If that structure averages out to be dome-shaped, then there is an actual horizon. Beyond that, you'll eventually reach sphere surface, but that's going to take a real, real, _real_ long time.

Yep.

Take a sphere approximately one AU in diameter.

On the inside of that, a hemispherical dome roughly 12,000 kilometers across, say, just wouldn't even be much of a pimple. Plenty of space to drop a pseudo-content, a few oceans, and such, and have it have a nice horizon.

I don't know if there's ever been a canonical, "This Is How It Is, Folks" post, but to me, that fragment, coupled with other hints, kinda makes me think of New Avalon as being a platter suspended from a pole, and the 'magic' that Cianbro wrought would be the manner in which they made the sun appear to be above instead of completely out of sight.

This would explain the shipyard complex appearing to be the night sky, as well as the horizon issue.

Of course, I could be completely off base here. There's more than enough room in the sphere to have them living on the inner surface of the shell and the shipyard complex to be between them and Zeta Cygni.

Or a bunch of other possibilities. But I like the idea of a pylon supporting a psuedocontinent, if for no other reason than it'd make sense from a logistical standpoint. Cargo could dock outside and be transported by elevator through the pylon.

Hmm... I'm remembering frieght being mentioned in-story, though, as landing in the city proper...

--sofaspud
--

I doubt that they would engineer it to be a half-dome; too much wasted space on the inside (not that a dyson sphere isn't a massively huge waste of space, at least for the first several millenia, until expansion really sets in...), and it would make it rather difficult to "expand" and connect to the next pseudo-continent that would eventually be constructed without a lot of divirting through the surface of the sphere itself.

I have thought of the pseudo-continent as rather flat, kind of like nebraska or the southwest, but on a grand scale. The actual inside circumference at 1AU would be 584 million miles, btw. Using some rough trig, if the (for purposes of the math, perfectly circular) pseudo-continent had a diameter of 12,000 km and was perfectly flat edge to edge (discounting mountains and such, just mean thickness) it would be about .54 km thick in the center. Bump that up to 2 km or so and give it a nice, gradual curve towards the inner surface of the sphere and you have a horizon, no problems, although one much flatter and more like the great plains that what someone from new england or the south would think of as a horizon. And it would be fairly easy for that scale of engineering to bring the next pseudocontinent up to it and create an ocean in between to get rid of the low spots when it is time to expand, and with the distances involved the transition should still look 'normal' to someone from a planet.

{On a tangent using these numbers (113 million square kilometeres, btw), and assuming that there is as much land proportionally on the pseudo-continent as there is on earth, it can probably support a half-billion to a billion sentients easily. (New Avalon is quoted as having a population of 20 million, most living quite comfortably). Probably a lot more, but that gets into environmental arguments, so lets use a billion. Easy to work with. As 1 degree of radius inside the sphere is something approaching three and a third trillion square miles or almost 9 trillion square kilometers (VERY rough math, don't shoot me for the fudge factors, please), that small section of the sphere could support almost 7.9 million times that population, or 7.9 million billion. 7.9 quadrillion? Even if I muffed the numbers somewhat, 6 to 7 quadrillion would still probably be reasonable. That's in a 1 degree by 1 degree section of the the Zeta Cygni sphere. Just something I was thinking of while cruching numbers.}

EDIT: got some of my labels crossed, all the math is done in miles, not km like I originally had, so had to redo a couple of numbers. Allows for even more people, actually. And it's double-checked this time.

And hell yes, it's granular detail, but I was almost a US Navy Nuke operator. We overthink things, its an occupational (and personal) trait.

-D-

-D-

Heck, why bother with attaching the psuedocontinent to the sphere at all? There's enough space inside the sphere to let the continent orbit freely, with miniscule corrections as necessary. If set up correctly, it may even be inherently stable (like the Lagrange points).

The only issue I have is gravity. I dunno how much trust I would place in artificial gravity generators, and without knowing a bit more about the material used to construct the shell (and presumably, the 'bedrock' of the continent), I can't do the math to figure out how much of that is needed to produce a Earth-like gravitational field.

Heh. Theoretical engineering is fun.

--sofaspud
--

If it's on the inside of the sphere? An infinite amount. Mass _above_ you on a sphere doesn't contribute either way to the gravitational pull -- only mass below you does.

