Multi-Planetary Empires

One day humanity may settle countless worlds, but could any nation hope to govern multiple planets or even star systems? Most of us grew up on classic space opera science fiction where multi-planetary empires are a staple of the genre and usually it’s a sprawling empire composed of many hundreds or even thousands of worlds spread over the galaxy. Often these are all connected by warp-capable ships or wormholes or jump gates or some other means of FTL, Faster Than Light travel and communication.

We’ll discuss those today too but as channel regulars know, we’re not very optimistic about FTL ever happening. Most examples of ‘theoretically possible FTL’ that we hear of in science are more accurately described as situations where we’re pretty sure the method is impossible but haven’t been able to prove beyond any reasonable doubt that it is, rather than there being any actual evidence it could be done. I’m a physicist and I don’t think so, and I don’t know any colleagues who do, but most of

us would love to be proven wrong. Your default warp drive runs on negative matter, so do stable wormholes, and that’s a material allowed under math but for which there’s no evidence that it exists and no real expectation it does either. Much as we don’t expect to find a negative dollar bill or a negative gallon of water, outside an accounting chart or spreadsheet. We could be wrong, but if we’re not, does that spell the end of our dreams of empires of many worlds? The good news is no, and we’ll

cover several cases today, but let’s start with that classic flaw of space opera. First, our galaxy has something like half a trillion stars in it and most will have planets that are at least as terraformable as Mars or Venus. Sci-Fi writers are often horrible at scale and even writers known for their scientific accuracy like Isaac Asimov tended to really lowball the number of planets and population we expect in a settled and FTL capable galaxy. Both Asimov’s Foundation series and Frank Herbert

’s Dune, two of the most influential sci-fi series out there, both have a human empire of a few million worlds at most. To their credit, we didn’t know how many stars were in the galaxy at the time as only the brightest stars could be seen, and most are a lot dimmer than our Sun. We also didn’t have much expectation about how often an Earth-like habitable planet in the Goldilocks zone would exist, but even using the estimates from their era, they should have been coming up with more like a billi

on worlds instead. That number is fairly vital to Drake’s Equation and SETI, the Search for Extraterrestrial Intelligence, as it gives us the number of low-hanging fruit worlds where complex life might emerge on its own or where we might be able to settle without vast effort or some of the higher-tech and more inventive approaches to settling planets we’ve developed since then. We don’t know what that number is yet, partially because we don’t know how to define it. We can’t give a precise estima

te of how likely a star is to have a planet with 80% or 90% or 101% of Earth’s mass, but even if we did, we don’t know how close to Earth’s gravity and composition a planet would need to be for comfortable and easy terraforming. Or to have complex native life. The number of Earthlike planets around such stars obviously varies. If 80% of Earth’s Mass is good enough, that's a huge difference than if even 101% is too much and 99% not enough. There’s also that question of how close to their star the

y need to be, and we can’t assume Venus’s orbit is too hot just because the Venus we know is a molten nightmare. Venus's weirdly long and backward day is likely the result of a huge collision, not its proximity to the Sun, and it's thought this is the prime factor in its horrible conditions. Meanwhile, a planet decently more massive than Earth out at Mars distance might be habitable too. The most conservative calculation I’ve seen on the matter in recent years was 300 million from Steve Bryson’s

team at NASA Ames, and that was their conservative figure of assuming only 7% of the 4 billion most sun-like stars in this galaxy would have the right planet in the right location, their high-end figure was 10 billion. This estimate is more generous with which stars to include and what percentage would have good planets. Time will tell which end of that range reality landed at. Though I would tend to say for colonization purposes that value was still very low. Higher technology always helps but

the most powerful colonization tool in our current kit is to scatter either shades or mirrors at a planet’s L1 or L2 Lagrange point, or in orbit of the planet, or moon, to add or subtract sunlight reaching that planet or to give it more terrestrial day night cycle of 24 hours. We’ve discussed that option on many occasions, most recently in our episodes on Statites & Lagites in January or the Lagrange Point Settlement episode from later that month, and the simple reality is building and maintain

ing one is no small feat but vastly smaller and easier than sending off a colonial ark ship to another star or terraforming a planet, or even para-terraforming a planet with domes. That basically widens your goldilocks zone to anything as close to the sun as Mercury out to further than Saturn and renders the type of star a lot less important, since that same approach can provide magnetic shielding from coronal mass ejections and other atmospheric stripping processes. As well as adjust the spectr

