It's cold out there in the Oort Cloud but someday it could be the place
where we keep the home fires burning for humanity.
Today we'll be talking about how to colonize our solar system's Oort Cloud and Kuiper
Belt, two fairly distinct regions of space but with a good deal of overlap into how they
would be colonized.
However we should start by talking briefly about how planets form and what a planet is
first.
The basics are simple enough, some region of space is thick with gas and something,
like the shockwave of a supernova, comes by and causes it to start being less evenly distributed.
Bits will emerge that compact into objects and have enough mass to suck in more material
but this often results in a protoplanetary disc.
Momentum, angular or regular, has to be conserved so you end up with a disc of material all
spinning in one direction and a star forms at its center and other clumps become planets.
Clumps of matter on the same orbit of this disc tend to combine.
There are accepted rules for what qualifies as a planet.
The first rule is that the object must orbit a star, otherwise it's not a planet, it's
a moon.
The second is that it needs to have enough mass to be basically a sphere-shape, otherwise
a soda can orbiting the Sun would qualify as a planet.
And the third is that it should have cleared the region it orbits through.
This third rule for what makes a planet is the one that demoted Pluto to dwarf planet
status.
Pluto is a bit more massive than the entire Asteroid Belt that orbits the Sun between
Mars and Jupiter, but the Kuiper Belt, out past Neptune, is a lot more massive than the
Asteroid Belt.
Any solar system might have an Asteroid Belt, or even multiple ones, but odds are most have
a Kuiper Belt, some region on the edge of the main protoplanetary disc that was too
spread out to form a planet, it's like the foam at the edge of a whirlpool.
Pluto is a Kuiper Belt object itself, part of why it was demoted from full planet status.
The region out past Neptune is full of icy bodies, many of which would make respectable
moons, that we variously call Trans-Neptunian Objects, Plutinoids, Kuiper Belt Objects,
or Scattered Disc Objects.
We don't know their combined mass with accuracy, but this region from 30 to 50 AU is estimated
to be 20 to 200 times more massive than the Asteroid Belt.
We often talk about how handy the Belt will be for space colonization, and this second
belt is as well.
Out past that is a more hypothetical region called the Oort Cloud, which probably has
two segments.
One inner one that is somewhat disc-like, sometimes called the Hills Cloud, and the
outer region is spherical.
Now we often call the Oort Cloud theoretical but there's no doubt that region of space
exists and has lots of tiny icy bodies, just the exact extent and nature of it is in doubt.
It's very hard to see a Kuiper Belt Object, and they are far closer to Earth and the Sun
than Oort objects.
Two identical objects, one ten times further from Earth and the Sun, are vastly different
in their detectability.
Being ten times further from us, we see only ten-squared or one-hundredth the light it's
closer twin gives off, at the same time it's ten times further from the sun, and only gets
ten-squared or one hundredth the light its closer twin gets.
So on Earth the closer one appears ten thousand time brighter, and only our best equipment
can see all but the largest Kuiper Belt objects.
The Oort Cloud is not ten times further away than the Kuiper Belt, it's more like a thousand,
so objects out there appear about a trillion times dimmer than their twins in the Kuiper
Belt.
For that reason we don't have much data on objects out there by direct imaging, so
we know there's plenty but can't speak with much certainty and have to limit it to
theory and models for now.
As an example, a clone of Earth and the Sun off at 1 million AU, about 16 light years,
would be a trillionth as bright too, because it's just far away from us, not its Sun.
Needless to say we have a lot of difficulties seeing such an object, but we know where to
look, the volume of space near a sun where you'd find planets is about a billionth
the volume an Oort Cloud would occupy.
On top of that, while we theorize the mass of the Oort Cloud to be several times that
of Earth, albeit with huge margins of error, the objects in it will tend to be a lot smaller
than a planet.
Of course you can have planets out in the Oort Cloud too, wandering ejected ones or
ones in such a loose orbit they barely know the Sun is there, and we call these Rogue
Planets, Nomad Planets, or Steppenwolf Planets.
We discussed the possibility of life developing on these way back in the Rogue Planets episode
and we briefly touched on settling them there too.
The basic upshot though is that Kuiper Belt, Oort Disc, and Oort Cloud probably are swimming
in tiny icy bodies of potential value to us, many of which might have some rocky material
in them too.
