Megastructure Death

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This Episode is brought to you by Brilliant.   To all good and great things there comes  an end, but it can be a spectacular end,   when it at last comes, and that  end can be a long time off.   Tomorrow, Sep 17 2021, we will celebrate  the 7th Anniversary of SFIA's first episode,   “Megastructures in Science and  Science Fiction”. So this seems  

like a great time to return to what  has become one of our favorite topics.   For those new to the channel, welcome. And while  I realize the episode title sounds like the name   of a heavy metal band, the megastructures  we discuss on this show are, often as not,   entire artificial worlds with as much or far more  habitable space than the surface of a planet.   The end of Earth is a popular topic of discussion  in science and philosophy, and the topic of a   recent episode on this show. But in science  fiction it’s also common to contemplate the   end of alien worlds far from Earth. So given  that it’s likely most of future humanity will  

live their lives on entirely artificial worlds --  immense megastructure habitats -- it is also quite   likely the deaths of these worlds will be of far  greater interest to future civilizations than will   dying planets. But I suppose contemplating  either of their endings would also be an   appropriate theme for a heavy metal album. So our focus today is going to be examining the   ways these might die, and their stages in  life, which will vary a lot depending on   the megastructure type. Their end might also come  about deliberately, in the way we might demolish   a building, or accidentally, in the way a design  flaw or unexpected natural event might contribute   to their end. We have two classic science  fiction examples we will look at for those,   with lots of Spoilers to follow, the O’Neill  Cylinder in the 90’s classic sci-fi series   Babylon 5, and the titular Ringworld  of Larry’s Niven Ringworld novels.   Now the saying goes that all good things come  to an end, but considering the sheer scope of   even the smallest megastructures, paralleling or  exceeding the largest modern cities, it obviously   is beneficial to build with durability in mind.  However we have two caveats worth noting upfront.  

First, the smallest megastructures are city  sized and even those in the Continent-Class   which we deemed more medium in scope  might be thought of as more nation-sized.   Cities and nations can certainly die but  in general their centers of population and   activity migrate. Many a long-lived river-city  has moved around as the river shifted, at the same   time sprawling up or down its banks, with areas  changing from farmland to affluent neighborhoods   to squalid slums and back again, as the city  slowly creeps along the river or the coast.   With that in mind, a megastructure might be in  a constant state of repair with whole regions   undergoing massive refit at any given time. Like  Thesseus’s Ship, they may still be called the   same place or thing even after every bit of the  hull has been replaced a hundred times over.  

Same, one might think of a city as being  composed of many structures akin to living   cells in our bodies, and those can repair  and replace themselves rather automatically.   One tech any megastructure-making civilization  would want badly is regenerative buildings   and structures, those able to heal or grow  themselves, or automated repair bots perhaps.   Such structures might be able to last  indefinitely, constantly recycling their material   powered by nuclear fusion, where a single  kilogram of fuel might run them for a year   while they had billions of tons of it on hand  to last them for eons. Indeed those powered by   matter to energy conversion or black holes might  outlive the stars themselves, and die by slowly   cannibalizing themselves, contracting in size  by tiny amounts, the snake eating its own tail   but taking a hundred trillions year to do so. Indeed we often tend to assume that a civilization  

that builds giant things in space has  already mastered such technologies as   automated repair and construction and cheap  energy, given the scope of the projects,   so that such structures might be thought of as  grown more than built. However it is worth noting   that a self-repairing system can still die, indeed  every known self-repairing system has a lifespan,   with the possible exceptions of some  stranger critters like Jellyfish, Lobster,   or Hydras. It is not too big a leap to imagine a  megastructure might get the equivalent of cancer,   or that some structure in it with auto-repair  systems might go off-kilter, though there’s no   guarantee an artificially designed repair  system would be prone to such faults.   There is also no guarantee we would get  such technology working or that if we did,   we would employ it for this purpose.  Self-repairing is also not the same as   reproducing, and the check on uncontrolled  replication of cells is telomere-triggered   apoptosis. A state of constant unchecked growth  is rarely a good thing for an organism either,  