um of light to filter it to something more preferable. Such being the case, rather than having maybe one in 100 stars be suitable for life and maybe finding a decent planet around 1 in 100 of them, we would expect at least 1 in 10 stars and probably better than 50/50 able to provide at least one decent planet to at least para-terraform. Meaning we’d expect something on an order of 100 billion habitable systems. But even that 1 in 100 stars with 1 in 100 having a good planet would still imply 40

million prime planets being available in the galaxy, and that tends to be our classic space opera setup with an assumption many belong to some alien empire or you’re only in part of the galaxy or that some worlds are lost. What it also means is that if you’ve got a star kingdom of a dozen planets, they might all be in the same star system. But more importantly, there are 60,000 stars within 100 light years of Earth and if only 1 in 10,000 was habitable, that means you’ve only got around 6 system

s with one planet we could colonize that could get a signal to us in under a century. Alternatively, most of those 60,000 stars probably have multiple planets that we could at least para-terraform and you might easily be able to get an empire of a million worlds stuffed into that volume, which itself isn’t even a millionth of the galaxy’s total volume. It also means you can be getting dozens if not hundreds of planets within several light years of Earth. And that’s all without factoring in artif

icial habitats like O’Neill Cylinders or including minor and dwarf planets in the count or rogue planets between systems. Now we can debate if it is plausible to have an empire stretched out over several light years and we’ll return to that point, but let’s get four caveats in right from the outset. First, as we just mentioned, there are a ton more worlds to consider when we start including larger moons, bigger minor planets, artificial habitats, and interstellar rogue planets. Most science fict

ion settings tend to act like an entire settled planet is one small county or modest city anyway, and that most mighty star empires of a million worlds from space opera act like they’ve got maybe a couple hundred actual planets. Given that, I think it makes it worth noting that you could have such large empires packed into just a handful of light years. Which brings up the second caveat, that an awful lot of places have stars far more closely packed than our area does. Even ignoring places like

the galactic core, where you might pack thousands of stars into a volume smaller than the one surrounding us before you’d get to Alpha Centauri, we have lots of star clusters where you might have hundreds or thousands of stars within a dozen light years of each other, each home to several planets. And there are thousands of clusters like that and plenty more places where stars are packed a lot tighter than here. Or looser for that matter. Third, any place that has ships able to move back and for

th between star systems – even just at modest sublight speeds – also could set up shop on objects too far from their sun to be running on a solar economy. Perhaps they’ve mastered cheap and abundant fusion energy, in which case every dwarf planet or icy body of note in their outer system, be it their Kuiper Belt or even Oort Cloud, should end up with some sort of outpost on it. Maybe it’s only a lone rotating habitat orbiting the snowball or buried under the ice there, home to just a few thousan

d folks, but it could as easily be millions, and whichever the case, that’s many millions of such communities out on the fringe of most systems. Fourth, those outskirts will be much closer and denser, if generally smaller in quantity, around most systems as most of them are red dwarfs with somewhere between half and a tenth of our Sun’s mass. Planets and outer bodies can pack in much closer on such systems while bigger stars might easily have a dozen planets in their normal habitable zone. Now I

did specifically title this episode multi-planetary empires and on this channel, we limit that to meaning big planets, Earth, Mars, gas giants and so on, while we tend to use the term ‘world’ to refer to settled moons, bigger asteroids and minor planets, or larger habitation megastructures, in addition to Earth-like planets. So, we’ll be focusing on actual planets in the remainder of the discussion but that doesn’t mean we have a future in which those other smaller but far more numerous minor w

orlds are non-existent or even big players. Indeed, odds are good that by sheer quantity they’ll hold the vast majority of humans. They just wouldn’t tend to be the highlights on the map, so to speak. It also has to do with the continuity of empires over big distances. We tend to talk about the difficulty of maintaining contact and control on some colony at Alpha Centauri or Tau Ceti and how difficult that would be and how it would take years to get help to them in event of a major disaster or r

ebellion. But beyond it being unlikely a whole planet would rebel out of the blue or suffer any planet-wide disaster, a planet is not a star system. In Larry Niven and Jerry Pournelle’s classic novel “The Mote in God’s Eye” we visit the New Caledonia system, which contains two major planets, New Ireland and New Scotland. The system is a local interstellar capital of that region of humanity’s current empire, the second one of note, and when the first empire fell into civil war that nuked Earth in

