It’s possible that the reason we appear
to be alone in the galaxy is because we’re the first lifeforms to
emerge here. But it’s also possible that we’re the
first to RE-emerge here. So today we are returning to our Fermi Paradox
series to consider the idea of Galactic Disasters, Natural or Artificial Events that might prevent
life from developing or wipe out civilizations. If you are new to the Fermi Paradox, it is
essentially the notion that the Universe is a vast and ancient place, probably containing
billions of billions of planets with conditions parallel to early Earth, and thus we would
expect to see a ton of intelligent life out there but we don’t seem to see any. This
apparent paradox has many proposed solutions, and the one we’ll examine is that something
– or someone – might have killed off life in our galaxy at some point in the past, and
that Earth is the first or among the first places where life has returned.
So, we’ll be considering a number of potential galactic disasters today, and also some extra-galactic,
universal, and even multiversal disasters. Let's discuss first, what would it take to
sterilize just a planet of all life? The most heat-resistant known lifeforms on Earth are
microbes that can survive at 130C for no more than a couple of hours. But it’s still rather
tricky because there are microbes living down in the deep ocean or caves where they might
survive our whole planet's surface being scorched sterile. They could then repopulate a planet
and with quite a head start since they already would have a lot of advancement on the early
microbes that probably inhabited our planet 3-4 billion years ago. Though at the same
time, if some disaster happened periodically, say every 100 million years, and that could
account for most larger land animals like birds and mammals, that probably would have
the same net effect of preventing any intelligent civilization from arising. It takes a long
time to go from microbe or insect to high intelligence so if you get crashed periodically
back to only simple life forms surviving in the ashes, the planet will remain empty of
civilizations even if it’s only barren for a few decades every hundred million years
or so. We always, in a Fermi Paradox solution context,
need to consider if some proposed solution would be in every galaxy or just our own,
because a strange or improbable event or chain of events might occur in one galaxy but if
it is not happening in neighboring ones it does not work well as a Fermi Paradox Solution.
You can colonize between galaxies even without access to faster than light travel so a single-galaxy
solution explaining an absence of civilizations in the Milky Way isn’t enough, if intelligence
is common and old, someone would have colonized the Milky Way from Andromeda or some other
galaxy by now. So for example, it’s possible that life
emerged in our galaxy 7 billion years ago, then some event caused a series of supernovae
that wiped out all of that life 4 billion years ago, and Earth was the first place it
emerged after that. However, you’d still have civilizations in neighboring galaxies
from planets billions of years older who might have been out on the interstellar scene billions
of years before us. With faster than light travel they could colonize their own galaxy
and neighbors in mere thousands of years but even without it, you should be able to get
your own galaxy colonized in a few million years and get to your neighboring galaxies
in at most a few tens of millions of years, not billions.
Still, if it happens in one place naturally, then it might happen in other places, and
of course Supernovae are a fairly universal phenomenon. We don’t know much about what
Supernovae near Earth do to our planet nor can we assume the impact would be the same
on other ones. For instance our main concern for a Supernova hitting us is that one that
goes off within 25 light years or so of us could be energetic enough to critically damage
our Ozone layer on the half of the planet exposed to that blast.
That is not a planet sterilizing event for Earth, but we did tend to assume it was for
some time. We had to revise our models from the 1970s that had thought a supernova event
50 light years away might destroy 90% of our atmosphere for centuries, and now think the
effects are much more mild and require higher proximity. Even in those older models though
it wasn’t life-ending, but more in the Asteroid Impact or Supervolcano scale of planetary
disruption that recovers with a new ecology emerging.
What actually happens if a Supernova happens near Earth? Well we’ve no eye-witness accounts
and even our geological record is rather flimsy in regard to Supernova detection at the moment,
but it does seem to happen periodically and mostly mildly. The volume of a sphere is proportional
to the cube of the radius, so there is 8x as much space within 50 lightyears than there
is within 25, and 64 times as much within 100 light years. Out beyond that they still
would impact us, potentially rather severely in an ecological sense of disrupting the existing
norm and leaving traces, but not in a planet threatening way.