or arguably the meta-organism that a city, nation,  or megastructure habitat might qualify as.   Now demolition at the end of life is easy enough  to understand. In Babylon 5 – spoilers – we are   shown the destruction of the Babylon 5 space  station repeatedly as vision of the future by   this or that telepath or seer or time traveler,  but in the end it occurs 25 years after its built   because its purpose has been served and nobody  wants to spend the funds to keep repairing it   so it gets a controlled and planned detonation  to prevent it becoming a navigational hazard,   along with a big ceremony. This happens to be one  of the most beautiful series finales in science   fiction history, titled “Sleeping in Light”.  It is my own personal favorite series finale,   and a rarity, as most shows’ last episode  are mediocre when not anticlimactic.  

Now it is an example of a major and unique  enterprise. It was basically the galaxy’s   UN headquarters and later its acting capital  for quite some time, along with a trade hub   as a result, much like the Citadel in Mass Effect.  Everyone in the galaxy knew where and what it was.   So one can see how economics would be secondary  both to keeping its repairs up and to eventually   deciding to decommission it too, rather than sell  it or let it just fall into scavenger hands.   We might do something similar to the International  Space Station sometime, but with better cause,   we have a lot of traffic in orbit and  would expect that to only grow with time,   so a controlled deorbit or detonation to blow  the debris down to burn up in the atmosphere   would seem likely and also cause for  commemoration. The Mir Space Station  

deorbit and burnup in early 2001 was a fairly big  deal in the news at the time, also the spring I   graduated from college in for those curious. It’s worth noting that it takes some skill to   detonate a large object so it doesn’t leave debris  incidentally, in practice you’re going to want to   shove it down into the atmosphere enough that  even debris moving up at high speed will still   fall down then detonate it. Such being the  case you would have to worry about that not   working as planned and dropping intact bits on the  populace below, potential megatons bits of scrap,   so I suspect the fate of a megastructure past  its prime would be disassembly not detonation.   Alternatively if we’re talking about some Space  Habitat, population 10,000, a minor rotating   space habitat built by SpacehabCorp, one of ten  thousand built by them to that specification then   it shouldn’t be a very big deal for all that it  would be to us. Same as the first skyscraper is   a big deal but then 997th is not, even if it's far  grander than the first was. Doubtless many people   would care about it, same as every town or village  has its own historic buildings and celebrations,   but it's not likely to be big news to the wider  world, and might be as minor a concern as some   modest and unremarkable home on the outskirts of  town falling into disrepair. It only interests  

the community because the Fire Marshall wants to  use it for practice or the police want it knocked   over to discourage vagrants, criminals,  or curious kids from hanging out there.   In the other direction, we often cite the US  Highway system as a candidate for a modern   megastructure, and with good reason as  it is enormous. Interstate Route 90 is   the longest part of that at just under  5000 kilometers or just over 3000 miles,   running from Boston, Massachusetts to Seattle  Washington and through many points in-between,   including my own backyard. Literally my backyard  since Sarah and I moved earlier this year,   but having lived in Northeast Ohio  nearly all my life it’s always had   a big footprint in my existence. It is the  road that all others lead to, so to speak,   and which millions of folks drive on for daily  commutes or cross-country road trips. I would  

not care to guess how many billions of dollars  of freight move down it every single day.   Nonetheless, I would have difficulty seeing much  fanfare or weeping if it was decommissioned in   favor of something new and better, not in the  way closing down a major monument might. Though   there are so many businesses for which it is their  revenue source, every gas station, restaurant, or   outlet or novelty store at an exit would obviously  have reason to miss it, and for some that might be   sentimental not just practical. That might be a  tiny fraction of our population but is still many   thousands, enough to populate many an ancient  kingdom, so it can’t be disregarded either.   So it is difficult to imagine any megastructure  going down from mere indifference by all,   just given the scale of them. We can imagine that  scenario and we looked at that in our Trash Worlds  

and Space Derelicts episode, and our Mega-Cities  episode for that matter. It could happen of   course. A trade port built for trade between  two stars might fall victim to new technologies   that let them be circumvented or even stellar  drift changing the path between those systems.   Such structures are not just immense  of scale in size, but also in time,   and may see the rise and fall of ten thousand  centuries before the warranty expires.   A civilization might be of such a scale that  their big defense outposts and border forts   had their own civilian populations and habitats  numbering in the millions which no longer had   resources coming in to support them after  a change in the diplomatic environment.  

