What TLs you need to have and sustain a ecumenopolis

[Astromancer]

Originally Posted by Anaraxes

Urban densities are generally given as population inside some political boundary. For purposes of this discussion, you really need to include the support systems for the city, which is a lot harder to look up. Farms, water supply, waste disposal, and so on, are often outside the city boundaries, but ought to be figured in. An entire planet covered in the density of Montreal wouldn't be like today's Montreal.

A planet-wide city doesn't preclude farms; you just put the farms on the roof. Still, about 40% of Earth's land area is currently devoted to agriculture. So you could get ten times the production without improving the density of agriculture at all. Trantor's 45 billion could be fed without any sort of internal / underground hydroponics setup or fleets of ships from granary planets.

You will need something else to get to 1 trillion -- and you'll also need an energy source, as covering the entire planet's surface with solar-absorbing plants isn't enough food. Luckily, plants are only around 3% efficient, so you could better that with your food production tech, perhaps even solar powered, or just something else like fusion.

Which makes dealing with excess heat the really big problem.

[Edges]

Shedding heat is only a problem if the planet is of proper, life-supporting temperature to begin with. If it started as a cold, inhospitable planet, adding the global city and the resulting heat could warm it up to just the right level. You won't be exclusively relying on solar power anyway.

[cptbutton]

Originally Posted by Astromancer

Which makes dealing with excess heat the really big problem.

As I recall in Niven's known space the Puppeteer planets were moved away from their stars to help with cooling.

[Flyndaran]

http://www.irregularwebcomic.net/396.html

Covers this along with the two previous strips linked.

[Sassy Psionic Space Squid]

I dunno, I imagine they'd use a huge amount of energy, but what be the absolute theoretical minimum to sustain it, assuming they use extremely energy efficient tech? Not really a well-defined question, but the concept isn't either...

If they were purely using solar power, they might also run into global cooling issues.

And of course there's also pantropy, which might make it more viable. I've been thinking about pantropy for urban living in general, seems an interesting reversal from the usual of making technology adapt to us.

[Crzyraccoon]

So taking all the information to account, it seem you would need (TL10 Agriculture, TL9 Architecture and TL10 power)?

[Phantasm]

Originally Posted by Crzyraccoon

So taking all the information to account, it seem you would need (TL10 Agriculture, TL9 Architecture and TL10 power)?

Yes, though through magic you might be able to figure it in divergent numbers (TL 5+5 Agriculture, f'rex, or TL 5+4 Transportation, with bound elementals providing power for steam engines or airships).

[ericthered]

Originally Posted by cptbutton

As I recall in Niven's known space the Puppeteer planets were moved away from their stars to help with cooling.

And they only lived on one of them. The others were devoted to food production. Scary civilization, that one.

[Astromancer]

Originally Posted by tbrock1031

Yes, though through magic you might be able to figure it in divergent numbers (TL 5+5 Agriculture, f'rex, or TL 5+4 Transportation, with bound elementals providing power for steam engines or airships).

If you had magic, then you could use GATES in the deep oceans connect to worlds like Europa. These ice covered water worlds would make great heat sinks.

[Anaraxes]

Originally Posted by Astromancer

These ice covered water worlds {like Europa} would make great heat sinks.

Hey, the Monolith clearly said "no landings", and we didn't "land" that gate.

Boil that dust-speck.