To colonize any of these objects one has to abandon solar or fission power as classic
options, in favor of fusion, the fuel for which they have plenty of.
There's two caveats on that.
You might find some fissile materials out there and you can export them, and so too,
while a solar panel won't work for direct sunlight, lasers on solar satellites nearer
the Sun can beam energy out to panels.
I'd always rather have my power plant on-hand, not so far off it might take a month just
for a message to reach them, but orbits are predictable things and keeping a laser on
a station out in the Oort wouldn't be that hard.
Lasers do spread out over distance, so it would arrive less as a tight beam and more
like a diffuse flashlight, and of course we might prefer microwaves over visible light,
a maser, but there's nothing too sophisticated or complex about supplying power this way.
I always like to stress the importance of fusion to humanity's future in space, but
I also always like to make I it clear that with a bit more hassle we can do most of the
same things by using the natural fusion reactor that is our Sun.
Normally when we start discussing these icy bodies for colonization it's in the context
of dragging them inwards to terraform Mars or Venus, but as we've seen in this series,
that classic image of colonizing the solar system by terraforming the planets in it is
seriously under-utilizing those resources.
We call those objects far out past Neptune icy bodies, but ice in this case is not just
water but methane, carbon and ammonia as well, and such objects often will have rocky material
in their centers or spread out in an ice and gravel fashion, like on the side of a road
that just got plowed for snow.
These other ices along with regular water ice are known as volatiles, and they contain
a lot of the materials we need for life, particularly ones that are not very abundant in the warmer
inner solar system.
That's why folks want to bring them in.
The thing is, while the Kuiper Belt Objects are perfect for that, the Oort Cloud really
is not.
It could take centuries to move such an object inwards in a fashion that wouldn't burn
up far more energy than its worth.
The Kuiper Belt also contains more than enough ices for terraforming all the planets and
making a lot of habitats.
Now if you want to go full on Dyson Swarm, you need a lot more, and the Oort Cloud probably
has a lot more, but even if it has dozens of times the entire mass of Earth in these,
it's still a lot less than the Sun has.
We talked about extracting resources from the Sun via Starlifting in the Starliftng
and Dyson Swarm episodes, and we'll discuss it a bit more in the next episode of the series,
Colonizing the Sun.
We can't be sure we can ever get such a process working, but it requires no new physics
and again is our topic for next time.
Assume for the moment you do get that working, and you do have fusion, and that you started
mining the Sun because you've already run low on materials in the inner system out to
and including the Kuiper Belt.
At that point the Oort Cloud no longer looks like a great place to bring material in from.
That's why this episode is titled Colonizing the Oort Cloud rather than the Kuiper Belt,
I'm sure we will colonize bits of the Kuiper Belt, sometimes just temporarily, and again
the colonization method is almost identical to the Oort Cloud.
However it's close enough to us, and easy enough to mine from the lack of gravity, that
I'd tend to expect us to bring the material in to use in settlements more often than settling
way out there.
However the Oort Cloud is even more way out there and while it probably contains far more
resources, it's nothing compared to what the Sun itself has.
So leaving those out there, especially if you can use them for something out there,
seems like a probable scenario for the future of our solar system.
Now settling one is actually trivially easy, if you can get out there and have a power
supply sufficient to live without the Sun, which you do if you can get out there and
slow down to land on one.
If you can get people out to the icy bodies you can colonize them.
The easiest method parallels how we do asteroids, you 'land', which due to low gravity is
more like parking at a space station, find a low spot or crater, and dig or melt your
way in, using the material you extracted to fill over the top, like an anthill.
Inside that you build a rotating habitat, or more likely just insert the one you and
the colonists came in, which can later be expanded.
Indeed, as with asteroids, since there is so little gravity in the way, you can always
expand your habitat, or chain of habitats, to be far larger than the original object
since you can pile all the material you are not using around you in a shell.
Thus you could start with an irregular shaped comet a dozen kilometers wide and end with
a nice polished icy shell the size of a decent moon full of habitats.
Such shells give nice protection from cosmic radiation and meteorite strikes too.
Of course the big question is why you would do this?
There are a lot of these icy bodies but they are spread far apart, your nearest neighbor
might be further from you than Earth is from Pluto and signals back and forth with Earth
could take many weeks or even months.
