Like I said, there would have to be some breakthrough physics here, like what "vacuum" actually means, or how dark dark matter is, etc. I'm just pointing out t

Like I said, there would have to be some breakthrough physics here, like what "vacuum" actually means, or how dark dark matter is, etc. I'm just pointing out that there are a number of logically possible solutions that don't involve violating the conservation of momentum, which may or may not be physically possible.