Yrurtj

Okay, so how feasible is it- if even possible- to put the Earth under 'one roof'?

So here is the premise. The world is heavily heavily over populated, so overpopulated in fact that almost all of the land has been covered in infrastructure. However, instead of visualising this as a huge mega city, imagine it more as... an apartment complex, or a mall.

Imagine if Earth was a giant mass of slightly crowded apartments, houses, indoor parks with glass roofs, conveyor-belt like roads, with no real free sky access (As everywhere you go there are stories and stories of shops, markets, cinemas etc above you. Even at the very top, there is only limited access to the open-sky)

Woodlands and Natural features such as lakes, and rivers have direct sky access, with a sort of wall/perimeter of infrastructure, and are still being desperately protected by organisations.

How realistic would this be?

Edit: keeping in mind that colonising/resource gathering on other planets are possible.

Could an entire neighborhood or even an entire city be that crowded?

Sure.

Hong Kong’s Kowloon Walled City was probably the densest neighbourhood in history, with more than 1,000,000 people per sq km. Photograph: Alamy

Kowloon Walled City was 119 times as dense as New York City.Greg Girard

While this example was just 33k people in 6.4 acres, it lasted for 40 years.

The streets and alleyways of the Walled City were narrow.
Most were barely wider than six feet and some were so narrow that one
had to walk sideways through them. A massive network of passageways in
the upper levels also made it possible to travel the distance of the
city without walking on a ground level street.

The Walled City had its own micro-climate,
due to the massive amounts of tubing, wires, and
open gutters snaking through the building. The lower levels were
constantly hot, humid, and damp...Because of the smelly, humid
conditions down below, the rooftops of Kowloon would turn into a
communal hangout during the afternoons and evenings. People would hang
out, do laundry or homework, or practice instruments.

"It was like a
strange, urban garden. There was tons of household refuse. It was a
bit of an eyesore, but compared to the area below, the air was light
and breezy. It was nice to come up there after living and working on
the lower floors."

In other cases, a somewhat less dense set of buildings can cover an entire city.

Delhi, India

Could this be most of the earth?

No.

People need to eat and to do that, you need farmland, oceans/lakes, factories or processing centers, and transportation ways. While you have some wild spaces and waterways accounted for, you still need massive amounts of flat buildable land to grow crops and raise animals for meat. Even if everyone is vegan, you still need an awful lot of space.

By 2050 the world’s population will reach 9.1 billion, 34 percent higher than today...It should be possible to meet
the future food and feed demand of the projected world population in
2050 within realistic rates for land and water use expansion and yield
development. However, achieving this will not at all be automatic and
several significant challenges will have to be met. (ref)

Can you feed your world? It depends what the population is. If agencies are projecting that feeding 9 billion people is doable with some work, then you can assume that larger populations will be even harder to feed. Not only are there more people, but there's less land to do it with, because the people take over arable land for housing and for other resources like schools, offices, warehouses, roads, parking, factories, distribution channels, etc.

Air quality: Half the world's oxygen comes from the oceans and the other half "via photosynthesis on land by trees, shrubs, grasses, and other plants." Some sources say the ocean's contribution is even higher, up to 85%. Land plants do contribute, though they don't affect oxygen levels much because of the total volume. Though wild spaces and urban trees are important for carbon dioxide sequestering and to reduce air pollution.

Our atmosphere has such an enormous reserve of oxygen that even if all
fossil fuel reserves, all trees, and all organic matter in soils were
burned, atmospheric oxygen would only drop a few percent.

Tree impacts on important atmospheric trace chemicals such as carbon
dioxide and...air
pollutants (ozone, particulate matter, sulfur dioxide, nitrogen
dioxide, carbon monoxide, and lead) will have greater significant
impacts on human health and environmental quality. Urban forest carbon
sequestration and air pollution removal along with other environmental
impacts of urban forests (e.g., water quality improvement, lower air
temperatures, reduced ultraviolet radiation loads) need to be better
incorporated within local and regional planning efforts to improve
environmental quality and enhance the quality of urban life.(ref)

Power generation: That's a whole other issue and should be a separate question. Wind generation is likely your best bet, as wind will be a factor in keeping your cities from collapsing, so generators around the cities will help deflect it. And you can have small generators on top of the buildings. Solar won't have much space to work. Fossil fuels are likely depleted since you have a "far-future" tag and that many people. There are other ways to generate fuel, including from the waste products of that many people, but you need some space to do it.

