> proportional to the speed In what reference frame? It's not obvious to me how this works in a space drive. How does it "know" how much speed it gets per unit

> proportional to the speed In what reference frame? It's not obvious to me how this works in a space drive. How does it "know" how much speed it gets per unit energy? I guess if it's a sort of Dean drive that swims through the gravitational field of the visible universe, then that's the reference frame. It's still weird!