The cheapest materials would be what can be acquired in space without having to launch from Earth. As a result, you're going to want to build your O'Neill cylinder out of some combination of iron, aluminum, titanium, and silicon dioxide.
The last of which might be particularly useful, as it is the main ingredient of fiberglass while also being the most common substance on Moon and asteroids. As a result, you probably want to build your cylinder primarily out of fiberglass. You can get pretty decently sized cylinders, as fiberglass has a higher strength-to-weight ratio than steel. Apparently, 24km diameter is a viable figure. Scale up length the same way, and you'll get 96km. So a 24km x 96km O'Neill cylinder made out of fiberglass.
That would be about 7238 km^2 of usable surface area. Half that to 3619 km^2 to make room for windows (as originally envisioned by O'Neill), and assuming a density comparable to New York City (about 11,300 people/km^2), you'll get around 40 million people. Or about the population of Tokyo.
That's seems plenty for any sensible space colonization strategy we might adopt in the future. And what's best is that you don't really need any fancy technology. Just use solar power to power mass drivers and deliver raw materials from the moon or asteroid via electricity. And it won't be any special materials either. Raw regolith can be made into fiberglass, so cost can be kept surprisingly low. The only question is scaling it all up, which may unfortunately be too expensive or will take a very long time to happen. Ultimately, this is still sci-fi, albeit on the hard side of it, since no fancy new technology is require.
I’d like to see a pressure vessel made of fibreglass that size… Not happening. Wall thickness in pressure vessels scales
Simple calculator, assuming steel… a 24 km diameter pressure vessel at 15psi is over 13 metres thick steel wall to contain the pressure. checalc.com/calc/vesselThick.html
Just the volume of steel required would be astronomical. You might be able to do this out of a similar mass of fibreglass… But forget launching it from Earth (would have to be made in situ).
And, largely, forget the fantasy renderings of what O’Neill cylinders look like – they are anything but lightweight.
This is sci-fi stuff. No one is seriously saying we could build this anytime soon. It will require a radical advancement in space travel capability. But the interesting part of this is that it doesn’t any new technology. It needs only the technology that we currently have, just scaled up massively.
As it is an O’Neill cylinder, the raw material needs will be truly huge. We’re literally building a city on the scale of Tokyo but in space. So we are just assuming that someday, we can move around that amount of stuff in space.
It’s far more than building a city the size of tokyo. It’s the mass required. If you weighed Tokyo, and then engineered a hypothetical Tokyo in space, you’d find that the mass of the equivalent materials would be orders of magnitude higher than even your worst estimates.
Back of the envelope, you put Tokyo in a cylinder with a similar surface area to actual tokyo, the volume of steel in the walls of the containing cylinder (just the pressure vessel) would be about … 60 billion cubic metres, or something like 450 billion metric tonnes of steel. As a point of comparison, tokyo tower is… 4000 tonnes.
As another point of comparison: our global annual steel production is currently around 2 billion metric tonnes per year. It would take 200+ years worth of global production to build just the pressure vessel for a tokyo in space. Unless you’re building this at your source of raw materials, it just doesn’t happen.
Yes, that's the point. It's far beyond the actual city of Tokyo in terms of construction difficulty and scale. But it doesn't need any new technologies to be invented to be doable. Just the ability to build on that scale.
But the point is if you get your materials from the Moon, for example, it’s vastly more economical to just build a Moon colony (or another Moon colony) than a space colony of the same size.
Then you'll have to deal with Lunar gravity, which may be unacceptable for long durations. Humans may have to live in giant space stations if we want to live in space. And since they can be truly massive, it may be more desirable than what some might think.
The ideal solution is probably not to build a colony in the middle of space, but rather find a celestial body with the necessary materials with gravity low enough to be acceptable.
Moon gravity too strong? Try smaller moons. Phobos? Europa? Charon?
I don’t know about scientific studies, but in my experience I sleep best when the mattress side of the bed is positioned towards the ceiling. Also, putting the bed in front of the door can be somewhat inconvenient, specially if the door opens inward. Other than that, everything else seems to mostly be fair game.
