (which would be rather odd), or • not be a problem until they destroy the Sun.)

Further, in that case, shielding the Sun before the event might be no less difficult than repairing it afterwards… although there is the issue of them possibly coming back.

Offhand, it looks to me as though you do need them to “devour planets”. This works in the immediate sense; we build a Dyson sphere (or some other fancy solution such as my original answer) or we die; their arrival must be prevented. (It is unlikely that any sort of military shielding of the Earth would work.)

Note that, given this, it does not really matter whether or not they destroy the Sun; presumably, they leave when the planets are consumed.

I am thinking, though, that, in terms of plausible life cycle, a swarm that comes and eats vast amounts of dirt (and possibly gas), reproduces (possibly destroys the star) and moves on is a bit B-grade movie. Maybe it is just how I am putting it, but I am thinking perhaps something more subtle… .

The core idea is that these things are phototropic — they go towards the light. If they do not consume the planets, then arguably the only reason they might leave is if they do indeed destroy the Sun… which is not especially “subtle”. Conversely, I am thinking that this — i.e. not eating the Earth — might work better for building a history around.

So… they do interfere with the Earth in some way, but not massive military-like destruction.

{Asterisk}[footnote/reference]
I had a couple of ideas around interfering with orbital mechanics, but I do not think it would work [insufficient mass], so I have deleted it. I thought the rest was okay, so I am still posting this.

Independently of that… stopping the Sun from shining would involve some dramatic change, but, even given that, significantly changing its mass would be an even bigger change ( unless the insects increase vastly in number when procreating, taking the differential mass from the Sun ).

[Passing thought: would a Dyson sphere interfere with orbital stability?]

If the insects do do something more subtle that would ultimately ruin the Earth, then the Earthians still do have to prevent them from coming. [I am assuming that their technology level is so high that restarting the Sun is on the cards.] This also has the attraction of involving a slow death (if they do end up coming).

…Except that, given the high level of technology, it might be feasible to have the insects come, and do their damage, and leave… and then set about repairing everything. [Again, this might work better for a long history.]

Conversely to all that… if the level of available technology is so high, arguably just about anything is not going to be a problem… and conversely again: just because we know how to (e.g.) move the Earth does not mean that it is trivial to do it, and similarly for any engineering that requires vast amounts of any resource.

Similarly for (eg) building a Dyson sphere; even if it is trivially easy in terms of knowledge, there is still the issue of physically getting the material and building the thing.

There is also the possibility of more subtle measures against their life cycle — possibly something discovered accidentally, such as that they are attracted to (military) electromagnetic shields.

• Your answer has raised some interesting issues. I had originally though of the insects as planet eaters but I want them driven by instinctive phototropism, so even after they have eaten a solar system, it the sun is still shining, it will be brighter than even the closest star. They would therefore just buzz around the now childless sun until they starve, leaving no great threat for the universe. I think I will answer this issue by making their procreation process somehow consume the sun. That would leave darkness behind an every growing swarm. Thanks for the help! +1 – Henry Taylor Jul 22 at 18:17
• make it more explicit what the insects do. OP skipped the fun part: deciding the objective. Instead they handed us an entrapping backstory with a simple question: how to entirely block out the sun. That's not the objective; survival is the objective. For that I need intel... all of it. +1 – Mazura Jul 23 at 0:25
• @OP: I am thinking you might have to flesh out the “insect” detail a bit. Do they travel at sub-light speed, or teleport…? (…And how?) Is there anything interesting about how they spot the next star? Do they prefer some types? How big are they? Maybe they hang around the now dead star for 6 months during the procreation period. What do they actually do to the planets (and why)? (Perhaps they interfere with planetary orbits… even if just by being there.) When they are about to leave, is their path predictable? (Do they notice radio or gravitic communication? Do you have ansibles?) – Carsogrin Jul 23 at 5:38

I think the simplest solution from a narrative standpoint would be to spray some sort of "pixie dust" that neutralizes the sun's gravity. It is the force of gravity that drives the nuclear fusion that powers the sun. The bigger the star, the higher the force of gravity, the faster it burns. Therefore, you just need some way to partially neutralize gravity. Not fully. If you do that it will dissipate.

Not sure how long it would take for the sun to shed its residual heat once fusion stopped, but if you have pixie dust to turn off gravity, you can have pixie dust "B" to accelerate heat loss, or just absorb it.

You then need to explain why the planets don't go spinning off into space now that the sun's gravity is gone, or just less.

Oooh! No, you just split the sun into a dozen (three dozen?) little "super Jupiter". Brown dwarfs that are a hundred times bigger than the planet Jupiter, but small enough that they cannot produce nuclear fusion. They stay in the same place, orbiting around one another. The gravity would be the same just more spread out.