Inside of the 25 lightyear radius you are getting walloped by X-Rays, Gamma-Rays, and
Cosmic Rays that are going to damage your ozone layer badly, exposing you to more intense
ultraviolet till it recovers, causing a big uptick in cancer in animals and wreaking even
more havoc on many microbial life forms especially those that need sunlight to live so can’t
be buried under protective layers of earth or water or whatever animal or plant they
live in. Those charged particles coming in break diatomic
nitrogen up into highly-reactive nitrogen atoms that form Nitric Oxide and other nitrogen
oxides and those individually can destroy hundreds of triatomic oxygen or ozone molecules
while they persist. The ozone layer would recover in a year or two but for another decade
or so you would be getting blasted by cosmic rays. This is not going to sterilize a planet,
life down in the deep sea or caves will continue, but if that event was happening every several
million years it’s not hard to imagine it preventing complex life gaining a foothold
and getting big brains and spaceships. Fundamentally though supernovae just are not
common enough to do that to most planets in a galaxy, even if we accept the more severe
side of the uncertainty of those models. Of course some events could cause an uptick in
star formation periodically and stars capable of going Supernova are short lived so that
can result in a wave of Supernova several million years later as all those bigger stars
formed in that wave of stellar formation start dying in short succession.
Still, even though supernovae are often described as the most powerful and destructive events
in space, they are just not powerful enough to explain a perpetual galaxy-wide kill-off.
We have a unit called the Foe, in which we measure Supernovae energy release, and its
10^44 Joules. Now this is a huge amount of energy, this is billion-billion times more
energy than our own Sun releases in any given second and comparable to all the energy it
will emit in its lifetime. However, if we think of this in the context of Einstein’s
E=mc², it’s only about the energy release of 10^27 kilograms of matter, around a 2000th
the mass-energy of our Sun, a single solar mass, and Type II Supernovae are of stars
more than a dozen times as big as our Sun. So a Foe is about half the mass-energy of
just Jupiter. Energy release in terms of its destructive
potential in space falls off with the square of distance, so if a supernova could critically
damage our atmosphere at 25 light years, one ten times farther away would need to be hundred
times more powerful to do the same. We happen to be about a thousand times further away
than that from our galactic core for instance, so a blast there would need to be a thousand
squared or a million times more energetic to have the same effect – but in this case
it would be a galaxy-wide one. Of course that would require about million times the mass-energy
or 10^33 kilograms, 500 solar masses, and the largest stars are not even a tenth of
that mass and do not convert anything like all their mass into a supernova blast. Even
Hypernovae, the most powerful recorded supernovae events, aren’t recorded at more than 10-100
times the normal supernovae release. Antimatter, which on encountering normal matter
releases both as energy, would be far worse than a star exploding. Just as an example,
it is entirely possible there are many other Universes out there and that half of those
are principally composed of antimatter rather than regular matter. In certain types of cosmology
these parallel universes could collide or interact in some fashion. If for instance
a wormhole opened up and an anti-Jupiter emerged through it, it could collide with another
large planet or star and emit the equivalent of about 4 Foe, a fairly strong supernova,
and indeed possibly a good deal more as antimatter would tend to catalyze fusion too. See our
Antimatter episode for details. If an anti-star came through, that would be
a thousand times more powerful and ought to wreck a volume of space a couple hundred thousand
times bigger than a normal supernovae… though that would still be a relatively tiny corner
of a galaxy. Needless to say an anti-galaxy sliding through would create a protracted
collision with some galaxy releasing a million-billion times more energy than a Supernova and that
sort of event should keep an entire region of the Universe thoroughly cooked for millions
of years after the energy blast reached a given piece of it, travelling at light speed.
And this would only be considering a small exchange of matter between a Universe fundamentally
the same as our own just with antimatter dominant, we’ll come back to some other cross-universe
disaster scenarios later. A moment ago I mentioned the energy needed
to have a near-Earth Supernova effect that took place a thousand times further away at
our galactic core. I didn’t pick the galactic core on a whim though, or just because it
is central to a galaxy and we are discussing galactic disasters. Very few processes can
fully convert mass into energy so that there's no matter left and you get the full E=mc²
yield or even a decent fraction of it. Hydrogen fusion in stars generally stays under 1% for
instance and often well under since most stars, especially big ones, never burn more than
a tenth of their hydrogen fuel. But a black hole can do way better, which is one reason
we often suggest them as a power source for advanced civilizations.
The destructive power of black holes tends to be badly misrepresented in science fiction.
