Dyson Sphere (shell) - Dysonica Anyone?

[Mentor]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Rather than real world science, I think "rubber science" or "magic" or "gobbledygook" if you prefer is the way to set up Dysonica.

 

*From the Terran Galactic Republic Encyclopedia.

 

*In the year 45000 BCE the Zeboid civilization population reached critical mass which was not matched by its projections of available energy.

 

Fortunately, due to the existing availablity of Quantum Fusion the process of creating Fantasium out of practically any material with sufficient carbon or hydrogen was barely sufficient to convert the worlds, moons and planetoids of three systems into the shell and topsoil of the habitat.

 

The perfection of the nanoreplication bots made the formation of habitats practically simultaneous with construction of the superstructure. Increased availability of solar energy during the construction process made the progress of Dysonica icrease geometrically. In a mere 1300 Earth years, the sphere was ready for habitation by the seventeen trillion Zeboids who survived the final years. Unfortunately, that was the time of the Ennui Wars in which the populations of the various habitat suffered from an induced form of apathy causing them to cease all education and production and even began to destroy the machines and bots maintaining Dysonica. Eventually, automated system control shut down or deactivated all systems not related to life support and environmental maintainence. Susequently the Dysonica population had been reduced to around a few hundred billion Zeboids, living a subsistence lifestyle in most cases.

 

Only since the arrival of the TGR exploration fleet in 4257 CE have the semi aware AI systems had any interface with living beings at the control center. Since Dysonica covers the land area of about 200 million Earths, it is not expected that there will ever be anything like control of the artifact by the 380 billion humans of the Terran Galactic Republic.

[austenandrews]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

If you have a Sphere' date=' you need not have FTL.[/quote']

Do you mean that a DS is large enough to support a story/novel/series/campaign? Or do you mean a DS would obviate the desire to travel to distant stars?

[Cancer]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Rather than real world science' date=' I think "rubber science" or "magic" or "gobbledygook" if you prefer is the way to set up Dysonica.[/quote']

You've got this correct. You certainly can't make a sphere with known science. No known material has the mechanical strength needed to maintain the spherical shape, whether it rotates or not.

[austenandrews]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Maybe the DS is a living thing.

[Basil]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

1)gravitational pull is an inverse square function of radius from center of mass.

2) mass of a hollow sphere of non-variable thickness t is also a square function, increasing with the radius of the sphere.

 

Let's plug in a radius of 150 million km for the outer shell, and 149.9987 million km for the inner shell. Volume is the volume of the larger shell minus the volume of the inner shell.

So far so good.

 

Raw estimated volume for this(mine) is 150 million^2, times 4 pi, times 1300 km.

Where did this come from? The volume of a sphere is four-thirds pi R cubed (4/3* pi * R^3).

 

If you check Play4Keeps' formulae, that's what he's doing.

 

Since the volume of the shell will remain fairly close to a mirror of the square function,

No, it's based on a cube function. Specifically, the difference between two cubes.

 

and the gravity will decrease as an inverse square function' date=' the range of the gravitation attraction will stay pretty steady, once the thickness/radius ratio is small enough(say, 1/1000, or higher). [/quote']

 

However, this is approximately correct. It could be better phrased by saying that as the thickness/radius ratio drops, the shell comes to approximate a zero-thickness shell.

 

IF! the shell were of zero thickness, yet had mass, the mass would be given by a formula based on the square of the radius; in that purely theoretical situation the surface gravity would hold steady for reasons you've already given.

 

It looks like the increase in surface gravity will be negligible.

Well, small at least. I'm not dead-sure it's negligible. Depends on how accurate your instruments are, I guess.

[Basil]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Well' date=' in the real world currently, the energy required for FTL travel is infinite, while the energy required for a DS, while vast, is not.[/quote']

 

An excellent point.

 

Rep for this, and all the other good points you've raised in this thread.

