> is there a viable way to slow down or speed up orbits of rocky planets? You can fly something massive near a target planet, while using some kind of engine t

> is there a viable way to slow down or speed up orbits of rocky planets? You can fly something massive near a target planet, while using some kind of engine to keep a distance. Gravity will do the rest. It may take some time of course, but all you need is to do maintainance on an engine regularly. > Like, wouldn't they be shooting a bunch of mass out of their system to even attempt this? It depends on a type of an engine. If you use solar sail for example it is not the mass but light will be thrown out. > one could build a Dyson sphere, is that more difficult or less difficult than engineering a system like this? Sphere seems to me more difficult. Not in a sense of energies involved, but from a standpoint of engineering.