Natural black holes tend to form in highly destructive events, but black holes by themselves
are not particularly destructive. If our Sun magically turned into one tomorrow it would
kill us but not by crushing us or tearing us apart, we would die simply because we no
longer were getting sunlight. That black hole Sun would only be a few kilometers across,
not a million like the Sun is, and you could get much closer to it safely than you could
a normal star because it has the same gravity as before but isn’t giving off scorching
amounts of radiation. Very little matter would fall into one as it is tiny in cross-section
compared to a planet or star, and anything not on a straight intercept trajectory would
simply fall into orbit around it. What happens though is that a lot of matter
would slowly drift nearby and fall into various orbits of that black hole. As more and more
gets added we get lots of occasional collisions and decaying orbits, picking up gravitational
energy and forming an accretion disk that emits a lot of energy in the deadly X-Ray
and Gamma ranges. Those near the event horizon are essentially picking up their mass-energy
in kinetic energy that can come off in those dangerous bands of radiation. When you dump
matter down into a black hole it can’t escape once it is over the event horizon but on the
way down it will pick up tremendous speed and if it’s colliding with stuff before
crossing the event horizon those collisions are releasing amounts of energy not much short
of what antimatter would, and they radiate that as heat energy principally in the X-ray
band - planets can also have an accretion disc, this is pretty parallel to a planetary
ring like Saturn’s, but the energy levels are much lower and would show up in the infrared
band. A black hole with a binary companion that
it starts to consume is going to release far more energy than a supernova but rather gradually
over a period of around a million years, not in a quick blast like a supernova. However
the centers of many galaxies are home to very large black holes that often contain several
million solar masses they presumably ate at an average rate of one solar mass a millennium
or Jupiter-mass per year. Indeed quasars, the brightest objects in the universe, which
we believe to be such galactic-core supermassive black holes actively consuming matter and
releasing energy, generally do so at a rate of around 10^39 watts of power – or a Jupiter’s
worth of mass energy every few days - with brightest doing as much as a hundred times
that or a Jupiter-mass per hour. That’s essentially a perpetual supernova
going off at your galactic core and while that power is very spread out by the time
it would reach a planet as far from the core as Earth is, it’s also a constant prolonged
effect. Now even though a quasar might be hundred trillion times brighter than our Sun,
and in the nasty gamma-ray zone for a lot of it, this is not actually that bright in
terms of light on a planet, because of that sheer distance involved. It would be more
luminous than our full moon but still only around a percent of a percent of the Sun’s
light. Still all that constant bombardment of high energy radiation and particles could
easily strip a planet’s entire atmosphere away after thousands of years.
What’s more, we have an effect called a Quasar Wind, or a Quasar Tsunami, of superheated
relativistic gas that can pulse out around a galaxy as a massive shockwave, disrupting
the whole galaxy’s normal star formation rate. So galaxies with Quasars in them are
not likely to be hospitable to life. The good news is that quasars are mostly gone
these days, we can only still see them because they are so bright we can see the ones far
away in space and thus far back in time. The nearest known quasar is Hanny’s Voorwerp
which is actually an extinct quasar, one which ran out of a large amount of new gas and matter
to eat. This recently extinct quasar is about 730 million light years away and appears to
have gone extinct maybe 70,000 years before that light we now see left that quasar and
has been cooling down since. The nearest active quasar is 1.7 billion light years away, much
older. Quasars are artifacts of an earlier and more
collision-heavy period of the Universe, peaking about 10 billion years ago, and they have
been getting rarer as time goes on, but they are believed to pop up in weaker form occasionally
during galactic mergers. They aren’t likely to be a concern for us but the Milky Way may
have been a quasar at some point in the past as might many galaxies. Past disasters, even
those billions of years back, are obviously of great interest to us in regard to the Fermi
Paradox though since if a galaxy was a quasar 5 billion years ago then it probably wasn’t
full of life then, even if it had been before. Indeed any galaxies that have a supermassive
black hole at their core probably have had many phases with an Active Galactic Nuclei,
a period where it is absorbing a large amount of matter. Now a quasar is an Active Galactic
Nucleus but the reverse is not true, this swallowing of gas or stars at the core is
not a steady flow in general and can vary a lot in intensity, the periods where a very
great deal of mass enters one in a relatively short period is a quasar, the period when
a fairly large amount of mass goes in is just an Active Nucleus and this is probably a phase
most galaxies like ours go through fairly often. A Seyfert Galaxy – which is about
10% of those we see, is essentially the same process as a quasar only far less powerful,
with the core only being about as bright as the rest of the galaxy combined as opposed
to hundreds of times brighter, and is a type of Active Galactic Nuclei.