[Cancer]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Ummm ... this is a freshman calculus problem sort of situation ... the two approaches ought to reach the same conclusion, since they are equivalent, as long as thickness of shell << mean radius of shell. (Errors will be on the order of ((shell thickness)/(shell radius))^2.)

 

Eyeballing the numbers in the post, the differences look to me to be at the level of machine or software precision (depends on who's using doubles or quads (etc.) for their floating-point arithmetic). Trivial, compared to other factors in what's going on. For example, the density of Earth-composition matter changes depending upon pressure, and you don't have the same pressure in that shell as you do in the near-spherical planet.

 

Astrophysical accuracy. "We don't care about factors of 10 as long as they aren't in the exponent," as my undergrad mentor said more than once.

[Curufea]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Do you mean that a DS is large enough to support a story/novel/series/campaign? Or do you mean a DS would obviate the desire to travel to distant stars?

 

I think both.

 

A Sphere would potentially have more inhabitants than a galaxy. All within sublight travel range. All on a place that is visitable without any unusual life support conditions.

 

After all - would there be more than 190 million earth-like planets in our galaxy? It really depends on a lot of guesswork - we currently don't know what percentage of solar systems could sustain life. But in my opinion, it would be less than 190 million.

 

Plus, if you have an entire campaign within a sphere - you can always make the whole thing break the tangent and have something happen outside that affects those inside. Personally I like the idea of a nocturnal race on the outside as well, sustained by the heat eminated as waste from the inside (hence the equivalent of 380 million worlds).

[megaplayboy]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

So far so good.

 

 

Where did this come from? The volume of a sphere is four-thirds pi R cubed (4/3* pi * R^3).

 

If you check Play4Keeps' formulae, that's what he's doing.

 

 

No, it's based on a cube function. Specifically, the difference between two cubes.

 

 

 

However, this is approximately correct. It could be better phrased by saying that as the thickness/radius ratio drops, the shell comes to approximate a zero-thickness shell.

 

IF! the shell were of zero thickness, yet had mass, the mass would be given by a formula based on the square of the radius; in that purely theoretical situation the surface gravity would hold steady for reasons you've already given.

 

 

Well, small at least. I'm not dead-sure it's negligible. Depends on how accurate your instruments are, I guess.

 

yep. I know the other formula, strictly speaking, is the correct one, but even if you use the correct one, then start at 150 million km radius, and "solve for t"(where t is the thickness of the shell/difference between inner and outer radii), the variance in t will be fairly small. If density is constant, then t will tend to be very close to (radius of Earth/3).

 

A sufficiently ludicrously-advanced civilization("The Malvans are amoeba compared to us") could deconstruct a galaxy or three and build a Terasphere, up to maybe a light year in radius(a crash pad for a macro-sized entity, perhaps?)--and have enough space inside to hold the occupants of, well, every system in the universe. You know, just until that whole entropy thing blows over.

 

They could call it, um, "Haeven" or something...

[Vestnik]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

A sufficiently ludicrously-advanced civilization("The Malvans are amoeba compared to us") could deconstruct a galaxy or three and build a Terasphere, up to maybe a light year in radius(a crash pad for a macro-sized entity, perhaps?)--and have enough space inside to hold the occupants of, well, every system in the universe. You know, just until that whole entropy thing blows over.

 

You know, you're likely already familiar with them, but if you're looking for a fictional treatment of a civilization that could do something like this, you might look at Greg Baxter's Xeelee novels. The Xeelee are so advanced they fight wars with superstrings (at a geological scale of time) and manipulation of stellar orbits.

[Curufea]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

You know' date=' you're likely already familiar with them, but if you're looking for a fictional treatment of a civilization that could do something like this, you might look at Greg Baxter's Xeelee novels. The Xeelee are so advanced they fight wars with superstrings (at a geological scale of time) and manipulation of stellar orbits.[/quote']

 

Sounds almost like Scientology to me