As children, we had fun playing on a merry-go-round
but one day, as adults, we will live in one. So today’s topic is the O’Neill Cylinder,
a giant rotating space habitat that’s more akin to a small nation than a space station. For many of our regular viewers this is a
familiar concept, though we’ll be exploring it in a lot more detail today, but first let’s
start by repeating the basics of what one is and why they are an attractive option for
the future homes of humanity. At a fundamental level you can terraform almost
any barren rock in space to be decently livable, but it requires vastly more effort than we
tend to portray in science fiction and the odds of finding a planet regular humans and
Earth-based life could just as comfortably live on without some form of terraforming
are virtually nil. Indeed entirely nil, as those conditions would
likely only exist if something already lived there and as we’ve discussed before, trying
to colonize a planet that already has an ecosystem on it much beyond basic bacteria is not really
a practical option even if you ignore some of the big ethical issues. We don’t have any place in this solar system
even vaguely meeting Earth-like criteria, and while some planet with a 23 hour day and
102% of Earth’s gravity and just 10% higher pressure might sound ideal, I’m writing
this on the Sunday after daylight savings happened and that missing hour is definitely
irritating, so I’m not sure even a 23 hour day would be very desirable, especially on
a daily basis. Of course the only planet even close to Earth’s
day length is Mars, where the day is half an hour longer, and I wouldn’t mind an extra
half hour of sleep a day but not at the expense of trillions of man hours of time into giving
the place an atmosphere to breathe or putting up with gravity 38% that of Earth’s 1G. To add to that, the Universe is not exactly
swimming in rocky material, and while your house probably doesn’t weigh too much more
than a loaded cargo truck, it’s sitting on millions of tons of rock directly below
you, while even a very avid gardener really only uses maybe the first meter of dirt below
them. All that rock is really doing is providing
gravity, and we have a cheat for that, we can spin things around and fake it for all
practical purposes. This is the basic notion of a rotating habitat
and we did an episode on those way back in the first year of the channel and have talked
about them many times since. The basic idea is easy, you build a big ring
or cylinder and dump some dirt, water, and air inside, provide light and grow plants
and build houses inside. It spins around and people are held in place
by centrifugal force. Technically a fictitious or pseudo-force,
but then so is gravity under general relativity anyway, and fictitious or not, it will hold
your feet to the ground just fine. If you spun the ISS around the astronauts
would be pinned to the sides by that same centrifugal force and you could spin it faster
or slower to provide more force. That would be very nauseating though, from
the rate of spin required to provide gravity with its small diameter, but if you continue
to build bigger, that rate of spin begins to decrease and eventually it rotates so slowly,
nobody would be able to tell that the gravity was artificial. The problem is that the bigger you make one,
the stronger it needs to be to simulate a given amount of gravity, and the strength
of the hull is identical to that of a suspension bridge under the same gravity with a length
equal to the circumference of that hull. This led to the inevitable question of how
big you could build one from modern materials with enough safety leeway for a decent amount
of mass inside and for some damage to be possible without ripping the place apart. And in 1976, in the peak of post-Apollo enthusiasm,
we got the answer from physicist Gerard K. O’Neill in his book “The High Frontier:
Human Colonies in Space”, in which he proposed various cylindrical space habitats including
one 5 miles in diameter and 20 miles long, 8 kilometers by 32 kilometers for metric,
at the effective safe limit for steel. You can actually push that out a good deal
further even with steel and do decently better with aluminum or titanium, and much better
with substances like Kevlar or Zylon, let alone Graphene, but such a structure is well
inside our production capability, ignoring its sheer hugeness, and became the standard
for discussing large cylindrical space habitats and got named the O’Neill Cylinder. The specific maximum dimensions of such structure
based on its material isn’t really the critical part, but the default large O’Neill cylinder
has 314 square miles or 804 square kilometers of internal area, which isn’t huge compared
to most countries but is on a size with a lot of smaller territories or subdivisions
like a County. My own home county of Ashtabula, here in Ohio,
is the largest in the state and only about twice that area and supports one hundred thousand
