I have a race that is famous for going over the top with solutions to problems. Their garbage trucks dump the waste directly into their sun. Entire cities move around the globe to keep the sun at "high noon" ... so they don't have to light the streets at night. "Can openers" have self-contained nuclear reactors. And so on. Now, they have decided that humans are a danger to them, because our solutions are simpler and more efficient. They have therefore decided to rid themselves of this danger. True to form they have built a time machine and are going back to the time when Earth was impacted by Theia and will use a singularity to keep the Moon from forming. See? Simple. My problem is I don't know if they'll need more than one singularity. They fussy, they just want Earth with no moon. So do they need something to keep Earth on the right orbit while the singularity pulls the debris away from a Terrestrial orbit? More than one? Orbital mechanics is Rich Purnell's field, not mine. Thoughts, suggestions, mud pies?