And remember the scale involved, some giant  space gun designed for blasting interstellar   armadas between warring K2 Dyson Spheres, might be  a cannon so big it’s gravity actually allowed for   pressurised environments in the various cracks and  valleys of the barrel and magazine. I’m not really   sure what you would do with a cannon designed  for blowing up planets when the conflict it was   built for was over, but it’s not hard to imagine  a civilization arising on it and getting attached   to it, and that would be a weird civilization.  Forget a cultural mythos of your world being   on the back of a giant turtle, your world was  forged by the gods to kill worlds and you’re the   post-apocalyptic tribes who hundred-times  great grandparents used to maintain it.   However while we can imagine situations where  a megastructure might slowly grow more and more   neglected, it just seems less plausible than  how we see that with neighborhoods or homes   in modern times and history. A  house can fall into disrepair   when it need not have simply because its  owners died or had their fortunes turn   and no one felt like buying it or their kids  did not wish it and their neighbors were few and   by chance maybe the dozen folks who adjoined it  were indifferent to its slow submission to time.   But megastructures are just too big,  and even if they were not populated,   there’s a good chance they might actually have  an onboard AI of human or superhuman capacity,   possibly many, that regarded the structure or  components of it as their home or even body.  

Some things can be constantly repaired, others  really are cheaper to break down and replace,   and it varies by type and technology and  circumstances too, but we would rarely expect   a habitat megastructure to simply be shut down  and evacuated rather than repaired gradually as   a patchwork. Even major hull work that might  require you de-spin it so you could repair   stressed materials is probably easier done by just  wrapping new rotating sheath around the outside.   This might amusingly make for many layers of new  hull, oldest to youngest as you dug down from   inside it, potentially allowing its inhabitants to  mine those older and higher layers for materials.   That’s an interesting option given how often  civilizations are imagined to have decayed   to being techno-primitives because they had no  metals in the ground on such habitats. Sort of   a reverse archeology too, the top layers are the  old ones. Repairing hulls with new outer sheath   might avoid every needing to shut one down. On the other hand, one that took a ton of  

damage at once, especially from something like  an attack during a war, might be evacuated or   even had everyone in it die, and nobody wants or  particularly needs to repair it. A burned-out husk   of a megastructure is a dead thing and probably  tricky to repair like a burnt house. Neighborhoods   can matter too, people rarely are rushing to  fix up a house in a bad part of town, or in a   demilitarized zone or the border of two hostile  nations. Except for fortresses of course and in  

that same way, a border fortress is expensive to  maintain and serves little point if the borders   move. Traditionally you either repurpose it  or wait for the local population to do so by   slowly stealing the stone and bricks. Of course,  automated construction and repair also permits the   idea of automated demolition too, instead of  blowing stuff up you let the robots carefully   cannibalize or demolish it. Though it also might  have automated defenses, such as those robots,   that attacked anything on site when that damaged. These set the stage for why a Megastructure might   perish, and there are many other reasons but some  are probably not as plausible as we often assume.   For instance in the novel Ringworld, we find an  artificial world with a million times the living   area of Earth but which for some reason  has little to no remaining technology.  