Your statement confuses me. Mass is mass - it exerts gravitational influence regardless of its relative position to you. Distance is the only factor.

Hmm... I think maybe you missed what I was saying. Picture the sphere. Now, inside it, place a psuedocontinent (PC), happily orbiting the star that lives at the center of the sphere (put it a safe distance away from the inner surface of the sphere, of course :). People live on the PC, with their feet pointing at the star (on the other side of the PC), and their heads at the inner surface of the sphere. Cianbro's magic accounts for the apparent location of the star to the inhabitants (could be done with mirrors, theoretically).

I assume the PC's foundation ('bedrock', if you will) is constructed of the same material as the sphere, simply because it would have been simple (!) to extrude/manufacture/transmogrify/arm-wave-into-existence a wee bit more (relatively speaking) of the same material as used to construct the sphere itself, while it was being built.

It seems to me (upon thinking about it) that the gravity problem is pretty much not a problem, *assuming* that the sphere material is incredibly dense (which is hinted at fairly often, if not outright stated). It should only require a layer that is moderately thicker than the sphere itself as the bedrock of the PC to form a suitably strong gravitational field. Give the foundation edges, akin to the mountain ranges at the edges of Niven's Ringworld, to keep air from spilling out, and you'd be all set.

--sofaspud
--

I decided I was being snarky without meaning to. Let me try again.

The net gravitational attraction between the psuedocontinent (PC) and the sphere will equate to 0, since the PC is completely contained within the spherical shell.

The net gravitational attraction between the PC and Zeta Cygni (the star at the center of the sphere) will be some non-zero figure. I can't begin to guess at what it would be, but it would certainly be enough so that the PC would need (a) a support pylon to keep it from 'falling' into the star (which attaches to the sphere and thus makes them one mass for our purposes), or (b) some amount of orbital motion, much like the Earth orbits the sun and thus does not get burnt to a cinder after a few millenia.

Likewise, the net gravitational attraction between, say, J. Random New Avalonian and the PC will be some non-zero figure. Between JRNA and Zeta Cygni? Negligible - much like we don't particularly notice our gravitational attraction to good ol' Sol. Between JRNA and the sphere? Zero - they're inside the hollow sphere.

--sofaspud
--

Okay, but that's entirely missing the point of building (or creating)a dyson sphere in the first place. You build the sphere to give yourself the maximum amount of useable space possible, which would be on the inner surface of the sphere, not in orbit around the star or hanging inverted from the surface on a pylon.

If the pseudo continent was made up of as much mass as it would take to create it in my example above, plus the mass of the sphere itself, plus a minute amount of spin to the sphere, gravity should take care of itself pretty much. The gravity of the star exerting itself on all points of the sphere equally would keep it positioned; at 1 AU (93 million miles) the mass of the pseudo-continent and the mass of the sphere, and therefore the combined force of gravity from the two, will affect J Random much more than the gravity of the star due to proximity. The mass required to make a dyson sphere is truly enormous, and it's going to exert it's effects on people. Gravity pulls towards the center of mass, and the curve of the sphere is so shallow (1 degree of arc is over a million and a half miles) that over any distance that means anything to a New Avalonian, the center of mass is towards the surface of the sphere. Even if the pseudo-continent is a hundred times smaller than my figures, the sphere is still there, and it's not going away.

And if anyone remembers the episode of ST:TNG with Scotty and the Dyson Sphere, it was the inner surface of the sphere that was developed; maybe that doesn't apply here, but it's the most obvious choice.

-D-

I shouldn't get into something this pointlessly geeky, but dammit this needs correcting.

The center of mass and gravity for any point on the Sphere would be centered on - is supposed be centered on - Zeta Cygni. Anything attached to the inside of the sphere, including the shipyards, Avalon, the terraforming widgets and whatever other stuff Gryph feels like pulling out of his hat on any given day, are included in the total mass of the Sphere. The net gravitational effect is such that anything not firmly attached to the Sphere's inner surface is going to fall into the frigging star at the rate of however many meters/second Zeta Cygni exerts at one AU.

The reason that all the loose junk around New Avalon (like cars, people, buildings, the atmosphere, whatever) don't exhibit this behavior is because they've got handwavium gravity generators making sure that down faces towards the Sphere and not towards Zeta Cygni. Same basic principle as what keeps people from floating around on the Enterprise.

To sum up all this wandering gibberish: Gravity don't work the way you think it works.