to oblivion, one of the planets remained loyal while the other rebelled and the two fought over it for a long time. It is not hard to imagine a planet around a distant star rebelling or seceding from its capital, especially when that capital might be tens of years of travel or even communication time away and the same for any neighbors. It’s a bit different if you have a colonized solar system of several different major planets and tons of lesser worlds orbiting that star and many more in the de

pths of interstellar space scattered every few light years. There’s also no compelling reason to assume all those planets got settled by the same group of colonists, or even that any single planet did. Let’s say tomorrow a few thousand interstellar ark ships magically dropped into our hands along with a few space towers to move people back and forth to them easily. Each ship can hold ten thousand people and happens to have a nice star chart with entries for every local star and planet of note. T

his is a thought experiment, so we don’t care how we got the ships, as we’re really just trying to look at this from the perspective of our civilization a couple centuries down the road with better automation for ship construction and improved space capability. I have no idea how we would divide those ships up, maybe one for each country and then divide the rest proportionally by population or some subtly veiled equivalent to military muscle, but there’s no reason to send each of those ships to

a different solar system or why a country with, say, five ships, would want to send them all to one system with five planets. Or even that a planet with five decent continents might not get five ships from five separate but reasonably friendly countries sending folks. Or that some country back here with a few ships but little interest in space might not sell ships, or some of their passenger slots, to countries or groups or individuals. Iceland, population 373,000, might end up with a ship but h

ave no interest in trying to come up with 10,000 citizens to load, and might sell it to the US or Canada or keep it but only send a contingent of a few hundred and an appointed governor while selling off slots of 100 people or less to various other groups. There’s a galaxy of billions of planets out there, but they can all be colonized eventually and in the meantime those closest are best, and some better than others, and one small continent of an Earth-like planet is probably more prized earlie

r on than an entire planet like Mercury or moon like Ganymede. And of course, once the ship gets to the destination, it can turn back around, return to earth, and grab more people, to go there or to another colony planet further away. Point being, of the 131 stars, brown dwarfs, and sub-dwarfs currently identified within 20 light years of Earth, that could be thought of as our neighbors on our border, nobody is likely to be in a position to casually claim the entirety of one of them and in a way

that can stick for the several centuries that would be needed for them to grow their own numbers up to something that might colonize that system rather than some small bit of it. We might see things negotiated or fought out of course, but it’s a lot more likely we would see several settlements scattered across a system and those may or may not have any shared history, culture, or early government with each other. Nor are the mighty nations of Earth, who all share just one planet, going to be ve

ry sympathetic to colonies complaining that someone else setup on another continent, let alone another planet in the system. Even if they did, let’s say the US in a few centuries sent a colonial fleet to a system that planted several colonies there on various worlds, what odds those all have the same grievances or issues with Earth centuries down the road? Why would all agree to band together and flat out leave? Why not one of them or maybe a few, or maybe one doesn’t rebel from ‘Earth’ but just

the US and joins Japan or France instead? And what is the grievance? Probably they weren’t built with any intent of seriously taxing them down the road and they probably rely on Earth for new data, science, and entertainment. The harder it is to send troops to some place, the lower the expectation you can get taxes out of them, and the harder it would be to guarantee a certain level of trade – though new settlements do tend to have strong trade relations with the country their settlers came fro

m due to similar language and cultural norms, all of which will probably fade through time. But the default downfall of big galactic empires in a no-FTL situation isn’t how far away the entire civilization is but how far away its neighbors are. If you’ve got a hundred settled planets within a few light years of you, several of which are within light hours, you not only have a reason for trade and relations, but a real concern that even if your homeworld or sector capital doesn’t send troops, if

you rebel one of your neighbors might instead. This hardly means maintaining a multi-planetary empire is easy, but it does mean it has some things working in its favor against the overwhelming vastness of space and time. We also tend to assume colonization of other stars takes place because we’re growing and looking for elbow room, albeit probably not with great urgency as we’re not likely to see super-huge families become the norm again anytime soon, so we sort of trickle out into space, but th

at dynamic shifts a bit if we get radical life extension. All of a sudden you can have kids when you’re 100, or 200, and aren’t in a rush to start a family but also have no cap on when you have to finish adding to one. That sort of shift is likely to see a rise in growth rates and with an intent to longer-term solutions, and if you don’t have an expiration date you can contemplate getting on board an arkship for a few decades much more easily. Particularly since you might do it while frozen if y

ou don’t want to be awake, as generally speaking the technology needed to restore someone from cryo is similar or even slightly more advanced than what you need to turn back the aging clock. All of that is debatable of course but tends to strike me as our most plausible scenario for the future, by plurality if not majority, assuming AGI doesn’t just murder us off to replace us, and in either case you have a civilization where folks with no real cap on their longevity are trying to settle space.

