User blog comment:IamJakuhoRaikoben/Chapter 461: That Perfume is for Somebody, Review./@comment-5303512-20151110172248/@comment-73.8.57.149-20151111070442

Urm, sorry, but physicsy rant here: Mass is defined as "the amount of matter in a substance," so if she manipulates matter, she is manipulates mass and vice versa. I agree that mass =/= weight. However, 100 kg = 100 kg; weight is measured in lbs or newtons. Size does not change the affect of gravity. Where in F=ma do you see size? Essentially, to change the weight of an object, one must change either the mass of the object or the acceleration due to gravity. Libra's and Chubby's (forgot her real name) powers are gravity change. They change the acceleration vector of gravity (I think). Don't know how, but ok, this would allow them to change the weight of something. Brandish's power, however, is stated to be mass manipulation (or something like that), but unless she is reforming mini-Marin with helium atoms or the like in the atmosphere (which would make him no longer functional as a human), she would be breaking the Law of Conservation of Mass. Meaning she broke physics. To really manipulate mass or keep a consistent density (= amount of matter (mass) is in a certain volume) as original-Mairn, maybe she just disperses little bits of Marin-molecules in an invisible cloud around him. And to make things more massive, she'd gather atoms from other things around the object and reform it into that thing, but bigger. Basically, rearranging mass at an atomic level. Does that somewhat make sense? I dunno... But this is manga and if we analyze every bit of "science" behind it, nothing would make sense and everything will go kaboom. So let's just nod along because this is Fairy Tail and it is entertaining.