Dyson Spheres
I was reading something earlier that got my mind buzzing. I had thought, in the past, of a dyson sphere that worked via 2 concentric dyson spheres. The outer one is a shell (ie. fake dyson sphere), and the inner one is a swarm of satelites (ie. true dyson sphere).
The inner sphere had 2 functions:
a) absorb and reflect a portion of the star's light to collectors at the poles of the shell (which themselves would absorb some, and reflect some back to the star, to manage it's volume, thus managing its rate of burn).
b) create negative-mass fields (via Mach's principle) that cause them to both float away from the star, and press outward on the inner surface of the shell (providing "gravity" to the inhabitants of the inner surface of the shell). (negative-mass fields behave exactly like positive-mass fields, except that they repel positive-mass fields, instead of attracting them)
(putting any form of uniform gravity or anti-gravity along the inside of the outer sphere is useless: they all sum up to a net zero gravity at any point inside the sphere -- the shell has no gravitational effect upon any object inside the shell, regardless of its material, density, etc.)
So, the two hand-waives are: a) that Mach's principle can actually be turned into a useful technology, and b) that you could get enough material of sufficient strength to build the shell.
So... today, I was reading something that talked about two concentric shells, with inhabitants living between the shells. They were talking about living on the surface of one of the shells, but I started to wonder...
What if, instead of living on the surface of one of the shells, you filled the gap between the shells with breathable atmosphere. The inner shell would keep the gas from collapsing, and the outer shell would keep the gas from escaping. There would probably be some atmospheric density issues near the inner shell (due to the star's gravity), but:
a) the gravity of the sun at 1 AU isn't that strong, so, it may be possible to have a very thick gap, but still not have too much worry about pressure differences,
b) if we're comfortable talking about creating negative-mass fields via Mach's principle, it shouldn't be unreasonable to think about anti-gravity fields along the outside of the inner shell, whose sole purpose is to regulate the atmospheric pressure throughout the gap.
So, now you've got a large gap of space that has breathable air... so, why not fill it with planetoids? Not planets, they're too big -- their mass would suck in the air, and you'd stop having this big air zone. Instead, things which are too small to have a meaningful effect upon the air gap's density. They'll need some form of artificial gravity at their surfaces, to create 1g for inhabitants, since they're too small to have 1g surface gravity on their own (and that will have SOME effect on the surrounding air gap, but hopefully not enough to deplete it).
The idea is, you could have a setting where you have conventional air craft flying from "planet" to "planet". This is sort of like Niven's Integral Trees, in a way, except that it's enclosed (and, I think, much larger in total volume). You could even have a Ringworld like tech level, where the inhabitants have long since forgotten how they got there, and even how the larger apparatus works (and, depending on certain things, they may not even be fully aware of the larger apparatus). They are, essentially, low-tech people living in a very high tech construct.
That, in turn, lets you mix all sorts of tech levels and societies, up through (at least) our 1940's. Some things might be even more advanced, some things might not have gotten much past that, or the 1960's (no space race to foster certain tech developments). Or maybe they'd be around our level (depending on how much you think the space race is necessary for our current tech level). You could also have evolution of larger flying species, which are used as mounts to fly from place to place (or to pull "ships" from place to place).
But... here's some questions:
So, assuming an air gap that's somewhere close to the orbit of the earth (inner shell and outer shell straddle a radius of 1-ish AU), and probably has a thickness that's negotiable (to make this all work out), and assuming medium-hard sci-fi (not ultra-realistic, not science fantasy, but as plausible as possible while still having it all work):
1) how much of an atmospheric density issue do you think there is if you DO NOT have some form of gravity manipulation along the outer edge of the inner shell?
2) about how big do you think you can make the planetoids before you have to start worrying about them depleting the air gap, and becoming big balls of dense atmosphere?
3) somewhat related to #2, how many of those planetoids do you think you could reasonably put into such a gap? (remember, the thickness of the gap will be largely dependent upon question #1 -- the goal is: somewhat uniform atmospheric density, through any means that satisfies the "medium-hard sci-fi" assumption)
I'm sure you could stuff it rather densely with planetoids without worrying about the atmospheric issues... and you don't want the density of planetoids to be TOO thin (you want some movement between planetoids, even by the lower tech civilizations). It seems to me that you could get a few thousand "worlds" in there, quite reasonably. And I'm sort of thinking "maybe moon (Luna) sized", but maybe they'd have to be smaller. How much smaller?
I'm also thinking maybe a gap that's .2ish AU thick, starting just a little inside the orbit of the Earth. (So, maybe from about .9AU from the star, out to 1.15ish AU ... or maybe a little more)
If there is a very dense air area near the inner shell, and a very low density of air near the outer shell, is there enough "livable" air density in between to still have a meaningful setting? (and, if that's the case, that could be how, even the more advanced, inhabitants aren't aware of the apparatus itself: they can't get close enough to it to observe it)
Obviously, I can waive this all away with science fantasy and/or magic. But, I'm sort of hoping to get a reality check from those who really know the physics involved ... and an idea of just how non-hard-sci-fi such a setting would have to be in order to work.