Witch at the Iron Core
Dreamed 1998/10/16 by Chris Wayan
I'm at a music festival in the North Coast woods. But the area is also known for wizards. They each live alone in hidden and inaccessable cabins and caves. Not just for privacy--they like to find new, unlikely habitable niches.
I meet one wizard who mistakes me for a colleague. Or IS he mistaken? Maybe he just sees the obvious, and I'm the blind one. I sure do find magic fascinating--especially the sort he tells me about.
A witch of their order has been quietly exploring the Solar System. She's discovered that some Luna-sized bodies have huge caves--old lava vents? Since gravity's lower, big ones don't collapse as readily as on earth. Some caves go right down to the surface of the iron core (if any). She had a wild idea, and tried it out on an obscure planetoid. She lured some icy comets in, aiming them into cave-mouths. Soon, gas and water pooled in these deep caverns.
Inside a homogenous sphere, gravity weakens as you go deeper, till at the center you feel weightless. (Sound wrong? Ask yourself: Where could you fall to?) But as you burrow down through lighter rock toward an IRON core, gravity can get STRONGER than on the surface! The iron's so dense and close to you that it outpulls all the stone above your head! Her chosen moon is this sort--gravity deep in the mantle, down by the core's edge, is stronger than Mars's! The air and water stay put, warm up due to compression, and form a gradient nearly as steep as Earth's. Almost none of it reaches up to the surface vents. So she has no need to pressure-seal the caves or worry about meteor punctures. Nothing's pressurized!
She homesteads a vast cavern-maze. Dark, yes, she must supply light, but she has thousands of miles of caves with livable temperature, gravity, air pressure and water. Just add energy from solar stations on the surface! She's building a tram to get in and out--she can send up whole ore trains, if she finds anything valuable, and enlarge the caverns as she mines. No airlocks needed! You get on the tram, and simply ride up a long slope... from a biosphere up to lunar gravity and vacuum. Riding a train to space.
She's found a whole new way to terraform small worlds economically.
NOTES IN THE MORNING
Strange as it seems, the dream's math is right. Density and proximity affect gravity as much as a world's total mass. The gravity deep inside Mercury (for example) near the edge of its large iron core, is actually higher than at the surface! If such caverns existed--and at a quarter or half Earth's gravity, they could--they wouldn't need sealing to hold air. If you stripped off Mercury's lighter crust, baring the core, the new surface would have near-Earth gravity and could hold an atmosphere!
Mercury, stripped or not, will always be too hot to live on, of course (the three rules of planetary success: location, location, location!) but that tiny core really could generate surface gravity stronger than Mars!
Planetary stripmining is (perhaps fortunately) beyond our technology for the foreseeable future, but the witch's simpler scenario, to find smaller bodies and dig or find deep caves, will be quite viable later in this century. With caves many kilometers deep, air-pools like this would work!
And, of course, the dream may be making a more immediate, personal point. Quite a few of us are unpromising bodies! Small, poor, battered, and barren on the surface. But we may hide depths ready to bloom--if you smack us with some snowballs in the right orofice...
We just need one good kick in the abyss.
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