The edge of the Oort Cloud is about a light year away after all.
What would a colony out there be doing?
Why did they go there?
What do they trade in, if anything?
What purpose does such a colony serve?
At first it would seem like none.
If the material they had was particularly valuable back in the solar system we wouldn't
colonize these objects, at most we'd set up a small and minimally manned outpost to
do maintenance on the engine moving it back into the solar system.
That's a point to stress too, one shouldn't think of the Oort Cloud as part of a solar
system, anymore than a farm a fifty miles from Chicago is part of Chicago, city or suburbs,
just because it happens to be closer to Chicago than Milwaukee.
If it is even nominally involved with the city it will be because it has roads and highways
there and is inside its economic sphere.
Remember that bit about highways as it will come up again in a bit.
Again though, it wouldn't seem like a colony in the Oort Cloud could serve a purpose.
Stations out there can't serve as waypoints to other solar systems for instance, as odds
are very few of the objects are on a roughly straight line to another neighboring star,
and more importantly, interstellar ships do not stop en route to refuel or let the passengers
off to stretch their legs.
A ship gets up to speed and coasts in interstellar space, it doesn't burn any fuel while coasting
except for life support.
And that life support doesn't cost much energy, for a ship or a habitat.
Oh, it's a lot of power compared to your electric bill, especially if you're providing
artificial sunlight for farms or parks, but it's tiny compared to the energy needed to
move a ship at any reasonable interstellar speed.
It takes a lot more energy to get a ship up to 10% of light speed than a simple calculation
of its kinetic energy would imply, but at a minimum you'd expect to need at least
10^18 joules of energy per ton of vessel, and even if we assumed each person only needed
3 tons of ship, cargo for the destination, and material for hydroponics, living room,
and so on, and the trip would take a century, or about 3 billion seconds, that's still
an average power supply of a gigawatt per person.
That's about a million times what a household tends to use and still a very low estimate
for total energy usage to move that ship.
It's also enough power to light up an entire square kilometer of land at perpetual noontime
lighting, which is way more space than anything but a hunter-gatherer civilization would need
per person.
10 to 100 kilowatts per person for all life support, even with onboard parks and gardens,
is more likely, and even using the high end figure there and the low end for energy to
move that ship, you still have a life support system using just 1% of 1% of the ship's
energy budget.
Go faster and you need more energy for speed and less for life support, shorter trip.
The only reason an interstellar ship can't have everybody living in their own cabin in
the woods is all the mass needed for that dirt and forest.
The power needs are a non-issue.
A space station or rotating habitat way out in the Oort Cloud doesn't have that issue,
it isn't moving things.
Now neither does a habitat in the inner solar system, but the point is in a fusion economy
living space is only an issue because you have to build it and invest the mass to make
it.
One kilogram of fusion fuel, even with fairly extravagant individual power usage and inefficient
equipment, can support a person's life support needs for a century.
So even if you can only use deuterium for fusion, the easiest fusion option, as opposed
to regular hydrogen, your typical comet-like body a few kilometers in radius is going to
have a megaton or more of it, enough to support one person for a hundred billion years or
a hundred thousand people for a million years, and you can boost that to 10 billion years,
the lifetime of the Sun, if you can use regular hydrogen.
Even longer if you have higher fusion that can step hydrogen up to heavier elements than
helium or have feedable kugelblitz black holes.
And we are talking about Colonizing the Oort Cloud, something that should be at least many
centuries off for anything but a few prototypes, so assuming some higher tech is probably okay.
So again living out there is no problem, any random comet could become a major metropolis
that mostly needed no imports or exports.
Again though the question is why?
On the one hand it is a lot closer than any stars, so if you just want a place to send
people who want their own private nation or people who want to get away from whatever
power or group of powers control the solar system, the Oort Cloud is a good place.
But even then, it's not too much harder or time consuming to get to another solar
system than an Oort object, and then you've got an entire solar system, not just one comet.
Of course those solar systems are probably claimed by someone, and if you just want a
small country of maybe a few million, arguing claims with some group that plans to colonize
another solar system to eventually support quadrillions of people is probably not worth
the effort.
A few of the potential drivers for colonizing the Oort cloud could be instability in the
solar system, be it from a war or a disaster.
