Welcome to a short in-between episodes episode. The reason I’m releasing this now is there
was a draft paper released recently, titled “The Fermi Paradox and the Aurora Effect:
Exo-Civilization Settlement, Expansion And Steady States” and it started getting discussed
and I had several requests to do a video explaining it, so I thought we’d go through it and
then get into some of the pros and cons for the theory. Let’s start with the title. If you’re watching this episode odds are
you already know what the Fermi Paradox is, which is the apparent contradiction between
how empty of life the Universe appears to be, and just how huge, ancient, and filled
with potentially habitable planets it is, or basically, where are all the alien civilizations? But the Aurora Effect is probably unfamiliar
unless you’ve read Aurora by Kim Stanley Robinson, author of the Mars Trilogy. We’ll use the definition from the paper,
that “Good worlds are hard to find”, which is to say, just because you might find a planet
you could settle and terraform, doesn’t mean it’s really one you’d invest the
effort into, or for that matter be able to transplant a civilization there that could
successfully grow. History is full of settlements that failed
or stalled out after all. Let me start by saying that I have issues
with the theory, which I’ll expand on once I’ve laid out what that theory is. So, let’s first go through that paper in
a more relatable way so we understand what it’s all about. If you assume that most systems don’t have
a place anyone wants to live or will thrive at, it really puts a dent in the classic expansion
model for the galaxy. That assumes you colonize in a first wave
from Earth, or our solar system anyway, and then those colonies colonize those near them
eventually, who do the same. This is a very common approach for modeling
galactic settlement timelines and we often refer to it as percolation because you can
then model it like a fluid going through some porous substance. How many worlds are viable for settlement
and how quickly those settlements grow to being willing and able to dispatch a daughter
colony of their own, rinse and repeat. Models based on this are very sensitive to
a number of variables, and can thus produce a wide range of galactic colonization timelines. For instance, if our colonists can and want
to settle every star system, can travel at 1% of light speed, and we assume the typical
colony begins with 10,000 people, doubles in numbers every 50 years like we did in the
20th century, and will colonize a new system when they get to 10 billion people, they need
to double 20 times, to go from 10,000 to 10 billion, and it will take them just a millennium
after settlement to get to colonizing their own new systems. Just to keep the math easy, if they only travel
at 1% light speed and only settle within 10 light years, it takes them another millennium
to get a colony ship to all those systems in range, so basically your colonization wave
percolates out at 10 light years per every 2000 years. It means you colonize at 0.5% of light speed,
you travel at 1% but spend half your time stopped and growing in numbers. Galactic Colonization, everything within 100,000
light years, would take 20 million years. That sounds like a long time, but to put that
in perspective, a single rotation of our galaxy takes roughly a quarter of a billion years. So, this 20 million-year timeline means not
much in our galaxy has changed, At the local level, a score of centuries won’t rearrange
the locations of neighboring stars much either, so we treat the galaxy as basically static. In other words, the stellar motion can be
ignored for colonization. However, you can play with those numbers a
lot, or even outright discard the model when using something like our Gardener Ship approach. If your ships can move at a modest fraction
of light speed, say 10%, then most of the percolation time is growing your numbers on
each new planet, and you can advance from each one a lot further for each step, since
they can hurl new colonial ships much faster & further each time. You might make steps of 100 light years every
two millennia, colonize at 5% light speed, and settle the whole galaxy in just 2 million
years. You are also way less likely to stall out
on any given front because you’ve got such a large range encompassing so many settled
worlds that if some don’t grow quick and send out colonies, many others are plugging
that gap, like broadcasting lawn seeds. On the flip side of this, if you have to go
slower, or if many worlds just aren’t desirable for colonization or if they grow much slower
or tend to lose a desire for colonization and don’t send out ships once they can,
then you percolate far slower and might even stall out completely. If we were assuming it took 100,000 years
to grow enough to make each new jump and it was 10 light years a jump, you’re creeping
outward from Earth at just a percent of a percent of light speed and will need a billion