people at a density of 56 per square kilometer, about double or triple the density we tend
to think of for pre-industrial civilizations, my county is considered quite rural, amusingly
bordering the smallest county in our state which packs in two and half times as many
people, and in spite of mostly being forested is still a net exporter of food so it’s
quite self-sufficient. And indeed, there are an awful lot of historical
kingdoms and city-states that were no bigger. Moreover, O’Neill’s design calls for two
of these to be coupled together with some additional facilities attached or nearby,
and there’s nothing limiting you to adding more to a connected grouping you could walk
or maybe float between. This is the key aspect, because you can certainly
build them larger or smaller, but that size is big enough you are no longer picturing
a space station that serves as a junction port for people and goods moving around but
an actual civilization that doesn’t need to import or export a lot, proportionally. At some point someone ran the numbers on mass
and came in at around 4-6000 megatons for the model 4 version, and if we assumed that
was mostly dirt, steel, and water, that means that the number of cylinders with mass equal
to our own planet would total over one quadrillion, or over a million billion, each having an
internal area equal to bit over a millionth of Earth’s. So if someone made a planet’s mass worth
of those you would have a couple billion planets’ worth of living space. This happens to be about identical to the
amount of sunlight the Sun cranks out relative to what hits Earth, a couple billion times
more, and another notion that was gaining popularity at the same time was the Kardashev
Scale and the Dyson Sphere or Swarm. So if you found an Earth mass planet you could
terraform it and now have a whole extra planet to live on, or your could turn it all into
O’Neill Cylinders in a swarm around a star and have a billion extra planets’ worth
of living area. And unlike terraforming a planet, which does
require about as much work per bit of new living area as just building it from scratch,
when you’re done you have a structure with identical conditions to that of Earth, since
you can dial it’s gravity up to whatever you want, and light the thing on whatever
schedule or temperature you want. You don’t have to mimic Earth’s conditions,
but you have that option. Again for channel regulars, this is kind of
old-hat but for those who aren’t it’s a big reason why I spend so much time mentioning
rotating habitats like the O’Neill Cylinders and Dyson Swarms, big clouds of these things
around a star. These are even more attractive to us on this
channel as we tend to assume some technologies being developed that make them even better. For instance, the classic O’Neill Cylinder
calls for either windows in the sides to let sunlight in or an elaborate mirror system
to bounce it in, we tend to assume we’ll eventually master fusion and just internally
power and light it, that’s not necessary but would certainly be handy. You can do the same with a big grid of solar
panels outside and some LED lights inside, but those weren’t very good options in O’Neill’s
day, again the book is from 1976 and he died of Leukemia in 1992, before we had relatively
cheap and efficient solar panels and LED lighting, indeed the latter were still pretty impractical
and uneconomic even a decade ago whereas now fluorescents and incandescents are mostly
being retired in favor of LED lighting which is pretty much better in every regard. We’ve also seen aerogel become more viable
for mass production, an ultra-light but sturdy substance that helps a lot for making your
interiors of such habitats a little less 2D. The normal way to add depth to a rotating
habitat is to pimple and dimple the shell so you don’t need as much dirt inside, a
hill is just a big pimple of steel with a thin layer of soil over the top and a deep
lake a dimple down off the hull. This is not really ideal from an engineering
perspective, or for reconfiguring your landscape, so being able to make a mound of aerogel covered
with dirt is preferable. We’ve also created stronger materials, and
odds are that graphene, which is simply carbon and very abundant in the Universe, could be
mass manufactured inside a decade or two. This allows much bigger habitats, but more
importantly perhaps, allows much thinner hulls on them that are also much stronger than a
steel one. Lastly, we’ve come a long way with automation
since O’Neill’s day, so the notion of building one of these things seems less daunting. Robots able to mine and refine the raw materials
from the Moon or some asteroid, and do all the assembly and welding don’t seem like
wild science fiction anymore, even if we’re not quite there yet, and as we saw earlier
this spring in our spaceports episode, featuring the Gateway Foundation’s huge spaceport,
that basic assembly technology now exists, even if the spaceport we saw there, while
dwarfing the International Space Station, would fit inside an O’Neill Cylinder like
