The DYSONSPHERE: one of ST's, & Sci-Fi's, greatest mysteries.
- Thread starter Aquehonga
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You have to treat it like a multi-body problem. Objects are only drawn to the barrycenter between the Earth and the moon when they're very far away from them; closer to them, either the Earth's or the moon's gravity is dominant.
So the star in the middle of the sphere is at the barrycenter of the whole system, but closer tot he surface of the sphere you are attracted to the nearest gravitational source, not the center.
Solar Radiation produces 2.5 pounds pressure per square mile at Earth orbit. Assumedly enough so solar radiation doesnt rip it. It takes 1.2 thousand years to orbit enough material to manufacture a simple O'NEILL CYLINDER. so it supect it would have to be built when the Solar System is so young that there is a cloud of "Carbon level Elements" occupying the Solarsystem that can be Nanobotted into a mesh to which more carbon will be microwave deposited by pressure of solar radiation. Potentially you could probably grow a Diamond Shell on a carbon nanoframe.
To verrify that such is possibile, you would need to do an experiment on the ISS where you Spray CO2 on a Carbon nanomesh in space and let the Sun microwave deposit it into a diamond sheet.
It just seems to me that a 2d ring of mass is a good way to model a cylinder, but not a sphere, since the mass along the curved surface doesn't all sit in a perfect 2d ring-like way, it curves around in 3d. So even though it's symmetrical, the forces don't all cancel away along the 2d plane you're using. If they don't cancel, then you can't simplify it that way. I think that's why we have the shell method and not the ring method for spheres. The shell method is more complex, but it's as simple as you can go while still getting a correct answer.
Granted, this is just my intuition, but I really don't think you can ignore the 3d curve of a sphere, which is why you might have ended up with a different answer. Assuming you did everything else right, you'd have the correct model for a ringworld though.
I guess it's possible to slice the sphere into many smaller and smaller radius thin rings, but that seems needlessly complex compared to the shell method, which is pretty complex to begin with.
http://www.nada.kth.se/~asa/dysonFAQ.html
In Star Maker, the universe is at one point inhabited by countless highly advanced 'world minds' and communities of world minds, telepathic entities spanning whole planets. One of these world mind communities starts building artificial planets.
I think this is the level of advancement you'd have to think about in relation to the TNG Dyson sphere: extremely advanced beings, on the same kind of level as Stapledon's world minds and sentient stars. Whatever happened with the Enterprise and the Jenolan was utterly insigificant to whoever built the Sphere, if they indeed still exist.
As for the purpose, who knows. It could've been for habitation, but it could be something different. A weapon? Protection against Doomsday weapons? A prison for a primal star-like entity? I think it is in its very essence supposed to be a mystery, and you can't really say much more than that.
In Star Maker, the universe is at one point inhabited by countless highly advanced 'world minds' and communities of world minds, telepathic entities spanning whole planets. One of these world mind communities starts building artificial planets.
I think this is the level of advancement you'd have to think about in relation to the TNG Dyson sphere: extremely advanced beings, on the same kind of level as Stapledon's world minds and sentient stars. Whatever happened with the Enterprise and the Jenolan was utterly insigificant to whoever built the Sphere, if they indeed still exist.
As for the purpose, who knows. It could've been for habitation, but it could be something different. A weapon? Protection against Doomsday weapons? A prison for a primal star-like entity? I think it is in its very essence supposed to be a mystery, and you can't really say much more than that.
GodThingFormerly
A Different Kind of Asshole
For those interested, this is a digital matte painting created by Eric Chauvin for the Dyson Sphere's interior. I have absolutely no idea how it ended up in my archives. 
TGT
TGT
Indeed, I don't think people fully appreciate the actual scale of one of these things. A quick back-of-the-envelope calculation reveals a dyson sphere with the same radius as Earth's orbit around the Sun would have an internal surface area something on the order of HALF A BILLION times that of Earth.
So in terms of population, if Earth can support 6 billion people, the Dyson sphere could support 3 QUNTILLION people. That's a number I can't even perceive it's so big.
3,000,000,000,000,000,000.
Ouch.
