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At a point of overpopulation in the future say 2045 and given what resources the world has at it's disposal and all manpower possible, what extreme depths could we dig down into the earth to create more living space? if this was to be a way of dealing with over population

I'm trying to see how I would develop a culture underground over 200 years and what conditions they will be dealing with

Living underground needs to become a way of life for a decent amount of our overall population

All world government's would be working as one in this scenario

Sorry if I haven't got enough info

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    $\begingroup$ Please take the tour and visit the help center to understand what and how to ask here. This question has nothing to do with dystopia, lacks background explanation and is rather unrealistic (unlimited resources and manpower) $\endgroup$ – L.Dutch - Reinstate Monica Dec 20 '19 at 9:09
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    $\begingroup$ Why dig down thought when you have all that free space above your head? $\endgroup$ – Guy with jewels' names Dec 20 '19 at 10:41
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    $\begingroup$ Could you edit so that it's clear what your question is? You talk about a bunch of things but I don't see a question mark in your question. $\endgroup$ – puppetsock Dec 20 '19 at 14:13
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    $\begingroup$ You don't need living space, you need food production space. Unless you have an energy source like cheap fusion, this has to be on the surface. $\endgroup$ – jamesqf Dec 20 '19 at 18:45
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    $\begingroup$ Issac Arthur has covered a similar topic here:youtube.com/watch?v=jZQP2oNDkAM $\endgroup$ – Seraphim Dec 20 '19 at 20:44
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NOT MUCH MORE THAN A KILOMETER

The main problem with living deep underground is the geothermal gradient. It simply gets warmer the deeper you get, at a gradient of roughly 25°C for every kilometer of depth. This fact is used to create geothermal energy. Given that the average global surface temperature is 15°C, then even at 1 km (40°C), refrigeration is needed, and the deeper you go, the more refrigeration is required. Since refrigeration requires energy, it generates excess heat that must be channeled away. This will not be easy when the surrounding rock is hot. You could pipe cool air down from the surface, and then pipe the excess heat up, but this also gets more difficult the deeper you go - and it could contribute to global warming.

It is difficult to set a hard limit, as you can add insulation and increase refrigeration the deeper you go, but it gets increasingly impractical. More importantly:

THERE IS PLENTY OF SPACE ABOVE GROUND

Though it may seem that the world is changing into one huge urban landscape, that is in fact not the case. Only 3% of the Earth's land surface is currently urban, and a lot of this is lightly populated villages and suburban areas.

Tokyo has a population density of a bit over 6,000 people per square kilometer. Turning the Earth's entire land surface (510 million square km) into megacities of this population density will make room for about 3 trillion people. Food will be a problem, even though this leaves the oceans free of population - but the same is true if you put people underground. And you could feasibly leave the most fertile half of the land free for agriculture if you double the population density.

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  • $\begingroup$ Not a wrong answer, but it fails to satisfy the OP's premises. With unlimited resources you can simply cool down and go on (that's why I pointed out the premises are meaningless) $\endgroup$ – L.Dutch - Reinstate Monica Dec 20 '19 at 10:04
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    $\begingroup$ @L.Dutch-ReinstateMonica. The OP doesn't specify "unlimited resources", only "what resources the world has at its disposal and all manpower possible". $\endgroup$ – Klaus Æ. Mogensen Dec 20 '19 at 10:11
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    $\begingroup$ What about using all this heat to fuel power plants to produce more energy to dig deeper to fuel power plants to produce more energy to dig deeper to fuel power plants to produce more energy to dig deeper to fuel power plants to produce more energy to... $\endgroup$ – Guy with jewels' names Dec 20 '19 at 10:43
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    $\begingroup$ @Guywithjewels'names: You can't simply use heat to generate energy - you need a heat differentialto do that. Refrigeration creates a heat differential, but requires more energy than you can get out of that differential (because entropy). What you could do is to pipe excess heat to the surface where it can be used as geothermal energy. But you will need to pipe it where the temperature is lower than the desired living temperature to get a net energy bonus. $\endgroup$ – Klaus Æ. Mogensen Dec 20 '19 at 12:12
  • $\begingroup$ Why not put turbines alongside those pipes, warm air would flow upward and cold one downward, isn't it enough to create net plus energy? $\endgroup$ – Guy with jewels' names Dec 20 '19 at 12:32

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