a bike wheel inside your garage. All of these concepts make the O’Neill Cylinder
and its various cousins much more attractive and plausible as a pathway to space colonization
for humanity. You don’t colonize other planets, you build
them, tailored in size and environment to what you want or need, and discussing a future
from that perspective rather than terraforming planets has been a big focus of this channel
since its inception. So that covers all the basic review of concept,
but folks will tend to ask what life inside one of these things is actually like. What’s the weather like? What’s the sky like? The landscape? What happens if it gets struck by some meteorite
or weapon? Would you realistically ever even build one
and when and where would we do our first ones? We’ll answer that last first, and generally
the place proposed for building the first one is at the L5 point of the Earth Moon system. Indeed the L5 Society was founded in 1975
based largely around O’Neill’s idea even though the book that popularized it wasn’t
out for another year. Its founder, Keith Henson, happens to be a
personal hero and inspiration of mine along with O’Neill and I got to talk to Keith
several times this last year along with getting introduced to a lot of the folks from L5’s
successor organization, the National Space Society, and obviously that was a great pleasure
and honor to get to correspond with those folks and pick their brains. The reason for the name is that in any two
body system you get 5 Lagrange Points, a place of modestly stable and stationary orbits that
don’t seem to move relative to the two bodies in question. For instance the L4 and L5 spots for the Earth
and Moon are out at the same distance from the Earth the Moon is, and remain 60 degrees
ahead or behind of the Moon on its orbit. Indeed they each form an equilateral triangle
with the Earth and Moon and are very good places to set up ports to send material out
deeper into space or receive incoming ships and they need virtually no station-keeping
fuel, which is otherwise a pretty hefty requirement for any satellite or space station and more
so for something as gigantic as a space habitat. You can put one lower and closer to Earth
or the Moon, but only even if you’ve got a means for station-keeping and again that’s
no problem in a fusion economy but requires a lot more relative effort without that, so
L4 and L5 tend to be considered the ideal first places. L1, L2, and L3 are still better than other
spots but less stable than L4 and L5, and the two are identical in their advantages,
to the best of my knowledge so I’m not sure why it was L5 over L4, maybe they flipped
a coin or liked 5 better. There really isn’t a specific size to these
cylinders. O’Neill gave four example sizes with rounded
numbers and the biggest, type 4, is the one that usually gets mentioned. I generally use it for any cylinder or cylinder
pair many kilometers in size but smaller than the giant Graphene versions. These giants are the Bishop Ring and McKendree
Cylinder, which I usually just call Continent Class habitats to save time and since O’Neill’s
three reference designs are Islands 1, 2, and 3, and the Graphene versions are too big
to classify as an island unless maybe you’re referring to Greenland. We see them in fiction a lot, though not so
much in film or TV. If you’re familiar with the Gundam Franchise,
an O’Neill Cylinder is pretty much the first thing we see on screen in the original animation
and it’s beautifully done. The eponymous space station from Babylon 5
is an O’Neill Cylinder, a spaceship version of one appears in Arthur C. Clarke’s classic
novel Rendezvous with Rama, and the Citadel from the Mass Effect Franchise is basically
one too. Okay, so why would you ever build one? That’s tricky for the same reason lots of
space concepts seem always delayed and ten or twenty years off, there’s a bit of Catch-22
with space that a lot of the cool things you can do up there require the other stuff be
built first, but this one is big enough I’ll just flat out say, you don’t build stuff
like this, especially the full blown multi-kilometer kind, until space flight is cheap enough that
most people can afford a ticket. If you’re living in a space habitat, you’re
living on alien soil because we wouldn’t mine the materials for these from Earth. You wouldn’t create one of these until you’ve
got some serious infrastructure in space and automation good enough that it doesn’t take
a lot of human oversight to scoop up some iron or aluminum from the moon, refine and
process it into structural bits, and weld it into place. The switch over to when they become a place
many people live, or even most of them, would then just occur organically at whatever point
building an acre of O’Neill Cylinder is about the same price as buying one down on
Earth. If Earth ends up going the Ecumenopolis or
Matrioshka Shell World path we’ve discussed before, that could easily result in land prices