I’d make the case that folks who live for centuries are probably going to be at least a little more willing to consider being part of an interstellar nation when many of the original colonists come from Earth and are still alive and kicking and probably very influential there. And the same back on Earth, where a lot of your senior leadership, no pun intended, probably have siblings or children still alive and off on those colonies who they keep in loose contact with. And you still have that issu

e of not being able to casually rebel when several of your neighbors can get fleets over to your planet quickly. And it isn’t like you could organize a planet wide rebellion quickly or quietly either. Not unless your planet was so sparsely populated that it only had maybe a million people on it, tops, and then you really do have to worry that Earth, or your local sector capital, can be sending armadas with more troops in them than you have people. You do still have the problem of time lag for a

representative style of government. If we imagined a cluster of space with 500 major worlds jammed into a 10-light year radius. If that’s evenly distributed, then not only do some folks have a 10-year communication lag to hear about what happened back at the capital – assuming it’s actually at the center – but the median delay is 8 years. 250 of your 500 worlds are 8 or more light years away, since over half of the volume of a sphere 10 light years in radius is in that last two exterior light ye

ars, while only an eighth of the volume and stars are in the 5 light year sphere stretching halfway out. Keep that in mind as it tends to imply a rising limit. If you find out that statistically your rate of rebellion or secession attempts tends to rise linear to your distance from the capital, so that about 1 of those 250 outer worlds was rebelling every year, then if you double the diameter of you imperial blob, your new outer half at 16-20 light years out contains 8 times as many worlds who a

re each twice as likely to jump ship, so you’re putting more like a score of rebellions down a year now, not 1, and while you’ve got 8 times as many worlds supplying ships and troops, they are taking longer to get to each hot spot and coordinate orders. But they probably are not coming from your home world. These are actual planets which might have several garrisons and fleets each, even when underdeveloped. And probably none are thinking about going their own way seriously until they have hundr

eds of millions of folks and feel like they can be supporting their own navy to fend off neighbors. It’s probably worth noting that in a lot of futuristic contexts ‘taxes’ aren’t exactly redundant but aren’t really your motivation for control either. Even nowadays most countries are not really looking to add territory by conquest and people to increase your taxes because you generally spend almost all of those on services and infrastructure for those folks. In a post-scarcity civilization, or a

near-equivalent, while raw materials for the long-term interests you still, your citizens probably aren’t really super-motivated about adding one more golden back scratcher to their collection by taxing the miners of some godforsaken rock harder. Those miners on that rock probably have considerably more luxurious lives than we do nowadays even on some distant barely settled colony. Rather your motivation is probably simply control of those around you. That might be entirely despotic, or it might

be something more democratic where colony planets are viewed as dangerous in isolation where some crackpot group or underregulated researcher might be playing with brainwashing viruses or rogue self-replicating AI. If your region of space just suffered a Hegemonizing swarm attack from some reckless colony they might decide their new motto for fledgling planets should be “Welcome to the empire… or else”. It obviously isn’t hard to imagine classic space empire tyrannies and I don’t want to just c

heerfully handwave that option away as there’s nothing inherent to technology and prosperity that makes despots vastly less likely to pop up. They also have some impressive technologies available, potentially like a brainwashing virus they can unleash or any of the sheer brute force mega weapons we’ve discussed over the years. Your maximum empire radius might be built around how much time lag a colony needs between them and your megaweapon to pull off a rebellion, rebuild, and build a defense to

outlast it or a megaweapon of their own for reciprocity. And you might not be willing to build copies of that doomsday device away from your capital where rebel generals might decide they would like to be lords of a smaller star kingdom of their own, and they can choose which way to point that space cannon you built them. Things get easier with FTL of course, we’ll be looking at Stargates and similar FTL two weeks from now and will deep dive that effect on a civilization more then, but it makes

any modern form of government viable again. Whereas a planet 10 light years from Earth electing a senator then presumably has to ship that person to Earth, which is likely to take more than 10 years, and so you need to start imagining some very long terms even compared to the longevity in office most US senators tend to have, 10 of them served over 40 years, but then again life extension technology might add to that a lot, or encourage term limits. I can’t really imagine a planet feeling that t