years to colonize the galaxy, during which time you can basically discard the notion
that humanity is even doing this, as your civilizations are diverging massively at each
step so that even your nearest neighbors or mother world are basically different species
and you might argue about who colonizes what, since there’s not likely to be much team
spirit even in your local expansion area. This is even more hindered if you can’t
expect to find a suitable candidate in 10 light years of you. If you can only make a successful colony around
maybe 1 in 100 stars similar enough to our own, and only maybe 1 in 100 of those has
a planet that’s a desirable candidate for terraforming, you’re only going to have
a couple candidates within a 100 light years of you, not the many thousands we normally
assume when discussing this topic here on SFIA. If your ships aren’t relativistic, and you’re
focused on terraforming planets, that’s a real long voyage to ask folks to make for
the honor of living on desolate wastelands for the many millennia it will take to terraform
them properly. And it is the basic reasoning behind the classic
scifi space opera of galactic empires with only a few million inhabited worlds. That colonization process is very slow and
very hard and very disorganized and can peter out as colonies fail or just barely prosper
and aren’t interested in repeating the Herculean task of colonizing again themselves. It also implies you might have dead colonies,
ones that just failed and that went extinct, and timelines long enough that even if an
older alien one did so on a world we came across, we might not even know they had. That’s also a popular notion in scifi, that
great civilizations arise and eventually end, leaving little or nothing behind in their
wake when a new civilization evolves and sends out its sons and daughters to do as they did
before us. On such timelines you really can’t treat
the galaxy as a static place either, not only might a civilization that once looked like
a vaguely spherical blob have smeared itself across the galaxy as all the stars moved around,
but they might actually be taking advantage of local stellar motion for colonization. If you are going the slowboat route of colonization,
taking many centuries to prepare for missions that might move not much faster than our modern
space probes, you might bypass nearer stars in favor of ones moving toward you. So the paper lists a number of parameters
and assigns various values to them, those values we need not consider, they weren’t
chosen out of a hat, but still are fairly arbitrary, even if reasonable guesses. And like Drake’s equation when you’ve
got a lot of parameters, many of which you can’t nail down to even an order of magnitude,
you can’t draw many concrete conclusions from them. We’re not going to walk through their math,
though it’s an interesting model. Some of those parameters are the fraction
of systems that are settleable, the density of systems, which is not uniform, some regions
of space will be near wastelands while others will be much closer and richer in worlds than
our own region. We’ve also got probe or ship range, and
velocity, as those both are major factors in not just how far and fast you can go, but
how many candidate worlds you have access to and if you’re even willing to do it. Others include probe or ship build and launch
times, lifetime of the settlement, average stellar motion if you’re going slow enough
you need to factor that in, and many more. This includes the notion that if settlements
are dying off, folks would have to resettle them to continue expanding. Now this gets back to the Fermi Paradox more
directly by reminding us of Michael Hart’s Fact A in his original conjecture about the
Fermi Paradox, which is sometimes called the Fermi-Hart Paradox because Hart is basically
the guy who began the discussion of the Fermi Paradox. “Fact A” is that there are no aliens currently
on Earth, obviously not everyone agrees with that but it’s the basis of discussion for
the Paradox, since there’s obviously no Paradox about where all the aliens are if
the answer is out in a farm field crushing corn stalks to make modern art. I also usually don’t like calling that a
fact, as a lack of evidence to me is more of an assumption than a fact. I’ve never seen leprechauns, don’t believe
they exist, but I’m hesitant to say “Fact: Leprechauns are not on Earth”. Whichever, it’s the basic assumption of
the Fermi Paradox along with the idea that while Earth and it’s life might be fairly
special, it’s probably not so special we wouldn’t expect lots of other places where
life can pop up and get a foothold and potentially be spawning other civilizations that might
be interested in colonizing new worlds too. But there’s a second half of that, because
while it says there are no aliens currently on Earth, it also implies none in the past
too. By fossils and genetics, we can rule out us