Furthermore, if it takes Data 5 seconds to scan an Earth-sized planet for lifeforms using the Enterprise's sensors, to scan the entire internal surface of the Dyson sphere will take 80 YEARS.
So, we're talking about a full scientific expedition here just required to find out if the thing is inhabited!
The Milky Way has something like 200 billion to 400 billion stars in it. A very generous estimate would be that 1/10th of these might have a habitable M-class world (and this is very generous as 85% of them are Red Dwarfs, so goes current thinking), then the Dyson sphere's internal surface area is equivalent to 1/40 of the entire combined surface areas of all habitable planets in the Milky Way Galaxy.
That's quite big, no?
Well, let's gas up a couple of shuttles and get started. We should be done checking to see if anyone's home right around the time the Federation is able to build these itself
I wonder if anyone thought of using this thing as some sort of emergency retreat during the Dominion conflict.
I've read a comic a long loooong time ago where a utra heavy star blew itself to bits and shed its outer shell, the star being a real heavy weight was already fusing carbon so somehow it created a thick ultra large carbon based sphere with a white dwarf in the middle of it, there were holes in the shell so ships could get in and out, damn annoying that I have absolutely no clue anymore what the title was and who wrote it...
If something alike would be possible then you'd only have to find one and claim it in the name of Mars
If something alike would be possible then you'd only have to find one and claim it in the name of Mars
Regarding Gravity on the interior of a Dyson Sphere. Make a note of how "thick" the Dyson Sphere is. It's not a thin shell. Judging by the amount of depth from Ground level to the docking door that the Jenolen holds open, there's a lot of dirt there. Hundreds of feet, if not thousands. I'm not going to pretend that I know the first thing about complex physics calculations, but something with that much mass has to generate a lot of gravity.. not just on the outside, but on the inside as well. Someone standing on the interior surface would more than like stay on the surface quite well, since it's the only meaningful amount of mass within about 1 AU.
In engineering/physics terms it is a very thin shell. At these scales it could be 10,000 miles thick and still be considered such. Even if it were mostly solid, with only a few hundred feet of hollowness in the center, that hollow part would feel no gravity forces. (ingoring the sun for the moment) A thick shell is the same as many thin concentric shells. So no matter how thick you make it, the (thin) shell theory still applies.
You would feel the sun's gravity, but nothing from the DS itself. When you're in the center, each side is still pulling on you, but they pull against eachother, cancelling out the net effect. So you would just fall into the sun the same as if the DS weren't there at all.
It only draws you to the center of the mass because that's usually where the most matter is. It's actually pulling you to the place with the most matter. Things don't need to be spherical to have gravity, the only thing they need is mass.
I understand that in relative terms to the size of the distance from the shell to the star, that it's going to be a "thin shell" but the dyson sphere is much more massive than a human is.
I would agree, as there is no mass in a hollow area, there is nothing for gravity fo have an effect on.
Since a dyson sphere has mass, it will always exert a gravitational force on things that have mass, like humans. If the human is on the interior surface, the immediate area where he is is exerting a lot of gravitational force on him. Meanwhile, the opposite side of the sphere is also exerting a gravitational force, but it's also 2 AU's away. The force of the matter near the human is much stronger than that of the rest of the sphere.
I agree that there is some altitude (or depth?) from the surface at which the gravity begins to balance out, and you'd get stuck in the center of the thing.. but I think for humans on direct contact with the interior surface would stay that way.
Actually, I should think that a star in the center of a dyson sphere would be pulled apart and it's elements spread about the interior surface of the sphere, since the mass of the dyson sphere would be greater than the mass of the star.
Being drawn to the center of mass is a net effect, and a simplification. In reality, each tiny 'grain' of mass pulls everything towards itself. Not towards some distant 'center'. But if you sit there with a calculator and a lot of time on your hands and calculate the net effect of each grain pulling every other grain towards itself, the net force ends up being towards the center of mass. It's pretty intuitive though so no one really bothers to do that except for simplified proofs with only a handfull of masses.
So? That doesn't mean anything.
There is still gravity inside the null zone, it just cancels itself out, so you feel no net force. All the gravity forces from each little grain of mass are still there, but they're working against eachother.