heir representative dispatched to the capital decades ago and receiving orders a decade old is really serving their interests all that well, and 10 light years is not a big size for an interstellar empire, and a quarter of light speed would be a respectable rate of travel for a ship, so that would be a 50 year lag from the day they got elected to when they sent back their first report. 50 years ago, the Senators from my state of Ohio were former astronaut John Glenn and Bob Taft 2, not to be con

fused with Bob Taft 1, who was also our senator, or Bob Taft 3, Ohio’s governor 20 years back. It’s not terribly uncommon for the kids of politicians to go into politics either and end up holding their parent’s seat one day, but it would be a bit amusing if we imagined a multiplanetary empire that didn’t have life extension or cryo – and again the latter strongly implies the former – and sent its politicians off in a generational ark ship back to Earth. Or opted for some type of elaborate clonin

g or duplication. We saw that in the Foundation TV series, with Emperor Cleon, one of the few innovations that wasn’t in the book that I actually liked. And that raises the notion of aristocracy or monarchies too and they don’t seem particularly favored or disfavored at the multiplanetary level. I could imagine a loose confederacy of worlds that wasn’t much more than a trade and defense arrangement having legal counsel and lobbies back on Earth with some firms known for their longevity and stabi

lity. There is a law firm out of Kent in the UK that’s been in continuous operation since 1570, almost half a millennium ago, and we might see folks skipping on democratic representatives in favor of some group like that which they can just send dated and general instructions too and otherwise represents their interests. Or they may use some sort of AI as their representative or spokesperson. Or use a brainwashing virus on someone elected to be that spokesperson to ensure loyalty. Ultimately, I

can make a case for just about any system of government working, it’s just an uphill effort in the absence of FTL and some types might have a harder lift both operating and justifying their existence. And even tyrants typically need to convince their lieutenants and viceroys they should stick with them rather than become their own sovereign power or join another team. We should also note that while some methods of governance or economics probably objectively work better than others, post-scarcit

y civilizations can probably get away with running systems they like better simply because their sheer abundance permits a lot of waste and abuse without breaking the wheels. For any nation to exist, rather than be a collection of smaller states, it must serve a purpose and by default that tends to be shared defense, and in this maximum range sort of context, whatever range allows meaningful shared military support is also one in which shared defense is plausible. If an ally can’t support me use

fully 10 light years away, then an enemy has those same sorts of constraints to invade me. The same would apply for trade, no mutual arrangements, regulations, or treaties serve a point if the distance is too far to allow regular trade. Those can be stretched out for vital things, so a treaty banning the development of some self-replicating murder machines might be in place or some agreement to a galactic standard for weights & measures and interstellar language or time & date is plausible too.

Likely as not that would be a host of people speaking in a variety of different native tongues that were automatically translated into some standard language nobody other than computers & interstellar lawyers actually spoke then translated into the recipient’s language. Or everyone uses Earth time and keeps doing it even though Earth itself manually adjusted its orbit to exactly 365 days. There’s also no guarantee every planet in each system would be part of that same empire, which may or may no

t have assets in other star systems too. It wouldn’t be hard to imagine in the year 4000 AD that Sweden still had the same borders as nowadays but also had a hundred major asteroid colonies, modest chunks of territory on Mars and Venus, one of the moons of Neptune, a dozen major Oort Cloud colonies, and was the patron and de jure ruler of a dozen planets scattered around some of the nearer stars. Same, the King of England is still king of a lot of various countries with their own parliaments and

who do not turn to him for much guidance, and that post may still exist for ages to come and you could easily have millions of planets out there who sincerely viewed themselves as members of that realm, so long as nobody wearing that crown or over at Number 10 Downing Street tries sending them any orders. Throw in FTL and the game shifts a lot, and it is also not hard to imagine most of the galaxy getting settled before someone back here in the core worlds finally figures out FTL. That’s a comm

on enough plot, early colonization done by slowboats and them getting caught up on by faster ships invented back home during their slow voyage. If that happened, somebody might decide to launch a great crusade to reunite all of humanity into one big happy family… or else. And you also have to consider scenarios like multi-planetary empires literally being physically linked by site-to-site transporters or wormholes or just vacuum trains running on active support tethers and moving at hundreds of

kilometers per second. Peter Hamilton has worked with this concept in quite a few of his novels, Night’s Dawn and the Commonwealth Saga in particular come to mind, and we encounter it in Larry Niven’s Known Space and Ringworld setting too, and many others. You might even build or move planets into a shared solar system to cut down on lag times and clear that space around the vacated star for intense starlifting and disassembly. As to what qualifies, it would probably be whatever the minimum was