Abandoned relics or worlds with once impressive  technology from bygone days is a common theme in   stories but not really very realistic. For  narrative purposes it allows the heroes to   explore it, and we discussed some more examples of  that in our recent Xenoarcheology episode, but it   would not make sense for a civilization to build  and people an artificial structure able to support   millions of times the population a planet can and  not expect some of them to go in for technology.   Now as a caveat, artificial worlds  often are assumed to be metal-poor,   with no large ore deposits, though the reasoning  for this is a touch debatable in some cases.   If you’ve got thick terrain on one to simulate  mountains and ravines, you might have done that   by just grinding up various asteroids and dumping  them down there, still rich in ore. Alternatively,   metal has no place to go, it doesn’t vaporize  by magic, so you can presumably recycle existing   material. And if you’re constantly spinning  new outer layers of protective sheath,   you can cannibalize the inner layers. In any event, Ringworld is an example  

of a megastructure built by a powerful and  advanced civilization that has disappeared   and whose technology is failing. While it seems  implausible that one that huge wouldn’t have   other new civilizations arise able to study  or fix the structure, the fact that it was   failing from neglect is certainly plausible. In Ringworld’s case, a ring spinning around a star   is not actually stable. It's common to describe  the Ringworld as a vast ring orbiting a star,  

about as wide in radius as Earth’s orbit of our  Sun is, lit by that Sun and relying on centrifugal   force to provide gravity. Except this is wrong,  it doesn’t orbit that star at all. Anything   orbiting anything else experiences microgravity  from that orbit. That’s how orbiting works,   you are in a constant state of free fall in regard  to that central body. The orbiting body can have   its own gravity or internal spin, like Earth does  or like an O’Neill Cylinder in Earth orbit would,   but that spin around the main object is not  an orbit if you’re not in microgravity from   it. Which means you are not actually stable.  The star pulls on the ring from each side  

but it’s subject to slow perturbation making it  drift off so that the ring might get roasted.   Now this matters for the Ringworld because  on reading it some folks saw that problem   and told the author and he added in stabilizing  engines in the sequel and getting them turned on   to save the Destabilizing Ringworld was a plot  point, and one would expect such engines to be   very sturdy and big. We often see things  orbiting Earth fall out of orbit and it   would be a concern for any megastructure  that gravity and time aren’t its friends.   Planetary orbits are not stable and eternal  things either, but they are a fairly natural   conglomeration and planetary decays around stars  are slow and can only happen when after millions   of years of formation, most of the unstable orbits  have decayed, merged, ejected and so on. So our  

existing planets in this solar system tend to  make us think these are unchanging, but they are   not. A megastructure could be built to be even  more resistant to time and perturbation than a   natural planet or moon but they need not be, and  that presumably takes a great deal of effort.   And realistically, when building big things  these days, we do not ask the architect   if his plans for maintenance included our  civilization going extinct or into a dark age.   The whole thing might rely on a few dozen  ten-cent washers that take about five minutes   to replace once a decade. If the factory making  them closes down, or is shut down by having a   mushroom cloud grow out of it as the civilization  falls into nuclear war, those washers might not be   getting replaced. Nonetheless I don’t think the  typical building inspector or investor would ask  

if you’ve checked to ensure your building is  able to survive a breakdown in supply chains,   unless it was for a survival bunker perhaps. On the other hand, let's not assume artificial   means fragile. A shellworld for instance can  seem an incredibly fragile place. It’s surface   is a thin layer of dirt, water, and rock sitting  on a firmament made of countless orbital rings,   containing either condensed gas below or a black  hole. Folks worry about what would happen if a  

hole got poked in it or the power went off. And  yet the typical planet is a thin layer of rocky   plates floating on a sea of superhot magma  surrounding a core of liquid metal, much of   which is highly radioactive uranium. Poke a hole  in that and you get a volcano, or much worse.   What happens when you blow a hole into a  Shellworld, or rotating habitats for that matter?   Well, we need to keep in mind that these are  artificial structures and usually built out of   super-strong materials. Now nukes beat matter  everytime, you should not expect to have any   material that can just shrug off an atomic  bomb except maybe those which operate on the   strong nuclear force for binding rather than  electromagnetic forces as mundane matter does,   like magmatter or stabilized neutronium, or  the Scrith from Ringworld that its built from.  