But these are still protracted events, very powerful and very long, you can have shorter
bursts of much higher power like a Gamma-Ray Burst or GRB, which are about a thousand times
more powerful than your average quasar and the most powerful recorded was a thousand
times more powerful than that and around a billion-billion times more powerful than the
Sun’s typical luminosity. Since these are short affairs of milliseconds to hours, not
centuries or millions of year, we are very unclear on both their mechanism of production
and rate of occurrence, and indeed it’s likely that there are several different mechanisms
ranging from hypernovae to a star getting eaten by a black hole in a short swallow,
particularly something like a white dwarf or neutron star which are much more compact
and whose remaining matter is much more gravitationally bound to them so not prone to leaking prior
to getting gulped or tidally disrupted which might then happen over a mere few seconds.
GRBs are nasty affairs, and typically come as more concentrated polar blasts than big
spherical detonations, and we still know little of them so they are a plausible candidate
for regular galaxy-spanning ruin, though this would still be more an issue of frequency
than strength since no single GRB would sterilize a galaxy even though it’s destructive blast,
or cone, is much bigger than a supernova. We do have one thing even more powerful than
a GRB, and that’s a black hole merger, though this energy release is far, far larger it
is as gravitational radiation, so isn’t wrecking atmospheres like high energy gamma
radiation or ionized particles would. Though it has been suggested that two shock fronts
of gravitational waves, say from two black hole mergers in a relatively small region
of space and time, might meet and form new singularities – or micro-black holes - which
would be short lived then bang off in black hole evaporation events. We’ve also only
observed fairly mundane black hole merging thus far, those in the tens of solar masses
region. Presumably during a galactic merger event it is possible for a pair of supermassive
black holes to merge - what we call ringdown - with far more energetic results and regardless,
galactic mergers are pretty galaxy-disrupting events too. Though it should be noted that
our galaxy is a terrible cannibal suspected of eating over a dozen others and some are
still partially extant. We always say Andromeda is the closest galaxy
and on a collision course with us in a few billions years, but we will amend that to
include the two Magellanic clouds, smaller galaxies orbiting the Milky Way nearly to
the point of overlapping, but at last count there are 59 small galaxies closer to us than
Andromeda, eaten remnants or tiny satellite galaxies. As I’ve often mentioned on the
show in terms of intergalactic colonization, there is plenty of junk between major galaxies
to serve as waypoints, it’s not just a couple million light years of nothing and no stars.
These sorts of galactic consumption events, while stretching over billions of years, are
one of many things that could disrupt the core of a galaxy to feed fresh waves of matter
into that core black hole and make it an active galactic nucleus for a while.
Such natural galaxy wide disasters could be the reason we don’t see older civilizations
– and indeed we believe they are a big factor in making the Universe inhospitable to life
for maybe the first half of its existence, but that would still be billions of years
before our planet formed, and a civilization that came from a planet just ten million years
older than ours and evolved at the same rate as us would probably have colonized the whole
galaxy by now. Or for that matter, a civilization from a planet that formed at the same time
as Earth but where life evolved just 1% faster than us would have a 20 million year head
start on us. Of course a civilization that much more advanced
could cause a galaxy wide disaster, accidentally or otherwise. We don’t know what kind of
technologies might be possible for us in the future of course, we might develop some capacity
to poke into other universes with antimatter as the dominant matter there or different
physical laws with destructive effects if they spilled into ours. We’ve no idea what
would happen if we cut a wormhole into a 4-dimensional universe and that extra dimensionality overlapped
into us for instance. And indeed, as we discussed in our episode on Parallel Universes, some
cosmological models like String or Brane Theory predict Universes or Branes colliding periodically.
