A civilization somehow constraining itself to merely use dyson swarms that block 50% of the light is implausible, it’s much better to just create a small black hole (say, by concentrating very powerful lasers into a small region of space) and throw it into the star. That way you store up all the star’s mass-energy for as long as possible until you use the Penrose process to extract however much of the energy you want from it. In fact, you could even launch these small black holes at close to the speed of light and aim them at stars, preserving their energy for the time it takes the slower-moving parts of civilization to show up.
And if this civilization converts every star they encounter, then this should show up as a completely dark sphere in the universe, which ought to be extremely obvious.
Unlike what you would expect with black holes, we can see that the Boötes void contains very little mass by looking for gravitational lensing and the movement of surrounding galaxies.
A civilization somehow constraining itself to merely use dyson swarms that block 50% of the light is implausible, it’s much better to just create a small black hole (say, by concentrating very powerful lasers into a small region of space) and throw it into the star. That way you store up all the star’s mass-energy for as long as possible until you use the Penrose process to extract however much of the energy you want from it. In fact, you could even launch these small black holes at close to the speed of light and aim them at stars, preserving their energy for the time it takes the slower-moving parts of civilization to show up.
And if this civilization converts every star they encounter, then this should show up as a completely dark sphere in the universe, which ought to be extremely obvious.
Which, notably, we do see (https://en.m.wikipedia.org/wiki/Boötes_void). Though they don’t conflict with our models of how the universe would end up naturally.
Unlike what you would expect with black holes, we can see that the Boötes void contains very little mass by looking for gravitational lensing and the movement of surrounding galaxies.