--
Mr. Fnord, free fallin'

The free-floating continent idea, or pylon-supported continent, would both work, AND have the advantage of following the laws of gravity. Assuming you orient them correctly, of course.

And it's not pointlessly geeky, it's entertaining, dangit. :)

--sofaspud
--

I'm going to be an asshole now. {EDIT: Well, people will probably think I am one, anyway.}

I made a couple of assumptions about the sphere, and you're right, Zeta Cygni WOULD exert a pull. The sphere, however, WOULD also exert a pull. Maybe an extremely weak one, like Phobos or Deimos, such that without gravity generators you could jump too hard (assuming your muscles are used to 1g) or throw something and leave the surface and therefore fall under the effects of Zeta Cygni, but there is a stupid amount of mass in the sphere, and it would have some influence.

If you want to think about why this is so, look in our own back yard, or rather in our orbit. The moon is tidally locked with the earth, so that one face of it always faces earth. If what you said was true, anything on the earthward side of the moon would automatically fall towards earth, since earth has a stronger gravitational pull than the moon. Since this doesn't, in fact, happen, then the mass of the moon must be able to keep stuff firmly attached to the surface.

You were right, all mass centers on ZC. From the OUTSIDE. Beyond that is where conventional thought gets a little screwy, both because of the sheer scale and because conventional thought was never intended to study or explain a dyson sphere. From the inside, I believe what I said above applies; think of it as a huge tidally locked lunar surface. Mars' moon Deimos, being shaped irregularly, is 9 miles at it's largest 'diameter' and 7 at its smaller, yet it generates enough gravity that you could walk on it. The sphere would be the same way, with the outer surface, the shielding, whatever 'stuff' is necessary to keep the access gates and such operational, and the pseudocontinent as well making up the sphere wall certain thickness, and the expanse of the surface compensating for the fact that it may only be a mile or two thick.

So, you were right about needing generators, at least to achieve 1g, unless the pseudo-continent and sphere were absurdly thick and/or the sphere spun extremely quickly. But stuff falling into ZC? Only if pushed.

-D-

Take a point on the inner surface of the sphere, A. Draw a line L through the center of Zeta Cygni, Z, and A, extending to infinity. Place a plane P normal to L at the point it intersects A. This will divide the sphere into two portions, S and S'. If S is the section of the sphere between A and infinity on L, S' is the larger portion of the sphere.

With me so far? Here's why the sphere exerts no pull on anything inside it: S has a 'positive' gravitational pull G (postitive, in this case, being defined as pulling the pseudo-continent away from the star). But S' _also_ has a gravitational pull, G', and since it's on the opposite side of A, it's pull is negative. S' is, on average, much farther away, but it is _also_ far, far more massive.

The result? G + G' = 0. G' is exactly the same size as G, but its sign is reversed, resulting in no net gravitational pull.

>
>If you want to think about why this is so, look in our own back yard,
>or rather in our orbit. The moon is tidally locked with the earth, so
>that one face of it always faces earth. If what you said was true,
>anything on the earthward side of the moon would automatically fall
>towards earth, since earth has a stronger gravitational pull than the
>moon. Since this doesn't, in fact, happen, then the mass of the moon
>must be able to keep stuff firmly attached to the surface.
>

The difference is that the moon is not a shell around the Earth.

>You were right, all mass centers on ZC. From the OUTSIDE. Beyond
>that is where conventional thought gets a little screwy, both because
>of the sheer scale and because conventional thought was never intended
>to study or explain a dyson sphere.

No, it has nothing to do with scale. The exact same thing would apply to a marble surrounded by a tennis ball. The key thing is the mass of the rest of the shell; you can't ignore it. If you could, what you are saying would be the case.

He'd fucking better be. He's only a single mathematical iteration.

--G.
you can stop now, by the way.
-><-
Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Admin
Eyrie Productions, Unlimited http://www.eyrie-productions.com/

I'm not 100% convinced, but mostly b/c I'm not sure we really understand gravity enough. But I'll shut up about it.

What's the advantage to a dyson sphere then, though? Being able to trap all the energy put out by whatever star is great and all, but what does one do with it? New Avalon is a drop in the ocean of surface area inside the sphere, what's being done with the rest of it?

