
The Fermi Paradox and the Aurora Effect: Exo-Civilization Settlement - pkrein
https://arxiv.org/abs/1902.04450
======
doctor_eval
I’ve always felt that the reason we haven’t heard from aliens is because they
know New Physics and they use it to communicate. Given how much of the
universe is made up of dark energy, dark matter and other unknown physics, it
seems reasonable that there are significant discoveries to be made which could
perhaps be exploited.

I mean let’s say we discover a new, non-electromagnetic way to communicate
reliably over vast distances using some kind of low power, high bandwidth
signalling system. We’d abandon EM in a geological heartbeat. In cosmic terms
we would emit a wafer thin EM shell just 150 light-years thick - and then we
would fall silent.

So basically I just think we don’t know enough physics yet. We are perhaps a
few discoveries away from being able to listen in on alien conversations.

~~~
fjfaase
Sean Carroll argues that all physics, which could matter to us, has been
discovered. See for example his talk "From Particles to People"
[https://www.youtube.com/watch?v=X5Fel1VKEN8](https://www.youtube.com/watch?v=X5Fel1VKEN8)

~~~
CJefferson
Before I set off watching a 28 minute video (where, worryingly, comments are
disabled), could you give an outline that suggests this isn't crazy?

There are obvious things which feel possible and would revolutionise so many
things, like room temperature semiconductors, which we don't have yet. Also
things we've better understood since 2012 like detecting gravity waves.

I don't understand how anyone could think we've "discovered all the physics
which could matter to us", when we know full well there are massive gaps in
our understanding.

~~~
fjfaase
He basically argues that there are no forces to be discovered which could have
a measurable effect on our day-to-day functioning. For example, so far, we
have not discovered any dark matter particles. This does not rule out that we
will discover them, but for us humans (consisting of protons, neutrons and
electrons) it will not have any effect. Because if it would, we already would
have discovered them. The existence of other particles, like neutrino's, which
zip through our bodies by the billions every day, also have no effect. We are
of course effected by photons in some energy spectrums. In view of this, I
think it is very unlickly that we discover any new physics which would allow
us to communicate with aliens.

~~~
whatshisface
That sounds kind of like a caveman arguing that there will never be a
practical temperature higher than their campfire, because anything hotter
would burn the meat.

~~~
TheOtherHobbes
But... math! Which can't be wrong, because obviously we already know all the
math there is to know. QED.

Carroll says strange things sometimes. Epistemology doesn't appear to be his
strong suit.

~~~
ncmncm
It's all win-win, for him. If we fail to discover anything, he's right. If we
find something, "nobody could have ever predicted that!".

------
_Nat_
I thought that we already conclusively ruled out alien life by observing that
there aren't huge, galaxy-sized smoke signals, generated from their massive
candles to heat their galaxy-sized cottages? I mean, if aliens were out there,
then surely they'd have sent us a notarized letter in the mail by now, as
would any civilized culture. I bet they use really fancy quill pens, too!

...seriously though, I can't fathom why people are so caught up on the _Star-
Trek_ -like predictions where hyper-advanced aliens are still essentially
humanoid. It's at least as absurd as
[protocells]([https://en.wikipedia.org/wiki/Protocell](https://en.wikipedia.org/wiki/Protocell))
assuming that all advanced life would be essentially protocelluar.

~~~
kayaeb
Some people claim to have ruled out type III civilizations [1], which I think
is what you're referring to.

I thought also that some researchers claimed a star had signals consistent
with a type II [2].

[1]
[https://en.wikipedia.org/wiki/Kardashev_scale](https://en.wikipedia.org/wiki/Kardashev_scale)

[2] [https://www.space.com/30832-kepler-telescope-alien-
megastruc...](https://www.space.com/30832-kepler-telescope-alien-
megastructure.html)

~~~
dvdkhlng
According to recent news, the alien megastructure proposed in [2] may just be
a shredded moon [3].

[3] [http://www.astronomy.com/news/2019/09/evaporating-exomoon-
co...](http://www.astronomy.com/news/2019/09/evaporating-exomoon-could-
explain-weird-light-patterns-of-tabbys-star)

~~~
stinky
That's no moon...

------
nabla9
Fill in time:

> unless the effective probe launch time is greater than 270 million years,
> the galaxy is old enough for every system to have been settled from an
> initial single civilization

Conclusions:

> When diffusive stellar motions are accounted for,they contribute to the
> Galaxy becoming fully settled in a time less than, or at very least
> comparable to its present age, even for slow or infrequent interstellar
> probes.

>While settlement wave crossing and fill-in times are short, consideration of
finite civilization lifetimes in a steady state model allows for conditions in
which the settled fraction X is less than 1. Thus the galaxy may be in a
steady state in which not every settleable system is currently settled.

Conclusion basically says that if there are expanding civilizations in our
galaxy, they spread very slowly, have filled the galaxy sparsely or have
limited lifetimes. Assuming they are not avoiding contact.