because somebody will declare they are one as soon as they can make a decent claim on it and that will probably stick. But I think you would need to do a bit better than being one of our larger modern nations with a large base on the Moon and Mars. Nonetheless I would imagine the first of each of these will probably be just a handful of centuries down the road and with several of them basing themselves off Earth and only controlling a modest fraction of a handful of other planets, moons, and maj

or asteroids in the solar system. I’d bet on at least half a dozen such entities that had large holdings not just on Earth but Mars and the Moon. I tend to think places that control the entirety of not just one system but several nearby it are more likely to first emerge in smaller star clusters we settle in a few thousand years and which spill out from whatever settlement there first took off, in an era where spaceships are easy to make and where most unclaimed stars are far enough away that no

body from Earth wants to try but few of the colonies closer to them have grown enough to want to send their own. But for those first multi planetary empires, I would guess quite a few of the existing countries around nowadays are still around then, and maybe some of us are still around then too if life extension takes off. Who knows, maybe your homeland will be a multi-planetary empire one day, and maybe you’ll be there to see it. We explored the practicality of multi-planetary empires today but

not what they do or who they are, and tomorrow, for April 1st, 2024, no fooling, we’ll be releasing our Monthly Nebula Exclusive, Galactic Beacons, to discuss one such project huge stellar empires might create and to ask how those would work, what types there are, and why you would or wouldn’t make them. And if you haven’t already seen it, this month NEbula Exclusive, Crystal Aliens, continues our recent discussions of alternative chemistries for life we had in our episodes ammonia based and si

licon based lifeforms. And again, Crystal Aliens is out now exclusively on Nebula, our streaming service, where you can also see every regular episode of SFIA a few days early and ad free, as well as our other bonus content, including extended editions of many episodes, and more Nebula Exclusives like last month’s episode Topopolis: The Eternal River, January’s Giant Space Monsters, December’s episode The Fermi Paradox: Hermit Shoplifter Hypothesis, Ultra-Relativistic Spaceships, Dark Stars at t

he Beginning of Time, Life As An Asteroid Miner, Nomadic Miners on the Moon, Space Freighters, Retrocausality, Orch Or & Free Will, and more. Nebula has tons of great content from an ever-growing community of creators. Using my link and discount it’s available now for just over $2.50 a month, less than the price of the drink or snack you might have been enjoying during the episode. When you sign up at my link, https://go.nebula.tv/isaacarthur and use my code, isaacarthur, you not only get access

to all of the great stuff Nebula offers, like Crystal Aliens and Galactic Beacons, you’ll also be directly supporting this show. Again, to see SFIA early, ad free, and with all the exclusive bonus content, go to https://go.nebula.tv/isaacarthur We’ll get to the upcoming episodes in just a moment, but on the topic of things coming up, this year’s International Space Development Conference, ISDC 2024, will be in Los Angeles May 23rd-26th, and it’s looking to be an exciting and informative event,

including an appearance by William Shatner to receive the Heinlein Award. I’ll be there and if you live in there area, I hope you’ll come by and say hi, but if you have some free time then, we always need volunteers, especially to help with the NSS Space Settlement contest, where we usually have a couple hundred student finalists from around the world giving presentations on their space settlement designs and needing a little shepherding. If you’re interested in volunteering, in any capacity, I’

ll leave a link in the episode description, isdc.nss.org/volunteer-at-isdc/ So that’s it for this month but join us as we start April off on the 4th with a discussion of space based solar power and several other clean energy options from space that might be able to help us power not only our orbital infrastructure, but Earth itself, including options like Earth’s own magnetic field. Then on the 7th will return to the Fermi Paradox to ask if the reason why we don’t see expanding alien civilizatio

ns is because they eat their own colonies, in the Cronus Scenarios. After that, we’ll have a look at Defending Earth, be it from asteroids, aliens, AI, astronomical explosions, or just mundane human threats, possibly including rebellious space colonies. If you’d like to get alerts when those and other episodes come out, make sure to hit the like, subscribe, and notification buttons. You can also help support the show on Patreon, and if you’d like to donate or help in other ways, you can see thos

e options by visiting our website, IsaacArthur.net. You can also catch all of SFIA’s episodes early and ad free on our streaming service, Nebula, along with hours of bonus content like Crystal Aliens, at go.nebula.tv/isaacarthur. As always, thanks for watching, and have a Great Week!