That Scrith was so tough it deformed when hit by  something like a dwarf planet to form an inverted   crater that looked like a volcano from the  inside, only far taller than any natural mountain,   and the air of the Ringworld slowly drained out  through it. We could imagine building habitats   so big that a collision just ripped a crater  that helped keep a lot of air and water inside,   but there are big limits on things like that  and nothing shrugs off a nuclear blast.   However, don’t fall into the trap of Hollywood  science where nukes obliterate everything,   they aren’t that powerful and their ability to  damage stuff is directly related to how powerful   an individual bomb is, be it low kilotons or high  megatons, which indicates difference of tens of   thousands of times the yield. Earth’s get hit  by nuclear bomb levels of energy in meteor form   all the time, thousands of tons of meteors hit  this planet every year, each carrying way more   destructive force than their weight in explosives,  and Earth getting hit by individual rocks weighing   thousands of tons is pretty common too. For raw vaporization of metals, it varies by  

the metal but usually you need several TNT-tonnes  equivalent to vaporize a cubic meter of metal,   which is something to keep in mind when blowing  holes in artificial structures with lasers or   big bombs or kinetic weapons. Don’t assume  some nuke, even a megaton sized one, can   just punch a hole into any megastructure that’s  kilometers wide. Don’t assume that they instantly   vent to space either. Air generally moves from  normal to vacuum at roughly the speed of sound,   and like that speed it decreases as the pressure  drops, which is one reason we like spaceships   and spacesuits at partial pressure, all oxygen  and no nitrogen, it leaks slower that way.   Punch a meter wide hole in some large space  station, one much, much bigger than a modern   space station, and if the internal environment  was Earth like, each square meter of hole in the   hull should be spitting out about 343,000 liters  or 420 kilograms of air each second. Which is a   lot of air loss but means it loses 36,000 tons  of air a day, an O’Neill Cylinder – our smallest   megastructure habitats – might be 8 kilometers in  diameter and 32 kilometers long, which would make   for an internal air volume of 1.6 trillion cubic  meters or 1.6 quadrillion liters, or 2 billion  

tons. Meaning it would take nearly a century to  drop to half-pressure and be barely livable even   then, all while having a hole big enough to  step through and losing all its air out it.   Assuming it ever did. Space Stations are likely  to have constant leaks everywhere and have  

systems constantly pumping new air in, able to  increase that production above normal capacity.   Aircraft for instance are not pressurized  statically, they leak and have compressors running   constantly to keep up with that, so do modern  space stations. Big space stations would probably   leak way less per unit of mass or hull surface,  but way more over all, in raw mass terms.   With that in mind, a McKendree Cylinder – the  big brother of an O’Neill Cylinder – might   contain millions of times that much air, meaning  even a kilometer-wide hole in one might take   centuries to drain it. And even bigger  H-bombs, the multi-megaton affairs,  

generally would not leave a crater that big  in a thick steel hull and layers of dirt like   we would expect from the larger rotating  habitats. A Ringworld on the other hand   should have an atmospheric mass of around 5 or 6  billion-trillion tons, given that it’s got around   a million times the living area of Earth and  Earth’s atmosphere masses 5500 trillion tons.   One quick note, for pressurized habitats  mimicking Earth’s atmospheric conditions,   there’s roughly 1.2 kilograms of air per  cubic meter, but on Earth and any place where   atmospheric pressure is achieved by gravity or  spin-gravity, continent-class habitats or bigger,   the air gets thinner as you go up and you expect  about 10 tons per square meter of surface area.   Of course air isn’t the only thing draining  through a big hole in your habitat,   though it's worth noting that since  most liquids can’t exist in a vacuum,   water draining out a hull puncture should vaporize  or freeze, and so for instance cutting a hole into   a space habitat with a laser whose beam diameter  was much thinner than the hull thickness,   poking a tiny but deep hole, would probably  have that hole clog with ice or dirt eventually.  

