2021-03-17, 11:30 PM (ISO 8601)
Re: What would a literal "under-world" look like?
I once 'designed', (plagerized,) a generation starship which was a massive cylinder that rotated for gravity. Its center was a massive cavern 3 1/2 miles in diameter and 10 miles long with a half-mile thick hull designed as a labyrinth of compartments for every purpose except farming, which was done in the center chamber. Along the axis was a tube through which a fusion reaction flowed, fed by Bussard ramscoops and supplemented by internal fuel tanks. The tube glowed white-hot when the available fuel was abundant and faded to red when the engine was running on onboard fuel. The engine provided electricity, light, and heat, but very little thrust. The 30 ly journey was planned to be completed in 900 years.
The floor of the cylinder was at .75g, but it reduced as one climbed the mountainous ends. Landing on the spinning cylinder was very tricky, (my players crashed into the small craft launch bay,) but launching was easy.
One could imagine this idea scaled up to world-size, with a central core containing the fusion plant which is suspended in the zero g zone on massive pylons which are invisible from the equatorial zone. Thus the mass of the 'sun' would not be great enough to negate even a tiny fraction of the centripedal pseudo-gravity. Even better: the sun can be regulated to be bright and hot in the day and to be turned off at night, with twilight as it heats up or cools down. By intensifying or dimming and longer or shorter on times, seasonal variety can be simulated, though it will be the same season everywhere in the world.
This can be made a magical artifact with a little thought. The sun is maintained by an efritti clan and its fire elemental servants who constantly wage war against the earth elementals along the length of the pylons, or something.
Last edited by brian 333; 2021-03-17 at 11:38 PM.