down on Earth running what they do in major metropolises and folks wanting to live in
one of these O’Neill Cylinders so they could have some cheap land. Needless to say for the near future building
one of these things would be much more expensive per square meter than even buying land in
downtown New York City or Tokyo, but that would drop a lot as you not only get cheaper
spaceflight but off-Earth sources of material. That would impact the four basic interior
densities we’d tend to see though. The cheapest path is the densest path, where
it’s basically a city with some gardens and parks and likely many layers, either in
the building or the actual cylinder itself. So long as you are wide enough that each layer
is only a little higher or lower relative to the diameter of the station you won’t
have much change in apparent gravity between levels. Lighting those levels only becomes an issue
if you need to get rid of heat, and you can have a ton of radiating fins poking out of
one, though by preference these should be off the non-spinning axis, not sticking off
the sides where they are under immense stress. Solar panels, incidentally, make handy radiators
since they already have a large surface area relative to their mass. A couple of notes on building these. First, especially early on, you are going
to be placing them where you want people and away from Earth, that’s likely to be in
asteroids with emphasis on in an asteroid, not on an asteroid or next to one. Excavating an asteroid is very easy - they
have virtually no gravity, so you just dig a hole a little bigger than the cylinder habitat,
line it with something, and stick the cylinder in there to spin around. You don’t have to excavate all the way in,
either, you can just land in a crater and excavate a little, and dump the unused stuff
around you as a protective shell, a blister sticking out from the asteroid rather than
a crater, and that would probably be a common approach, essentially expanding the asteroid
as you hollowed it out. Incidentally this is why we often see these
things in pairs, it’s much easier to give such habitats their spin, and maintain it,
if you have something to push against, so a twin rotating in the opposite direction
or a big asteroid with thousands of times the net mass is ideal. You can link more cylinders together over
time as you hollow an asteroid out for its raw materials and eventually even just construct
a big spherical shell around the whole lot of them with a thin layer of rock on it. Actually, there’s another reason we go with
a pair of these and that is because of something called precession, which you would have encountered
if you’ve ever looked at a spinning gyroscope. The gyroscope doesn’t stay exactly still
and instead traces out a circle, which is caused by the torque of the spin on it. Now, in space, that precession movement is
made worse and the entire habitat can quite suddenly flip over. Besides being extremely unpleasant, everything
inside would be exposed to large forces that could rip the cylinder apart as everything
changes direction. Fortunately, with two such habitats joined
together spinning in opposite directions, that torque and the resulting precession are
largely eliminated. If we stick the habitat into that asteroid,
you are effectively providing it with a very capable shield from radiation, micrometeors
and weaponry. For this reason you’d not expect to ever
see a naked O’Neill Cylinder actually spinning in space as you approached it, though we always
show them that way. It’s just easier to build one with a big
shell around it that is heavier and a storage facility for things you need but don’t need
gravity, and that superstructure would either not spin or do so in the opposite direction
and slower. That spoils the visual effect though, so again
we don’t show them that way much. Nor probably with hundreds if not thousands
of smaller ancillary facilities connected to that superstructure or hidden within it,
some possibly with partial or full rotational gravity themselves. So we know what the outside looks like, but
what about the inside? Classic image is a big flat cylinder with
the horizon rising but I suspect this is false too. That’s not an ideal look, seeing a reverse
horizon or your neighbor’s yard hanging overhead, so I suspect they’d go a lot more
3D, lots of hills and valleys to disrupt that rising horizon along with the sun not rising
or setting with it. So while the easiest landscape to do would
be a flat one, I expect you’d see a lot more up and down, more Scottish Highlands
than Kansas plains with lots of hills or trees to break up the horizon. Of course that depends on density, you could
populate one of these as heavily as a metropolitan area, with many millions of folks and agriculture
being done hydroponically in lower levels or attached smaller and cheaper stations nearby,
or you could go suburban or rural or even near deserted. We’ve talked about using these as wildlife
reserves because they are closed environments but big enough to support a mostly self-sufficient