For a big wide gash considerably wider  than the thickness of the structure though,   I wouldn’t count on clogging unless the structure  had some ability at self-repair that way.   On the other hand for these real megastructures,  stuff in the continent class or bigger like Bishop   Rings, Banks Orbitals, or Ringworlds, we  often imagine them having hulls measured   in a thickness of kilometers not meters or  centimeters like we imagine with spaceships,   and likely made out of diamond hard materials. It is not actually that hard to bandage over a   hole into space. Movies make folks think you  could get a finger-sized hole in a ship and  

folks would be sucked through it like a sausage  grinder. If you want a more realistic example,   turn your vacuum on and stick your hand over the  intake. From normal atmosphere to total vacuum   is a much smaller pressure drop than a hole  in a water pipe or garden hose. You obviously   cannot duct tape a football field sized hole in  a space habitat with actual duct tape but don’t   assume any particular hyper-strong materials or  near-instant deployment is needed to fix this.  

Patches might vary from some spider-like  robot spinning a web over it to some rapidly   solidifying patch material you could spray on,  which isn’t too hard considering liquids don’t   do well at lower pressures or exist at all in  vacuums. Though if it's leaking, you won’t have   zero-pressure at the edge of the leak, it should  stay at roughly the internal pressure. Voided   stations that leaked everything out already  though, derelict and empty to space, would   be very easy to reseal and pressurize in most  cases. Especially if their rotation had slowed.   This does not mean a typical O’Neill Cylinder made  of plain old steel, or even something like Kevlar,   is surviving a nuclear blast, but it is plausible  a lower-yield nuke on a larger end O’Neill   Cylinder might survive, and for a bigger blast,  it’s worth keeping in mind that a smaller hole   followed by a missile that went inside and  detonated in the internal landscape would kill   everyone too, in the same way one detonating over  your town will. It’s all a numbers and scale game,   but don’t assume you insta-kill space  habitats with nukes or cutting lasers.   There’s also defenses too. As I often  note on the show, a rotating habitat  

is probably going to be nested inside a bigger  non-rotating or slow rotating superstructure,   and you might actually do several layers  of rotating drums nested inside each other,   with outer ones rotating slower or faster and  just being a thin hull, so that various gaping   holes quickly spun shut to choke off leaks.  Spaceships might play this same trick with   multiple rotating shells of armor so that gashes  through several at once would all rotate out.   Probably worth remembering that a thick  stream of gas jetting out your space station   is going to shove the space station around too,  though this can be mostly ignored for the big   habitats whose atmospheres are significant but  pretty small compared to overall station mass.   One in orbit of planet might be de-orbited by  this happening too, though since the hole is   probably spinning around in a circle the  jet coming out of it might negate out.   I also would be surprised if any attack that  didn’t utterly scatter a megastructure as gaseous   debris managed to kill everyone on it. You’re  bound to have lots of compartments, even on a  

space habitat, that can be sealed and pressurized.  As a comparison with nukes, we usually say any   hardened underground structure will remain intact  and pretty undamaged even just half-again the   radius of the blast crater away, and potentially  even less. It’s also plausible that even normal   homes on space habitats would be built with  the ability to act as a bunker or lifepod.   So for those contemplating military engagements,  yes you probably would need to send in the drones   or clones or space marines to go clear out  every single compartment on a battleship or   space station if you were hoping to seize it  vaguely intact, same as a city, only fighting   through a megastructure is likely to be even  more nightmarish than urban warfare. Especially   given that if it's self-repairing to any degree,  that most likely means automated repair drones   and the ability to deploy and manufacture them,  which is likely very, very easy to militarize.   Kind of brings a different flavor to the term  ‘Megastructure Death’ when you contemplate   battling through one while it cannibalizes  itself to throw ten-trillion murderbots at you.  

