This is the sort of black hole which produces 1g at 1 astronomical unit radius from the black hole, so gravity is taken care of. Let's assume this is an artificial black hole that was carefully grown from a stellar mass black hole to minimize the accretion disk. Matter is carefully aimed at the black hole so that is falls within three radii of the event horizon where no orbits are possible. On possible way to do this is with a gigantic particle acceleration, where the relativistic mass of the particles as well as the rest mass gets added to the black hole 1650 Solar Masses are added to the black hole in this way. Now we have to figure out how to produce day and night for this Dyson Shell, it doesn't rotate for this, it is much too big. The solution seems to be to have 6 type G0 II yellow giant stars in orbit around this black hole, each of these stars has a Dyson swarm around it. They orbit their respective stars in such a way so as to block visible light for 20 hours out of 24, for the remaining 4 hours, the star's light is unblocked and allowed to reach the surface of the Dyson shell. Only one star out of the 6 is unblocked at a time, so the sun appears to jump 60° across the sky at a time, as all 6 stars are identical in size, luminosity and appearance, each star has the mass of about 8 suns. They may not last a long time, but the surface of the Dyson shell has the surface area of a billion Earths. A day on the Dyson shell looks like this: it is dark out, the sky is full of stars, and the morning Sun suddenly winks on, it appears 30° above the morning horizon. (All six stars are in synchronious or it with the Dyson shell by the way, their distances are such that their disks appear the same angular size as the Sun does from Earth.) The morning sun shines from 6:00 AM to 10:00 AM and then it suddenly winks off at 10:00 AM and simultaneously the Moon Sun winks on and stays shining from 10:00 AM to 2:00 PM. At 2:00 PM the noon sun winks off and the afternoon sun winks on and stays lit till 6:00 PM and then it winks off producing a night that lasts 12 hours.
By - tomkalbfus
I honestly don't see humanity in the far future bother building mega-structures that specifically fit the gravity and/or day night cycles needs of *current* humanity. It is almost certain that bio-techs will have long render these issues mute before we even step outside of the solar system, not to mention possibility of forgoing a carbon based body all together. A more probable scenario is we will have so many different types of "humans" that each one will have their own preferred environment. I feel any mega structure we build intending on housing the greatest extend of humanity will just have a microgravity baseline, and people can just modify their own little habitat to suit their needs.
Also, the strength needed for a structure like this might well exceed that of any possible material. Even for exotic yet-to-be-discovered allotropes and nanostructures, there are simply hard limits to how strong molecular bonds can be. With the energy and matter needed to build something like this, you could create millions of Banks-style orbitals.
>...Now we have to figure out how to produce day and night for this Dyson Shell... We really do not. Window blind technology is well developed. People will prefer control. >...carefully grown from a stellar mass black hole to minimize the accretion disk... Better to just use an accretion disk. You can have 1665.6 solar mass of orbital rings around a 1 solar mass black hole. In the beginning it is sort of an Alderson disk. Use the astrophysical jet as the light source. The hot ball rides the jet up to infinity. It is a nice glow changing on horizon. Not really like a Sun but definitely can be on a 24 hour cycle. At night energy is inside a shielded positron beam. Other parts of civilization can live on the gamma rays. The magnetic fields can help stabilize and support the structure. The ring rotors can follow elliptical orbits for a much larger disk. That lets heat be radiated. The inner most part of the disk is just plasma. Positive charge iron nuclei are dropped into the black hole. Electrons flow out and to the poles. Where electron beams (see cathode ray tube) launch them into deep space. The positrons complete the circuit.
You could have orbital rings without anything in the center, the Dyson Shell could have nothing but vacuum on the inside and if you make the shell tick enough to have its own gravity on the outer surface, then no black hole will be needed at all. So you will need 1,666⅔ Solar masses of Dyson Shell. The mass of the Sun is 1.989 × 10\^30 kg, so the mass of the Dyson Shell would be 3.315 × 10\^33 kg. The surface area of the sphere would be 2.82743 × 10\^17 km\^2 You would have 1.172 × 10\^16 kg/km\^2 of mass to produce 1g at the surface. A square kilometer has 1,000,000 square meters, so its 1.172 × 10\^10 kg/m\^2 The density of iron is 7800 kg/m\^3 by dividing 1.172 × 10\^10 by 7800 we get the thickness of the shell if it were made of iron which is 1.5 × 10\^6 meters, which is 1,500 kilometers of iron, that is all we'd need to produce this gravity field. Its hard to find that much iron. The density of hydrogen is 0.08375 kg/m³ so dividing 1.172 × 10\^10 by 0.08375 we get 13.994 × 10\^10 meters or a shell 139,940,000 kilometers thick assuming 1 bar of hydrogen pressure, this pretty much fills out the entire volume of the sphere. Of course all that hydrogen will tend to gravitationally compress at the center unless prevented from doing so, so we need a series of concentric dyson shells every 1,000 kilometers inward to prevent all that hydrogen from forming a star at the center, we need to compartmentalize the areas between the shells in a honeycomb like structure to keep the hydrogen evenly dispersed, so we're talking about 139,940 shells each one spaced 1000 kilometers apart.
Iron is not hard to find. It is the end product of fusion. The heat generated by fusion is less than what you get dropping mass into a black hole. Hydrogen is easier to deal with when mixed with carbon and oxygen as water, plastic, and carbohydrates.
An iron nebula would be somewhat hard to find, and we need 1666.7 solar masses of it, but if we had it, we'd only need a shell 1500 km thick, the inside of it would experience zero gravity and the outside would experience 1g, so for every 150 km you passed through, depending on direction the gravity would either increase or decrease by 0.1g, inside the shell would be nothing, no need to make a black hole, all you'd need to do is produce a 1500 km thick iron shell, so long as it was 1500 km thick, it would produce 1g on the outside., you still would need orbital rings to keep it from imploding under its own gravity, and 1666.7 solar masses of iron would produce a black hole.
I don't see the stars orbiting the Dyson shell. If the gravity is 1g at the shell surface and it drops off with distance there shouldn't be enough pull to orbit a star.
why not, 1666.67 solar masses should produce plenty of gravity at 1 AU that is 1g, at 2 AU that is 0.25g and so on.
Jupiter is 0.09% the mass of the sun. so that kind of mass ratio isn't out of the question. Tidal forces would absolutely wreck a dyson shell though.