These disasters could be artificial or natural.
Natural ones include a close encounter with a rogue Jupiter, star or star remnant disrupting
the planets and flinging them out of the system.
Another natural one could ultimately be the Sun getting hotter and brighter as it ages
causing the inner Solar system to become inhospitable.
As to artificial disasters, the Oort cloud might also be used in an attempt to hide from
an aggressive domestic or alien civilization.
That is their one really valuable and unique feature, isolation and safety.
Even in an emerging interstellar empire, our topic for next week, where every large rock
in a solar system and every solar system for hundreds of light years around might be colonized
and the rights to it fiercely contested if it is not, it's very unlikely anyone is
dispatching armadas to go claim a single mountain-sized chunk of ice and gravel trillions of kilometers
from the nearest sun and many billions of kilometers from even its nearest neighboring
icebergs in space.
In many ways you're more isolated out there than some colony ten thousand light years
away would be because over time those places would all develop and grow in population.
There's always folks for whom being far away from civilization is a plus, not a minus,
and if you want to stay that way, picking prime real estate isn't the best option.
If your goal is to have a civilization far from anybody else, claiming a distant fertile
valley hundreds of miles from that civilization out in the wilderness just ensures maybe a
few generations before new neighbors arrive near you, and a distant solar system is likely
to be the same.
Worse too because if you leave on some arkship for a several thousand year journey to build
your own distant Utopia, there's a good chance faster and better ships will have arrived
in the meantime, constructed centuries later by folks who probably don't know or care
you claimed that system already, and certainly won't care if they settle the one next to
it and you complain you didn't want neighbors.
In an expanding and growing civilization, if you want lots of space to yourself for
generations worth of time, you either need to be willing to pack up every so often or
pick a place people don't really want.
A random Oort object probably qualifies.
Of course that other option is viable too, any such colony is basically a spaceship sitting
inside a mountain of spaceship fuel, so if the neighborhood gets crowded or uncomfortable,
you just build an engine, or turn it on if you still have the one you used to get there,
and head off on a nomadic journey.
It's an interesting dynamic we'll talk about more next week, on the one hand interplanetary
and stellar empires are likely to be far more immense and populous than science fiction
tends to portray them, because people don't just colonize planets, and should be hard
to manage as a homogenous unit.
On the other hand what allows such populations is that independence of actual planets because
people are living in habitats that can be easily turned into spaceships.
So it's more like an RV than a house or farm, you can just pick up and leave if you
don't like the neighborhood.
Which could have the strange byproduct of having space-city habitats just pack up and
leave whatever empire they belong to or move into another.
But surely we can do better than just isolation as a motive for living there though?
It's probably enough, isolated farmsteads typically are more about the isolation than
the farming, which is just about getting enough revenue to buy what you need and can't make,
and these are fairly self-sufficient colonies; still, what other purposes do they have?
They can make some money just serving as radar stations and relays, making sure interstellar
space is clear of dangerous debris or accurately marked where not, and picking up and retransmitting
signals.
They could maybe charge a tax or tariff for passing through their space which they keep
clear and safe, and those three things might be more than enough to pay for information
and entertainment from the inner solar system.
They could sell some bulk raw materials, ammonia, nitrogen, and so on, particularly if starlifting
never got going.
Nitrogen is likely to always be in demand when you're building living space, people
don't need it but plants do.
Not much but we do have one other option.
I said interstellar starships don't slow down, so they don't need fuel and rest stops,
but about a year ago we did an episode called Interstellar Highways where we discussed how
to do ships that travel far faster and more efficiently than even a fusion drive would
permit by being pushed by powerful lasers.
Lasers have range limits, as they do expand, and what's more you can get more mileage
out of them by bouncing the beam between places.
You can see that episode for details but the basic notion is to string out a long chain
of beaming stations between two stars and use them to push a ship up to speed or reverse
that, push back against them to slow them down.
So these Oort Colonies could serve that function, and since they are innately mobile they can
move themselves to be part of such a chain too.
One of millions of such stations spread over hundreds of such laser highways to all our
neighboring systems though still very isolated, no closer to their neighbors than Pluto is
to us.
Such systems, as discussed in that episode, allow travel between stars far faster and
cheaper than not only fusion, but even systems like antimatter or black hole powered ships,
which still suffer from the limitations of the rocket equation as they have to carry
their own fuel.