For some reason i read this and i get the feeling it's an dystopian world, I mean how can it not be?

In our petit planet we only cover about 3% of it's area, just saying.

Feasible? Probably, a good idea? Probably not.

"So we will have an Earth size hollow sphere with 3 m (9 feet) thick walls. The volume of all this concrete is 1.54∗10^15cubic meters... that means a square surface mine with 1240 km (770 miles) on a side and 1 km (0.6 miles) deep."

That's a big mine, assuming we'll take the resources from earth. But that is only taking in consideration a hollow sphere, are we covering the oceans too? Are buildings going to have multiple floors (I'd assume yes)?

So to make this more plausible we'd be probably mining planets and asteroids for that to be possible, are animals sheltered in like zoos? Do we even care about animals? Is this a working class planet and titan is the rich people's planet? That would be fun. I'd assume rooftops would be really sought after.

I really like the idea and do really think it's plausible, specially if we have colonized other planets. I'm not sure i got the vibe you wanted but i definitely got a dystopian feeling from what i read.

Hollow sphere earth numbers:
https://www.quora.com/Could-we-build-a-spaceship-larger-than-the-Earth-itself

Assumptions

• Population density according to your description even this might be less dense than your world but I will work with this


• Water to land ration like on earth


• Animals are of no concern

So few things that have to be met (without getting to deep into fiction/fantasy):

• More planets/asteroids available than only the one mentioned


• The top of your building(s)? is covered by wind turbines and solar panels


• Health care is great


• Some of the build upon area is use for food production

The Numbers

Based on Kowloon City Density and the land mass of earth and reserving 20% for food generation. We arrive at a measly 154 quadrillion people inhabiting your world.

Food production in 2009 when accounted for population this was about half a ton per person which would amount to 77 quadrillion metric tons per year or 2 439 435 497 tons per second.

Results/Consequences

this was only food and population but the numbers for water/fluid consumption and power will be equally high. I highly doubt any greenhouse even when sized at one fifth of all land mass an earth would produce these numbers so your civilization should already have a partial dysonsphere or something like that in place to generate the power and food demands of this crowded planet.

It is very unlikely that anyone who has the money would stay there so you'll need a good explanation for that. Considering that you need other planets/asteroids and even partial dysonspheres to get this to work in the first place.

Conclusion

Possible but very unlikely. Except when it is something like a big lower class world where the majority of people have to live because of their limited power/influence/money supply.

everywhere you go there are stories and stories of shops, markets, cinemas etc above you. Even at the very top, there is only limited access to the open-sky

Why?

There's actually a very good reason why: That open-sky view is being used for power generation.

It sounds like you want a "high tech" but not "very high tech" situation. Let's suppose these people have near-perfect photovoltaics and can capture 6$kWhm^{-2}$ each day, or 168$kWhm^{-2}$ each month. (Reference) That means that if each person has 80$m^2$ of living space (whether or not that's "crowded" is subjective, I'd call it normal), the roof of the top-story apartment will be generating 161$MWh$ per year.

How's that compare to real-world energy production?
India has 1,300,000,000 people and generates 6,444,000,000$MWh$ per year (see here, and double-check my unit conversions). That's 5$MWh$ per year per capita. For the United States it works out to 72$MWh$ per year per capita.

So far it looks like this could work; your "global building" could be as much as 30 stories tall (deep) provided you're not expecting too many people to have modern amenities like electricity or refrigerators.

But where does the food come from? For that matter, where does the oxygen come from? CO$_2$ concentrations can be a problem even in existing buildings.

I think your best bet for a plausible world would be one with much less land-mass than ours.

You'd basically have a water-world, with people living on barges and civilizations powered by floating wind turbines and eating farmed fish and seaweed, and then there'd be this big island or chain of islands, say the size of Japan or Madagascar, that, as the only firm ground in the entire world, had been developed into a single contiguous 100-story-tall megastructure.
For that matter, does your story even need to be set in the fixed mega-structure? Can you imagine living in a cruise ship the size of a city-state?

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not physically impossible but why not just burrow into the earth?
It would be easier, also don't forget about food it is hard to grow food without sunlight and if the planet was one big apartment complex that is just so much more food you need seeing as there would be about something trillion people. I say either burrow or build a sky scraper into space several times, it also leaves more space for food.