This also gives us one more plausible  scenario for Megastructure Death.   In theory if you’ve got mass and energy and  automation you can keep repairing and refitting   one indefinitely from pretty much any blow it  might take and not be obliterated outright by,   be it a natural meteor or manmade bomb, a rapid  event or the creeping destruction of time.   However, that assumption of robots doing the work  leaves us open to needing to abandon one because   those repair or growth systems went haywire, or  its defense system did – and indeed such things   might be so close to alive as to qualify  as having an immune system. So they could   get diseased or cancerous or hacked and have  repair systems running around inside mutating   it or killing anything that’s not supposed to be  there to make new patches for the hull out of.  

I am guessing if this happened there’s a chance  the place would be quarantined rather than   obliterated and might be left semi-derelict till  a cure or purge team or whatever could be sent.   Takes a lot of firepower to utterly vaporize  something like that and if you don’t, it is   possible every thumb-size scrap of it remaining as  debris now flying everywhere is infected with grey   goo. So you might need to surround a megastructure  gone diseased with an armada that’s just pounding   it with atomic ordinance and vaporizing every  bit of flying debris with point defense systems.   Or blow its radiators off and shine a  lot of light on it to bake the thing,   like sterilizing something in an oven.  Which sounds like a good approach   except depending on your technology, you  might just be feeding it tons of energy to   build ten-trillion murderbots  out of to attack your fleet.  

In such a case I could imagine instead  spinning a cocoon or membrane around the whole,   or hitting it with EMPs, installing physical or  metaphorical quarantine beacons and leaving it.   However there would likely be in-between infection  states where you’re actually trying to combat it.   That really might be horrifying too, with some  chunk of a station trying to cannibalize itself to   murder its inhabitants while the rest cannibalized  it to fight them off, make escape pods,   and try to hold the place while fleets  arrived to evacuate one or fight the plague.  

That’s just space habitats too, imagine  megastructures designed for other purposes   like a system’s actual defense guns, asteroid  disassemblers, or megastructure manufacturing   sites. Remember we’ve contemplated structures  designed for disassembling whole stars before,   or others with black holes in their basements,  or for ripping holes in spacetime. I don’t think   you want to be in the same galaxy as one of  those if it goes rogue, let alone on board it.   Odds are the designers of any megastructure  invested a lot of time and thought into failure   modes and attacks on it, which is an upside,  most would probably be more survivable than the   typical structure, or even planet in the case of  artificial planets vs natural ones. Though it also  

probably means whatever killed it was the sort of  weapon best used for demolishing worlds.   So as mentioned at the beginning, this episode  celebrates the 7th Anniversary of our original   episode and I want to talk about that before  we get to our upcoming schedule, but first I   wanted to thank one of this show originals and  longest sponsors, Brilliant, for helping make   this show possible. We’ve grown a lot over the  years, constantly seeking to improve the show,   and so have they. Brilliant is an educational  site just a couple years older than our show  

and dedicated to that same core mission,  increasing people’s knowledge and love of math   and science, and it’s been a fun time working  with them and seeing the constant expansion   of topics and improvements to interactivity. That’s fundamentally critical to learning or   teaching, the topic has to be interesting and  is always best when interactive and hands-on.   Brilliant is focused on learning  not memorizing, for instance,   most folks know that the area of a circle is  pi-R-squared, but rarely why it is pi-R-squared,   and Brilliant’s Geometry Fundamental Course,  explains why and is full of intuitive lessons like   this that let you see and interact with Geometric  concepts in ways you've never done before.   You learn best while doing and solving  in real-time, not by long lectures or   memorising formulas and facts, and Brilliant  understands that and has something for   everybody — whether you want to start at the  basics of math, science, and computer science,   or go straight to advanced material. If you'd like to join me and a community   of 8 million learners and educators today, click  the link in the episode description down below or   visit: brilliant.org/IsaacArthur. So today wraps up our seventh year of the show,  

and the anniversaries are always right around  my birthday on September 20th - I’ll be 41 this   year - and so it tends to be an extra time of  reflection for me. It’s become a bit of tradition   to commemorate the occasion personally by going  back and watching that first episode, though   I tend to cringe a bit at the audio, video, and  overall presentation, as I suppose is unavoidable   for anyone who's been doing something for years  and comes back and sees their original work.   Truth be told, I don’t recommend watching any  of our first year of videos except for folks who   never had a problem with my speech impediment even  in its early form. Years of practice and speech  