Obviously.
However, there is a lot more matter distant from you than near you which is why the combined forces of the distant parts of the sphere will still cancel out with the strong force of the small part of the sphere near you. They are direct inverses to eachother when dealing with the perfect symmetry of a sphere shape.
No. There will never be a net gravity field away from the center of any massive object, sphere or no sphere, which is what you'd need to produce gravity towards the inner surface of the shell.
No, the star experiences no net gravitation from the sphere. Read my link earlier in this thread on the shell theory. It's not made up, it's a logical and accepted fact about how gravity works. There is no net force inside a hollow spherical mass. None. Anywhere. This isn't something I just came up with, Newton was the first person to realize this. It's really quite cool, I recommend reading up on it.
Depending on the distance and the size of the object you're talking about. The Center of mass of the Earth-moon system is near the Earth's core, and yet Neil Armstrong didn't fall off the moon after he climbed out of his ship.
Not quite correct. The effect of gravity falls off at a distance as you know, so the fact that the sphere is a solid object doesn't mean you can treat it as a complete mass point. The solar system itself constitutes a singular massive object from a far enough distance, and yet here on Earth we are drawn towards the most massive part of it, not the center of the entire system.
So local gravitation winds out over the gravitation of the whole system, which is only the cumulative effect of the entire system at a distance. Close to the surface of the sphere (on the inside) you would indeed be attracted to the surface of the sphere, because the mass of the shell near you has more gravitational influence than the shell on the opposite side of the sphere. Depending on the density of the shell it might not have more influence than the STAR, though.
Newton first came up with the shell theory because he needed to calculate the mass of the Earth so he could use it to find G, the gravitational constant of the universe. Which he did find correct to an amazing number of decimal places despite using approximations.
Anyway, he could figure out the size of the Earth (by measuring the locations of stars in two different cities at the same time) but he knew he couldn't just take the density of rock, and apply that to the calculated volume of the Earth because the desity of the Earth changes as you increase in depth. So to solve this issue he instead treated the Earth as a series of layered shells, each one being more dense as you approached the center.
Anyway, he also realized that, as you approach the Earth's core, the net gravity decreases until at the center there is no net gravity at all. This is because as you get closer, only the shells below you are acting on you. And once you reach the middle there are no shells below you, thus, no net gravity force. But this also works if you hollow out the center.
The pressure becomes too great for humans to handle deep in the Earth, but if you tunnel below a certain level, gravity starts decreasing. Since Earth isn't 100% spherical though, that turning point isn't right at sea level.
No, this is wrong. For a perfect sphere, there is never going to be an 'up' gravity field. No matter how large, all perfect spherical shells MUST obey Newton's shell theory.
Here's why: If you make the spherical shell bigger, it must become more massive (because it's bigger), but the far side also becomes further away (because it's bigger). The inverse relation of distance and mass will remain in balance no matter what size you make it.
Anyway, he could figure out the size of the Earth (by measuring the locations of stars in two different cities at the same time) but he knew he couldn't just take the density of rock, and apply that to the calculated volume of the Earth because the desity of the Earth changes as you increase in depth. So to solve this issue he instead treated the Earth as a series of layered shells, each one being more dense as you approached the center.
Anyway, he also realized that, as you approach the Earth's core, the net gravity decreases until at the center there is no net gravity at all. This is because as you get closer, only the shells below you are acting on you. And once you reach the middle there are no shells below you, thus, no net gravity force. But this also works if you hollow out the center.
The pressure becomes too great for humans to handle deep in the Earth, but if you tunnel below a certain level, gravity starts decreasing. Since Earth isn't 100% spherical though, that turning point isn't right at sea level.
Ok, if you're talking about a system of massive objects then each does have it's own little gravity field. Of course they're still falling towards the center if they're orbiting the center.
No, this is wrong. For a perfect sphere, there is never going to be an 'up' gravity field. No matter how large, all perfect spherical shells MUST obey Newton's shell theory.
Here's why: If you make the spherical shell bigger, it must become more massive (because it's bigger), but the far side also becomes further away (because it's bigger). The inverse relation of distance and mass will remain in balance no matter what size you make it.