ecosystem, certainly on any short timelines and you can make them bigger or artificially
introduce genetic diversity when it is needed, but short of very large creatures or apex
predators, one is big enough for most species to exist without genetic bottlenecking. The big issue causing these to be different
from Earth is the sky. Not the sun itself, whatever you use for that,
be it a big mirror or lightbulb, makes no difference, people don’t look at the Sun
and that’s why folks are often a little surprised at its actual appearance when they
see photos of it dimmed down. It’s just a big whitish-gold blob and that’s
very easy to fake nowadays with LED lighting or mirrors. However unless you want a perpetually cloudy
day you need to take some special efforts if you want the classic blue sky or starry
night. Those don’t have to be terribly extreme
or high tech, even just a big thin blue cylinder higher up that had some light on it at night
arranged to mimic our own constellations would do the trick and you just keep your ceiling
decently higher than birds fly. You can also play with the atmosphere content
to absorb green light or your sunlight to have more blue and less green, or tweak it
for reds in the evenings, but that’s the one area where you can’t quite perfectly
mimic Earth with a little artificial effort. Now nobody wants perpetual clouds but we do
want some and folks ask what the weather is like on these, and that’s very hard to generalize
because it depends a lot on the size of a station. One of the big factors in our own weather
is the spin of the Earth and the Coriolis Effect produced by that, and rotating habitats
have that too and would have Inertial Circles in the air and water like Earth does. Very generally the bigger they are, the closer
they will tend to match Earth. You definitely get weather, wind, rain, and
waves on these but it will be different in patterns than on Earth. For instance in smaller ones there’s very
little change in pressure with altitude, you’re essentially a pressurized can rather than
a place where a lot of air sits on more air being squeezed denser by it, so cloud effects
are going to be different there, as the sky only goes so high and the closer you get to
the middle, the lower the gravity is. It’s actually hard to predict much on this
because someone always notices another little detail that would be different. I remember a discussion of it on the channel’s
Reddit group last year where someone pointed out that a raindrop starting near the axis
up high initially falls much slower than close to the ground; gravity is lower while air
drag remains about the same as near the ground. Unlike on a planet, the atmosphere, doesn’t
thin out as much in the volume of an O’Neill Cylinder, though it does in the really big
versions like a Banks Orbital or Ringworld, where more of your surface air pressure is
a result of the atmosphere above you. In many versions you could also get a sideways-looking
vortex of clouds as stuff loops around that central, low gravity axis, and one can imagine
birds adapting to learn to fly in low or no gravity at the higher altitudes. I wouldn’t be surprised if a lot of places
opted to hang fake clouds spinning at the same rotational rate as the station and stuck
lower-gravity environments up there or skipped the cloud look for flying islands or cities
and you might get some very interesting three dimensional ecologies that way. Again, you can make these very like Earth
but you don’t have to, and since the sky is the hard part to mimic Earth with, I’d
tend to expect that to be the one folks most casually take artistic license with. I’d be remiss if I didn’t point out that
these need not be cylinders either. You could cap the ends with cones or curves
instead of a flat plate as a sort of fake mountain range with lower gravity, which is
appealing as a place to visit if you want to climb mountains or go hang gliding through
ravines with less risk and exertion. You can, of course, do a simple sphere, but
then you have no gravity at the poles and the highest gravity at the equator. You’d also have issues with water collecting
down, basically forming a big equatorial ocean band with desert or tundra up nearer the poles
and nothing at all right on the poles with no gravity to stay down. That’s okay if you are using those as your
space port though. Many geometries are possible but the cylinder
is the most obvious and pragmatic one. You generally want them longer than they are
wide too, so it’s worth noting that you can treat them like rods and connect them
to each other at the ends in a big wireframe to add more space without needing additional
structural strength and in doing so create some truly enormous regions of living area. There’s no real limitation on length, just
width, and I often picture folks making these as big connected wireframe globes, possibly
with concentric layers, out of some original small asteroid that’s being eaten up to
