12. "RE: A question on Dyson Spheres & UF"
In response to message #11
LAST EDITED ON Nov-30-17 AT 07:40 PM (EST)
>The thing about any Dyson sphere is that building it would involve the >utter demolishing of literally thousands, if not tens of thousands, of >solar systems in order to gather the required mass. (You could use >every speck of dust available in our solar system and it wouldn't even >construct a ringworld around the sun, to say nothing of a Dyson >sphere.)
That sounds way too high, to me. Niven claimed order of 20 Jupiters to build his Ringworld (including the shadow squares and the kinetic energy of spinning it all up) and I have no idea if I should believe him, but he's clearly estimated it much lower. And https://www.aleph.se/Nada/dysonFAQ.html#ENOUGH estimates that if you demolish one solar system's worth of planets (not the star, just the planets) you get 600kg of "usable raw material" per square meter of 1AU-radius sphere; obviously there's no good way of knowing whether that's "enough", considering that you have to convert it into an impossibly strong substance, but all told I think there's a strong case that you could do the job with less than one solar mass of input. Good enough for soft SF, anyway.