> And you still need a cold end to your hot end. That is interstellar space @ 2.7K :) I actually just went through the calculations on my blog and to achieve

> And you still need a cold end to your hot end. That is interstellar space @ 2.7K :) I actually just went through the calculations on my blog and to achieve a 99% Carnot efficient Dyson sphere (emitting at 58K) it would need to have a radius of ~7 AU - somewhere between Jupiter and Saturn [1]. There is plenty of mass to achieve that in the solar system and it would be also be undetectable in the infrared. 1. https://www.tillett.info/2016/08/03/carnot-efficient-dyson-spheres-are-undetectable-by-infrared-surveys/ https://www.tillett.info/2016/08/03/carnot-efficient-dyson-s...