Re: Earth Goes Poof, Wherefore Art Thou Luna?
I'm not sure (rarefied territory for me) but he might be thinking of stuff to do with transfer of momentum.
The following thought experiment grossly over-simplifies a complex problem, but consider.
Imagine tying a weight to a length of string and whirling it around. Once the twirling is up to a certain speed, things are nice and stable. The more weight at the end, the slower this speed has to be - you expend more effort to get it going but, once it is, again nice and stable.
So what happens if the string is suddenly shortened? The "Orbit" becomes smaller and the weight whips around faster - same energy, just less distance. So, what happens if the string remains the same length, but a very big part of the weight suddenly vanishes? Whatever is released will zoom off somewhere, and the portion still attached?
Add to that picture, suppose the string is elastic, and only partially stretched. When all that weight at the end vanishes, I imagine that the elastic will probably try to "pull in" whatever is left.
The dynamics of the Sol-Earth-Moon system are a heckuva lot more complex than this simplistic premise, but I hope the idea is helpful.