~~~
johnchristopher
What if we are the probe and we haven't figured it out yet ? Or what if we
somehow didn't get the memo telling everyone to stay hidden because of
_danger_ , because we are late to the party ? What if there's a natural/alien
occurring culling of some kind and we somehow slipped through and now we are
alone ?

^^

~~~
has2k1
> What if there's a natural/alien occurring culling of some kind and we
> somehow slipped through and now we are alone ?

You are referring to what is known as "The Great Filter". The more troubling
question is, What if we are alone because all the more advanced civilizations
have been culled?

~~~
kiliantics
climate change certainly looks to be a very likely contender for a filter

------
mprev
The Fermi Paradox always strikes me as hubris.

As Douglas Adams wrote, “Space is big. You just won't believe how vastly,
hugely, mind-bogglingly big it is. I mean, you may think it's a long way down
the road to the chemist's, but that's just peanuts to space.”

We've been looking for alien life for, what, 50 years? And we've made various
assumptions about what we should be looking for. Oh, and we've been doing so
on a very limited budget, with the technology available to us, in a tiny part
of the sky .

~~~
goatlover
Yes, but Fermi's Paradox is based on calculating that it would only take an
alien civilization a few million years at the most to colonize our galaxy,
which has been around for billions of years. Add to that the likelihood that a
slightly more advanced civilization than ours would be able to make self-
replicating probes. And it only takes one civilization to do it. So where are
they?

Think about it this way. If human civilization persists and continues to
advance, what's stopping us from spreading out to nearby stars within the next
thousand years? And that's nothing on the cosmic timescale.

~~~
neuronic
Uhhh that assumes alien life has the same intent as _current_ us. Intelligent
alien life may just as well have explored a lot, figured "meh..." and build a
few Dyson spheres to spend the rest of their existence in a perfectly pleasing
simulation.

People already get sucked up by Warcraft and not even 100 years after
computers made their breakthrough we fiddle around with haptic dual-4K VR.

~~~
naasking
It only takes one expansionist species to populate the whole galaxy. Thus, if
intelligent life were common, we should detect them. You'd have to argue that
_no advanced species_ would ever do this, which is possible, but seems less
plausible.

------
xcq1
[https://arxiv.org/abs/1902.04450](https://arxiv.org/abs/1902.04450)

~~~
sytelus
Another relevant paper:
[https://arxiv.org/abs/1612.03238](https://arxiv.org/abs/1612.03238)

------
OscarTheGrinch
One universal law that these discussions usually fail to consider is
opportunity cost. There are a near infinite number of constraints and
competing priorities at every stage of civilisional development, and that's
why we don't see any Dyson spheres or similar grandiose outputs.

------
roca
They talk about planets and generation ships. Isn't it obvious that a
multimillion-year spacefaring civilization would be mostly autonomous machines
that have no need for habitable planets and can sleep for aeons?

They also talk about civilization lifetime and interstellar resettlement. But
interstellar resettlement doesn't make sense to me; simpler for machine
civilizations to hedge their bets by putting resettlement sleeper ships in
highly eccentric orbits with some desired period. Maybe there are
civilization-killing effects that disable those resettlers, but they would
apply to interstellar resettlement too.

~~~
ymolodtsov
Well, no. That assumption is as good as any.

------
YeGoblynQueenne
\- Where are my socks?

\- Did you look in the drawer?

\- Why, I've searched everywhere! I can't find them!

\- Well, then - you must have no socks. Your socks never existed.

------
YeGoblynQueenne
>> Unless the individuals in the species driving the settlement have very long
lifetimes (> 100 y) it is dicult to see how a galactic scale culture can
arise (i.e. commerce etc. Krugman (2010)).

Why is a mere "more than 100 years" considered a "very long lifetime"? Is
there any reason to assume that the majority of intelligent species, capable
of technological civilisation, that may inhabit the galaxy, will not have a
lifetime measured in thousands, or even hundreds of thousands of years?

The lifetime of the averarge _star_ is a few billion years. We can assume that
mos species will not have naturally evolved lifetimes lasting bilions of
years, but a) species may evolve lifetimes lasting _millions_ of years, or, b)
a technologically advanced species may extend its lifetime indefinitely.

A species whose individuals lived for a few hundred thousand years would have
plenty of time to visit the Earth by travelling in sub-relativistic speeds,
from a significant portion of the galaxy. A species whose individuals lived
for a few million years would have plenty of time to visit the Earth and wait
for our own civilisation to die out. A species whose individuals lived for
billions of years could pay us an intergalactic visit and still have time for
tea.

Extremey long lifetimes are not impossible and they are not even particularly
improbably. Here we are wondering whether there are other technological
civilisations among the stars. Why should we assume that they are anything
like we are?

