Author: @[email protected]
First, a little background about my world. I like to think of it as an inside-out planet. A vast open space surrounded by earth on all sides, with a sun in the middle and everything interesting in the world on the inner surface. Much like Pryan from the Death Gate Cycle books, which inspired this shape.
The sun, Sore, is a while hole with a gravitational push. It generates light and heat, and stops the planet from collapsing in on itself.
Outside of the world is, as far as anyone knows, a lot of rock and not much else. But some time ago (no idea when, my notes aren't dated) i wondered, if this place is an inside-out planet, could there be other planets? I don't see why there couldn't be.
Means of travel between these planets would have to be pretty different from normal space travel. Basic movement requires that you either break up the ground in front of you and move it behind your ship, or somehow lower the pressure around your ship enough to liquify rock without melting it to (or and) your ship, and let it slide past you (if i'm not totally misunderstanding phase transitions).
You can't see through solid rock like you can through the vacuum of space, so you need snar (sonic navigation and ranging) to make sure you don't hit another ship or something like the bottom of an ocean.
Gravity would grow weaker as you get further from a planet, then stronger from a different direction as you approach another. You need to be able to rotate the ship so the cabin isn't suddenly upside-down, while keeping whatever digging implements are at the font of your ship facing the right way.
Ports for these ships would have to have snar beacons that ships could listen for, but these signals would have to be able to be heard over a long distance and not stop ships from hearing each other.
And of course, ships need to be able to move over land or in water, because the end and beginning of long trips won't be through solid stone.
While writing this, i wondered for the first time why people would bother. I'm sure the planets are quite far apart, and you can only safely move so fast when your awareness of the things around your ship is so limited. Imagine trying to drive around at race car speeds at night with weak headlights. Space stations, underground areas big enough to seem like they're above ground aside from the lack of sunlight, could exist, but you probably wouldn't want people drilling tunnels around such a place. I certainly wouldn't want to spend my life designing a small artificial world only to have the sky collapse on it and ruin everything. Trying to travel to another planet for the sake of finding other life sounds worthwhile to me, but i don't see any way to detect these other planets at great range. You'd have to set off it an arbitrary direction and hope you hit something good soon.
So while my world could have space travel (for the closest thing to outer space it has), i'm not sure it realistically should. Maybe a similarly "inside-out" universe could have travel between worlds, but i don't see it working for me.