• Unobtainium is a standard fall back for questions on this forum. Few problems can't be solved by a little pixie dust and the judicial application of massless metal. Two different mythical materials in a single answer is something new however. Thanks for that. A couple of the earlier answers have also touched upon the idea of splitting up the sun to sub-critical mass. I loved that approach when the question was new but now that I have fielded many answers, I'm leaning towards obscuring rather than destroying our light-giver. Thanks for the Help! +1 – Henry Taylor Jul 24 at 20:03

I love your premise, but maybe it would be easier to make earth look uninhabited by putting some surface above the whole thing or just all going underground. So it looks completely void, and the bugs pass by. You in effect snuffed out the sun for earth, but really the light is still shining on an outer shell. Oh, and bonus, everything you talked about as far as your plot would then make sense. Everyone is living in the dark basically for hundreds of years. You could also put into your plot or a book about people trying for years to figure out a way to put out the sun, and have that be the focus that people fight over until some part of civilization realizes that will never work and they just go underground. And the sun-eaters die!

• Very nice! There is a certain cultural relevance to having the problem solvers and the problem deniers arguing until it is too late and finally only a few get to choose a severely diminished existence over annihilation as the insects arrive. That works in a lot of ways but leaves our solar system still infested. I like it a lot for the first book but don't like where it leaves my characters going forward. I will have to keep thinking about it. Thanks! +1 – Henry Taylor Jul 22 at 22:09

Your first problem is one of scale. Thinking about a K2 civilization's technology is like asking the artists who painted the cave paintings in France to speculate about smartphones. But moreso.

A K1 civilization solution is more imaginable. You'd wrap the Sun in a blanket. That blanket would be extremely hot, but at a modest distance it would be hot in the infrared, not the visual spectrum. The energy it puts out would be the same as our Sun, as there is no practical way to store the Sun's energy output; you'll radiate basically all of it as black body heat. That will look a lot different than a star; dumb swarms may not recognize it as a star.

It is possible to emit most of the energy in a direction away from the swarm through heroic effort. Now, space is 3d, and the swarm isn't going to be on interplanetary scales until extremely close; so there will be plenty of directions to send the energy until the swarm gets really close.

Restricting what directions you are emitting is going to be hard, the more you emit the easier it will be.

If we assume this is sufficient to fool the swarm (the swarm might be relatively unintelligent), power is the least of your worries. The system capturing the sun's energy has something like 13 orders of magnitude more power than we use in our civilization, and 10 orders of magnitude more power than would be required to literally hang solar lamps over the entire planet and shine with solar-level light 50% of the time (simulating the sun).

That is, 10000000000x more energy than you need to do that. Give or take a 0.

For a fraction of the work required to build a Dyson sphere around a Sun, you can build a firmament shell around the Earth. Add in a tight-beam energy transfer system that powers the shell, and the Earth could have lights hanging from firmament that simulate daylight and night time and even stars.

The exterior of this shell would emit light in the infrared. The material it is made out of would be some kind of unobtanium, possibly forged using the energy of the sun itself. My personal favorite unobtanium nowadays is post-trans uranic elements (PTUs); elements from a hypothetical island of stability far beyond the end of our periodic table that cannot be reached even by neutron-star/neutron-star collisions, but could be reached by a K1 civilization with K2 civilization help. To avoid explaining why neutron-star neutron-star collisions (way outside of K1 energy scales; that is where most of the Universe's gold come from, among other elements) don't produce PTUs, you can require "seed" PTUs to build PTUs using K1 civilization energy scales. The initial PTU produced by the K2 civilization may even have been gifted or left over by a K3 civilization.

At these energy scales, living on Earth is an affectation; sort of a wildlife reserve. It would be easier to build planet-scale spaceships or space stations than protect Earth in this way, because we are literally building a space station that encloses the Earth.

But in the short term, that might be the least traumatic way the K2 civilization probe can protect civilizations. Not all pre-K1 civilizations will be able to scale up to K1.

The K2 civilization probe drops off some Von Neumann worker bots who (a) start encasing the sun (dismantling planets and mining the sun to do so), (b) build the PTU forge, (c) start encasing the intact planets in firmaments. As part of this process, beanstalks are lowered from the firmament. Living spaces in the firmament are provided, as well as launch beanstalks.

The conservator civilization's bots encase even relatively small planetoids, like the moons of mars, Luna, Ceres, Charon, and the Kuiper Belt planets, in firmaments. There are also firmament-habitats hanging off the sun's shield.

Much of humanity stays home; some leave to colonize the system. Some even turn asteroid-firmaments into generation ships and flee the solar system, carrying along with them some Von Neumann conservator probes.

• Excellent answer! You are right about the scale and about encapsulating earth being wasteful compared to building ships/stations. I also appreciate the reference to Von Neuman devices. I have heard of them before but hadn't really considered them for this project. Thanks Again! +1 – Henry Taylor Jul 23 at 16:41

If you can synthesize food without plants, then I imagine you're dealing in some kind of star-trek level replicator, which performs nuclear transmutation on "generic" deconstructed matter.

If that's the case, and if you're ok with inserting some Kurt Vonnegut-esque handwavium, then your problem is solved by injecting a seed of [some equivalent to Vonnegut's Ice 9] into the sun. Rather than freezing water, but by similar handwavy-principles, this seed triggers an alternative radioactive decay chain in the sun, enabling you to skip a few steps in the typical solar radioactive decay chain, and in short time leaving you with a large hunk of hot lead or bismuth in place of the sun. However, rather than losing tons of energy by means of accelerated decay, the sun simply utilizes its existing energy for a harmless endothermic transmutation into cold shining metal.

