m. c. de marco: To invent new life and new civilizations...

BDO of the Day: Megasphere

At galactic size, today’s Big Dumb Object (BDO) may be the biggest and dumbest out there. The Megasphere is a Dyson sphere with a surface area of “tens of millions of light years” [sic] built around a galactic core. As with a double Dyson, people would enjoy a Virga-like life in the space above the sphere. They would have to adapt to the microgravity, but would have an atmosphere that was “scores of light years” deep, in which they could build other megastructures and float between them at their leisure.

megasphere (modified from public domain image from Wikimedia)

The megasphere is apparently the creation of Larry Niven, who described it in his classic megastructures essay without crediting anyone else. He also doesn’t mention the heat and drag effects of rotating huge megastructures within a vast atmosphere, never mind the more basic issues of radiating heat from the depths and of the atmosphere collapsing upon itself without magic to counteract the force of gravity.