therapy later, and several hundred episodes,  livestreams, interviews, and so forth under the   bridge, it's hard to reflect on that first effort  and remember that originally I’d just wanted to   practice a new feature of Microsoft Powerpoint for  unrelated work and picked a random topic to do.   In this case, I’d been missing talking about  science and scifi much as my work at the time   wasn’t nearly as geeky as college, grad school,  and the military had been, and I mostly used   social media to keep up with old friends from  the service but had joined a couple of facebook   forums, one for scifi writing and worldbuilding  because a member had asked me join to answer a   couple physics questions for some of the authors  there and another on the Fermi Paradox. I always   got a bit frustrated how few authors ever  wanted to do anything but classic space opera,   one or two planets per solar system with  homogeneous culture on them, so often mentioned   megastructures and space habitats and decided it  would be a fun practice topic and did a video on   it figuring it would be easier and better  to do the topic that way over the text-only   or text-and-image website or blog approach. That’s more or less the origin of the videos   and why to this day it remains essentially a  script that I narrate and put visuals up for.   It is sadly why we don’t do more megastructures  episodes though because the reasoning in the   first place was that these structures are hard to  envision and need images or animations for them,   and there just aren’t many around. Probably about  half the graphics assets for space megastructures   in existence were developed for this show with  most of the remainder being for Orion’s Arm,   and I did want to take a moment to thank  all our animators who’ve volunteered their   time and art to the show over the years. If you animate for a hobby and want to try  

your hand at doing any of the megastructures  we discuss, I can honestly say that a handful   of animations of one of them is usually the  difference between whether or not we do an episode   on a given megastructure. And we are always  looking for folks to help animate, edit scripts,   brianstorm up episode ideas, and moderate our  various social media so if you’ve got some free   time and want to let me steal it from you, just  shoot me an email at Isaac.Arthur.utube@gmail.com,   and youtube is spelled U-T-U-B-E in this case and  is on our channel’s About page if you lose that.   Anyway, the episode’s already on the long  side, and while I take partial credit for   encouraging other science shows to break the  norm and do episodes longer than 5-15 minutes,   I do try to keep them shorter than half an hour so  we’ll wrap up here and do the upcoming schedule,   but I did want to thank everyone for  making the last 7 years such a fun and   rewarding experience for me personally,  and I hope to keep doing it for another   7. I occasionally get asked if I ever worry  about running out of topics and the answer is  

no, not even a little bit, we’ve tons of  Science & Futurism topics waiting to be done   and the nice thing about the Future  is there’s always so much more of it.   Speaking of upcoming episodes, we still  have 3 more outings for this month,   and we’ll be returning to the Fermi Paradox on  September 23rd for a look at the notion of Hidden   Alien Civilizations. Then we’ll have our Monthly  Livestream Q&A on Sunday, September 26th at 4pm   Eastern Time before closing the month out by  asking if it’s possible for future civilizations   to exist without money, on Sept 30th. Another  thing about all these huge megastructures is   they are designed to let humanity grow our  population comfortably into the countless   trillions, and we’ll open October up by asking  how someone could stand out in such a vast sea,   then on October 14th we’ll ask how we might  feed all those folks, as we look at the future   of farming in the next few decades and beyond. Now if you want to make sure you get notified  

when those episodes come out, make sure subscribe  to the channel, and if you enjoyed the episode,   don’t forget to hit the like button and share it  with others. If you’d like to help support future   episodes, you can donate to us on Patreon,  or our website, IsaacArthur.net, and I will   shamelessly remind everyone it’s my birthday  too, and patreon and our website are linked in   the episode description below, along with all of  our various social media forums where you can get   updates and chat with others about the concepts  in the episodes and many other futuristic ideas.   Until next time, thanks for watching for  the last 7 years, and have a great week!

2021-09-18

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