Opinion
Personally, I do not believe in Arcs understanding of the feat
When the feat happens we see that moon is traveling towards the
earth as is ablaze, the same as how objects are on reentry, not only that but we even see that Faerie calls it a
"moon fall" and directs his hands down and implies further so by saying that the
"moon which has come so close can't not be pushed back", implying that it has moved closer and the earth being moved to it (
Thanks Damage finding this) . We clearly se that both by visually and of the person performing the feat that the moon is falling down to earth. We also see that the moon coming closer is
causing havoc, as the moon controls the tidal forces, etc... of the earth
When Shinra stops the event, he stops the moon and not the earth, which is still ablaze. Arc believes that Earth is moving and if so Shinra would need to kick the earth to stop it, not the moon. Also going with the understanding that the earth is being pulled, everything on the surface would have been flung off the and directed to the moon due to the its greater gravity, which
isn't the case in the chapter.
Another issue is assuming that he is increasing the mass, which while he can, it is nowhere said or limited to him only doing so, and is important to keep in mind of my new outlook/proposal
Conclusion and New Outlook
In terms of of Arcs understanding of the feat. He understands his powers but not the feat, and I feel to come to understand what is happen. Faerie is not launching the moon and not the earth, but this isn't because he is is increasing the moons mass, but decreasing. Why is my understanding more valid.
1- Through all the visuals, the moon is falling, being ablaze and is coming toward the earth. (Visually)
2- The persona performing the feat affects the moon and even calls it a moon fall and is even talked about as if it have come closer. (stated to be)
3- The general understanding/narrative is that the moon came to the earth, not the other way. (general narrative understanding)
4- Never stated to only increase mass. (No specific limit on powers)
TL;dr Faerie manipulates the gravitational attraction of objects by altering the mass of objects, which in this feat he decreases the moons, causing the gravitational pull of the earth to pull it in.
Where From here?
So where do we go from here. In terms of calcs, i believe that
Pr3digy version best fits the feat, in which it takes account for a decreased mass (albeit assumed mass) and that the moon moved towards the earth, however, if we can calculate the mass of a moon needed that can be pulled in by the earth, that would be substituted into the calc instead