~~~
ryandvm
Long _natural_ lifetimes are a fundamentally at odds with evolutionary
progress. The lifespan of a species is directly related to how quickly that
species can iterate generationally. Fewer generations mean less natural
selection, which means a less evolved life form. Also, if the organisms don't
die off fast enough, they end up competing with their own offspring for
resources.

That said, I would imagine that once most life forms get to the point that
they are able to extend their lifespans with technology, they probably always
do. They just don't evolve anymore...

~~~
YeGoblynQueenne
>> Long _natural_ lifetimes are a fundamentally at odds with evolutionary
progress.

I'm not sure I see that. For example, humans live many orders of magnitude
longer than bacteria and yet we have both evolved just fine.

Anyway, I don't see why a species is pressed to evolve quickly in absolute
terms. If all species on a given world evolve lifetimes many orders of
magnitude longer than on the Earth, then there's no reason for any particular
species to hurry.

I think how long or short a species' lifetime is can only be understood in the
context of the environment in which it evolves. In any case, we don't know
anything about life on other worlds, and my point is that we can't really make
such big assumptions based on the single example we're aware of.

------
solotronics
All of these calculations are predicated on us existing in a physical universe
and not a simulation (simulverse?) it could be we are the only life in this
specific simulated existence, even though the mathematical rules of the place
would make it appear there should be others.

~~~
tsimionescu
The assumption is that there is a set of laws of physics which are consistent
with our observations, that are the same across space, that do not vary with
time, and that all phenomena in the universe are ultimately caused by these
laws.

Whether these are the laws of nature, the laws of a simulation, or the laws of
some Gods playing around, it makes no difference.

Unfortunately, without these assumptions it is impossible to have any kind of
scientific knowledge - if we can't assume that the sun rising for the last
hundred thousand years means it will rise again tomorrow, or if we don't
assume that the universe extends in the past as well as the future, there is
nothing meaningful to study.

Note: the laws of physics I am talking about above could be very different
from what we know today - just as QM and Relativity are to Newtonian physics -
but that would not change the assumptions I'm talking about.

~~~
solotronics
Even if my half baked thought experiment was true I agree in that it shouldn't
make any difference in our goals or ideals. I was merely positing a
possibility for why if statistically our spacetime could be packed with
neighbors we haven't noticed anybody. Another reason could be there are
visitors they just exist on dimensions perpendicular to the 3d space we
perceive, maybe even our concept of spatial dimensions is a oversimplification
or a small slice of a full spectrum.

------
aylmao
Here's the thing— we're assuming advanced civilizations want to expand in the
first place. Why?

Life in OUR planet was shaped by competitive evolution and we have reason to
believe life in other planets has been as well— it's how natural selection
works after all, and at least in our planet it's proven to be an effective way
to go from primordial soup to complex, intelligent life that can out-smart its
competition hoard all the resources.

But how do we know that this is not a behaviour that civilizations, well,
outgrow once they've hoarded all resources?

Unbound growth is an effective strategy in a competitive scenario like the
evolutive stage of species, in large part because it's also one of simple
incentives. When a species becomes dominant though, it is very dumb, because
the species will just end up reaching the limit of available resources and
burning through them, thus killing themselves, like bacteria in a petri-dish
multiplying until all the food has been eaten and they all starve to death.

The argument goes, that's when a civilization would expand. Those bacteria
would try to find another petri-dish. The species finds more resources so it
can keep growing, but, can this incentive of "we have to keep growing" stand
the test of time?

Simply from a practical standpoint, Alpha Centauri is 104691 times further
than Mars. The technological gap between sending a colony to a planet in your
system, versus one in another star is gargantuan.

First of all let's consider that planets are all ballpark similar in size and
resources, therefore value. Is the investment even worth it? Is traveling
104691 times more for the same resources a stronger incentive that simply
learning to find equilibrium with the resources easily available in your
system?

Even if for the sake of argument the civilization decides it is, could they
even achieve it before running out their available resources? It'd be a race
against the clock.

There is reason believe the civilization would be forced to find stability and
equilibrium within their existing system before developing the technology to
be able to feasibly colonize a neighboring star system for the purpose of
extracting resources. And if not to extract resources, why put the effort to
continue expanding?

Fear? Of what? A nonexistent galactic empire?

Pride? If their history is anything similar to ours (which, since we're
talking about similar motivations, is perhaps a feasible assumption to make),
they would've learned colonizing far and wide does anything but promote a
stable, unified, timeless nation.

Therefore, my guess is one of two things might happen:

1\. They achieve stability because it's the only way to survive, and the
motivation to expand to another system dies off. Probe and explore, perhaps.
But if in a stable system, there's no incentive to introduce instability once
again by adding another habitat. On the contrary, the prospect of instability
is incentive to not.

2\. They don't achieve stability in their system, and so collapse.

In a nutshell, I don't think there's incentive for unbound expansion once
stability has been achieved, and I don't think unbound expansion can be
achieved before stability. Of course, this is all just my opinion, but it's
worth thinking perhaps the entire premise of extrapolating primitive evolutive
behaviors to an advanced civilization is out of frame.

Consider the future world of Brave New World by Huxley, or even the Time
Machine by H. G. Wells. Neither seem to have galactic empires; instead opting
for (very distinct) forms of stability (and decay).

