Originally posted by karajorma:
Okay a couple of points to make here
1) Re: dyson spheres. Just had a though about this. The gravitational pull inside a sphere is zero. The only gravitational pull inside a dyson sphere would be that of the sun in the centre.
This could explain why the shivans built a dyson sphere. If they have adapted to being zero G creatures they would have trouble living on a planet but maybe they still need large nearly flat areas to build things on.
Another point. Who says they live on the inside of the sphere? Maybe they use the inside for energy collection and live on the outside (which would have gravity!)
Re: Capellan supernova
I`ve heard two explainations for why a star goes nova. One said it was due to the build up of iron in the core making the star to heavy. The second said it was due to the star losing energy through the fusion of iron rather than gaining it. Either way could you make a star go supernova by jumping a large iron asteroid into its core? Maybe that's how the shivan's did it. (shouldn`t cause a large increase in mass either since the asteroid goes right into the centre of the star)
On gravity in a Dyson Sphere: surface "gravity" would be provided by centrifugal force as the sphere spins around the "common point" (where the star would be parked)at center. The star would "anchor" the spin. If you don't spin the sphere, you'd have stability and drift problems.
On Shivans living outside, and collecting energy inside: interesting idea. Why don't you develop this a bit further.
On iron, stellar cores, and asteroids: a star fuses hydrogen into helium until that "fuel" runs out. Then it compresses, because fusion energy is no longer there to "hold up" the immense mass. At some point in the comression, the energy level soars, and fusion of helium into heavier elements begins. When all the helium is converted, the star compresses again, and these heavier elements began fusing into still-heavier elements, until the "iron horizon" is reached. Nothing except extremely exotic conditions can convert iron into heavier elements, so the star collapses catastrophically under its own mass. If it's the mass of the sun or less, it becomes a white dwarf. If it's several times the mass of the sun, the collapse "rebounds" when the "strong force" horizon is reached, when the star can no longer compress without distorting the strong force that holds the internal components of its atoms together. That rebound will blow off about half the star's mass into space, and that's your supernova.
So an iron asteroid won't do it. Even dropping a chunk of iron the size of Jupiter into a small star like the sun wouldn't have an appreciable effect.