FTL would defeat causality and even "just" controlling gravity would be basically equivalent to god-like powers (it would mean assuming direct control over spac

FTL would defeat causality and even "just" controlling gravity would be basically equivalent to god-like powers (it would mean assuming direct control over spacetime itself). Controlling gravity would negate the need for colonisation entirely - it would provide basically limitless power plus full control over your host star's lifetime. Aside from that, almost all papers on the topic including this one focus on subluminal space travel. Sure, once you incorporate technology that goes beyond your current understanding of the universe, many counterpoints go out the window, but this level of technology only serves as an argument against the need for expansion in the first place (with the exception of "because they can"). FTL would be fantastic for research and science expeditions, but expansion into random nearby star systems would be even more pointless, since such civilisation would be able to pick exact/close to exact matches to their home world as candidates for settlement. Such worlds could then be thousands of lightyears apart, as neither communication nor travel would pose a problem. This would also easily explain the lack of (radio-) signals, as exchanging information would be carried out via FTL travel, not radio waves. Why would a civilisation capable of FTL choose to go through the trouble of terraforming or building megastructures around random stars? Wouldn't they rather choose to harness the power of black holes then? A planetary mass BH could power a civilisation for trillions of years for example.