However, just inside known physical laws there’s a lot of room for galaxy-wrecking accidents
or intentional damage. There is a theoretical device known as a Nicoll-Dyson
beam that’s essentially a Death Star, you convert an entire star into a weapon by wrapping
it in mirrors and lenses and pointing it at something you want thoroughly dead. Our sun
is nowhere near the brightest, some are a million times brighter, but if we made our
Sun into such a device it could burn off the whole crust of a planet down to the mantle
in the time it took that planet to spin around once, and only that long because you would
need to keep the beam on it till the planet spun around. The nastier version of this instead
uses that light to push on mirror-backed missiles with lasers, what we call a relativistic kill
missile or RKM, so that you can simply time a volley of such missiles to arrive in one
big blast or spread out over a day and thus only need apply enough energy to torch the
surface. A single such device can purge an entire galaxy
of hospitable planets and keep doing it over and over again. Indeed it could do it to many
neighboring galaxies and there’s no reason it need be built around your own sun, in favor
of a bigger brighter one, or in favor of converting many thousands of stars into these weapon
platforms. After all our galaxy contains hundreds of billions of stars so converting just a
fraction of a percent of them into these gives you millions of them, and enough to eradicate
planets throughout an entire galactic supercluster. Of course such devices need guidance systems
and the ability to detect and alter course a bit to hit a planet, especially across a
galaxy, and you might instead use smart machines to go to those planets and simply dismantle
them too. Variations on grey goo, tiny little machines that simply build more of themselves
till they convert everything into themselves, or berserker probes, bigger smarter machines
that go someplace and annihilate it via on board weapons or simply parking nearby and
building more of themselves or doomsday weapons, are something that someone might intentionally
build but could also be created on accident. You might create terraforming von Neumann
probes or grey goo designed to turn entire solar systems into Dyson Swarms for future
colonists and have that mutate in design or intent with disastrous results - we see an
example of this in Alsatair Reynolds’ Revelation Space series where von Neumann terraforming
machines - the Greenfly - meant to create trillions of plant-rich habitats around a
star run amok turning everything into such habitats so that stars turned green with the
only light reflected away being those bouncing off green leaves. Such a thing is not just
a threat to your own galaxy but everywhere else, spreading out a relativistic speed as
it encounters new construction materials and spawns new fleets to reach to new stars and
new galaxies as fast as their starship drives could take them.
Though if you are focused on eradicating life and quick, you probably go the RKM route.
The RKM is much faster than grey goo approaches since no need to slow down is required, you
are literally ramming a planet. Or a star for that matter. Hypothetically two large
and relativistic objects could be shot at a star to hit it from both sides and plow
down to the center causing a shockwave and a detonation.
You could also artificially be producing most of the effects we discussed today only in
a more timed and controlled fashion, and we looked at various ways to weaponize black
holes in our episode “Weaponizing Black Holes”.
As usual in regard to galaxy-spanning disasters of an artificial and intentional variety,
it does beg the question of why the civilization doing it didn’t just colonize the whole
galaxy instead of blowing it up, but there are some scenarios where they might opt to
do that and we looked at those in our episode “Fermi Paradox: Sleeping Giants”, like
being so xenophobic they don’t even want to colonize because the colonies would be
mutant strains of themselves they would want to wipe out too.
Accidents though are more likely, in terms of the galaxy we see now, one apparently uncolonized
but in which we exist, and exist many billions of years after it would seem plausible civilizations
should have arisen if life was prone to popping up on earth-like planets and evolving to intelligence
rather than being something less common than winning the lottery.
You are not likely to eradicate your galaxy on accident under known physics but there’s
unknown physics presumably and we do have some theories for things like False Vacuum
and accidentally destroying spacetime by puncturing it and basically draining reality away. But
that wouldn’t leave us around unless it was the sort of effect that only destroyed
a limited region and was something that tended to be done accidentally by basically every
species once they reached a certain point. Amusingly a lot of our candidates for faster
than light travel have some scenarios for that sort of thing. FTL tends to be intrinsically
linked to time travel and it's possible that time travel would tend to wipe a civilization
out simply by employing it, via scenarios like the Self-Consistency Principle… see
our Time Travel episode for details. You might turn on a FTL drive and delete your civilization
backwards in time. Another thing often overlooked with FTL concepts is the huge amounts of energies
involved. A highly-relativistic missile massing just as much as an ICBM is coming in with
destructive potential on par with the asteroid that killed the dinosaurs and an ultra-relativistic
skyscraper-sized RKM is the sort of thing that would rip the whole crust off a planet.
However, in science fiction folks tend to ignore that those big spaceships massing about
that much and moving faster should presumably be far worse if they impacted, after all it
takes infinite energy to get any piece of mass up to even light speed let alone faster.
But even the hypothetical and fictional FTL devices that play with warping spacetime rather
than endless and impossible acceleration tend to be energy gluttons comparable to RKMs or
more. Remember what I said earlier about if two gravitational radiation shock fronts collided,
the possibility of many micro-black holes briefly forming and rapidly evaporating explosively.