build a big exterior fake globe full of these and immersed inside a bigger reservoir of
gas, be it fusion fuel or even air you could fly around in without gravity. Friction isn’t an issue as again you’d
usually sheath such a cylinder with a second non-spinning protective layer and just have
a vacuum between those two layers. There are tons of possibilities and we’ve
discussed many of them in other episodes, but this is the basic O’Neill Cylinder,
arguably the first space-based megastructure you would build and the one I tend to think
a few hundred years from now are where most humans will live. They don’t take much mass, so you can build
trillions of them in a solar system. They are actually mobile, unlike a planet,
so you can move one if you need to dodge an asteroid or leave an area that’s become
unfriendly or unwelcoming. They also have next to no real gravity, so
getting materials into and out of them is really easy because there is no gravity well
to contend with. They’re also about the minimum size for
a respectable sovereign entity. I’d imagine most would be the equivalent
of maybe a county or a state inside a larger nation, but they are big enough to administrate
themselves and have all the specialists they need and a population large enough that you
can move around inside one if you don’t like your old neighborhood and encounter people
you’ve never met, but also small enough for a genuine feeling of intimate community
and for most business and civic roles to be filled with some variety. Depending on scale and density, you’d expect
populations anywhere from 10 thousand to 10 million and again are easily directly linked
together to allow groups of them to form integral wholes. One downside is they’re not really ideal
spaceships because they are fairly massive and not really designed with acceleration
in mind, though they can be designed to be better at that, it’s just hard to reconfigure
one to that setup if you didn’t start that way. Using one as the core of an interstellar space
ark is a fairly common notion, we see it in Clarke’s Rendezvous with Rama and in the
Expanse with the spaceship Nauvoo. Or the Marigold Fields design from artist
Rapid Thrash. But it’s the difference between an airplane
and a mobile home, our O’Neill Cylinder needs a bit of time to get going but can move
itself to a new spot and indeed if it’s fusion powered, a whole new solar system. That’s one reason I stress them as big enough
for a complete functioning civilization because while I’d imagine you’d see a lot of them
formed up in alliance of thousands or millions of them as a single nation, if the population
doesn’t like things, they can just move, and it’s the sort of structure that you
pretty much can only blow up, not conquer, because invading a can like that is a basically
a deathtrap. Not that they’re fragile, as I mentioned
in interplanetary warfare they can be armored up quite nicely and wrapped in point defense
systems and a whole cloud of smaller facilities doing manufacturing or agriculture and defense,
and be just as sturdy as any planet at least as far as the folks living on it are concerned. Remember on a planet you’ve got thousands
of kilometers of protective rock but it’s all underneath you, only the atmosphere protects
you from orbital bombardment. In a rotating habitat all the rocks and metal
are between you and any hostile invader. Such being the case I tend to think they’d
serve as the sort of bottom rung of any nation-states we see in space because they don’t really
need anybody else. They’ll doubtless be vulnerable to economic
sanctions and blockades of trade, physical or digital, but that’s about the limits
of your diplomatic options short of ‘kill everyone’ so it’s entirely a guess but
I suspect most would be pretty touchy about maintaining most of their local authority
and not centralizing it much, more of a city state or feudal setup than what we tend to
see in nations after the industrial revolution got fully into swing. We could go the other way entirely, of course. But there would still be a lot of trade; Interplanetary
Trade, as we discussed in that episode, is quite problematic for anything but data, but
these aren’t interplanetary, they are smaller and way more numerous. That means you’re a lot closer to your neighbors
and you also have no gravity well to fight, indeed you could often make the trip to your
nearest neighbor by just going out to the outer hull in a spacesuit and timing your
release, then drift off at 200 meters per second for the next station that might be
a thousand kilometers away, but you’d cover that in 5000 seconds, or an hour and half. Fire a few puffs of gas to correct your course
and grab onto the side spinning at the same speed you were and climb on in. I could easily imagine that being a common
sport. Even where the stations aren’t physically
connected by a pressurized connection or long tether, you could build a spaceship able to
reach that distance in your garage with some sheet metal, some fire extinguishers, and
