Theory:Doctor Who television discontinuity and plot holes/Kill the Moon


 * Mass is constant. That means that the moon will not have grown any larger or gotten heavier. That the moon "gained weight" because the creature grew larger suggests that mass was created out of thin air, which is impossible.
 * Remember that mass only remains constant if there is no change to the object itself. Since the creature grew larger, its mass would obviously increase. However in this case, the subject of mass does not apply here, since we're talking about the moon gaining weight. Mass and weight are not the same, as weight is affected by the force of gravity. Since the creature grew larger, its weight would obviously have increased, which in turn affects the moon's weight as well.