> The real question is therefore not whether a space-time solves Einstein’s equations, but whether the distribution of mass and energy required to make it a solution to the equations is physically reasonable.
> And for the Alcubierre drive the answer is multiple no’s. First, as I already said, it requires negative energy. Second, it requires a huge amount of that. Third, the energy is not conserved.
> [...] Bobrick and Martire explain that if you want superluminal motion, you need negative energy densities [in their new paper about slower than light, physically realizable warp drives]. If you want acceleration, you need to feed energy and momentum into the system. And the only reason the Alcubierre Drive moves faster than the speed of light is that one simply assumed it does. Suddenly it all makes sense!
Also, even if it were, the amounts of mass/energy required to achieve the motions that are being claimed would make these ships extraordinarily easy to detect (for some of the claimed accelerations, they would likely turn into black holes before actually accelerating that fast!).
Also note that the number of planets in the galaxy is irrelevant as long as we have no idea about the likelihood of abiogenesis (and we don't).
[0] http://backreaction.blogspot.com/2020/11/warp-drive-news-ser...