~~~
mytailorisrich
IMHO, human nature means that people will settle other planets or simply space
if they have the technological capabilities.

Just look at SpaceX and co. and all the people interested in that. If the
technology exists some people will go. This does not have to be a large number
compared to the overall population. That's enough to kick-start the process in
a chaotic and unplanned manner...

------
coolspot
> Using our steady-state model we constrain the probabilities for an Earth
> visit by a settling civilization before a given time horizon. These results
> break the link between Hart's famous "Fact A" (no interstellar visitors on
> Earth now) and the conclusion that humans must, therefore, be the only
> technological civilization in the Galaxy. Explicitly, our solutions admit
> situations where our current circumstances are consistent with an otherwise
> settled, steady-state galaxy.

------
julius_set
I mean if there are no other intelligent civilizations (yet) in the universe —
which seems highly unlikely based on the numbers, then we have an obligation
to seed the universe with ourselves and propagate other species through
genetic enhancement and grooming.

We might be the progenitors of other intelligent species who might look back
at us fondly and remember our shepherding.

Again highly unlikely, but a good point that we should not kill ourselves
beforehand.

------
hoseja
I find the assumption that a space-faring civilization would need ideal
planets to settle on somewhat questionable.

~~~
XorNot
I mean a lot of this all turns on what happens to us in the next 200 years.
Which... That's slightly less time then federated America has existed.

Are we at the peak of what people achieve on temperate world's? Maybe
technology doesn't meaningfully advance much beyond what we already know - you
get a computing boom, Moore's law ends and then a couple decades of
discovering no substantial alternatives to the silicon chip.

~~~
simonh
I've been homing in on this conclusion, or a neighbour of it for a while. Take
the periodic table. That's it people, we already know all the stable elements.
Nobody's going to discover unobtanium. Aside from some high energy physics and
some details of quantum mechanics, we probably know most of the useful
practical physic there is. The open frontiers are biology and chemistry, but
those are all about combinging things we mostly already know about in new and
interesting ways. Eventually we'll figure all of those out as well. Then what?

I'm not saying it's impossible we'll discover some amazing, paradigm shaking
new physics that will upend everything. Maybe. But we can't bank on it and
it's entirely possible no such civilisation shaping new physics exists.

If that's the case, then the future will all be about engineering based on
parameters we already pretty much know. I often see the Daedalus project held
up as 'proof' interstellar travel and even interstellar colonization are
possible. That was a designs for a very modest space probe payload, but even
so the resources required to build them would pauper our whole civilization.
Even if, or when, we master the resources of our whole solar system, those
probes would be a significant cost and it seems likely they're way too puny to
deliver a robust self-replicating bootstrap infrastructure. There's nothing
inevitable or necessary about interstellar colonisation. The universe doesn't
owe us Star Trek.

------
tiku
Given the scale and vastness of the universe, if there was/is other life we
have a good change of finding some remnants of them, most likely spaceships?

~~~
tzfld
Given the vastness of the Universe, I would say there is low chance finding
some spaceships wandering out there even if they are present.

~~~
14
This is how I feel as well. Some will say it would be so obvious by now we
would have seen some sort of indication but then I think of all the planes
that crashed without a trace and we have not been able to find even with an
idea of where they were flying. The universe is huge. We have no idea how they
will try and communicate maybe it's not something as obvious as radio
transmission but maybe they have figured out quantum entanglement
communication or something beyond our means but super obvious and useful to
species who have figured it out. I grew up watching all the Star Trek shows. I
have to believe the universe is filled with other civilisations waitin to talk
with us.

------
andrewfelix
Interesting premise. Pity I can't read the article.

~~~
archi42
Maybe the link was updated? It now points to arxiv, from where you can
download the paper (or does arxiv implement some geoblocking?).

~~~
andrewfelix
yep, was just abstract earlier