being an alien colony that got abandoned, unless it either happened a few billion years
ago, since we can see a clear relation to other life on Earth and a common origin, or
that they took more of the bioforming route and basically adapted themselves into our
existing world very subtly, which is possible but tends to involve a lot of weird choices
and handwaves to make much sense without ramming into the fossil record. That brings us to an outright failed colony,
one that just didn’t take off and was being done to minimize disruption to the local and
current life, and could maybe escape notice in the fossil record. Just to throw one out there for daydreaming,
if some aliens came here 65 million years ago and settled near Yucatan, they might have
domed things over at their base to avoid too much back and forth ecological leakage while
they were setting up and since they and their own life would probably not match well for
existing conditions. That’s something we’d do, even if we meant
to totally replace the ecosystem already on a world, we’d want to study it in detail
first and keep ourselves isolated. If after a few centuries things just weren’t
working out, we weren’t growing much, and many of those born since were fond of the
existing ecosystem and didn’t want it destroyed, I could see them abandoning the colony or
setting the reactor to blow up and vaporize all the extraterrestrial life, leaving behind
a big crater. This would effectively erase most of the evidence
they were here, and time would do a good job removing the rest. This is an example of how you can decouple
Hart’s Fact A, no aliens here now, from no aliens here ever. So the paper argues there’s an effective
temporal horizon that would obscure our ability to see previous visitors or settlements. See the Cyclic Apocalypse episode though for
why this normally won’t tend to work for expecting time to erase signs of prior civilizations,
or short form, bones aren’t the only things that fossilize or otherwise leave a long-term
remnant, and civilizations would tend to leave a ton of mysterious right angles in their
geological records. The caveat here is you must have been a fairly
large civilization to leave enough of those kinds of footprints that we’d be likely
to have some survive and numerous enough we’d find them. So this is the basic notion: civilizations
arise probably not too often, don’t find too much to colonize, take a very long time
to do it, and often have local pockets grind to a halt or die off. When new civilizations arise, the time between
these civilizations and their smaller scope, means you could easily not even see them if
they’d had a colony next door at some point or maybe even on your own planet. We’ll mostly bypass the paper’s discussion
of stellar motions because I think that overdoes things, if you are already assuming colonization
so slow that each colonization front is incorporating the motions of stars and the galaxy not being
static into their plans, I’d think you could just assume they will throw their hands up
in the air and not colonize just because of the time needed. Whether you’re doing it by slowboat generation
ships or probes that arrive and unpack and replicate and build a civilization, time remains
a hurdle that many are not going to want to try jumping over, especially if that’s such
a long time that whatever is doing the colonization isn’t going to even vaguely resemble what
their mother system has mutated into or the original colonists who left. Hard to get the dinosaurs to colonize the
galaxy if they know it will be humans who actually arrive, essentially. All right, that brings us to the question:
what’s the flaw in the paper’s reasoning? Channel regulars are probably raising an eyebrow
with me at that “Good worlds are hard to find” aspect, asking why you even care about
finding good worlds since we normally wouldn’t even expect spacefaring civilizations to much
care about planets, to quote my friend Fraser Cain, “Gravity wells are for suckers”
you’ve just gone to all that effort to escape your own planet’s gravity well, why would
you go set up shop on another one? So, when we talk about colonizing other star
systems, we usually emphasize that you start not by landing on a planet there, but by linking
up to various resource-rich low gravity objects like Asteroids and Moons, build rotating habitats
there if you want or need gravity, and settle planets if you want to, but only after you’ve
setup your basic space based industry and infrastructure. Planets may or may not have their value and
might end up very prized by civilizations as potential centers, but in their own right
are no bottleneck to expansion. If we assume that approach, it pretty much
ends the theory under discussion today right there. Interstellar colonization is mostly done by
civilizations that back home already mostly don’t live on planets, as they build and