From some quick searches (so not a definitive answer, but a place to start), it seems that sound waves are most likely longitudinal which doesn’t cause shear. However, shear forces can be created by sound waves when they hit a surface.
From that information, I don’t think the shear energy imparted by a sound wave is very large. Since non-newtonian fluids only thicken under shear, they may not actually behave very differently than a regular fluid in these conditions. Preventing sound waves from traveling is usually accomplished by causing lots of scattering (open cell foam) or by absorbing the energy in a viscoelastic material (usually polymers).
Not that any of that would work, but just as a thought experiment: under sudden sonic pressure the fluid would become more crystaline and would then actually make the sounds travel with less resistance, so maybe that would actually make it worse?
Well that just kicks the can down the road, and is also probably not accurate. People move today for better jobs, to escape warzones, because they like a country’s laws, and more reasons. Most of those reasons didn’t apply to hunter gatherers living thousands of years ago.
Really? What if the better hunting grounds were taken? What if a rival tribe kept harassing another and people just didn't want to fight? What if the ambitious youth didn't agree with the tribal leaders, so they moved to make their own fortune?
At our core, we really haven't changed all that much from our ancestors.
Could really be the same reasons for them too.
People moved for better hunting/grazing areas. To escape areas of warfare. They didn’t like the tribes rules, and more reasons.
But, as far as resistance to UV and immiscability with UV resin, testing would be required, as I’m assuming you intend to replace the FEP film layer with a dense liquid.
Mercury? Isn’t it opaque and fully reflective? Or does UV light pass through it?
For initial testing, the FEP would remain, but as this liquid would theoretically not stick to the resin, the FEP would remain intact, pretty much eliminating risks that have anything to do with it.
I have seen something like this before, but it uses two different lightwaves in order to make the denser liquid remain inert, so it’s impossible to try it with consumer printers.
Ah, yes on the first count at least, though that criteria wasn’t on your bulleted list, I guess it was in the title.
That being said, UV breakdown might not be as concerning in the short term if the substance is removed fairly often. I wonder if a clear gelatin or glycerin layer would last long enough?
I’ve also seen resin-infused paper-like substrate layers of material like carbon fiber attempt to bypass the requirement of an FEP. Each print layer was a new sheet and once the print was done the un-cured material was blown away.
Assuming we’re talking about refractive index here, metals technically still have a refractive index despite being reflective (light can penetrate a very short distance through metals). In the UV, the refractive index of mercury is <1 and of course it’s very dense. But that’s probably not going to be useful to you.
For transparent materials, water actually has a lower refractive index than most liquids (around 1.34 in the UV). You can check this website to see if there’s anything better (probably an organic), but I doubt it would be by much.
I don’t know much about 3D resin printing, but I assume you a focus an image (in the UV) onto a resin layer to selectively cure it. As you suggest, the presence of a liquid would refract the focusing light rays and change the position of the focal plane. This could in principle be accounted for by changing the distance from the focusing optic, though there could be some (perhaps minor) blurring of the image.
Should we hope to get drugs/treatment to cure this in the next 10/30/50 years?
I sure hope not. What a shit show that would be. People need to die, it’s just part of life. Assuming it would even be possible, don’t think for a second us normies would be eligible. This would be for Trump, Musk, Bezos, etc. I couldn’t imagine how it would impact resources and population overtime.
In a vacuum c=nu*lamba or the speed of light is equal to the frequency times wavelength. So nu=c/lamba. If you plot 1/x, you don’t get a straight inverse line. You get a multiplicative inverse. So not only is the data flipped, but it also has a distortion that will compress portions and stretch others.
As to why the functions peak at different colors, I believe this is due to an oddity in the axis units. Notice how the irradiance is in W/m^2/nm in the first and W/m^2/THz in the second. Are you familiar with histograms? Think of it like binning the power intensity per nm bin and power intensity per THz bin. Since THz and nm are inversely related, the width of the bins is changing when the basis is changed. This leads to another stretching in the data that is less intuitive.
the width of the bins is changing when the basis is changed.
Thank you. Why would they compress/decompress based on how light is measured? I would assume that the x-axis would reflect the same range of light regardless if the light is measured by length or frequency. Why give different ranges of light?