I agree it's hella cool, and would be intimidating as all hell to the 99.umpty-9% of people who don't know how it was created and look at it and go "They BUILT that thing?". And you certainly would never run out of space. But the more I think about it, the more I think the concept in general is beyond nuts.

-D-

Photovoltaic cells.

>I agree it's hella cool, and would be intimidating as all hell to the
>99.umpty-9% of people who don't know how it was created and look at it
>and go "They BUILT that thing?".

More and/or better reasons than these were not required by the Reconstruction-era WDF.

--G.
-><-
Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Admin
Eyrie Productions, Unlimited http://www.eyrie-productions.com/

-D-

(Heh. The phrase "open-air fusion reactor" just rolled through my mind, which is in effect what a Dyson Sphere could be.)

As for the positioning of the psuedocontinent: I personally believe in Murphy's Law. So, were I designing a Happy Fun Dyson Sphere Community, I'd make sure that no matter what that pesky misbehaving star got up to, I (and by extension, the other shambling meatsacks occupying my city, dagnabbit) would be safe.

Ergo, put the strongest material in the universe between myself and that nuclear holocaust known as Zeta Cygni. Just in case. It costs nothing (compared to the cost of the sphere itself, anyway), makes some things easier, and solves the problem in a foolproof way. Bounce the light I want (minus harmful radiations) around using mirrors to simulate the day/night cycle.

I wouldn't necessarily go so far as to say that the sphere material is strong enough to contain, say, a supernova... but then again, it might well be. It stopped a Kryptonian artifact moving a relatavistic speeds, after all, with minimal damage... ;)

--sofaspud
--

Nope. Because it was Lord Farfegnugen who actually provided the sphere, not UF-G.
Still, subsituting Lord F for G in the above...

Hmm. Ok:

"It was made by a Wizard. Lord Farfegnugen, who's technology is sufficently advanced as to be indistinguishable from magic."

I miss Farvie. He was fun.

I also, sometimes, get to wondering just what Big Cosmic Evil!!! he supposedly created the Wedge Rats for in the first place. That particular bit of UF history seems to have been negated by events in UF-Core-4, but I still go cross-eyed sometimes when trying to puzzle it out. ("Lord F created the Rats... but Rats from OUR universe created the UF-verse... and created Lord F... oh dear me, there I go again. Ow.")

If Teh Evil was Surtur, then I'd have thought Wolfie'd have put in an appearance during the Twilight arc. We know he's not all-powerful - heck, he's not as tough, physically, as a Kryptonian (cf. Decker's assassination attempt) - but he does have as-yet-unexplained Vast Frickin' Resources.

If nothing else, I can accept that Lord F possesses the requisite technomagical competence to have engineered the Zeta Cygni Dyson sphere, however it was actually constructed and planned.

(Though part of me still insists it was done by UF-Gryphon, after proving his innocence but before reconciling with Kei. I dunno, it just seems like something he'd have done. Lord F seems less... imaginative?)

--sofaspud
--

Still, I have to wonder just what the timescale was for the Sphere's construction. It seems... unlikely that such a large project would have been built in a couple of years. That makes me think that while Gryphon is in on it (whether after the fact or not), Lord F was the motivating factor behind the Sphere itself. Not New Avalon as a city but the Zeta Cygni Sphere.

That almost makes sense, actually. Lord F seems like someone who would have had the almost-insane vision for the Sphere but Gryphon, eccentric soul that he is, would almost be required for the city. If I remember correctly, the headquarters for the WDF was based out of the yards for a while, right?

*Googles*

Well, I'm going to guess that this was a reference to the modern Cianbro Corporation which is a construction firm. Still, given the tech involved, Lord F is a pretty likely backer for the whole thing... and technology is nothing without vision which, admittedly, Lord F cannot be said to have lacked.

Quite so. I worked for Cianbro in the summer of 1992. I still work for them, sort of, in that I do public relations writing for the firm that handles their account. I had a long-standing fondness for the company's safety culture and its management's focus on employee relations. You don't see open-shop (or, as they like to call it now, merit-shop) employee-owned general contractors with safety standards higher than the government's all that often. I felt they deserved to be immortalized, after a fashion.

--G.
-><-
Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Admin
Eyrie Productions, Unlimited http://www.eyrie-productions.com/

People will take any excuse to argue about something. Speaking as someone who has absolutely no authority here whatsoever, I wouldn't worry about it. :) The forum archive for the original UF archive is quite... large.

--
Druid