Then, to reverse the process, you bombard the sun with specialized, energized particles of a similar handwavy nature, adding unstable particulate to the metals and preparing them for transmutation back into a hot sun. The process takes significantly longer, and it would take more energy than what is available on earth. So, cold metals on the sun are harvested, deconstructed, transmuted, reconstituted, and reacted in orbiting space stations, so as to use them as fuel to generate the high-energy particulate used in the process of re-igniting the rest of the sun.

For your reference, here's the section in which Ice 9 is explained, in Chapter 20 of Cat's Cradle (excuse the weird text; I got this from archive.org):

"There are several ways," Dr. Breed said to me, "in which certain liquids can crystal 1 i ze--can f reeze--several ways in which their atoms can stack and lock in an orderly, rigid way."

That old man with spotted hands invited me to think of the several ways in which cannonballs might be stacked on a courthouse lawn, of the several ways in which oranges might be packed into a crate.

"So it is with atoms in crystals, too; and two different crystals of the same substance can have quite different physical properties."

He told me about a factory that had been growing big crystals of ethylene diamine tartrate. The crystals were useful in certain manufacturing operations, he said. But one day the factory discovered that the crystals it was growing no longer had the properties desired. The atoms had begun to stack and lock--to freeze--in different fashion. The liquid that was crystallizing hadn't changed, but the crystals it was forming were, as far as industrial applications went, pure junk.

How this had come about was a mystery. The theoretical villain, however, was what Dr. Breed called "a seed." He meant by that a tiny grain of the undesired crystal pattern. The seed, which had come from God-only-knows-where , taught the atoms the novel way in which to stack and lock, to crystallize, to freeze .

"Now think about cannonballs on a courthouse lawn or about oranges in a crate again," he suggested. And he helped me to see that the pattern of the bottom layers of cannonballs or of oranges determined how each subsequent layer would stack and lock. "The bottom layer is the seed of how every cannonball or every orange that comes after is going to behave, even to an infinite number of cannonballs or oranges."

"Now suppose," chortled Dr. Breed, enjoying himself, "that there were many possible .ways in which water could crystallize, could freeze. Suppose that the sort of ice we skate upon and put into highball s--what we might call i ce-one--i s only one of several types of ice. Suppose water always froze as ice-one on Earth because it had never had a seed to teach it how to form ice-two, ice-three, ice-four . . . ? And suppose," he rapped on his desk with his old hand again, "that there were one form, which we will call i ce-ni ne--a crystal as hard as this desk--with a melting point of, let us say, one-hundred degrees Fahrenheit, or, better still, a melting point of one-hundred-and-thi rty degrees . "

• +1 for the Vonnegut reference. I am going for something more feasible than matter replication and transporters. My thoughts on food generation are closer to chemistry only slightly above our current level, applying the abundant energy to reconstitute digestible proteins from waste products. Not very appetizing but functional. – Henry Taylor Jul 23 at 22:12

Your insect swarm of doom (ISOD) is like a heat-seeking missile, guiding itself toward the light of the sun. Fighter jets have tried shielding themselves against guided missiles, but it's an extremely hard thing to do effectively. Instead, they frequently deploy flares as a countermeasure. The flares produce an intense heat signature that resembles that of the jet's engine. The jet releases the flare and abruptly changes course, and the missile follows the flare instead of the jet.

Hiding the sun is impractical due to the sheer amount of energy you'd have to somehow absorb. Instead, build a space-scale flare, an artificial star the size of a small moon. Fling it out of the solar system towards the ISOD. It's far smaller than the sun but since it's significantly closer, its light will be far more intense and the glare will prevent the sun from being seen (like trying to see the stars during the daytime). The ISOD will follow the flare away from any inhabited planets. The trick will be in designing the trajectory: it has to be noticed by the ISOD while it's in the outer parts of the solar system, and when the ISOD catches up to it (or when it burns out) the ISOD needs to be closer to some other star than it is to Sol.

The downside of this plan is that your artificial star is way too small to be built like an actual star. It will have to be more like a slow-burning ball of fuel, generating energy through more traditional chemical means than by nuclear fusion. The energy emitted will mimic the output of a star closely enough to fool the ISOD, but will unfortunately also generate massive amounts of exotic, high-energy particles that don't interact well with organic matter. There's no way to ignite this thing and send it on its way without bombarding Earth with enough radiation to cause a mass extinction event. Therefore, your scientists have constructed large-scale shielding systems to block the deadly radiation. This shields also block most of the light and heat from the sun in the areas they cover, so the Earth becomes a patchwork of cold, dark protected areas and regions scoured of life by radiation.

• I like the flare technique. If I get as far as the sci fi sequel which illuminates the direct combat with the insects I will definitely use this. I'm beginning to see a very nice theme emerging for that story. Humanity fighting with desperation because they have no choice while the K2 civilization hides. Thanks for the help! +1 – Henry Taylor Jul 24 at 4:02