The x-axis range spans the same region of “photon energy” space in both plots. The data starts at about 280 nm in the first plot, which is 1000 THz (the maximum value in the second plot).
The stretching effect caused by working in different x-axis units is because the units don’t map linearly, but are inversely proportional. A 1 nm wide histogram bin at 1000 nm will contain the histogram counts corresponding to a 0.3 THz wide region at 300 THz in the frequency plot. Another 1 nm wide bin at 200 nm will correspond to a 7.5 THz wide region located at 1500 THz in the frequency plot.
You can get a sense of how this works just by looking at how much space the colorful visible light portion of the spectrum takes up on each plot. In the wavelength plot, by eye I’d say visible light corresponds to about 1/6 the horizontal axis scale. In the frequency plot, it’s more like 1/4.
That normalization is necessary because otherwise exactly how you bin the data would change the vertical scale, even if you used the same units. For example, consider the first plot. Let’s assume the histogram bins are uniformly 1 nm wide. Now imaging rebinning the data into 2 nm wide bins. You would effectively take the contents of 2 bins and combine them into one, so the vertical scale would roughly double. 2 plots would contain the same data but look vastly different in magnitude. But if in both cases you divide by bin width (1 nm or 2 nm, depending) the histogram magnitudes would be equal again. So that’s why the units have to be given in “per nm” or “per THz).
Somewhat tangential, but I’m reminded of that “viral” email that made the rounds back in the day.
An e-mail that circulated around the internet about 7 years ago claimed that this is true by stating “Aoccdrnig to rseaerch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a ttoal mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.” It turns out that many of the claims that are made in this e-mail are false; readers do display reading difficulties when reading jumbled text (Rayner et al., 2006, White et al., 2008) and no such research has been conducted at Cambridge University. However, the assumption that the exterior letters are more important than interior letters in lexical processing does seem to hold up in a laboratory setting.
I mostly use mine for reheating stuff, but cook the occasional two minute noodles or frozen pie. Never had it be disgusting, at worst it can be cold if not done long enough. Cutting the food up and stiring it around halfway through helps.
Yup, also primarily use it for reheating food. Sometimes, when I’m lazy and just want sth to eat, I’ll make myself microwave potatoes. And I also use it to defrost frozen vegetables or fruit sometimes.
However, when I was living in a one bedroom apartment, which didn’t have an oven in the kitchen-corner, I had a microwave with integrated oven and with that I was able to bake myself anything that fits into a pizza sized round baking tray. Still love that thing. It’s a 30 y/o hand me down Siemens from my uncle that still works perfectly. It’s also rather large (about twice the size of a normal microwave) and sadly doesn’t fit into my current kitchen…
Microwaves are fantastic cooking tools, and I’m pretty confident you’re not using yours to its potential. Defrosting, reheating, steaming, boiling. Does it all in half the time with half the mess. All those settings on the keypad do something good. Most people just wack a few numbers in and let the microwave literally cremate the food on full power. Those reheat and defrost settings apply microwave then switch to low or no power, leaving the applied heat to radiate internally before repeating. Different densities and starting temperatures are accounted for.
Obviously you wouldn’t cook a stir fry or a steak in a microwave. Potatoes before roasting though? Dumplings? Frozens? Yes please Mike.
I don’t think I specified, but much like cooking rice on a stove top you won’t run it at the same temperature. The microwave will use less energy than a traditional stove top, not sure about induction ones. And after learning to boil things with it, I do it all the time.
Just get it to boiling then 450 then if needed 300
It does passable baked potatoes too, but if you microwave it for about half the time and then toss it in some oil, kosher salt, and pepper and put it in a hot oven, you get great baked potatoes in far less time than in the oven alone. You’re basically boiling the middle and baking the outside. Great combo.
I like how instead of imagining there might be something you don't know about microwaves, you just kind of assumed everyone bought a dust and popcorn machine for no reason. It's such an "am I so out of touch?" moment.
Yes, microwaves are a poor substitute for an oven but they work fine for vegetables that you might otherwise use a steamer to cook. Stuff like broccoli, beans, carrot pieces etc. Corn on the cob works well too, just give it a few minutes in the microwave with the husk still on.
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