a blowtorch. Even more than moving around an asteroid belt,
spaceships inside a system with lots of O’Neill Cylinders hardly require crack teams of engineers
and precise manufacturing. So between the relatively small population
and the relatively small distances, I would expect a lot of specialized manufacturing
and trade, and for that same reason I would not expect to see these places opting for
isolationism or total sovereignty much either, but probably be more like an alliance of city
states or islands in an archipelago. You can probably see by now why I tend to
always mention these things as ubiquitous in the future, they are a very attractive
option if your civilization has decided to stay mostly human rather than pursuing various
bioforming or cybernetic techniques or has gone transhuman or for a digital existence. And of course assuming they’ve got the resources
and automation to make these places cheap enough that regular folks can afford to buy
a home on one. We’ll be exploring more about the consequences
and challenges facing post-scarcity civilizations more this spring, and we’ll see that there
actually are a lot of those even if as a whole life is much better than now, much as life
is much better now than a couple centuries ago but not without its challenges, some the
same as our ancestors faced and many unique to us. Now we were talking about the weather on these
earlier and I mentioned how minor changes to size, rotation rate, or geometry could
seriously alter the dynamics of weather patterns in one. If you're curious to know more about how that
functions, I'd recommend Brilliant's course "Out In Nature", which will walk you through
everything from seasonal impacts to the Coriolis Effect. One of the things I like about Brilliant is
that they’ve got a core set of 8 principles for learning that match up very well with
my own philosophy on the matter and three of those are that it has to be exciting and
cultivate curiosity and questions, but another is that it has to be active. This channel definitely goes for the long
and in-depth side of the spectrum as science videos go but even if the episode were ten
times as long it can’t replace that hands on aspect of taking examples and actually
working them out yourself that’s necessary for true understanding and mastery of these
concepts. So if you’d like improve your understanding
of math and science, and help support the channel while you’re at it, go to brilliant.org/IsaacArthur
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that link will get 20% off the annual Premium subscription. Next week we will return to the Fermi Paradox
to discuss Alien Beacons, and ask just how far away you can say hello to civilizations
if you want to, as well as what other reasons you might have to build such an enormous transmitter. The week after that we’ll take a look at
the kind of civilizations that can afford to make things like giant beacons or telescopes
as we start an expanded series on Post-Scarcity Civilizations. And the week after that, we’ll be exploring
how far away you can see, with a look at megatelescopes, and just how big you can make a telescope.. For alerts when those and other episodes come
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have a great week!
Here is a rather interesting video on O'Neill Cylinders, miles wide space habitats using spin gravity to more comfortably mimic Earth than any known planet could.
PS: The YouTuber has a slight speech impediment, if you have trouble understanding him his videos come with closed captions, hope that helps.
I've always wondered about something with these things. Maybe one of you can answer this if I can explain it well enough.
Imagine one of these things already spinning and with an atmosphere. If you started out in the very center of the cylinder you would be floating because the centrifugal force wouldn't be acting on you right?
Now here is my question. If you somehow moved closer to the edge of the cylinder (the ground) would you be floating the whole time until you touched the cylinder? Could you sort of float a few feet above the ground as it spins beneath you? Would you somehow get dragged down to the ground? Maybe the atmosphere spinning pulls you down somehow? Or would you appear to be flying to everyone that is on the ground?
I kind of remember a part of rendezvous with Rama that dealt with this issue. A guy floats from one end of the cylinder to the other through the center using some sort of glider. He loses "altitude" somehow and cant get back to the center and falls to the edge. I cant remember the details. It might have been from part 2 of that series too.
How would you attach the spinning cylinder to a superstructure without needing thrust to counteract the friction? It seems that these could never be fully self-sufficient as they would always need a fuel supply.
It's a great video, but is anyone else having difficulty understanding what the narrator says? His accent is a bit weird.