breed their way up to K2 civilization status, and while Earth-like planets might be highly
valued, or not, most folks live in artificial habitats already. They’ve lived on one for the long trip to
the new system, and ought to be happy enough in one at the destination or even prefer those
over spending centuries to terraform a planet. Such being the case, virtually every star
and planet, habitable or not, becomes prime real estate, because to you they are really
just an electric outlet and building supply shop. But even if those systems are more valued,
as they may well be, you will tend to backfill as you go, same as settlers always claim the
best spots first and fill in over time. So, let’s get into the meat of my objection. This concept is very dependent on the notion
that colonists are likely to be either limited or picky about what systems they settle and
might tend to fail even then. That’s a perfectly reasonable assumption
inside the usual space opera context of just settling Earth-like planets, but even ignoring
the notion that we’re likely to build most of the places we live in, not terraform them,
we aren’t going to make our first colonized world around another star. We’d try for Mars or Venus first, and either
we find out that’s not practical, and either stay at home or go the artificial habitats
route, or for a more cybernetic or digital existence, or we’d have gotten practice
making places like Venus and Mars habitable, in which case we already know how to do it
and if we can do them, then “Earth-like” gets very unimportant. Worlds of similar mass and temperature to
Earth might not be too common, but if we widen the range to include wretched miserable rocks
like Mars and Venus, then odds are you won’t ever have to look far for a star that’s
got a candidate, and you also have a couple planets whose inhabitants won’t find them
unappealing and can supply colonists. Even if you expand the habitable world definition
to be safe, amenable star systems, without exposure to dangerous stellar events like
supernovae, pulsars and quasars, the time horizons and backfilling of systems from continued
growth will just leave gaps in your galaxy’s colonization, not roadblocks. The second flaw is that it probably won’t
be a process of planet-hopping anyway. Even if planets are preferable, especially
to folks who live on them, a future population of this solar system is likely mostly to be
people who weren’t born on a planet, and live inside a great big cylinder, or on a
computer chip, and neither of those cares much about either travel times or the destination’s
planets, just so long as the destination has free matter and energy to exploit. The former already live on a spaceship, since
a rotating habitat is a spaceship, and the latter can literally just send copies of themselves. Remember, we all suffer from confirmation
bias, the tendency to search for, interpret, favor, and recall information in a way that
confirms one's preexisting beliefs or hypotheses. We all currently live on a planet, so our
bias is to naturally think that planets are good things to live on and in the future,
our descendants will continue with that trend. However, that’s dangerous thinking because
if we asked a farmer a couple of centuries back whether the majority of the world’s
population would live in cities in the future, they would have laughed at us. They would have rightly argued that the majority
of folks live as farmers and if everyone moved to towns or cities, there wouldn’t be enough
farmers to feed all the city dwellers. Now, we know from our history that the farmer
was ultimately wrong. Mechanization and technology revolutionized
farming and today, the majority of folks now live in urban environments. We have to be careful not to apply the same
confirmation bias to the notion that humanity will always want to live on planets too. By the time we’re ready to aim for galactic
colonization, we’ll be a K2 civilization or moving toward that. Our solar system will be peppered with thousands
or millions of space habitats, possibly far more, and the majority of humanity will not
have set foot on a planet let alone lived on one. They won’t be wedded to the notion that
planets need to be colonized any more than we are wedded to the notion that most of us
need to be farmers. Another objection is just this general notion
that civilizations can go extinct — they don’t. They can collapse and we’ve tons of examples,
but they don’t just die off without external pressures, usually a rival civilization eroding
them, even more so when they are high-tech and thus resilient to things like natural
disasters. Collapse is not synonymous with extinction
then, it’s just an alteration, usually to something tougher and stronger, except for
when discussed by a historian who had a crush on the civilization under discussion and dislikes
the barbarians who ended them. I don’t usually like to broaden the term
