Advanced Sci Fi and TV

Watched new X Files last night. Hadn't really planned to, but there it is.

Just as crazy as before…hope this time it will move the main plot a little faster. I lost interest last time around, and missed a few things like "CSM" being Mulder's dad. Scully/Mulder shoulda killed him years ago. But no, everyone is back, and in classic form, no one can be trusted.

But one thing that got mentioned, in passing, clearly as an aside to the SciFi fans, was "Dyson Sphere".

Read about it here:

https://en.wikipedia.org/wiki/Dyson_sphere

A clever idea, and probably sort of true, but in no way practical. "W" article talks about some of this.

Eventually it says "probably not enough material in the solar system to actually create such a thing" Nor is the material we have actually innately strong enough.

Why not? It'd have to rotate to have "gravity", there'd be coriolis tension and compression and shear, drift around the star…

Imagine a large balloon enclosing a baseball, both perfectly spherical. How thick, how much reinforcement/bracing, and other clever crazy stuff would we have to have so that it didn't disintegrate…

Where would enough atmosphere come from to "fill it" let's say 10 miles thick? Oh, no, you wouldn't do that at all. You'd make a flat layer whose inside surface is glass, and the air is trapped between that and the outer layer, so that you stand inside the outer layer and are looking up through the glass inner layer; maybe it's 20 feet thick. Well, there's plenty of sun, then, and the air is contained. Lots less air needed. Still…a lot of air. I don't think we have enough. We'd have to mine air from…um…we'd have to make it.

A test case, avoiding any thought of the coriolis aspects:

The earth is 8000 miles diameter. Let us imagine it is solid iron. How thick an outer surface do we need? Other aspects will determine that, but let's say it's one inch.

The Dyson radius always used is 1 AU, or 93 million miles. You probably wouldn't actually build it that distance, but for convenience we'll say 100 million.

The surface of the sphere is 1.7E26 square inches. 

Earth = 8000 miles sphere of iron = 268082573106 cubic miles = 7.5 E18 cubic feet = 6.8E25 cubic inches. A little short. 

But only a little. That's interesting, and less damning than I thought. 

We could only build 1/2 inch thick shell. We probably really need more like a foot thick, but we aren't making tall buildings, no point; that, and they'd be unsafe to create. And the sphere would be one billion times more square miles than the entire surface of the earth, of which we currently use very little. We'd still be all bunched together because of the need for fresh water. We'd end up distilling the entirety of the oceans into fresh water. And managing the location...that'd be weird because we couldn't build oceans (the "depth" would create other impossible tension stress forces that would be totally destructive: a half-inch-thick shell couldn't "handle the weight".

Huh. Not so bad as I thought. 

Of course, it'd be vulnerable to things from the outside.  Earth's atmosphere prevents the surface from looking like the Moon, but the outside of a sphere would have no equivalent thing--there would have to be huge team of people and "somethings" whose job was to continually deal with attacks. We'd have to clear the stellar vicinity and the Oort cloud. 

There are a variety of smaller/simpler things also discussed, where we don't actually build a full sphere, but rather a close-in constellation of power collectors. Similar vulnerabilities, of course, but no catastrophic failures likely.

The "W" article give a brief mention to "Niven Ring" which is of course Ringworld. It's a 1AU strip around a star. Much more doable, not that wide and not subject to coriolis shear forces. It rotated, so it has gravity. There's no "roof" so you could fly up/out. Still vulnerable: remember how Ringworld had a "mountain" in one place where a large asteroid had punched through from the back?

We still aren't doing it, tho. The engineering of such a thing is beyond us. The materials are beyond us. Maybe carbon nanotubes would be the thing.