Those are warping spacetime and if you are doing the same artificially by warp drives
or wormholes you might get effects like that. Wormholes are extreme curvatures of spacetime
much like black holes, which would tend to involve lots of gravitational waves. Gravitational
waves propagate at light speed so two systems opening something like that up, a pair of
wormholes or some other spacetime-twisting gate, might blow themselves up some decades
later when the waves meet those coming from another distant gate. While science fiction
often shows folks disrupting wormholes or other space gates to prevent an invasion,
and theoretical wormholes can be disrupted or broken by dumping too much matter into
them, the effect is likely to be very, very explosive even in astronomical terms. You
do not blow up the incoming fleet you blow up the solar system, that sort of thing.
Needless to say that all relies on highly speculative physics but it is plausible that
folks trying to bust out of the constraints of known physics might succeed, but only briefly,
and with galaxy spanning results. Even some scientists on the Manhattan Project discussed--and
placed bets on-- the possibility that the unnatural event they were forcing might create
some hyper-stable pocket of spacetime or form of matter around which the rest of the universe
might collapse. In science fiction we often see ambitious experiments at the ragged edges
of a species’ understanding of science, with grand results that turn out to be far
more revealing than anticipated. Some scientific civilizations out there might find this out
first hand, and the hard way—as might everyone else in their galaxy… or their Universe.
It is possible that the solution to the Fermi Paradox is not that life is all that rare,
but that every time a galactic firstborn civilization arises, it turns itself into the last.
Science Fiction shows us a lot of catastrophes on the galaxy level or even wider, some of
the classics include Larry Niven’s known Space series or Alastair Reynolds’ Revelation
Space or Thanos and his gauntlet from the Marvel Comics, but perhaps the greatest of
these comes from the Grandmaster of Science Fiction himself, Isaac Asimov, and his 1972
novel “The Gods Themselves”. I don’t want to spoil the novel with any discussion,
but it is often considered Asimov’s best standalone novel, and it won the Nebula Award
for Best Novel, the Hugo Award for Best Novel, and the Locus Award for Best Novel.
I’ll also toss my own recommendation in there by giving it the SFIA Audiobook of the
Month. Asimov’s skill as an author needs no elaboration, and the audiobook is wonderfully
narrated by Scott Brick, one of my favorite narrators, and it is available from Audible.
Audible has literally got centuries worth of audiobooks if you need to escape away during
these troubling times, but they also have tons of non-fiction, news & fitness programs,
podcasts, and other original audio shows. However, in response to the crisis they’ve
launched stories.audible.com, a collection of free books available to anyone, focused
on younger audiences to help out parents and teachers. In addition there’s a lot of sci
fi classics up there like Frankenstein and Brave New World, so make sure to check those
out. As an avid audiobook listener since I was a kid, I can testify what a great option
they can be for getting kids into reading, and again it's free. The content is available
in several languages from computer, smartphone, or tablet, and there’s no ads, no sign up
or login, just click, stream, and listen. Of course Audible’s normal inventory can
still be accessed for a 30-day free trial, and Audible members not only get discounts
on any audiobooks they buy, but a free book every month. Additionally, they are now giving
unlimited access to their audible originals. You can start listening today with a 30-day
Audible free trial. Just visit the link in the episode description, Audible.com/Isaac,
or text “Isaac” to 500-500. So next week we’ll be taking a look at Future
Types of Governments, both variations on modern ones that might occur with new technology
like artificial intelligence and how some old ones might re-emerge as we move into space
colonization. Then we’ll finish up the month of August with our Monthly Livestream Q&A
on Sunday, August 30th, at 4pm Eastern time, and you can join us then to get your questions
answered. We’ll then head into September, and start
the month out with a look at space nomads and nomadic fleet based civilizations. Then
in three weeks we’ll move on to Part 2 of our new series, Becoming an Interplanetary
Species, as we look at Colonizing Cislunar Space and the Lagrange Points.
If you want alerts when those and other episodes come out, make sure to subscribe to the channel,
and if you’d like to help support future episodes, you can donate to us on Patreon,
or our website, IsaacArthur.net, which 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, and have a great week!
Oh i wonder if he'll mention ringworld...
I cannot find subtitles for this one other than Youtube's auto-generated ones. P-{
edit: they exist now. P-}