evolution to include social aspects, but it’s valid on longer timelines and particularly
in this case. Applying the survival of the fittest litmus
tests to a large sample size, you should generally expect civilizations over time to get better,
not worse, at surviving. You can argue that evolution, which generally
breeds to make things tougher and more adapted to their area, does not apply to high-tech
civilizations, but it basically doesn’t because through forethought, planning, and
strategy we can do better than random odds. Which again kind of negates the notion that
such civilizations will dwindle on new worlds, when they’re drawing on centuries of planning
and prior experience and know what challenges await them. And even if we accept the idea that a combination
of slow colonization, a low fraction of settled worlds of stars available, and modest long-term
success rate for colonies would create “silent bubbles” in our galaxy, that won’t necessarily
solve the Fermi Paradox. It will strongly depend on the visibility
of civilizations; even if Earth is in the middle of a thousand-light-year bubble of
space that’s not settled yet, or not anymore, the closest Dyson swarm or space beacon may
still be visible. Especially as the folks living there know
they are not alone and not hidden, since their launch would have been a big and recorded
event, thus have every reason to be heard and none to hide, and we see none. Or short form, it’s a good theory for the
more classic notions of planet colonization but like a lot of Fermi Paradox approaches
for intelligent life being reasonably common, it’s leaning too heavily on classic notions
of settling new places. What we’d tend to expect is our own system
boasting many trillions of people living in space habitats that aren’t too interested
in living on or colonizing planets. If you’re curious about some of the solutions
we’ve discussed for that, check out our Generations Ships Series and Outward Bound
Series, and if you want to know more about other solutions for the Fermi Paradox or the
problems with them, try our Fermi Paradox series. And of course all of those, along with this
paper, focus on the idea that while our technology will improve, it probably won’t get a lot
of the neater advantages often seen in science fiction that tend to violate the speed of
light or the laws of thermodynamics. This upcoming Thursday we’ll relax about
that a bit and contemplate some of those more hypothetical technologies so advanced they
are indistinguishable from magic, and what their implications would be for the civilizations
that wield them, in Clarketech. For alerts when that and other episodes come
out, make sure to the subscribe to the channel. And if you enjoyed this episode, hit the like
button and share it with others. You can also support the channel on Patreon. Until next time, thanks for watching, and
we’ll see you Thursday!
Bonus SFIA Sundays are the best Sundays.
It's a good video. KSR's Aurora scenario basically relied on human beings requiring exposure to the general Earth atmosphere and biosphere to stay healthy, and had this be something that's virtually ineffable - the only way to create it was by either being on Earth or terraforming another world to be Earth-like.
If that's not true, then there's no issue with people spending those whole lives in space habitats.
"Gravity wells are for suckers" (14:53) but the SFIA ship Unity is still flying to stars. "You just spent all that effort escaping..." the Sun's "...gravity well why would you go set up shop on another one?" The Milky Way has more Jupiter mass rogue planets than stars. There should be an even larger number of Earth mass rogue planets. Rogue planets can accrete and retain deuterium and 3-helium. Rogue planets can retain asteroids and moons. Why not fill up the fuel tanks from objects that require less fuel to stop at or leave?
Aliens could have pillaged most of the Kuiper belt. We do not have a good reference so we do not know how much is missing. We do not even have single pixel images of objects in our Oort cloud. Measurements of dust indicate that the solar system is a relatively cleaned out. Alpha Centuari, for example, has 100x as much dust. It is quite possible that our Oort cloud is not dense enough to be worth expending effort.
Colony ships might use stars as gravity assists so that they can move to new regions (rendezvous with Rama). A binary star system is much more useful. Anyone coming into the Sun's neighborhood would aim for Sirius or Alpha Centuari. You might want to use high velocity stars to colonize further in which case Barnard's star would look much more appealing than our Sun. Regardless, aliens using the Sun for gravity assists would leave no evidence. It is only very recently that we have the ability to see a large ship passing through the solar system.
I love this episode and that I instantly knew what he was talking since I read that book when it came out. Very good, highly recommended.