On the other hand fuel can be moved down these highways quite cheaply, in tankers or even
beamed, and since you can accelerate particles quite quickly, you could actually send raw
material to or from the Oort station and a ship, just a particle beam carrying oxygen
to a ship, or metals from a ship to a station needing them, or even fusion fuel from the
station to a ship that would need it to slow down if it went past the highway's end or
somehow drifted off it.
And now suddenly these Oort Cloud colonies aren't sparse poor villages in the distant
reaches of space but big truck stops or even fortresses, considering those giant pushing
laser cannons are, well, giant laser cannons with a clear field of view over empty space
light hours across.
Needless to say, as many solar systems are colonized, it might be advantageous to have
a ton of defense stations light-months out from your system proper, if your interstellar
neighbors aren't the friendliest bunch.
So you've got signal relays, pushing lasers for interstellar ships, defense screens, and
radars for hazards or debris or sneaky neighbor ships.
Between all of those, you not only have the ability to make such Oort Colonies but a clear
motivation to assist or subsidize making them.
We don't have a great guess on mass total or distribution in the Oort Cloud, but it's
guessed there may be trillions of icy bodies a kilometer or more across, and any one of
those has more than enough water and organic-critical materials for an entire O'neill cylinder
for few hundred thousand people, and certainly more than enough for a decent sized community
of a few thousand.
Of course there are probably far more even smaller bodies sufficient for such smaller
communities too.
Any Oort Cloud civilization would be a very spread out thing, likely with at most loose
alliances of neighboring ones if not totally independent, and utterly eclipsed by the far
more massive civilizations that could exist in the inner solar system.
But with trillions of such objects, each potentially supporting hundreds of thousands of people,
you could easily have the Oort Cloud home to hundreds of quadrillions of people, small
compared to a Dyson Swarm but still more than a million times Earth's current population
and huge compared to your typical fictional interstellar empire.
Next week we will be heading out beyond the solar system to examine the concept of Interstellar
Empires, where we'll be discussing the flaws in commons assumptions on this topic and some
realistic approaches.
Our sponsor, Brilliant.org, has an excellent course, "Worlds Beyond Earth", that explains
concepts of interstellar travel, locating exoplanets, and how we determine which ones
might be habitable.
Worlds Beyond Earth is an excellent primer for that topic and let's you transition
from viewing interstellar colonization from a science fiction perspective to viewing it
the way a physicist does.
To support the channel and learn more about Brilliant, go to brilliant.org/IsaacArthur
and sign up for free.
As a bonus, the first 200 subscribers will get 20% off the annual Premium membership.
After next Week's Interstellar Empires we will head out of the galaxy and out of 2017
to discuss Intergalactic Colonization.
We will then return to Outward Bound series at the beginning of the year, but rather than
heading further out from Earth and the Solar System, we will visit the center of our solar
system to discuss Colonizing the Sun itself.
For alerts when those and other episodes come out, make sure to subscribe to the channel,
and if you enjoyed this episode, hit the like button and share it with others.
Until next time, thanks for watching, and have a great week!
For more infomation >> Color Therapist Mark Wentworth - We all have a Life Path Color - Duration: 17:59. 
For more infomation >> Seven: The Days Long Gone - godzina quaza - Duration: 11:04. 
For more infomation >> MitiS - Moments (Feat. Adara) [LYRICS] - Duration: 4:30. 
For more infomation >> Star Wars: The Last Jedi special med Gex og Max Marius! - Duration: 7:28. 
For more infomation >> Lethal Weapon Season 2 Trailer "80's Retro" (SUB ITA) - Duration: 1:25. 
For more infomation >> France vs. Oman | Group F | 2017 JCA World Cup Germany | PES 2017 - Duration: 24:14. 
For more infomation >> Minecraft Twerion.net-/Labern über alte Zeiten-Jack Freescape - Duration: 1:55:22. 
For more infomation >> Сомнения неофита. Говорить ли родителям о воцерковлении? - Duration: 2:30. 
For more infomation >> 2018: o Ano dos Ciclos e Potenciais - (Ashtar) - Duration: 15:40. 
Không có nhận xét nào:
Đăng nhận xét